34th IVS Annual Meeting - BGUrubin/papers/Book Of Abstracts IVS 2016.pdfSession ID - Nanophotonics...
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1 34 th IVS Annual Meeting Monday, September 12 th , 2016 Ben Gurion University of the Negev, Beer-Sheva Conference Chairs: Prof. Nurit Ashkenasy and Dr. Iris Visoly Fisher IVS president: Prof. Shachar Richter IVS Science, Technology & Applications
Transcript of 34th IVS Annual Meeting - BGUrubin/papers/Book Of Abstracts IVS 2016.pdfSession ID - Nanophotonics...
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34th IVS Annual Meeting
Monday, September 12th, 2016
Ben Gurion University of the Negev, Beer-Sheva
Conference Chairs:
Prof. Nurit Ashkenasy and Dr. Iris Visoly Fisher
IVS president:
Prof. Shachar Richter
IVS
Science, Technology & Applications
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Sponsors
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Commercial Exhibitors
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Table of contents: IVS- 2016 Program 5 Plenary Lectures 10 Oral Presentations 13 IA- Advanced in Nanofabrication 14 IB- Molecular and Biomolecular electronics 20 IC- Sustainability and Environment 26 ID- Nanophotonics 32 IIA- Bio-materials and interfaces 39 IIB- Magnetic and electronic materials 46 IIC- Surface Science and Characterization 52 IID- Theory of Materials and Thin Films 58
Posters 64 BI 65 EM 77 G 84 ME 92 NF 105 NP 113 SE 119 SS 128 T 138
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IVS- 2016: Program
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8:00-10:30 Gathering & plenary session I
08:00- 09:10 Registration and Gathering Building 35, lobby (floor -1)
09:10-10:00 Plenary Session 1 Chair: Iris Visoly-Fisher (BGU) Building 35, Hall 001
09:10- 09:20 Welcome Prof. Shachar Richter, IVS president
09:20-10:00 Plenary lecture Paul E. Sheehan, U.S. Naval Research Laboratory; Chemically Modifying Graphene for Advanced Functionality
10:00-10:30 Coffee Break
10:30-12:30 Parallel Morning sessions
Session IA – Advances in nanofabrication Chair: Mark Schwartzman (BGU) Building 35, Hall 002 (floor -1)
10:30 - 11:00 IA1- Roy Shenhar, HUJI (invited) Block Copolymer-Templated Assembly of Polyelectrolyte Multilayers: A Facile Route to Nano-Patterned Materials
11:00 - 11:20 IA2- Hadar Ben-Yoav, BGU Nano-Biofabricated Electronic Films for Functional Lab-on-a-Chip Micro-Systems
11:20 - 11:40 IA3- Yachin Ivry, Technion Nanostructures with Augmented Superconductivity for Quantum Technologies - Beyond the Proximity Effect
11:40 - 12:00 IA4- Nina Armon, BIU Nano Particle Assembly by a Modulated Photo-Induced Microbubble
12:00 - 12:30 IA5- Ernesto Joselevich, WIS (invited) Nanotube Coils
Session IB - Molecular and biomolecular electronics Chair: Ayelet Vilan (WIS) Building 35, Hall 003 (floor -1)
10:30-11:00 IB1- Michal Lahav, WIS (invited) Electron Transfer in Coordination-based Molecular Assemblies
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10:30-11:00 IC1- Viatcheslav Freger, Technion (invited) New Insights into Mechanism of Salt Transport Through Thin Polymer Films in Membrane
11:00-11:20 IC2- Maya Bar Sadan, BGU Designing Bimetallic Reduction Co-Catalysts – Correlating Atomic Structure with Properties
11:20-11:40 IC3- Hannah Noa Barad, BIU Fabrication of CexNiyO3 as a New Absorber for Photovoltaics Using Combinatorial Material Science
11:40-12:00 IC4- Yevgeni Rakita, WIS Conversion of Single Crystalline PbI2 to CH3NH3PbI3: Structural Relations and Transformation
12:00-12:30 IC5- Avi Niv, BGU (invited) High Intensity Microparticles Optical Drive
Session ID - Nanophotonics Chair: Yaakov Tischler (BIU) Building 35, Hall 116 (floor 1)
10:30-11:00 ID1- Yonatan Sivan, BGU (invited) High Temperature plasmonics
11:00-11:20 ID2- Lihi Efremushkin, BIU Designing Plasmon-Molecule Interactions
11:20-11:40 ID3- Priyadarshi Ranjan, WIS Tubular Photoactive Gold Nanoparticle Assemblies
11:40-12:00 ID4- Lena Yadgarov, TAU Optical Imaging of an Exaction- Plasmon Wave Functions Confines in a Single WS2 Nanotube
12:00-12:30 ID5- Alina Karabchevsky, BGU (invited) Nanophotonics on a Chip: From Fundamentals to Emerging Applications
12:30-14:30 Poster session, Exhibition & Lunch
14:30-16:30 Afternoon sessions
11:00-11:20 IB2- Edith Beilis, TAU Effect of Protein Layer Morphology on Charge Transport
11:20-11:40 IB3- Muhammad Bashouti, BGU Growth and Surface Engineering of Si Nanowires for Optoelectronic Applications
11:40-12:00 IB4- Ofer Kedem, Northwestern U. IL, USA Ratcheting of Photo-generated Carriers in an Organic Bulk-heterojunction
12:00-12:30 IB5 - Yoram Selzer, TAU (invited) Plasmon Controlled Molecular Junctions
Session IC- Sustainability and environment Chair: Moshe Herzberg (BGU) Building 35, Hall 115 (floor 1)
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Session IIA - Bio-materials and interfaces Chair: Liraz Chai (HUJI) Building 35, Hall 003 (floor -1)
14:30-14:55 IIA1-Ronit Bitton, BGU (invited) Polysaccharide Hydrogels Cross-linked via Thermo-Responsive Peptide-Dendrimers
14:55-15:15 IIA2- Rivka Elbaum, HUJI Open Sesame: The Secrets Behind Hygroscopic Movement for Sesame Seed Dispersal
15:15-15:35 IIA3- Haguy Wolfenson, Technion Micro-Fabricated Elastomeric Pillar Arrays for Studies of Cellular Sensing of Extracellular Matrix Rigidity
15:35-15:50 IIA4- Roi Asor, HUJI Following Virus Like Particles Assembly Using Time Resolved Small Angel X-Ray Scattering
15:50-16:05 IIA5- Assaf Gal, Max Planck Institute, Potsdam, Germany Biological Control Over Site-Specific Mineral Templating in Coccolithophore Algae
16:05-16:30 IIA6- Gil Goobes, BIU (invited) Hooking Up to Diatoms to Form New Bioinspired Silica by Peptide Catalysts (Material Design with Structural NMR Spectroscopy)
Session IIB - Magnetic and Electronic Materials Chair: David Nessim (Intel) Building 35, Hall 002 (floor -1)
14:30-14:55 IIB1- Mor Baram, Applied Materials (invited) Defect Review Material Analysis Challenges in Semiconductor Industry
14:55-15:20 IIB2-Daniel Rich, BGU (invited) Probing Plasmonic Effects in Metal-Coated Semiconductor Nanostructures with Time-Resolved Cathodoluminescence
15:20-15:45 IIB3- Ariel Ismach, TAU (invited) Synthesis and Characterization of MoS2/WS2 Heterostructures
15:45-16:10 IIB4- Doron Naveh, BIU (invited) Graphene Triodes: Achieving Control Over Leakage Currents
16:10-16:35 IIB5- Shlomo Mehari, Technion (invited) Electron Trapping Effects in Gallium Nitride-based High Electron Mobility Transistors
Session IIC - Surface Science and Characterization Chair: Yaron Paz (Technion) Building 35, Hall 115 (floor 1)
14:30-15:00 IIC1- Yossi Paltiel, HUJI (invited) Probing Self-Assembled Monolayer Molecular Transport Properties Using the Superconducting Proximity Effect
15:00-15:20 IIC2- Edward Bormashenko, Ariel Self-Propulsion of Liquid Marbles: Leidenfrost-Like Levitation Driven by the Marangoni Flow
15:20-15:40 IIC3- Ronen Dagan, TAU Carrier Lifetime of Ordered Ga0.51In0.49P at High Temperature
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15:40-16:00 IIC4- Andrew D. Chew, Edwards Vacuum, UK Evolution of Vacuum Pump Requirements for Surface Science and Liquid Chromatography Mass Spectrometry
16:00-16:30 IIC5- Alon Hoffman, Technion (invited) High resolution electron energy loss spectroscopy studies of hydrogenated polycrystalline diamond film surfaces with grain size varying from the nano-meter to micro-meter range
Session IID - Theory of Materials and Thin Films Chair: Amir Natan (TAU) Building 35, Hall 116 (floor 1)
14:30-15:00 IID1- Leeor Kronik, WIS (invited) Understanding Collective Effects at Organic/Inorganic Interfaces from First Principles
15:00-15:20 IID2- Oswaldo Dieguez, TAU Using Strain to Tailor the Polar and Magnetic Properties of Perovskite Oxides: A First-Principles Study
15:20-15:40 IID3- Ilya Grinberg, BIU First Principles Based Design of Perovskite Oxides for Visible Light
15:40-16:00 IID4- Micha Polak, BGU Equilibrium Adsorption Under Nano-Confinement: Prediction of Distinct Entropic Effects
16:00-16:30 IID5- Dan Mordehai, Technion (invited) Nucleation-Controlled Plasticity in Crystalline Nanoparticles
16:30-17:00 Coffee Break
17:00-18:30 Plenary session II, Awards ceremony Chairs: Nurit Ashkenasy (BGU); Shachar Richter (IVS) Building 35, Hall 001
Plenary lecture
Efrat Lifshitz, Technion Investigation of the Magneto-Optical Properties of Individual Colloidal Quantum Dots from II-VI Semiconductors and their Diluted Magnetic Compounds to Perovskites
Award ceremony
The IVS Excellence Award for Research; The IVS Excellence Award for Surface Science; The IVS Excellence Award for Technical skills; The Intel IVS2016 female scientist award; The IVS Excellence Award for Student Posters
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Plenary Lectures
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Plenary 1
Paul E. Sheehan
US Naval Research Laboratory
Pristine graphene has many superlative mechanical, thermal, and electronic properties that have been
heavily researched in the past few years. While exploration of these intrinsic properties continues to
impress, realizing graphene’s full potential will likely require a deeper understanding and control over
its chemistry. Probing graphene’s chemistry is challenging because graphene is both relatively inert
and atomically thin, requiring a search for forceful chemistries that functionalize the graphene without
destroying it. To complicate matters, graphene’s reactivity can depend on the underlying substrate, a
bizarre property not typically associated with thin films. We have examined many different routes to
functionalize graphene and so to maximize its performance in different applications. These
applications range from direct write circuitry to biomolecular sensors to surface engineering. We will
discuss the highlights of our efforts and compare the relative strengths and weaknesses of the
different approaches.
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Plenary 2
Efrat Lifshitz
Investigation of the magneto-optical properties of individual colloidal quantum dots from II-VI
semiconductors and their diluted magnetic compounds to Perovskites
Schulich Faculty of Chemistry, Russell Berrie Nanotechnology Institute, Solid State Institute, Technion, Haifa
32000, Israel.
Colloidal semiconductor quantum dots (CQDs) have been at the forefront of scientific research for
more than two decades, based on their size tunable properties. Although implementation of CQDs in
opto-electronic devices already occurs, various fundamental issues with a direct impact on technology
are left as open questions. Recent years showed an interest in the investigation of magneto-optical
properties of various CQDs with substantial importance for opto-electronic and spin-based devices.
The talk includes the study of two different CQD platforms: (1) Synthesis and magneto-optical
characterization of spectrally stable pure and diluted magnetic semiconductor CQDs from the II-VI
semiconductor family (e.g., Mn@CdTe/CdSe); (2) Magneto-optical characterization of perovskite
CQDs of the type APbBr3(A - methylamonium or Cs+). Both systems show intriguing spin properties of
special scientific and technological interests. The uniqueness of the spin properties and their novelty
will be the focus of the plenary talk.
Mn+2@CdSe/CdS and CdSe/ Mn+2@CdS: The Mn+2 doping induces internal spin interactions between
photo-generated species (electron and hole) and the dopant spins, leading to giant magnetization or
to an internal energy transfer into the dopant orbitals, and consequence emission from host-dopant
hybrid- or from dopant atomistic-states. The current study developed a method to position the Mn
ions selectively either at the core or at the shell, in host CQDs that possess quasi-type-II character (viz.,
electron and hole are partially separate), hence Mn spins are coupled either to the hole or to the
electron. The magneto-optical measurements, including the use of optically detected magnetic
resonance, exhibited resonance transitions related to the coupling of the Mn spins with the individual
photo-generated carriers. The information gained put a grown for designing the spin properties of
CQDs of significant importance for applications.
APbBr3 (A=Cs+, methylamonium): The perovskites are minerals that have been studied extensively in
the past. They are the focus of new interest in recent years, due to their exceptional performance in
photovoltaic cells. Perovskites semiconductors possess high absorption coefficients as well as long-
range transport properties. Currently, they are also prepared in the form of CQDs with very interesting
properties including ferroelectricity, magnetism and exciton effects. The magneto-optical
measurements of excitons in APbBr3 as individuals were investigated by monitoring the micro-
photoluminescence spectra in the presence of an external magnetic field, while monitoring either the
circular or linear polarization components. Gradual band splitting occurring upon the application of a
magnetic field, deviating from a common Zeeman interaction behavior, proposes the existence of a
more complex mechanism, when Rashba split is one of the plausible interpretations. Theoretical
considerations strongly supported the existence of Rashba split in the studied materials, emanated
from structural polarization and distortion, viz., breaking of an inversion of symmetry.
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Oral Presentations
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Advances in nanofabrication (IA)
Chair: Mark Schwartzman (BGU)
Hall 002 (floor -1)
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IA-1
Block Copolymer-Templated Assembly of Polyelectrolyte Multilayers:
A Facile Route to Nano-Patterned Materials
Roy Shenhar*
The Institute of Chemistry and the Center for Nanoscience and Nanotechnology,
The Hebrew University of Jerusalem
E-mail: [email protected]
Nano-patterned materials exhibit unique properties, such as increased surface area and
morphology-dependent response. However, obtaining nanoscale patterns usually requires the
involvement of electron beam lithography, which is limiting when device-scale patterns (typically
spanning square centimeter areas) are sought.
The presentation will describe a modular approach for the construction of nano-patterned
polyelectrolyte multilayers. This approach utilizes the nano-patterns that are formed spontaneously
in thin films of block copolymers as templates, which guide the assembly of polyelectrolytes using
electrostatic layer-by-layer deposition.
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IA-2
Nano-Biofabricated Electronic Films for Functional Lab-on-a-Chip Micro-
Systems
Sudheesh K. Shukla, Hadar Ben-Yoav*
Department of Biomedical Engineering, Ben-Gurion University of the Negev, Beer Sheva,
8410501, Israel
*Corresponding author. Tel: (+972) 86479717; Fax: (+972) 86479628; E-mail:
Electrochemical Lab-on-a-Chip (LOC) devices are translational and mobile biosensing micro-
systems that provide numerous advantages in clinical diagnostics, bringing bench top
methods to the point-of-care. However, these micro-systems suffer from limited biosensing
performance due to miniaturization challenges such as low signal-to-noise ratio that is mainly
governed by the small surface area of the sensing micro-electrode. Designing new electronic
surfaces that selectively amplify the electrochemical currents generated by analytes, and can
be easily integrated with conventional micro- and nano-fabrication techniques will improve
the sensitivity and limit-of-detection of these devices. In this work, we will discuss the use of
a stimuli-responsive biopolymer chitosan for a controlled nano-biofabrication approach with
a high spatiotemporal resolution that enables functional and sensitive bioelectronic surfaces
in microfabricated LOC devices. For example, we will demonstrate the utilization of
nanometers-size films of chitosan modified with redox-active catechol moieties resulting in a
redox-cycling system for electrochemical signal amplification. The redox-cycling system is
used to amplify the electrochemical signal of a redox-active medication clozapine (CLZ)
through a continuous cycle of CLZ oxidation followed by catechol reduction of CLZ. We will
also present the use of chitosan to encapsulate carbon nanotubes and the ability of the
resulted electrocatalytic bio-composite to amplify the electrochemical signal generated by
CLZ. Nano-biofabrication of films with unique electronic characteristics for seamless
integration in biosensing micro-systems will enable rapid and low sample volume analysis of
markers in biofluids (such as blood) and will hopefully improve personalized health
monitoring.
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IA-3
Nanostructures with Augmented Superconductivity for Quantum
Technologies - Beyond the Proximity Effect
Yachin Ivry*
Department of Materials Science and Engineering, and Solid State Institute, Technion – Israel
Institute of Technology, Haifa, 3200003, Israel
Nano superconductors are vital for quantum technologies, including computation,
communication and encryption. However, realizing the great technological potential of
superconductivity at the nanoscale is a real challenge because of the limited number of
available superconducting materials as well as the limited control over the superconducting
behavior at this lengthscale.
We developed several unconventional methods to fabricate 2D and 1D superconducting nano
structures and devices not only with controlled characteristics, but also with augmented
functionality. These methods have already proved useful for fast, and efficient single-photon
detectors and for phase-modulated quantum devices, helping realize next-generation quantum
technologies.
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IA-4
Nano Particle Assembly by a Modulated Photo-Induced Microbubble
Nina Armon*, Udi Greenberg, Hagay Shpaisman
Chemistry Department, Institute for Nanotechnology and Advanced Materials
Bar-Ilan University, Israel
The laser induced microbubble technique (LIMBT) has been previously demonstrated for
assembly of various materials. The principle of this method is that a microbubble formed by
laser heating leads to material deposition at the bubble/substrate interface. Moving the focused
beam relative to the sample results in the migration of the microbubble and constant deposition
of additional material. The major limitation of this technique is its instability, resulting in non-
continuous deposition.
Here we show how modulation of the laser, thus controlling the construction and destruction
rate of the microbubble, allows formation of significantly thinner and more continuous
patterns. We verify the continuity of the formed patterns by measuring the conductance of
deposited metallic nanoparticles.
We furthermore apply this improved technique to construct more complex structures than
previously possible using metals, oxides, polymers and various combinations of the former
(hybrid structures). This exemplifies the ability of this method to be used for various foreseen
applications such as transparent conductors and sensors.
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IA-5
Nanotube Coils
N. Shadmi, A. Kremen, Y. Frenkel, Z. J. Lapin, L.D. Machado, S.B. Legoas, O. Bitton, K.
Rechav, R. Popovitz-Biro, D.S. Galvão, A. Jorio, L. Novotny, B. Kalisky, and E. Joselevich
Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100,
Israel
Carbon nanotubes are promising building blocks for various nanoelectronic components. A
highly desirable geometry for such applications is a coil. However, coiled nanotube structures
reported so far were inherently defective or had no free ends accessible for contacting. Here
we demonstrate the spontaneous self-coiling of single-wall carbon nanotubes into defect-free
coils of up to more than 70 turns with identical diameter and chirality, and free ends (Nano
Lett. 2016, 16, 2152). We characterize the structure, formation mechanism and electrical
properties of these coils by different microscopies, molecular dynamics simulations, Raman
spectroscopy, and electrical and magnetic measurements. The coils are highly conductive, as
expected for defect-free carbon nanotubes, but adjacent nanotube segments in the coil are more
highly coupled than in regular bundles of single-wall carbon nanotubes, owing to their perfect
crystal momentum matching, which enables tunneling between the turns. Although this
behavior does not yet enable the performance of these nanotube coils as inductive devices, it
does point a clear path for their realization. Hence, this study represents a major step toward
the production of many different nanotube coil devices, including inductors, electromagnets,
transformers and dynamos.
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Molecular and biomolecular electronics (IB)
Chair: Ayelet Vilan (WIS)
Hall 003 (floor -1)
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IB-1
Electron Transfer in Coordination-based Molecular Assemblies
Michal Lahava
aWeizmann Institute of Science, 7610001, Rehovot, Israel. Email: [email protected]
Directional electron-transfer events are the basis of many technologically important systems
and biological processes. In this study, we demonstrate how the distance over which electron
transfer occurs through organic materials can be controlled and extended.1-3 Coating of
conductive surfaces with nanoscale layers of redox-active metal complexes allows the
electrochemical addressing of additional but distant layers that are otherwise electrochemically
silent. We also show that our composite materials can pass electrons selectively in directions
that are determined by the positioning of redox-active metal complexes and the distances
between them. These electron-transfer processes can be made dominantly uni- or bidirectional.
Our design strategy involves 1) a set of isostructurally well-defined metal complexes with
different electron affinities, 2) a scalable metal-organic spacer, and 3) a versatile assembly
approach that allows systematic variation of material composition, structure, and electron
transfer properties. We control the electrochemical communication between interfaces by the
deposition sequence of the components and the length of the spacer, and therefore we are able
to program the bulk properties of the assemblies. The electrochromic properties and devices of
these materials will be discussed as well.4
Figure 1. Examples of Rerouting Electron Transfer by Composite Molecular Materials.
References:
1 Balgley, R.; Shankar, S.; Lahav, M.; van der Boom, M. E. Angew. Chem., Int. Ed., 2015, 54, 12457- 12462. 2 de Ruiter, G.; Lahav, M.; van der Boom, M. E. Acc. Chem. Res., 2014, 47, 3407-3416. 3 de Ruiter, G.; Lahav, M.; Evmenenko, G.; Dutta, P.; Cristaldi, D. A.; Gulino, A.; van der Boom, M. E.
J. Am. Chem. Soc., 2013, 135, 16533-16544. 4 Shankar, S.; Lahav, M.; van der Boom, M. E. J. Am. Chem. Soc., 2015, 137, 4050-4053.
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IB-2
Effect of protein layer morphology on charge transport
Edith Beilis1, Hagai Cohen*3, Shachar Richter*1
Shachar Richter: [email protected]
In this study, we will focus on the relation between adsorbed protein layer morphology to the
layer charge transport properties. Specifically, “chemical resolved electrical measurements”
(CREM) which combines elemental specific chemical analysis in situ to electrical
measurements helps us explore the protein layers I-V characteristics. CREM allows
differentiating between possible element's tendency to accumulate charge (specifically holes
or electrons) within the protein layers. We and others showed that protein layer morphology is
greatly affected by the amount of water contained in the system. Though only a few tightly
bound water molecules remain within the protein-molecular layer, it can dramatically alter the
overall electrical properties of the system. Additional aspects influencing charge transport
explored here are the molecular conformation and orientation upon adsorption. In addition, it
has been found previously one can control molecular conformations and protein dehydration
by adding specific molecules to the protein molecules, hereafter addressed as doping. Doping
effect on protein layer morphology and charge transport will be shown as well.
Beilis, E.; Belgorodsky, B.; Fadeev, L.; Cohen, H.; Richter, S. Journal of the American Chemical Society 2014, 136, 6151.
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IB-3
Growth and Surface Engineering of Si Nanowires for
Optoelectronic Applications
Muhammad Y. Bashouti, †,* Jürgen Ristein, § Silke H. Christiansen ∥
†Department of Solar Energy and Environmental Physics, Swiss Institute for Dryland Environmental and Energy
Research, J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus,
84990, Israel. §Department for Laser Physics, University of Erlangen-Nürnberg, Staudtstr. 1, Erlangen D-91058, Germany.
∥Max-Planck Institute for the Science of Light Günther-Scharowsky-Str. 1, 91058, Erlangen, Germany.
Email: [email protected]
Nanowires (NWs) are a promising candidate for the realization of highly integrated electronic,
photonic and optoelectronic devices as well as for fundamental studies in natural sciences.
Remarkably, as the dimensions are scaled down, the surface and interface area of NWs become
more critical – to the level that they might control the whole NW opto-electronic properties. It
is therefore essential to understand the surface properties and charge exchange between the
NW surfaces and their bulk on a microscopic level. In particular, we show molecular approach
to modify the NW surfaces through covalent bonds related electronics. The main analytical
tool adopted in our research towards this goal is photoelectron spectroscopy and kelvin probe.
Band diagrams will be extracted from based on this analysis and correlated with electrical and
material properties of the NWs. Along this route, we have developed a new surface doping
technique in contrast to the conventional doping approach (doping via Boron or Phosphorus to
obtain p and n type respectively). Our technique based on a combination of work function
engineering and phys/chem adsorption of appropriate dopant molecules (organometallic
complexes) at the surface.
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IB-4
Ratcheting of Photo-generated Carriers in an Organic Bulk-heterojunction Ofer Kedem,1 Bryan Lau,1,2 and Emily A. Weiss1,2*
1 Center for Bio-Inspired Energy Science, Northwestern University, 303 E. Superior Street, 11th
floor, Chicago, Illinois 60611-3015
2 Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, IL 60208-3113
*corresponding author. Email: [email protected]
Ratchets are non-equilibrium devices for rectifying motion without a bias force, and are
responsible for many types of biological transport, which occurs with high yield despite
strongly damped and noisy biological environments. Ratchets operate by breaking time-
reversal and spatial symmetries through application of a time-dependent potential with
repeating, asymmetric features. Here we experimentally demonstrate ratcheting of
photogenerated carriers within a highly scattering organic bulk-heterojunction layer
(P3HT:PCBM), using an architecture that enables the application of arbitrarily-shaped
oscillating electric potentials. The system (Fig. 1) is based on nanoscale electrodes with an
asymmetric thickness profile, fabricated using focused ion beam deposition. We show
illumination, modulating the carrier density, can enhance or diminish the measured current, as
predicted by theory, and that the ratcheted charge carriers can do work against a bias. The
devices display complex behavior, with a strong dependence on the frequency and amplitude
of the applied field, including reversals of the direction of current. The response to light raises
the possibility of using ratchets as switching components, turning the current on, off, or even
reversing its direction in response to light. The developed system is a powerful tool for
investigation of the rich behavior of electron ratchets and suggests a fundamentally new route
for increasing the efficiencies of soft-material or nanostructured photovoltaics.
Figure 1. Schematic representation of a typical ratchet potential in the “ON” and “OFF”
states (left); simulated electric potential around an asymmetric electrode (middle); and a 3x3
µm atomic force microscopy image of the asymmetric electrode array (right).
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IB-5
Plasmon Controlled Molecular Junctions Yoram Selzer
School of Chemistry, Tel Aviv University, Tel Aviv, Israel
The ability to squeeze light by means of plasmons into nano-scale metal gaps offers exciting
possibilities to probe, control, switch, and gate the conductance of nano-scale and molecular
junctions.
I will present several experimental systems that demonstrate plasmonic steering of various
conductance processes within molecular and single atom junctions.
Initial results demonstrating experimental capabilities to perform ultrafast (~70 fsec resolution) time
resolved conductance measurements of molecular junctions will also be shown.
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Sustainability and environment (IC)
Chair: Moshe Herzberg (BGU)
Building 35, Hall 115 (floor 1)
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IC-1
New Insights into Mechanism of Salt Transport Through Thin Polymer Films
in Membrane Desalination
Viatcheslav Freger*, Noga Fridman-Bishop, Vesselin Kolev,
1Wolfson Department of Chemical Engineering, Technion - Israel Institute of Technology, Haifa
32000, Israel
e-mail: [email protected]
Despite >50 years of industrial membrane desalination, salt transport in thin-film composite
membranes, its relation to membrane structure and the membrane structure itself are still
insufficiently understood. A serious obstacle towards better understanding the relevant structures
and mechanisms is that thin selective films in desalination membranes are manufactured in situ
and cannot be prepared in a bulk form suitable for conventional structural and transport
examination. Our group has studied the mechanism of salt transport in membrane using two
methods: (1) theoretical analysis using molecular dynamics (MD) and (2) experimental
measurements using electrochemical impedance spectroscopy (EIS) of genuine membrane films
as well as model polymer films. Some open fundamental questions we tried to address were:
1) What is the actual bottleneck of water and salt transport in RO/NF: a nanopore or a dense
polymer?
2) What is the charge of the membrane and how does it affect salt uptake and transport?
3) How much are salt uptake and salt transport related?
4) What role ion-specific effects (including H+ and OH-) play in salt sorption and transport?
Even though some questions still remain open, MD and EIS supply (partly surprising) answers
to some of the above questions, which will be presented in the talk.
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IC-2
Designing Bimetallic Reduction Co-Catalysts –
Correlating Atomic Structure with Properties
Maya Bar Sadan*, Department of chemistry, Ben Gurion University of the Negev
Correlating structure and function is fundamental for the design of functional materials.
Specifically, the atomic rearrangement within a nanoparticle has a direct effect on its properties
and overall performance as a building block. While synthetic efforts have succeeded in
producing diverse complex materials, the rational design of new materials is still a challenge.
Our approach is using atomic resolution transmission electron microscopy to unravel
the atomic structure of the particle, therefore allowing the understanding of the growth process
and the origin of the functionality of the structures. We believe that by doing so, design rules
can be offered to optimize the available nanoparticles for their designated role as functional
units.
The above-mentioned rationale was used for understanding the enhanced activity of
Au-Pd metal tips on seeded rods of CdSe@CdS, by studying the effects of structure both on
efficiency and stability. I will show that a structure of Au@alloy is the most efficient
photocatalyst and also more stable in longer illumination times (50 hours). The degradation
mechanisms will be unraveled and potential strategies to prevent them will be suggested. In
addition, I will present the evolution of the structures through the synthesis stages, showing
how that atomic re-construction of the particles during the initial synthesis of the structures
might have detrimental consequence on their stability.
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IC-3
Fabrication of CexNiyO3 as a new absorber for photovoltaics using
combinatorial material science Hannah Noa Barad*, Kevin J. Rietwyk, Adam Ginsburg, Maayan Priel, David A. Keller, Ilya
Grinberg,, Assaf Y. Anderson*, and Arie Zaban
Department of Chemistry and Center for Nanotechnology and Advanced Materials, Bar Ilan
University, Ramat Gan, 5290002
[email protected], [email protected]
All-oxide photovoltaic devices are an emerging type of solar cells, due to their low-cost, high
abundance, and easy fabrication methods. These characteristics allow the metal oxides to be
potential absorbers, and electron/hole conductors in solar cells. Perovskite metal-oxide
structures have recently been studied as absorbers for solar cells since the perovskite structure
has shown interesting characteristics, which allow better charge transport in photovoltaic
devices. As such, development of new metal oxide perovskites, with lower bandgaps as
absorbers for solar cells, is important.
In this work, combinatorial material science was used, to form CexNiyO3, a new perovskite
metal oxide. The CexNiyO3 was synthesized in a combinatorial library by sequential cycles of
pulsed laser deposition (PLD) using targets of CeO2 and NiO, which are wide bandgap (3.3 eV
and 3.5eV, respectively) semiconductors. The combinatorial library was fully characterized by
x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS) to detect the
perovskite phase and determine the Ce-Ni-O ratios. Seebeck measurements and Kelvin probe
analysis show a change in the conduction type (n- or p-type) with variation in the chemical
composition throughout the library. Optical characterizations reveal that the obtained bandgaps
for the CexNiyO3 range from 1.48-1.77 eV, which are much lower than those of the original
starting materials. The low bandgaps and the energetics of the CexNiyO3 indicate its potential
to be used as an absorber material in all-oxide photovoltaic devices.
30
IC-4
Conversion of Single Crystalline PbI2 to CH3NH3PbI3: Structural Relations
and Transformation Dynamics Thomas M. Brenner1, Yevgeny Rakita1, Yonatan Orr1, Eugenia Klein2, Ishay Feldman2, Michael
Elbaum1, David Cahen*,1, Gary Hodes*,1
1 - Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel, 7610001
2 - Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel, 7610001
* - Corresponding Authors: [email protected]; [email protected];
Abstract: The realization of high-quality optoelectronic properties in halide perovskite semiconductors
through low-temperature, low energy processing is unprecedented. The toolbox of preparation
procedures for halide perovskites is growing rapidly. Understanding the unique aspects of the formation
chemistry of these semiconductors is a critical step toward understanding the genesis of high quality
material via simple preparation procedures. The prototypical reaction is that between lead iodide (PbI2)
and methylammonium iodide (CH3NH3I, abbr. MAI) to form the perovskite CH3NH3PbI3 (MAPbI3),
which we discuss in this work. We investigate the conversion of small, single-crystalline PbI2
crystallites to MAPbI3 by two commonly used synthesis processes: reaction with MAI in solution or as
a vapor. The single crystal nature of the PbI2 precursor allows definitive conclusions to be made about
the relationship between the precursors and the final product, illuminating previously unobserved
aspects of the reaction process. From in situ photoluminescence microscopy, we find that the reaction
in solution begins via isolated nucleation events followed by growth from the nuclei. We observe via
X-ray diffraction and morphological characterization that there is a strong orientational and structural
relationship between the final solution-reacted MAPbI3 product and the initial PbI2 crystallite. In all
these measurements we find that the reaction does not proceed below a certain MAI threshold
concentration, which allows the first experimental determination of the formation energy of ~0.1 eV.
From these conclusions, we present a more detailed hypothesis about the reaction pathway than has yet
been proposed: Our results suggest that the reaction in solution begins with a topotactic nucleation event
followed by grain growth by dissolution-reconstruction. By similar techniques, we find the reaction via
vapor-phase produces material lacking a preferred orientation, suggesting the transformation is
dominated by a deconstruction-reconstruction process due to the higher thermal energy involved. We
also find that the crystal lattice structure of the vapor-reacted material is clearly different from that of
the solution-phase reaction due to the temperature conditions of the synthesis.
31
IC-5
High Intensity Microparticles Optical Drive Avi Niv
The ability to extract forces on micro or nano scaled objects is imperative if mechanics is ever to
achieve the scalability and integration level common in microelectronics. Light-induced forces play a
crucial role in this endeavor due to their inherent ability to pear into the micro, and even sometimes
to the nano, world. Opto-mechanical manipulators, known as Optical Tweezers, are today a mature
with ample of application. This approach is based on radiation pressure, which is the momentum
transfer between the electromagnetic field and the particle. A major limitation of this approach is the
relatively small force it produces, typically in the pico-Newtons range. While this force is enough for
pulling or repelling a single micro-particle, it will not due if a dens collection of such particles is needed
to be acted upon. The reason is that the momentum content of electromagnetic radiation is, after all,
quite feeble. It is clear, therefore, that if larger forces are needed, a radically different approach should
be devised. This presentation deals with this kind of approach - an alternative to radiation-pressure
based optical forces. We show that it is possible to overcome existing limitation by using, not the
momentum field, but the energy of the electromagnetic field. We will show that this approach is
capable of extracting forces six orders of magnitude larger then achieved to date.
32
Nanophotonic (ID)
Chair: Yaakov Tischler (BIU)
Hall 116 (floor 1)
33
ID-1
High Temperature plasmonics
Dr. Yonatan Sivan
We solve the Maxwell and heat equations self-consistently for metal nanoparticles under intense
continuous wave (CW) illumination at visible wavelengths. Unlike previous studies, we rely on
experimentally measured data for the metal permittivity at increasing temperature. We show that the
thermal nonlinearity of the metal can lead to substantial deviations from the predictions of the linear
model for the temperature and field distribution, and thus, can explain qualitatively the strong nonlinear
scattering from such configurations observed experimentally. We also show that the incompleteness of
existing data of the temperature dependence of the thermal properties of the system prevents reaching
a quantitative agreement between the measured and calculated scattering data. This modelling approach
is essential for the identification of the underlying physical mechanism responsible for the thermo-
optical nonlinearity of the metal and should be adopted in all applications of high temperature nonlinear
plasmonics, especially for refractory metals, both for CW and pulsed illumination.
34
ID-2
Designing Plasmon-Molecule Interactions Lihi Efremushkin* and Dr. Adi Salomon
Department of Chemistry, Institute of Nanotechnology, Bar-Ilan University, Ramat-Gan,
Israel
In this work we show theoretically and experimentally that a molecular system at very low
concentration can be strongly coupled to plasmonic modes. Upon coupling new hybrid states
are formed, lower and higher polaritons. These modes have the characteristics of both
molecular and plasmonic states and also new characteristic different from those of the
molecular and plasmonic states. As the coupling strength grows increasing of molecular
concentration asymmetric splitting is observed giving rise to enhanced transmission through
metallic hole arrays. Moreover, we have also succeeded in reaching a linear dependency of the
Rabi splitting value on the square root of the absorbance which is another proof for strong
coupling.
We also show that by tuning the plasmonic modes we are able to be on/off resonance with
respect to the molecular system and therefore generate new photonic-exciton hybrid states at
different energies and as a consequence with unique properties. Moreover, we show that by
changing the distance between the plasmons and the molecules we can design the strong
interactions between the two systems.
(a) Schematic illustration of the system used. The system is composed from fabricated Ag film placed
between glass and PVA or porphyrin derivative embedded in PVA. (b) Absorbance spectrum of
porphyrin derivative embedded in PVA spin coated onto glass. The absorbance is ca. 0.016. The inset
is a SEM image of the fabricated Ag film.
35
ID-3
Tubular photoactive gold nanoparticle assemblies
Priyadarshi Ranjanϯ,§, Ronit Popovitz-BiroƮ, Iddo PinkasƮ, Sidney CohenƮ, Michal Lahavϯ, Reshef Tenne§*, and Milko E. van der Boomϯ*
ϯDepartment of Organic Chemistry, §Department of Materials and Interfaces, ƮDepartment of
Chemical Research Support, Weizmann Institute of Science, Rehovot,7610001 Israel
*Corresponding authors
email: [email protected] & [email protected]
Nanotubes of WS2 (INT-WS2) have been uniformly decorated with 5 nm tetraoctyl ammonium bromide
stabilized gold nanoparticles (AuNPs) with interparticle distance of 2 nm. This self-assembly process is
likely driven by the lattice matching between the nanotube outer wall and AuNP and strengthened by
the affinity of disulfide binding with Au. By controlling the degree of binding of the AuNPs to the INT-
WS2 surface The optical band gap of INT-WS2 can be varied from 1.82 eV for the bare nanotube to
1.75 eV for full AUNP coverage. These gold-coated nanotubes are further modified by treating with
robust pyridine-based ruthenium complexes which adhere and link the surface-bound AuNPs through
ligand exchange. The resulting network of AuNPs forms a coherent, tubular shell that persists even
after complete removal of the underlying INT-WS2 with hydrogen peroxide. This oxidation process is
studied by electron microscopy and optical microscopy which show a gradual etching process of INT-
WS2. Interestingly the process can be stopped in the middle to get functionalized, few-layered WS2
tubes. Raman spectroscopic measurements of the single-walled AuNP tube shells depict the presence
of the metal complex which was masked when INT-WS2 scaffold was present. The mechanical
properties of the AuNP-tubes are studied by AFM-based nanoindentation indicating an elastic
structure with stiffness dominated by interactions between the AuNPs. Energy/electron transfer of
the AuNP tubes is studied with femtosecond transient absorption spectroscopy revealing an extended
absorption region around 500 nm which appears in these tubular AuNP assemblies in contrast to the
individual functionalized AuNP.
36
ID-4
OPTICAL IMAGING OF AN EXCITON - PLASMON WAVE FUNCTIONS CONFINED
IN A SINGLE WS2 NANOTUBE
Lena Yadgarova,b #, Eitam Vinegrada,b, Michael Mrejena, Haim Suchowskia and Ori Cheshnovskyb
1School of Physics and Astronomy, b School of Chemistry, Tel Aviv University ([email protected])
Over the last decades vast efforts were devoted to understand and utilize the unique properties of
transition metal dichalcogenide (TMDC) layered compounds. Such compounds have strong (covalent)
bonds in the layer (a-b plane) and weak van der Waals forces along the c-axis which hold the layers
together. The high energy stored in the dangling bonds of these compounds induce the formation of
closed-cage nanostructures (NS).1 Due to their unique properties and promising applications, the study
of these NS is a rapidly growing field. Recently, it was learned that the semiconducting MS2 (M=Mo,W)
NS, maintains the excitonic structure of the bulk together with a new plasmonic scattering resonance
(which does not exist in the bulk).2 The optical properties of such NS can be modified and controlled
by verity of methods, including doping, size, aspect ratio etc.3-5 Thus, in addition to current application6,
MS2 NS can be also used for nano-optoelectronics.
Here nano-imaging is used to study the properties of plasmonic and excitonic photo-induced response
in an individual WS2 nanotube (NT) in the visible and IR region. Surface waves were detected and
imaged with 2-5 nm resolution at 633 nm using a scattering-type scanning near-field optical microscope
(s-SNOM) (Fig. 1). Interestingly, these waves were not observed at 1500 nm. These findings coincide
with the assumption that WS2 NT plasmons occur mainly in the visible and near IR region. The standing
wave appears with specific incident light polarization and is anticipated to be induced by interference
between the tip-excited wave and its reflection from the NT. In addition, single particle spectroscopy
microscopy (SPSM) was used in order to measure absorption and scattering of individual NTs over the
spectral range of 420-720 nm. Here again, surface waves with specific incident light polarization were
detected in the visible light range (Fig. 2). The s-SNOM or SPSM techniques provide a unique way to
study the light-matter interactions in a single NS. Furthermore, the combination of these techniques and
the unique properties of MS2 NS allow generation of exciton and/or plasmon resonances over a wide
spectral range (400-2500nm). Since the optical modes in MS2 NS vary as a function of incident waves,
polarization etc., they can be used for nanophotonic circuitry and as saturable absorbers. Moreover, the
MS2 NS are not toxic and are optically active in the visible area, thus can be used for optical tracking
during medical diagnostics, targeted drug delivery or medical diagnostics.
37
Figure 1 (Left) Plot of the near-field
scattering intensity spectra along a
representative WS2 nanotube on a silica
substrate. The standing wave can be
clearly observed. (Right) Topography
image of the same nanotube obtained
using atomic force microscopy.
Figure 2 3D (Left) and 2D (Right) Plot of the reflectance intensity
spectra along a representative WS2 nanotube obtained using SPSM.
1. Tenne, R., et al., “Polyhedral and cylindrical structures of WS2“, Nature, 1992. 360(6403); 2. Yadgarov. L., et al., “Plexciton in WS2 nanotubes”, In preparation
2016.; 3.Yadgarov, L., et al., “Dependence of the absorption and optical surface plasmon scattering of MoS2 nanoparticles on aspect ratio, size and media” ACS
nano, 2014. 8(4). ; 4. Sun, Q.C., Yadgarov. L., et al., et al., “Observation of a Burstein–Moss shift in Re-doped MoS2 nanoparticles”, ACS nano, 2013. 7(4); 5.
Yadgarov L., et al., “Controlled doping of MS2 (M= W, Mo) nanotubes and fullerene‐like nanoparticles, Angew. Chem. Int. Ed., 2012. (51); 6. Visic, B. and R.
Tenne, 2015, Wiley-VCH Verlag; 7. Pardo, M, et al. "Low cytotoxicity of inorganic nanotubes and fullerene-like nanostructures in human bronchial epithelial
cells: relation to inflammatory gene induction and antioxidant response." Environmental science & technology 48.6 (2014): 3457-3466.
1.5
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m
m
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495 n
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m460
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38
ID-5
Nanophotonics on a chip: from fundamentals to emerging applications
A. Karabchevsky1* 1Electrooptical Engineering Unit and Isle Katz Institute for Nanoscale Science
and Technology, Ben- Gurion University, Beer-Sheva 84105, Israel *[email protected]
Nanophotonics is where photonics merges with nanoscience and nanotechnology while spatial
confinement considerably modifies light propagation and light-matter interaction. Here, we overview
the fundamentals of nanophotonics and address the spectroscopy at nanoscale [1] on a glass made
chips. The history of making glass can be traced back to 3500BC in Mesopotamia. Found in nature
glass has been used by Stone Age societies for manufacturing cutting tools made of obsidian. An
extensive glass production was occurring by the 15th century BC in many places across the globe.
Over centuries the glass has been used for many applications in science and technology; however its
potential contribution to emerging applications such as vibrational overtone spectroscopy on a chip is
underestimated.
Figure 1: Nanophotonics on a chip -Methylaniline
-grating
overlayer, nano-rods overlayer and bow-tie overlayer as shown in (c).
Figure 1a shows absorption cross-section of organic molecule N-Methylanliline and the sensitivity of
our structures (Figure 1b) calculated with nanoscale overlaers shown on Figure 1c. We have
discovered a strong increase in the absorption of amine band of N-Methylanliline and a dramatic
modification of its spectral shape in the presence of nanoscale overlaers. Similar effect was observed
in enhanced chemiluminescence of a luminol flow [2]. Practical implementation of the discovered
effect will include improving the detection limits of absorption for sensing and spectroscopy, research
in biology and chemistry, and a number of commercial applications.
REFERENCES 1. Karabchevsky, A. and Kavokin, A. V., “Giant absorption of light by molecular
vibrations on a chip,” Nature Scientific Reports, Vol 6, 1-7, 2016. 2. Karabchevsky, A., Mosayeebi,
A., Kavokin, A. V., “Tuning the chemiluminescence of a luminol flow using plasmonic
nanoparticles,”Nature Light: Science and Applications, doi: 10.1038/lsa.2016.164, 2016.
39
Bio-materials and interfaces (IIA)
Chair: Liraz Chai (HUJI)
Hall 003 (floor -1)
40
IIA-1
Polysaccharide Hydrogels cross-linked via Thermo-Responsive
Peptide-Dendrimers
Yulia Shmidov, [a] Mingjun Zhou,[b] John B. Matson, [b] Ronit Bitton*[a]
[a] Department of Chemical Engineering and the Ilze Kats Institute for Nanoscale Science
and Technology, Ben-Gurion University of the Negev, Beer-Sheva, 84105 (Israel)
[b] Department of Chemistry and Macromolecules and Interfaces Institute, Virginia Tech,
Blacksburg, VA 24061 (U.S.A.)
Elastin-like peptides (ELPs) are molecules that have been used to confer thermos-responsive
characteristics onto various materials, however to this point mostly linear ELPs have been
studied. Dendritic and other highly branched structures are of importance in biomaterials since
their topological features may lead to useful properties, including substantially improved
resistance to proteolysis of branched peptides compared to linear ones.
Here we present a systematic investigation of a class of dendritic ELPs based on the
GLPGL pentamer repeat unit, as potential building blocks for thermoresponsive
polysaccharide hydrogels.
The effect of peptide topology (e.g. peptide length, generation no. etc) on the ELP’s transition
temperature (Tt) in solution was examined using circular dichroism to study the peptide
secondary structure transition, SAXS and TEM to characterize the nanoscale changes and
turbidity to measure the macroscopic phase transition (coacervation). Our findings support a
phase transition model that consists of three neighboring processes: a secondary structure
transition, related to intramolecular interactions thus not effected by the peptide topology;
Followed by continuous nanopartical formation associated with intermolecular interactions and
concertation. The temperature in which both occur depends on the dendrimer’s core length and
its generation number. These ELPs were than utilized as cross-linkers for hyaluronic acid
using carbodiimide chemistry.
41
IIA-2
Open sesame:
The secrets behind hygroscopic movement for sesame seed dispersal
Rivka Elbaum1, Benny Bar-On*2, and Ilana Shtein2
1 RH Smith Institute for Plant Sciences and genetics in Agriculture, Hebrew University of
Jerusalem, Rehovot; 2 Department of Mechanical Engineering, Ben-Gurion University of the
Negev, Beer Sheva,
*Correspondingauthor [email protected]
Plants are sessile organisms that need to disperse their seeds for their progenies to thrive. Some
seed dispersal mechanisms are based on hygroscopic movement: contraction of tissues in
predefine directions in reaction to their desiccation. The contraction of an active tissue layer is
resisted by a stiff layer, to create a basic movement of a bend, a coil, or a twist. Here we study
the structure and distribution of active and resisting layers in the fruit of sesame (Sesamum
indicum L.), which fractures open as it dries. Microscopic observation revealed that an inner
fibrous layer is built of a bilayer of radial and longitudinal fibre cells. The fiber cells are built
of crystalline cellulose microfibrils that lie along the cells, rendering them stiff and non-
contracting. The bilayer, which is built as plywood seems to protect the seeds within the fruit
from impact of birds or other herbivores. The outer layer is built of relatively spherical thin
walled cells, untypical for a tissue with a mechanical role. Nevertheless, we found that this
tissue layer contracts by 30% as it dries, and activates the fruit opening mechanism. The sesame
fruit actuating tissues are not uniform throughout the device, but changing gradually. A
biomechanical model based on the relative thicknesses of the layer successfully simulated the
opening curvature. Hygroscopic movements in the capsules of other plant species and families
may follow similar mechanistic principles, which may be used as a source of inspiration for
the design of novel synthetic actuators.
42
IIA-3
Micro-fabricated elastomeric pillar arrays for studies of cellular sensing of
extracellular matrix rigidity
Haguy Wolfenson1,2,*, Shuaimin Liu3, James Hone3, Michael P. Sheetz1,*
1Department of Biological Sciences, Columbia University, New York, NY 10027
2Current address: Department of Genetics and Developmental Biology, Rappaport Faculty of
Medicine, Technion-Israel Institute of Technology, Haifa, Israel
3Department of Mechanical Engineering, Columbia University, New York, NY, 10027
*correspondence to: [email protected]; [email protected]
The mechanical features of the microenvironment surrounding cells affect many important aspects of
cellular behavior, including cell growth, differentiation, migration, and death [1,2]. To respond to
microenvironmental mechanical signals, cells have to actively test the environment, but the
mechanisms of such mechanosensing are not clear. Recently, the development of specialized micro-
and nano-fabricated surfaces that can be bio-functionalized has opened the possibility of studying
mechanosensing events with high accuracy, including sensing of extracellular matrix rigidity [3,4]. I
will describe our recent results using micro-fabricated elastomeric pillar arrays that allow tracking
cellular forces during rigidity sensing. We found that cells form local actomyosin-based contractile
units at their edges, which periodically pinch the environment through cell-matrix adhesions. Once a
certain force level is reached in the contractile units, adhesion reinforcement is activated by
recruitment of additional adhesion-related proteins. Depletion of the actomyosin regulatory protein
tropomyosin leads to significantly increased forces and aberrant rigidity sensing. These results may
explain fundamental processes that occur in cancer cells, which also do not properly sense
microenvironmental rigidity.
_______________________
[1] T. Iskratsch, H. Wolfenson, and M. P. Sheetz, Nat. Rev. Mol. Cell Biol. 15, 825 (2014).
[2] J. D. Humphrey, E. R. Dufresne, and M. A. Schwartz, Nat. Rev. Mol. Cell Biol. 15, 802 (2014).
[3] S. Ghassemi, G. Meacci, S. Liu, A. A. Gondarenko, A. Mathur, P. Roca-Cusachs, M. P. Sheetz, and J.
Hone, Proc. Natl. Acad. Sci. USA 109, 5328 (2012).
[4] H. Wolfenson et al., Nat. Cell Biol. 18, 33 (2016).
43
IIA-4
Following Virus like particles assembly using time resolved small angle x-ray
scattering
R. Asora, L. Selzerb , A. Zlotnickb, O. Ben-Nun-Shaulc, Ariella Oppenheimc and U. Raviva,*
aThe Institute of Chemistry, The Hebrew university of Jerusalem, Jerusalem, Israel,91904
bDept. of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405
c Dept. of Haematology, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
Viruses are evolved examples of self-assembled structures. This ability to self-assemble can be
harnessed for nano- and biotechnology. Viral capsids and capsid proteins have been used to assemble
structures for guided synthesis of inorganic and organic nanostructures, as cages for packaging cargos,
and as vectors for gene therapy. The mechanisms by which spherical viruses assemble from hundreds
of capsid proteins around nucleic acid, however, are yet unresolved.
Using time resolved small angle x-ray scattering (TR-SAXS) we were able to directly visualize
Simian Virus 40 (SV40) viral proteins encapsidating short ssRNA molecule. The assembly process
yields T = 1 icosahedral virus-like particles (VLPs) comprised of 12 protein subunits and one RNA
molecule. The reaction is nearly 1/3 complete within 35 milliseconds, following a rapid two–state
kinetic process with no detectable intermediates [1].
As opposed to SV40 derived VLPs, core capsid proteins of the Hepatitis B Virus (HBV) can
assembled without a nucleic acid template, forming either T = 4 or T = 3 icosahedral empty particles,
comprised of 120 or 90 protein subunits, respectively. This one component, assembly system presents
a simplified, yet much more challenging case for studying the basic principles governing the assembly
process of icosahedral viruses.
To follow the assembly process of HBV derived empty VLPs, we are combining static and time-
resolved SAXS data from 3rd generation synchrotrons, structural data form x-ray crystallography,
unique SAXS analysis tools, developed in our lab, and maximum-entropy optimization algorithms.
Using our modeling tools we are able to generate scattering intensities of a large number of possible
assemblies, ranging from a single dimer to a complete 120-mer capsid. Together with global fitting
procedures we are trying to find the distribution of assemblies that best fit our TR-SAXS data at each
measured time point during the assembly process.
Our most recent results indicate that only a small number of intermediates structures are dominant
throughout the assembly process. The same intermediates appeared throughout the assembly at
different solutions conditions implying these are possible critical stages for a successful assembly of
the capsid.
References
[1] Kler and Asor, et al., J. Am. Chem. Soc., 2012, 134 (21): 8823–8830
Corresponding Author: [email protected]
44
IIA-5
Biological control over site-specific mineral templating in
coccolithophore algae
Assaf Gal1,2*, Damien Faivre1, André Scheffel2
1Max-Planck Institute of Colloids and Interfaces, Potsdam, Germany 2Max-Planck Institute of Molecular Plant Physiology, Potsdam, Germany
Many organisms, from simple bacteria to plants, vertebrates, and humans, form
elaborate mineralized structures usually referred to as biominerals. These biominerals are
constituted of superstructures of highly organized crystals and organic macromolecules.
According to the ruling paradigm of biomineralization, the localization of crystals within these
structures is determined by the direct interactions of specific nucleating macromolecules with
the mineral phase. We study the formation of coccoliths, highly ordered arrays of calcite
crystals produced by marine microalgae and show that, preceding mineral nucleation, specific
interactions between soluble organic molecules and organic backbone structures direct
inorganic constituents to their deposition sites. Combining the insoluble organic coccolith
scaffold with coccolith-associated soluble macromolecules in vitro, we indeed found a massive
accretion of calcium ions at the sites, where the crystals form in vivo. The in vitro process
exhibits striking similarities to the initial stages of coccolith biogenesis in vivo. This
localization control by macromolecular recognition before crystallization may present a
widespread mechanism in biomineralization.
45
IIA-6
Hooking up to Diatoms to Form New Bioinspired Silica by Peptide
Catalysts (Material Design With Structural NMR Spectroscopy)
Nurit Adiram-Filibaa, Yasmin Geigera, Hugo Gottlieba, Ümit Akbey b,c, Hartmut Oschkinatb, Gil Goobesa*
a Department of Chemistry, Bar Ilan University, Ramat Gan, Israel
b Department of NMR Supported Structural Biology, Leibniz‐Institute for Molecular
Pharmacology (FMP), Robert‐Roessle‐Strasse 10, Berlin 13125, Germany
c Interdisciplinary Nanoscience Center (iNANO), Aarhus University, street, Aarhus C, Denmark
Environmentally friendly material design is making big strides at mimicking more closely Nature's ca
pabilities of engineering complex and excellent materials. Replacing polymers by natural biopolymer
s, e.g. proteins and carbohydrates, is one important step towards achieved "greener" chemistry. Com
mercial porous silica is manufactured nowadays with organic templates such as cetyl bromide or pluo
ronic acid. Alternatively, inspired by the capability of diatoms to synthesize robust porous siliceous c
ell walls using special proteins, one may be able to prepare silica using natural templates. A family of
enzymes called silaffins was recently shown to be the key element in directing and controlling the bi
osilicification process in diatoms. Silaffins pre‐
assemble to form micelles which act as a template and a catalyst for silica precipitation. Peptide segm
ents containing five lysines, termed pentalysine clusters, in the sequence of the enzyme were identifie
d as the primary domains responsible of the protein's function in silicification.
The pentalysine peptide PL12, KAAKLFKPKASK, is the shortest potent segment derived from the d
iatom T. Pseudonana silaffin. Here, we have investigated the effect of PL12 and its mutants on silica
polymerization and characterized the organic‐
inorganic interface formed when the peptide catalyzes silica formation. The time course of silica prec
ipitation was examined using electron microscopy and spectrophotometric measurements. Sensitivity
‐
enhanced DNP solid NMR and liquid NMR were utilized for rapid 2D NMR measurement of PL12 i
nside the silica and free, which underpinned the conformation changes as the peptide co‐
precipitates with silica. Structural differences between lysines in two regions in the peptide were foun
d as well which hinted on a separate functional role. Based on the differences, mutated PL12 peptides
, KAAKLFAPAASK and AAAALFKPKASA were designed and used in silica synthesis. These pre
parations showed that the first group has weaker functional role in catalyzing silicification while the l
atter group is directly responsible for the catalytic capability of the peptide and for significant morph
ological changes of the silica particles formed.
46
Magnetic and Electronic Materials (IIB)
Chair: David Nessim (Intel)
Hall 002 (floor -1)
47
IIB-1
Defect Review Material Analysis Challenges in Semiconductor Industry
Mor Baram*, Dror Shemesh
Process Diagnostics and Control, Applied Materials, Rehovot, Israel 7670109
Defect review is an integral part of the chip making process in the semiconductor industry. In
addition to the defect physical parameters, there is a growing interest in its chemical
composition, which can later assist in understanding the defect’s root cause. Therefore, Energy
Dispersive Spectroscopy (EDS) in Scanning Electron Microscope (SEM) is regularly used in
an automatic manner as part of the defect review process. This method is well used for material
analysis in SEM for its ease of operation and analysis, but one of its shortcomings is the x-rays
big interaction volume. Therefore, there are quite a few challenges regarding of the use of EDS
for material analysis. For example, as dimensions getting smaller, so are the defects and it
becomes harder to perform an EDS measurement accurately. In addition, in contrast to bare
silicon wafers, pattern wafers which may contain quite a few layers of different materials pose
another obstacle in isolating only the defect composition (and not the substrate). This talk will
present the different challenges and our solutions to overcome them, which promotes the use
of material analysis during chip making process control.
48
IIB-2
Probing plasmonic effects in metal-coated semiconductor nanostructures
with time-resolved cathodoluminescence
Dan Rich
Department of Physics, Ben-Gurion University of the Negev, Beersheva, Israel
Email: [email protected]
The enhancement of the spontaneous emission rate (SER) for silver, gold, and aluminum films
deposited on three different quantum heterostructures and nanostructures was probed with
time-resolved cathodoluminescence (CL). We show that such metal films on (i) GaAs/AlAs
core-shell nanowires,1 (ii) InGaN/GaN quantum wells,2,3 and (iii) multilayer Si nanocrystals
(SiNCs)4 lead to an increase in the SER which is attributed to the coupling of excitons and
surface plasmon polaritons (SPPs). Exciton-SPP coupling for metal-coated nanostructures was
investigated as a viable option to enhance the SER and to improve the internal quantum
efficiency of light emitting devices. The CL technique is found to be an ideal method of
excitation for metal-covered nanostructures which may be opaque to laser/light excitation.
Electron-hole pairs were generated in the metal-covered samples by injecting a pulsed high-
energy electron beam through the thin metal films. The enhancement of the SER was observed
by direct measurements of the changes in the temperature-dependent excess carrier lifetime.
The three chosen plasmonic metals of Ag, Au, and Al facilitate an interesting comparison of
the exciton-SPP coupling for metal films that exhibit varying differences between the surface
plasmon energy and the excitonic transition energy of the three foregoing material systems. A
modeling of the temperature dependence of the Purcell enhancement factor (Fp) included the
effects of ohmic losses of the metals and changes in the dielectric properties due to the
temperature dependence of (i) the intraband behavior in the Drude model and (ii) the interband
critical point transition energies which involve the d-bands of Au and Ag.
1 Y. Estrin, D. H. Rich, A. V. Kretinin, and H. Shtrikman, Influence of Metal Deposition on Exciton-Surface
Plasmon Polariton Coupling in GaAs/AlAs/GaAs Core-Shell Nanowires Studied with Time-
Resolved Cathodoluminescence, Nano Lett. 13 (4), pp. 1602–1610 (2013).
2 Y. Estrin, D. H. Rich, S. Keller, and S. P. DenBaars, Temperature Dependence of Exciton-Surface Plasmon
Polariton Coupling in Ag, Au, and Al Films on InGaN/GaN Quantum Wells Studied with Time-Resolved
Cathodoluminescence, J. Appl. Phys. 117, 043105 (2015).
3 Y. Estrin, D. H. Rich, S. Keller, and S. P. DenBaars, Observations of Exciton-Surface
Plasmon Polariton Coupling and Exciton-Phonon Coupling in InGaN/GaN Quantum Wells Covered
with Au, Ag, and Al Films, J. Phys.: Condens. Matter 27, 265802 (2015).
4 Y. Estrin, D. H. Rich, N. Rozenfeld, N. Arad-Vosk, A. Ron, and A. Sa’ar, Enhancement in
the excitonic spontaneous emission rates for Si nanocrystal multi-layers covered with thin films of Au,
Ag, and Al, Nanotechnology 26, 435701 (2015).
49
IIB-3
Synthesis and Characterization of MoS2/WS2 Heterostructures
Gal Radovsky and Ariel Ismach Department of Materials Science and Engineering, Tel Aviv University,
Ramat Aviv, Tel Aviv 6997801, Israel. [email protected] , web: http://www.eng.tau.ac.il/~aismach
Following the recent exciting scientific results on graphene, 2D atomic-films in general have attracted
extensive interest in the scientific and technological communities due to the wide range of potential
applications these materials (and their combination) offer. Among layered materials, the so-called transition
metal dichalcogenides (TMD) with the MX2 structure (M=W, Mo, Nb, etc. and X=S, Se, Te) are of particular
interest due to their semiconducting nature and the possibility to tune their bandgaps by the number of layers,
chemical composition, phase or stacking order. A main challenge for the implementation of TMD materials
into applications would be the development of synthetic strategies for their rational formation with the
desired chemical and physical properties. This is the main goal of our lab, the 2D materials laboratory. In
this talk I will review recent advances in the growth and characterization of single- and fewlayer transition
metal dichalcogenides (TMDs). Then I will describe the research in our lab and focus on our efforts to target
the controlled synthesis of TMDs and TMD-based heterostructures, specifically MoS2-WS2. The difference
in the formation, structure and properties will be discussed.
50
IIB-4
Rectified Currents in Graphene Lateral Triodes
Doron Naveh
Faculty of Engineering and Bar-Ilan Institute of Nanotechnology and Advanced Materials, Bar-Ilan
University, Ramat-Gan 52900 Israel
Graphene, a zero-gap material, features excellent conduction of both electrons and holes due to its
almost perfectly symmetric bandstructure. Rectified current in graphene are desired for numerous
application such as energetically efficient transistors, photodetectors and more. However,
rectification is hard to realize in good conductors such as graphene, even with field-effect induced
homojunctions. In this talk, a new class of rectifying devices will be presented, showing sub-pA leakage
currents and four decades current-span. This new class of devices can open new opportunities for
graphene electronics and optoelectronics.
51
IIB-5
Electron Trapping Effects in Gallium Nitride-based High Electron Mobility
Transistor (HEMT) Structures
Shlomo Mehari1,*, Moshe Eizenberg2, and Dan Ritter1
1 Department of Electrical Engineering, Technion-Israel Institute of Technology, Haifa,
Israel, [email protected]
2 Department of Materials Science and Engineering, Technion-Israel Institute of Technology,
Haifa, Israel
Over the last few years, gallium nitride (GaN)-based transistors have been demonstrated to be excellent
for high frequency applications (radars, mobile communication devices, etc.) and for power electronic
applications (power converter, photo voltaic inverters, electrical cars, etc.). A large fraction of electrical
energy worldwide can be saved by improving the performance of the important branch of electronics
termed “power electronics” (PE). While approximately 30% of all power generation utilize PE
somewhere between the point of generation and its end use today, by 2030 it is expected that up to 80%
of generated electricity will utilize PE. The road to enhance the efficiency of power electronics for high
power applications is well understood: replacing the current silicon technology by a more efficient one
using large bandgap semiconductors such as GaN. The GaN technology has already revolutionized the
lighting industry, offering efficient semiconductor based LEDs, which save tremendous amounts of
electricity today. Transistors based upon the same material are expected to improve the efficiency of
power electronics. The AlGaN/GaN high electron mobility transistor (HEMT) structure offers a unique
combination of a wide energy bandgap with low resistive 2D electron gas (2DEG) channel, enabling
device performance well beyond the Si limit. But to date, the implementation of GaN-based power
electronics is impeded due to a lack of a fundamental understanding of the technology. In this work we
study the parasitic charge trapping effects that are still major obstacle in realizing this technology,
causing high dynamic on-resistance (RON) and current collapse. In spite of their major role, the location
and nature of the defects in GaN transistors is yet unclear. We have previously shown that the gated
van der Pauw method provides an opportunity to study electron trapping effects in the HEMT structure,
as well as at the III-N/insulator interface. We show how transient measurement using gated van der
Pauw test structures help discriminate between different electron traps in AlGaN/GaN HEMT structure
on Si substrate. We also show the importance of electron transport across the AlGaN barrier in the
tradeoff behavior between a low Schottky gate leakage current and an improved dynamic behavior.
52
Surface Science and Characterization (IIC)
Chair: Yaron Paz (Technion)
Hall 115 (floor 1)
53
IIC-1
1.1 Probing self-assembled monolayer molecular transport properties
1.2 using the superconducting proximity effect
Yossi Paltiel
Applied Physics Department, Center for Nano Science and Nano Technology
Hebrew University, Givat Ram, Jerusalem 91904, Israel, [email protected]
Molecular electronics research focuses on the study and application of molecular building blocks
for the fabrication of nano-scale electronic devices, and utilizing their self-organization properties to
achieve large-scale electronic circuits. One of the key issues in molecular electronics is identifying the
conduction mechanism along the molecules. More specifically, whether the junction behaves as a tunnel
barrier, or rather there are electron or hole conduction channels through the molecule. Due to the large
energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied
molecular orbital (LUMO), it is usually assumed in calculations that the molecule supports one
conducting channel of either electrons or holes. Experimentally, measurements using a local-probe tip
or a small gap between two metallic leads strongly depend on the nature of the linkage between the
molecules and the contacts, which is hard to optimize. In this talk, I present a new approach to study
the electronic and transport properties of molecules using the superconducting proximity effect.
Namely, insight into these properties is gained by monitoring the modifications of the superconducting
properties upon linking nanoparticles to the superconductor via the studied molecules. The new
approach does not require two external contacts to the molecule.
54
IIC-2
Self-Propulsion of Liquid Marbles: Leidenfrost-Like Levitation Driven by
the Marangoni Flow
Professor Edward Bormashenkoa,b
aAriel University, Physics Department, P.O.B. 3, 40700, Ariel, Israel
bAriel University, Chemical Engineering Department , P.O.B. 3, 40700, Ariel, Israel
Self-propulsion of liquid marbles filled with aqueous alcohol solutions and placed on a water surface
is reported. The characteristic of velocity of the marbles is ca. 0.1 m/s. The phenomenon of self-
propulsion is related to the Marangoni solutocapillary flow caused by the condensation of alcohol,
evaporated from the liquid marble, on a water surface. The Marangoni flow in turn enhances the
evaporation of alcohol from marbles. Addition of alcohol to the water supporting the marbles
suppresses the self-propulsion. The propulsion of liquid marbles is mainly stopped by water drag.
The velocity of the center of mass of marbles grows with the increase of the concentration of alcohol
in a marble. The velocity of marbles’ self-propulsion is independent on their volume. Impact of
external fields on the self-propulsion is discussed.
0 s 0.60 s 0.90 s
10 mm
55
IIC-3
Carrier lifetime of ordered Ga0.51In0.49P at high temperature
Ronen Dagan1, Yossi Rosenwaks1, Abraham Kribus2, Alexander Walker3, Frank Dimroth3
1School of Electrical Engineering, Tel-Aviv University, Israel.
2School of Mechanical Engineering, Tel-Aviv University, Israel.
3Fraunhofer Institute for Solar Energy Systems, Freiburg, Germany.
Ronen Dagan – Ph.D. candidate under the supervision of Prof. Yossi Rosenwaks, Dean of
engineering faculty at Tel Aviv University.
Related to: Session IID – Surface Science and Characterization.
The bulk lifetime of high-quality ordered GaInP lattice matched to GaAs and the surface recombination
velocity at its interface to AlInP were measured using time-resolved photo-luminescence (TRPL) in the
temperature range of 77 − 500 K. The surface recombination velocity was found to be relatively low
(100– 600 cm/s) over the full temperature range studied. The bulk lifetime varied greatly from ~100 ns
at 77 K, increasing up to nearly 400 ns at 300 K, and then decreasing down to 20 ns at 500 K. The
variations in the bulk lifetime are explained by considering the separate contributions of radiative and non-
radiative recombination and their respective dependencies on temperature.
56
IIC-4
Evolution of vacuum pump requirements for Surface Science and Liquid
Chromatography Mass Spectrometry
A D Chew* and I Olsen
Edwards Vacuum, Burgess Hill, UK
The market segmentation of the vacuum industry classifies the ‘Instrumentation’ sector to include
Surface Analysis, Electron Microscopy and Metrology as well as Mass Spectrometry. In this paper we will
focus on the historical evolution of primary and secondary vacuum pump requirements in both Surface
Science and Liquid Chromatography Mass Spectrometry (LCMS). This will be discussed in relation to
pump types and capacity divergence, vibration and magnetic field characteristics, capital cost, cost of
ownership, environmental impact, servicing, safety and communications protocols. Future trends and
market developments will also be discussed.
57
IIC-5
High resolution electron energy loss spectroscopy studies of hydrogenated
polycrystalline diamond film surfaces with grain size varying from the nano-
meter to micro-meter range
A. Hoffman
Schulich Faculty of Chemistry, Technion, Haifa 32000, Israel
Understanding and controlling the interaction of hydrogen with diamond surfaces is of large importance
both from a fundamental and technological perspective. However its detection is most difficult and only
very few methods are sensitive to its bonding configuration. In this talk we review our recent high
resolution electron energy loss spectroscopy (HR-EELS) studies of hydrogenated diamond films surfaces
with grain size ranging from micro- to nanometer size. We present our vibrational peaks assignments
through isotopic exchange studies of surface species. In particular, special attention is paid to establish the
sensitivity of the vibrational losses to the near surface crystalline perfection or quality of the diamond films.
Grain boundary C and H bonding configurations were detected by analyzing stretching modes of C-H
vibrations of diamond films consisting of grains of different size. Then, we discuss nano-size effect
detected by HR-EEL spectroscopy for films composed of different nano-diamond grain size. These studies
were supported by molecular dynamic calculations as well as by complimentary techniques. Eventually,
HR-EELS analysis was applied to study dissociative D2/H2 chemisorption onto hydrogenated, bare and
defective diamond surfaces and characterize hetero-epitaxial diamond deposition on 3C-SiC(100)
substrates.
58
Theory of Materials and Thin Films (IID)
Chair: Amir Natan (TAU)
Hall 116 (floor 1)
59
IID-1
Understanding collective effects at
organic/inorganic interfaces from first principles
Leeor Kronik
Department of Materials and Interfaces, Weizmann Institute of Science,
Rehovoth 76100, Israel.
E-mail: [email protected]
Organic/inorganic interfaces have attracted much interest from both the basic science and the applied
science points of view. Technologically, their understanding is essential to (at least) organic and molecular
electronics. Fundamentally, they often force us to bridge two different “world views” – that of molecular
orbital theory, which underlies much of organic chemistry, and that of delocalized electron waves, which
underlies much of solid-state physics. Specifically, one often encounters “collective effects”, i.e.,
phenomena that the individual components comprising the interface do not exhibit. Here, I will review our
recent progress in understanding important classes of collective effects from first principles. I will focus on
analysis and/or prediction of specific experiments, with a focus on the “fingerprints” that collective effects
leave in experimental data.
60
IID-2
Using Strain to Tailor the Polar and Magnetic Properties of Perovskite Oxides:
A First-Principles Study
Oswaldo Diéguez ([email protected])
Department of Materials Science and Engineering,
Tel Aviv University, and
The Raymond and Beverly Sackler Center for Computational Molecular and Materials Science,
Tel Aviv University
Transition-metal perovskite oxides are a family of materials that covers a large range of applications
where dielectrics, piezoelectrics, or ferroelectrics are needed. In recent years, members of this family
have also been identified as possible magnetoelectric multiferroics---materials that display both
ferroelectricity and magnetic ordering, lending themselves to the possibility of having, for example, a
magnetization manipulated by an electric field. In this talk I will describe how first-principles calculations
can be used to learn how these materials can be modified to extract from them the ferroelectric and
magnetic properties of interest in magnetoelectric multiferroics. In particular, I will describe how the
strain caused by the interface of these oxides with other materials can turn a paraelectric material into
a ferroelectric (such as in BiMnO3
), or even into a ferroelectric ferromagnet (such as in Bi2
NiMnO6
).
61
IID-3
FIRST-PRINCIPLES BASED DESIGN OF PEROVSKITE OXIDES FOR VISIBLE LIGHT
ABSORPTION IN PHOTOVOLTAICS
Ilya Grinberg*1, Fenggong Wang2, Andrew Rappe2
1 Department of Chemistry, Bar-Ilan University, Ramat-Gan, Israel
2 Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA
Ferroelectric (FE) materials have recently attracted increased attention as a candidate class of materials for
use in photovoltaic devices and for coupling of light absorption with functional properties. Their strong
inversion symmetry breaking due to spontaneous polarization allows for excited carrier separation by the
bulk of the material and voltages higher than the band gap (Eg), which may allow efficiencies beyond the
Shockley-Queisser limit. Until recently, the use of FE oxides in PV devices has been blocked by the wide
band gaps (Eg=2.7-4 eV) of FE oxides, which allow the use of only 8-20% of the solar spectrum and
drastically reduce the upper limit of photovoltaic efficiency. Ab initio calculations and crystal chemical
analysis are powerful tools for the investigation of oxide solid solutions and are well-suited for making the
connection between the local, Angstrom-scale interactions, nanoscale effects and structural features and the
macroscopic physical properties. In this presentation, I will describe our computational studies1-3 of a
variety of ferroelectric perovskite oxides and show that the physical behaviors of these materials are
governed by the simple local structure, chemical bonding characteristics and nanoscale effects; these can
then be modified to rationally design new materials with light absorption through the visible range that
enables the use of these materials in photovoltaic applications.
1) F. Wang, S. M. Young, F. Zheng, I. Grinberg, and A. M. Rappe, "Substantial bulk photovoltaic
effect enhancement via nanolayering", Nat. Commun. 7,10419 (2016)
2) F. Wang, I. Grinberg,and A. M. Rappe, "Band gap engineering strategy via polarization rotation
in perovskite ferroelectrics", Appl. Phys. Lett. 104, 152903 (2014)
3) I. Grinberg, D. V. West, M. Torres, G. Gou, D. M. Stein, L. Wu, G. Chen, E. M. Gallo, A. R.
Akbashev, P. K. Davies, J. E. Spanier, and A. M. Rappe, "Perovskite oxides for visible-light-
absorbing ferroelectric and photovoltaic materials", Nature 503, 509 (2013)
62
IID-4
Equilibrium adsorption under nano-confinement:
Prediction of distinct entropic effects
Micha Polak* and Leonid Rubinovich
Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel
A nanoconfinement entropic effect (NCECE) shifting the chemical equilibrium relative to the macroscopic
thermodynamic limit (TL) was previously introduced using original statistical-mechanical analysis [1]. A
prerequisite is the participation of a small number of reactant molecules confined to a nanospace. The effect
was verified by evaluation of experimental data concerning DNA hybridization inside nano-chambers [2].
While our previous studies dealt with regular chemical reactions, the present study reveals the manifestation
of the effect in the case of gas adsorption on a solid surface. The NCECE, associated with significant
pressure fluctuations, is evaluated in the combined framework of the ideal-gas and ideal lattice-gas models
for several nondissociative adsorption processes, such as H2 physisorption on Ti-doped graphene surfaces
or Li-doped carbon nanopores. The computations, based mainly on published DFT data, mostly predict
NCECE-induced extra adsorption in comparison to the TL coverage (Figs.1,2). The results seem to have
practical implications, such as the enhancement of H2 storage capacity and CO2 capture in nano-porous
materials.
1. Micha Polak and Leonid Rubinovich, Nano Letters 8, 3543 (2008).
2. Leonid Rubinovich and Micha Polak, Nano Letters 13, 2247 (2013).
Fig.1. The NCECE computed for the adsorption of n molecules on n sites (n/n):
(a) Isotherms of H2 under confinement and the macroscopic Langmuir isotherm (Eb = adsorbate binding
energy); (b) Constant-volume (per molecule) extra adsorption.
V=103
nm3/molecule
Eb = -357 meV T = 300 K
(a) (b)
63
IID-5
Nucleation-Controlled Plasticity in Crystalline Nanoparticles
Dan Mordehai, Roman Kositski, Yosi Feruz, Koren Shreiber, Doron Chachamovitz
Department of Mechanical Engineering, Technion, 32000 Haifa, Israel,
Materials drastically change their mechanical properties when their size is reduced to the nanoscale. In
particular, defect-free crystalline nanostructures reach strengths that are close to their ultimate shear
strength, since their deformation is controlled by dislocation nucleation from the surfaces. For instance,
it was shown experimentally that Au nanoparticles yield abruptly under compression at stresses in the
GPa regime, where the smallest ones are the strongest. In this talk, we elucidate the microstructural
origins of the size effect in strength and extend the discussion to defect-free crystalline nanoparticles of
different materials.
Using Molecular Dynamics (MD) simulations we show that the strength of Au nanoparticles is
determined from the stress needed to nucleate dislocations at the vertices, which are points of stress
concentration. Extension of this study to other FCC materials shows a similar size dependency. Based on
the MD simulation results, we develop a size-dependent dislocation nucleation model to explain the size
effect in strength and its dependence on material properties. The size effect is shown to be suppressed
in Ni3Al intermetallic nanoparticles under compression, since the stress concentration vanishes in this
geometry. An analysis of the dislocation evolution in Ni3Al nanoparticles shows that partial dislocations
are nucleated at the vertices, shearing the nanoparticle with large complex stacking faults planes.
When -Fe nanoparticles (BCC structure) are compressed, dislocations also nucleate at the vertices on
two slip planes simultaneously. In contrast to the previous examples, we found that the strength of -Fe
nanoparticles (BCC) exhibits hardening after the first nucleation event, which arises from consecutive
nucleation events and the formation of dislocation pile-ups. The hardening is terminated abruptly when
the dislocations at the head of the pile-up react in a mechanism we coined as cross-split of dislocations.
This mechanism allows dislocation to escape away from the pile-up. Finally, the effect of temperature
on the strength is studied by pre-heating the specimens before compression. These simulations allow us
calculating the activation parameters to nucleate the dislocations at the vertices.
64
Posters
65
BI-1
An ultrasensitive method for protein and DNA detection at the single molecule level
Haya Dachlika,a Anat Iosub-Amir,a Roman Zhuravel,a Rey Capangpangan,b Dvir
Rotem,a Shlomo Yitzchaik,a Yu Ju Chen,b Assaf Friedler*a and Danny Porath*a
a Institute of Chemistry and The Harvey M. Kreuger Family Center for Nanosciene and Nanotechnology, Safra Campus, The Hebrew
University of Jerusalem, Israel.
b Institute of Chemistry, Academia Sinica, Taipei, Taiwan
We demonstrate a general single molecule method for ultrasensitive detection of macromolecules such as
DNA, proteins and biomarkers. The method is based on conjugation of two nanoparticles to target
macromolecules followed by imaging of the specific dimeric structures formed using electron microscopy.
Detection of macromolecular biomarkers such as disease-specific DNA and proteins provides essential
information that allows early diagnosis, prognosis and management of diseases. Today biomarkers
detection is limited in sensitivity and therefore detection often comes at a late disease stage. Therefore new
techniques are required to enable rapid and immediate diagnosis from physiological samples. Critically,
such a system must be capable of detecting very low levels of biomarkers, as many of them are present at
minute concentrations during early disease phases. These methods should be generic for a wide range of
macromolecules and based on affordable detection tools.
The proposed method presents ultrasensitive detection of macromolecules at the single molecule level using
NPs. The method is based on conjugation of two different ligands, which bind the target macromolecule at
two different binding sites, to two NPs with different sizes. The formed complex, in which each
macromolecule is flanked by two easily recognizable NPs (a dimer), is then detected and characterized
using EM. The surface concentration of the dimers can be calibrated to the concentration of the
macromolecule in the sample.
We will use model systems to validate the general proposed concept of dimer formation and highly sensitive
detection. The first model system will be a target DNA, which is detected using two single NPs each bearing
a complementary ssDNA. The second model system will be a target protein, which is detected using two
NPs covered with conjugated peptides that bind specifically to two different sites in the protein. Following
the implementation of those model systems, we will utilize the proposed method for various
macromolecules and biomarkers detection.
66
BI-2
LED sol-gel coating based on PGM-protein matrix with embedded dyes
Julia Gotta, MSc candidate under supervision of Prof. Shachar Richter
Department of Materials Science and Engineering
Faculty of Engineering & University Center for Nanoscience and Nanotechnology
Tel Aviv University, Tel-Aviv, 69978, Israel
Email: [email protected], [email protected]
LEDs (Light Emitting Diodes) are the latest and most exciting technological advancement in the lighting
industry. They are small and extremely energy efficient. Of a special interest are the White-LEDs which
are the most used today.
Today white LEDs are made by coating Blue or UVE LED with a phosphor that absorbs a proportion of
the blue light emitted by the diode and emits light across the rest of the visible spectrum. Phosphorus is an
essential nutrient for plants and animals in the form of ions PO43- and HPO4
2-. It is a part of DNA-molecules,
of molecules that store energy (ATP and ADP) and of fats of cell membranes and also a building block of
certain parts of the human and animal body, such as the bones and teeth. Phosphorus is widely used in many
fields like science, drug industry, agriculture, food-industry and more. According to scientist's suggestion,
current high-grade reserves will be depleted within 50–120 years.
To overcome phosphorus problem and to achieve wide white spectrum, we are interested to produce white
LED coating in other ways.
The first way is to produce sol-gel coating based on mixture of three primary dyes, which emit red, green
and blue light, using PGM protein (porcine gastric mucin) inside. This glycoprotein can serve as a matrix
to separate RGB dyes (Red- 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran, Green-
8-Hydroxypyrene-1,3,6-trisulfonic acid trisodium salt, Blue- 1-Aminopyrene) in order to prevent Förster
resonance energy transfer between these three color components, which causes shift in emission spectrum
and prevents white-light emission. Due to its structure, this protein also helps to solubilize hydrophobic red
and blue dyes. The second way is to embed Au-quantum dots into the sol-gel coating.
We believe that those techniques can significantly reduce the usage of phosphorus.
67
BI-3
Tailoring Surface Electronic Properties of Indium Tin Oxide by Specifically
Designed Peptides
Naomi Kramer, Maor Engel, Ido Sivron and Nurit Ashkenasy*
Department of Materials engineering,
Ben-Gurion University of the Negev, Beer Sheva, Israel
Controlling energy band alignment at the interfaces of indium tin oxide (ITO), one of the most
commonly used electrode in optoelectronic devices is crucial for improving device performance. Organic
monolayers assembled at the interface have been shown to be an attractive tool for this task. In this respect,
bioinspired peptide monolayers seem to be perfectly suited for such applications, due to their versatility,
and ease of design and preparation.
As a first step to reveal peptide design rules, the effect of peptide side chains on the electronic
properties of ITO was studied in the context of monolayers of single amino acids. Monolayers of positively
and negatively charged, neutral and aromatic amino acids were assembled on ITO in order to study the
effect of their side chains on the work function and surface photovoltage of the surface. In most cases, a
correlation between the molecular dipole and changes in the surface work function was found, though
deviation from this trend was revealed for tyrosine with a phenolic aromatic side chain. Monolayers of
tyrosine were also found to strongly passivate the surface. Similar correlation was found for a series of
unnatural aromatic amino acids, indicating that the dipole effect depends on the conformation of amino
acids on the surface.
Based on the single amino acid studies, a series of peptides with varying amount of positive charge
were designed, aiming at reducing the ITO work function. Indeed, a correlation between the amount of
positive charge and the WF was observed, where the larger the peptide charge was, the smaller the measured
work function. These results demonstrate the tunability gained by using amino acids and peptides for
tailoring the electronic properties of ITO.
68
BI-4
Electro-assisted Deposition of Calcium Phosphate on Self-Assembled
Monolayers Modified Gold Substrate
Noah Metokia, Noam Eliaza, Daniel Mandlerb
a Biomaterials and Corrosion Lab, School of Mechanical Engineering & The Materials and
Nanotechnologies Program, Tel Aviv University, Ramat Aviv 62204, Israel.
b Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem91904, Israel.
Calcium phosphate (CaP) bioceramics have received much attention and have been clinically applied
on orthopedic and dental implants due to their excellent biocompatibility and osseointegration. The coating,
usually applied to titanium and its alloys, interacts with the bone around it via dissolution. Coatings are
commonly applied using the plasma-spray process. Yet, much interest in electrodeposition has evolved
during the last two decades.
The main goal of this research is to study the nucleation and growth of electrodeposited CaP coating
formed on chemically altered substrates using self-assembled monolayers (SAMs). For that aim we used
well defined surfaces- gold substrates. Specifically, the electrodeposition of CaP was studied both on bare
gold and on gold surfaces covered with 2-mercaptoacetic (MAA) acid and 2-mercaptoethanol (ME) SAMs
at short and long periods of times.
In the early stages of deposition, both the phase content and the mass gain are similar with or without
SAMs. Nevertheless, a different growth mode is evident from different surface morphologies that are
revealed by HR-SEM. While the deposition is slower and less efficient on a MAA-covered surface, surface
cracking was essentially eliminated due to reduction of the crystallographic mismatch. The carboxylic acid
may facilitate CaP growth by attracting Ca2+ ions to the surface, which could explain the higher amount of
side reactions occurring at the beginning of the deposition.
Scheme 1. CaP proposed electrodeposition mechanism on MAA-covered SAMs.
69
BI-5
Jellyfish derived nanofibers for wound dressing and tissue engineering
applications
Roman Nudelman1,2 , Shachar Richter*2,3
1 School of Chemistry Faculty of Exact Sciences
2Center for Nanoscience and nanotechnology
3 Department of Material Science and Engineering Faculty of Engineering
Tel- Aviv University, Tel-Aviv, Israel,
The global jellyfish problem is raised into worldwide attention with publication of special U.N report in
2013 which warned the global community about the threat of global jellyfish infestation. There are
several proposals to deal with the jellyfish problem that can be divided to long and short term solutions.
One of the most promising short term solutions involves finding proper commercial use of jellyfish
proteins, namely collagen and mucin.
In our research we utilized these proteins in the development of smart wound dressing materials. We
used electrospinning technique in order to prepare non-woven mats made from nanofibers that contain
jellyfish proteins as a main raw material and polycaprolactone (PCL) co polymer. By controlling the
experimental parameters such as applied voltage and needle-collector distance, several scaffold
properties such as: fiber diameter, scaffold porosity, hydrophilic properties and fiber density can be
controlled. By utilizing the natural reduction properties of jellyfish proteins on the outer shell of the
nanofibers we managed to reduce silver ions into silver nanoparticles. Cytotoxicity and cardiac cells
proliferation experiments showed that due to high presence of jellyfish collagen and mucin on the outer
layer of nanofibers they present a suitable material for tissue engineering application.
70
BI-6
Hierarchical Structure of Polysaccharides-Peptides Hydrogels
Guy Ochbaum1 and Ronit Bitton1, 2*
1 Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva
84105,Israel,
2* Ilse Katz Institute for Nanoscale Science &Technology, Ben-Gurion University of the Negev,
Beer-Sheva 84105, Israel. E-mail address: [email protected]
Polysaccharides such as alginate and hyaluronic acid have been utilized in the fields of regenerative
medicine and tissue engineering to allow cell growth in impaired regions, by providing an artificial bio-
surrounding (scaffold) similar to the natural Extra Cellular Matrix (ECM). A drawback of polysaccharides
as a scaffold's building block is their inability to form specific cellular interactions. On the other hand self-
assembling peptides can be designed to present specific cellular interactions, however, in many cases the
mechanical properties of peptide scaffolds are inadequate. Complex hydrogel scaffolds composed of
polysaccharides and self-assembling peptides have the potential for creating scaffolds (hydrogels) with
superior properties.
The peptides are expected to act directly on cells, however they may also modify the hierarchical
structural organization and mechanical properties of the resulting material, thus affecting the cellular
response indirectly.
The aim of this research is to seek possible relationships between the Nano-structure of self-assembling
peptides and the physical properties of Alginate/peptide hydrogels.
Here we present a systematic investigation of the effect of self-assembling RGD- containing peptides
on the structural features and mechanical properties of the Alginate/peptide hydrogels network by using a
variety of experimental techniques including Small Angle X-ray Scattering (SAXS), Rheology and electron
microscopy.
Our findings show that a peptides' ability to self-assemble in aqueous solution affects the spatial
organization of the alginate and the mechanical properties of the alginate/peptide hybrid hydrogel, both
when the peptide is covalently attached to the alginate backbone and when peptide and alginate solutions
are simply mixed together. Therefore should be taken into consideration in the design of hybrid
biomaterials.
71
BI-7
Polysaccharide Hydrogels cross-linked via Thermo-Responsive
Peptide-Dendrimers
Yulia Shmidov, [a] Mingjun Zhou,[b] John B. Matson, [b] Ronit Bitton*[a]
[a] Department of Chemical Engineering and the Ilze Kats Institute for Nanoscale Science and
Technology, Ben-Gurion University of the Negev, Beer-Sheva, 84105 (Israel)
[b] Department of Chemistry and Macromolecules and Interfaces Institute, Virginia Tech,
Blacksburg, VA 24061 (U.S.A.)
e-mail: [email protected]
Thermo-responsive hydrogels have gained much interest in the past decade due to their reversible
temperature responsive behavior and potential applications (e.g. drug delivery system, smart surface
modification, nanotechnology, catalysis etc.).
Elastin like peptides (ELPs) are artificial biopolymers based on Elastin. Similar to elastin, ELP’s have been
shown to exhibit an inverse temperature transition (Tt), characterized by micro phase separation and a
change in the peptide secondary structure, making them ideal building blocks for thermo-responsive
materials.
Hyaluronic acid (HA) is a naturally- occurring linear polysaccharide present in the ECM of all animals and
have been used extensively in the past decade as a biomaterial for tissue engineering, drug delivery etc.
Combining HA and ELPs can result in thermo-responsive hydrogels suitable for biomedical applications.
Here we present a systematic investigation of a class of dendritic ELPs based on the GLPGL pentamer
repeat unit, and their potential as cross-linkers for HA thermo-responsive hydrogels.
The effect of peptide topology (e.g. peptide length, generation no. etc) on the ELP’s transition temperature
(Tt) in solution was examined using circular dichroism to study the peptide secondary structure transition,
SAXS and TEM to characterize the nanoscale changes and turbidity to measure the macroscopic phase
transition (coacervation).
Hydrogels were created covalently binding ELPs and HA using carbodiimide chemistry: SEM images
confirmed a 3D network was formed. The Hydrogels’ thermo-responsiveness was explored by tracking
food dye release upon heating as well as swelling tests.
72
BI-8
Proton Self-Doping in Peptide Fibrils
Ohad Silberbush1, Moran Amit1, Subhasish Roy1 and Nurit Ashkenasy*1, 2
1Department of Materials Engineering, and 2The Ilse Katz Institute for Nanoscale Science & Technology,
Ben Gurion University of the Negev, Beer- Sheva, Israel
The chemical diversity, ease of synthesis, and self-assembly propensity of peptides make them
attractive materials for bioelectronics applications. The presence of hydrogen donating and accepting
groups, such as carboxylic acid and amino groups, at the peptide side chains and its termini may facilitate
affective proton conduction along peptide self-assembled nanostructures. We present studies of the
dependence of protonic conduction of amyloid β- based peptide fibers on the peptide sequence.
We show that the introduction of amine and carboxylic acid side chains to self-assembled peptide
nanofibers enhances their conductivity. An exponential dependence of the resistance on the relative
humidity for both type of fibers indicates that the conduction is dominated by proton charge carriers. We
find that the carboxylic acid reach fibers exhibit lower resistance. This is as a result of higher concentration
of protons (vs. proton holes in the second case) and their higher mobility. Moreover, the mobility ratio of
the two type of peptide fibrils resembles that of weak acid and base solutions. Our findings demonstrate
that protonic conduction of peptide fibers may be tuned by a proper peptide sequence design. The ability to
generate both proton and proton holes may lay the ground to proton based switches, diodes, batteries and
transistor devices.
Figure 2 : Left: Scanning electron microscope image of proton donor rich peptide fibers network between two gold
electrodes, which are observed at the upper and lower parts of the image. Inset includes electric force phase of cross-
section of individual fibers, indicating higher polarizability for proton donor rich fibers (red) than for proton acceptor rich
fibers (blue). Right: Resistance of the peptide fiber networks at varying relative humidity conditions.
73
BI-9
Aspen Tree Protein SP1 as a Biological Nanopore
M. Akerman1,3, N. Attias2,3, L. Nesiel2,3, M. Gofer 2,3, K. Liu1,3, A. Karmi1,3, Y. Nevo2,3,
D. Rotem1,3, O. Shoseyov2,3, D. Porath1,3
1. Institute of Chemistry. 2. Institute of Plant Science. 3. Center for Nanoscience and
Nanotechnology
The Hebrew University of Jerusalem, Israel
Nanopores have been used as stochastic sensors for the detection of analytes that range
from small molecules to DNA, RNA, and proteins. Proteins in a planar lipid bilayer platform can
be used as nanopores in order to study and identify these biological analytes. In this approach,
individual analyte molecules modulate the ionic current flowing through a single nanopore. SP1
(stable protein 1) is a ring-shaped, highly stable homododecamer protein, originally isolated from
Aspen trees (P. euphratica). SP1 is stable under extreme conditions such as high temperatures,
detergents and organic solvents, and over a wide range of pH. SP1 has a relatively large pore
diameter (3-4 nm) which can be manipulated in order to specifically detect a variety of analytes
(DNA, RNA, Proteins). It was recently shown that SP1 can be embedded into lipid bilayers, thus
creating a nanopore. The protein can be modified in order to change the charge distribution on its
surface to further increase its stability in the lipid bilayer; this can be done via site directed
mutagenesis and/or chemical modifications to increase surface hydrophobicity.
74
BI-10
Highly sensitive C-dot embedded ascorbic acid hydro gel for ROS sensing
Dr. Sagarika Bhattacharyaa, Prof. Raz Jelineka,*
a Department of Chemistry, Ben-Gurion University of the Negev, Beer Sheva – 84105, Israel
email: [email protected]
Reactive oxygen species (ROS) are generated as a natural byproduct of normal metabolism
of oxygen.[1] Overproduction of ROS can lead to cause acute and chronic bacterial infections to
chronic diseases such as cancer, cardiovascular disease, etc. So far, small organic fluorescent probe
has been utilized for ROS detection using. Carbon dots (CD) have attracted research interest due
to their structural and photo physical property. CD entrapped in hydrophobic hydro gel
environment flaunt a substantial enhancement of the CD fluorescence.[2] Hydro gels are soft
materials consisting of entrapped water molecules within its network, formed by the self-assembly
of gelator molecules. Highly hydrophilic Vitamin C converted into an amphiphilic gelator
molecule by the insertion of hydrophobic alkyl chain into the ester derivative, then also its radical
scavenging capacity retains.[3] The amphiphilic CD,[4] we have synthesized, were initially
dispersed within the hydrogel pores giving rise to high fluorescence emission. However, when
ROS were added to the CD/hydrogels, the oxygen radicals oxidized the ascorbic acid constituents,
leading to disintegration of the hydrogel scaffold. As a consequence, the CD aggregated giving
rise to quenching of the fluorescence emission. We demonstrate this novel sensing modality for
high sensitivity detection of different ROS.
2
Figure 1. Schematic presentation of detection methodology (A) and photograph of gel under
regular light and UV light (B).
References:
[1] B. Halliwell and J. M. C. Gutridge, Free Radicals in Biology and Medicine 1989, Oxford, UK, Clarendon Press.
[2] A. Cayuela, S. R. Kennedy, M. L. Soriano, C. D. Jones, M. Valcarcel and J. W. Steed, Chem. Sci. 2015, 6, 6139.
[3] S. Nandi, H.-J. Altenbach, B. Jakob, K. Lange, R. Ihizane and M. P. Schneider, Org. Lett. 2011, 13, 1980. [4] S. Nandi, R. Malishev, K. P. Kootery, Y. Mirsky, S. Kolusheva and R. Jelinek, Chem. Commun. 2014, 50, 10299.
B
ȯH
75
BI-11
Impact of peptide side chain on energy level alignment at monolayer-conductor interface
Cunlan Guo,1,2 Sivan Refaely-Abramson,1 David Egger,1 Israel. Pecht,3 Satoshi Kera,4 Nobuo Ueno,4
Leeor Kronik,1 Mudi Sheves,2 David Cahen*1
Depts. of 1Materials and Interfaces, 2Organic Chem., 3Immunology, Weizmann Inst. of Science, Rehovoth,
4Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
Email: [email protected]
Biomolecules like proteins and peptides are of interest as diverse building blocks for future functional
molecular electronic devices 1. A peptide has a relatively simple and rigid structure, with possibility for
structure design, which makes it suitable to bridge conductive electrodes of solid state electronic devices.
To design peptide junctions in solid state devices we need to understand the electronic structures of a
peptide molecule monolayer/electrode interface, which is directly related to the energy barrier and
electrode-molecule coupling of the resulting junctions 2. Meanwhile, studying how the electronic structure
of a peptide determines its electron transport is also a key to understand protein charge transport in
biological energy conversion and signaling systems.
For this purpose, we systematically compare the electronic structure of dipeptides (2Ala and 2Trp) in gas
phase and in a monolayer, bound to a Au substrate through a thiol linkage, using ultraviolet photoelectron
spectroscopy (UPS) experiments and first-principles density functional theory (DFT) calculations.
Electrons are delocalized over a large part of the molecule for 2Ala dipeptides, and are localized on the
indole rings for 2Trp dipeptides. The highest occupied levels of 2Trp are lower in absolute value than those
of 2Ala in both gas phase and as monolayer on Au. The drop in ionization potentials from gas phase to
monolayer is similar for both dipeptide series. Furthermore, in the monolayer case, the work functions of
monolayer-covered Au electrodes are similar for all dipeptide monolayers. These results indicate that Au-
S binding of the dipeptide (via the linker) causes screening of the interaction of Au with amino acid residues
on dipeptides 3. The parts of the peptide beside linker are not directly involved in the energy alignment
with electrodes. We find that for various peptide junctions the differences in energy barrier between the
electrode’s Fermi level and the closest molecular level of the peptide are mainly determined by the type of
amino acid that makes up the peptide, i.e., the side chains.
Reference
1. Facci, P., Biomolecular electronics: bioelectronics and the electrical control of biological systems
and reactions. 2014, 1-240.
2. Neaton, J. B.; Hybertsen, M. S.; Louie, S. G., Physical Review Letters 2006, 97, 216405.
3. Xie, Z. T;, Baldea, I.; Smith, C. E.; Wu, Y. F.; Frisbie, C. D., ACS Nano 2015, 9, 8022-8036.
76
BI-12
Carbon Nanotubes Biopolymer based Biosensor for the Electrochemical
Detection of Neurotransmitters
Sudheesh K. Shukla and Hadar Ben-Yoav*
Nanobioelectronics Laboratory, Department of Biomedical Engineering,
Ben-Gurion University of the Negev, Beer Sheva, 8410501, Israel
*Corresponding author. Tel: (+972) 8-6479717; E-mail: [email protected]
One of the many applications of carbon nanotubes (CNTs) is electrochemical biosensors where their
catalytic activity is being used for decreasing the applied electric potential and improving the overall
sensitivity. Recent advances to incorporate CNTs within a biopolymeric matrix enabled the integration of
these high surface area bioelectronic interfaces with biosensing micro-systems. The intimate contact
between the biopolymer and the CNT results in better access to analytes due to the extended time of the
analyte at the interface and the simultaneous electrocatalytic reaction. However, the low stability of the
biopolymer-CNTs film at the electrode surface and the relationship to its physicochemical properties are
not fully understood hence inhibiting the integration in electrochemical micro-systems. In this work, we
study the encapsulation of CNTs in a chitosan (CHIT) biopolymeric matrix and its integration in an
electrochemical biosensor for the detection of the neurotransmitter dopamine. The structural surface
properties of the CNTs-CHIT biocomposite were characterized by scanning electron microscopy, X-ray
diffraction and ellipsometry. Electrochemical characterization techniques elucidated the electrode reaction
and mass transfer kinetics at the bioelectronic composite surface. The incorporation of the CNTs resulted
in a negative relationship with the electron transfer resistance property and improved the generated
electrochemical current. The electrochemical current of the optimized CNT (5% loading) in a CHIT
polymeric matrix was 0.16 mA approximately 2 time higher than without CNTs. As one of the major
challenges of dopamine electrochemical biosensing is the poor differentiation from other interfering
species, the capability of the CNTs-CHIT biocomposite to alter the standard reduction potential (Eo) of
dopamine (Eo = 0.63V vs. Ag/AgCl) was examined. The selectivity of the CNTs-CHIT biosensor to
dopamine was tested in the presence of the interfering species ascorbic acid (Eo = 0.35V vs. Ag/AgCl) and
uric acid (Eo = 0.59V vs. Ag/AgCl) and was compared to a non-modified bare biosensor. This investigation
will improve the understandings of the CNTs-CHIT interface and will result in guidelines for its better
utilization in electrochemical micro-systems for the molecular detection of analytes.
77
EM-1
Magnetic response of epitaxial Erbium silicides on vicinal Si(111) substrates
Federico Cesura*1, Matan Dascalu1, Yotam Camus1, Mario Levinshtein1 and Ilan Goldfarb1 1Tel Aviv University.
E-mail address of corresponding author: [email protected]
Erbium silicides grown on Si (111) substrates have been object of many studies because of their
interesting electronic features and their low lattice mismatch with the substrate surface make them good
candidates for epitaxial growth of high quality crystals [1, 2]. This research work aims to analyze the
magnetic response of different types of Erbium silicide structures grown epitaxially on vicinal Si(111)
substrates. In order to control the morphology of the epitaxial structures [3], three different samples were
prepared by depositing metallic Erbium through MBE on p-type atomically clean vicinal Silicon (111)
substrates; the first two samples [(a) and (b)] were obtained respectively by SPE (RT deposition and
subsequent 400°C annealing) and RD (at 500°C) of a sub-monolayer amount of metallic Er, while the third
one (c) was obtained by RD (at 500°C) of an amount of deposited metal Θ>1ML. The resulting surfaces
have been characterized in-situ by indirect (LEED/RHEED) and direct (STM/STS) methods. Chemical
analysis (XPS) and magnetic response analysis (SQUID) have been performed ex-situ.
STM characterization of the annealed surfaces showed the formation of 3 distinct structures – sample (a)
appeared to be populated only by nano-islands growing both on the terraces and the step bunches in a rod-
shaped anisotropic fashion parallel to the [1 -1 0] and equivalent directions; sample (b) was characterized
both by anisotropic rod-shaped islands and 2D hexagonal patches growing on the terraces; due to the higher
metal coverage sample (c) was covered by a quasi—continuous multilayered silicide film.
SQUID analysis (the in- and out-of-plane magnetization reversal loops at different temperatures were
recorded along with zero field cooled (ZFC) and field cooled (FC) magnetization versus temperature
measurements) were performed on the samples in order to investigate the dependence of the magnetic
behavior of the epitaxial structures from different factors such as the dimensions, shape and ordering factor
of the RE-silicides and the direction of the applied magnetic field.
References
[1] P. Wetzel et al., Phys. Rev. B 56 (1997).
[2] A. Saranin et al., Jpn. J. Appl. Phys. 43 (2004)
[3] I. Goldfarb, Nanotechnology 18 (2007)
78
EM-2
Femtosecond-scale switching based on excited free-carriers
Marat Spector1 and Yonatan Sivan2
1 Ben Gurion University of the Negev, Department of Physics, 84105, Beer- Sheva,
Israel, email: [email protected]
2 Ben Gurion University of the Negev, Unit of Electro-Optics, 84105, Beer-Sheva,
Israel, email: [email protected]
Ultrafast switching is one of the oldest and most important applications of nonlinear optics. Traditionally,
it is based either on Kerr nonlinearity, which is instantaneous, but weak, or on free carrier nonlinearity,
which could be much stronger, but comes at the cost of a substantially slower turn-off time. Here, we
demonstrate simple schemes that enable us to enjoy the best of the two worlds - to have an ultrafast and
strong switching, based on free-carrier generation. Specifically, we describe novel switching schemes
operating on femtosecond time scales, which are based on a periodic pattern of free-carriers (FCs) which
serves as a transient Bragg grating. Such gratings can be generated by a resonant pumping of a
semiconductor or metallic waveguide. In the first realization, we rely on diffusion to erase the initial FC
pattern, hence, to remove the reflectivity of the system. We show that the grating erasure time is
quadratically proportional to the effective wavelength, so that the high refractive index of semiconductors
or the effective index of plasmonic waveguides makes this time scale sub-picosecond under realistic
conditions. In the second realization, we erase the FC pattern by launching a second, delayed pump pulse
which is shifted by half a period compared with the first one. We discuss the advantages and limitations of
the proposed approach and demonstrate it for switching ultrashort pulses propagating in silicon waveguides
and plasmonic waveguides. We show reflection efficiencies of up to 50% for 100fs pump pulses, which is
an unusually high level of efficiency for such a short interaction time, a result of the use of the strong FC
nonlinearity.
Due to limitations of saturation and pattern effects, the scheme can be employed for switching applications
requiring femtosecond features but standard repetition rates. Such applications include switching and
modulations of ultrashort pulses, femtosecond spectroscopy (gating) and time-reversal of short pulses for
aberration compensation.
79
EM-3
Direct observation of confinement-induced charge inversion at a metal surface
Ran Tivony1, Dan Ben Yaakov1, Gilad Silbert# and Jacob Klein1,*
1Dept. of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel
#Current address: Adama Makhteshim Ltd., Beer Sheva, 84100, Israel
*Corresponding author: [email protected]
Surface interactions across water are central to areas from nanomedicine to colloidal stability. They are
predominantly a combination of attractive but short-ranged dispersive (van der Waals) forces, and long-
ranged electrostatic forces between the charged surfaces. Using a surface force balance (schematically
shown in the inset to Fig. 1), we showed that electrostatic forces between two surfaces across water, one at
constant charge (a dielectric) while the other (a molecularly-smooth metal surface) is at constant potential
of the same sign, may revert smoothly from repulsion to attraction on progressive confinement of the
aqueous intersurface gap (Fig. 1). This remarkable effect, long predicted theoretically in the classic Gouy-
Chapman (Poisson-Boltzmann) model but never previously experimentally observed, unambiguously
demonstrates surface charge reversal at the metal-water surface.
Figure 1. Interaction profiles Fn(D)/R between gold and bare mica surfaces across water with no added salt
(pH5.8) under different applied potentials Applied, color-coded as in legend. Inset: Schematic of the 3-
electrode configuration of the SFB.
80
EM-4
Vortex dynamics manipulation by means of Bi-Layering (BL)
Author: Guy Bareli, [email protected]
Better understanding of vortex dynamics in type II superconductors can be achieved by
manipulating their motion characteristics. This can be done by creating easy vortex motion
channels along the superconductor material. In the framework of the current research we use
samples manufactured as bi-layers specimens, where the YBCO superconductor thin film is
deposited on a Manganite substrate with specific magnetic domains, in order to alter the
superconductive characteristics in a certain pattern of channels across our specimens. We then
perform transport measurements, namely I-V and R(T), in order to explore vortex motion within
the channels and interactions between vortices. After examining the data from our measurements
we can verify the manipulation done on vortex motion by the magnetic domains and relate it to
the angle between vortex motion direction and domains orientation. We believe that our findings
can greatly impact type II superconductors fabrication in future applications and open new
prospects for such technologies.
81
EM-5
Bimodal HD-KFM and Resiscope Atomic Force Microcopy characterization of bidimensional materials and solar cells
Nicolas F. Martinez1 and *Louis Pacheco1
1Concept Scientific Instruments, 2 Rue de la Terre de Feu, 91940 Les Ulis, France
*email corresponding author: [email protected]
Over the past 30 years, Atomic Force Microscopy has evolved from a microscope to measure just the
surface topography to a wide variety of measurement modes that provides a way to characterize other
atomic interactions or physical properties like magnetic field, electric field, nanoscale dissipation processes,
thermal conductivity, electrical conductivity, resistance, surface potential, piezoresponse, Young
modulus,… Electrical nanocharacterization with AFM has emerged as a powerful tool to map electrical
properties at the nanoscale, like surface potential (work function) and conductivity. However, traditional
setups in AFM make difficult to obtain accurate and repeteable results over several types of samples.
In this article we will show the capabilities of two new developed AFM modes: High Definition Kelvin
Force Microscopy (HD-KFM) and (Soft)Resiscope that overcome the intrinsic difficulties of electrical
nanocharacterization with AFM. This two techniques have been applied on a wide variety of substrates:
bidimensional materials, like graphene or molibdene disulfide, organic solar cells and nanoparticles
providing high stability, sensitivity and lateral resolution.
Figures
a) HD-KFM image on Graphene b) HD-KFM image on Molibdene disulfide
1.G. Binnig, C.F. Quate, Ch. Gerber, Phys. Rev. Lett. 56, 930 (1986).
2.Houzé F, Meyer R, Schneegans O, Boyer L.. Appl Phys Lett. 1996;69:1975.
3.D.W. Abraham, et al, J. Vac. Sci. Technol. B 9,703 (1991)
4.T.R. Albrecht, P. Gr¨utter, D. Horne, D. Rugar, J. Appl. Phys. 69, 668 (1991).
5.T.R.Rodriguez and R.Garcia App. Phys. Lett. 84(3):449-451
6. J. Colchero, A. Gil, A.M. Bar´o, Phys. Rev. B 64, 245403 (2001)
1 ML 9 ML
9 ML
(a) (c)
1 ML
2 ML
(b)
82
EM-6
THE MANY LOCAL MINIMA IN THE ENERGY SURFACE OF BISMUTH FERRITE: A
FIRST-PRINCIPLES EXPLORATION
Akansha Singh1, Enric Canadell2, Jorge Íñiguez2,3 and Oswaldo Diéguez1*
1Department of Materials Science and Engineering, Faculty of Engineering, Tel Aviv University, IL-
69978 Tel Aviv, Israel
2Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, E-08193 Bellaterra, Spain
3Materials Research and Technology Department, Luxembourg Institute of Science and Technology
(LIST), 5 avenue des Hauts-Fourneaux, L-4362 Esch/Alzette, Luxembourg
Multiferroic bismuth ferrite is one of the most studied materials in the last decade because it is one of the
very few that shows polar and magnetic orderings coexisting at room temperature [1]. BiFeO3 displays a
variety of phases under different conditions of temperature, pressure, and epitaxial strain. In previous work
[2], we identified these phases as local minima in the energy surface of bulk BiFeO3, and we reported that
this multiferroic shows a large amount of other phases as local minima. In the present first-principle study,
we used a unbiased search scheme based on an evolutionary algorithm [3] to systematically map these low-
energy phases of BiFeO3. In order to assess what makes BiFeO3 different from typical perovskite oxides,
where the number of local minima is much smaller, we have also explored the energy surface of BaTiO3,
PbTiO3, BiScO3, and BiCrO3.
References:
1. G. Catalan and J. F. Scott, Adv. Mater. 21, 2463 (2009).
2. O. Diéguez, O. E. González-Vázquez, J. C. Wojdeł, and J. Íñiguez, Phys. Rev. B 83, 094105
(2011).
3. A. R. Oganov , C. W. Glass, J. Chem. Phys. 124, 244704 (2006), A. R. Oganov. H. Stokes, M.
Valle, Acc. Chem. Res. 44, 227 (2011).
83
EM-7
3X Taller Carpets of Vertically Aligned Carbon Nanotubes through Differential
Preheating of Hydrocarbon Decomposition and Water Vapor Formation
Eti Teblum, Anat Itzhak, Efrat Shawat-Avraham, Merav Muallem, Reut Yemini, and Gilbert D. Nessim*
The Department of Chemistry and Institute of Nanotechnology, Bar-Ilan University, Ramat Gan, 52900,
Israel
Corresponding author: Tel: 972 37384540. E-mail address: [email protected] (G. D. Nessim)
Using a sophisticated system of multi-zone thermal chemical vapor deposition (CVD) furnaces in
parallel and in series, we performed differential preheating of the incoming gases to independently control
water vapor formation (from oxygen and hydrogen) and hydrocarbon decomposition to grow vertically
aligned carbon nanotube (VACNT) carpets. We identified specific process parameter sweet spots for water
vapor formation and for hydrocarbon decomposition that led to over three times taller CNT carpets
compared to the reference process with in-line gas preheating. For instance, we showed that additional
external preheating of oxygen and hydrogen to form water vapor was beneficial to CNT growth while
external preheating of the hydrocarbon precursor dramatically hindered CNT growth. Additionally, the
catalyst was active for at least two hours, with CNT height approaching 5 mm.
Using gas chromatography – mass spectrometry (GC-MS), we correlated specific carbon species
resulting from ethylene decomposition from specific process points to reveal which species favored and
which species hindered CNT growth. From this analysis, we identified that hydrocarbons composed from
one benzene ring connected to different substituents favored CNT growth while hydrocarbons composed
by multiple aromatic rings hindered CNT growth. This study can further our understanding of the CNT
growth mechanisms and to help designing more efficient CVD systems for more efficient synthesis of
CNTs.
84
G-1
Metal Oxide Coatings on Carbon Nanotubes (CNTs)
Yacov Carmiel*, Eti Teblum, Daniel G. Nessim and Chaim N. Sukenik
Department of Chemistry and Institute of Nanotechnology & Advanced Materials
Bar Ilan University, Ramat-Gan 52900, ISRAEL
Liquid phase deposition (LPD) and atomic layer deposition (ALD) were used to deposit different
oxides on Vertically Aligned (VA) and bundled CNT substrates. TiO2 was deposited on CNT
electrodes, making them more robust and stable to mechanical and thermal threats. ALD of TiO2
on these electrodes demonstrated the importance of adequate diffusion time for ALD processes on
porous materials. Short VA-CNTs (7 µm tall) were coated with TiO2 and SnO2 by LPD and ALD,
with high uniformity and linear growth rate. Dense forests of long (200-800 µm) CNTs were
coated by ALD, and the diffusion time required for deep penetration was investigated.
85
G-2
Synthesis of Core-Shell MoS2 Fullerene-Like Incorporating Gold Nanoparticle
Au@IF-MoS2
A. Lavie1, L. Houben2, R. Popovitz-Biro2, R. Tenne1,*
Materials and Interfaces Department, Weizmann Institute of Science, Rehovot 76100, Israel
Electron Microscopy Unit, Weizmann Institute of Science, Rehovot 76100, Israel
Nanoparticles and more specifically gold nanoparticles (AuNPs) attracted a great scientific and
technological interest in the last few decades. Their popularity is attributed to their unique optical,
electrical and magnetic properties when compared to the bulk. However, one of the main problems
of AuNPs is their long-term stability. On the other hand, MoS2 nanoparticles (NPs) and single
layers show great chemical stability, and exhibit excellent mechanical and tribological properties
as well as being biologically benign. Moreover, it is known that MoS2 can form conformal coating
on topologically complex surfaces. Finally, due to the MoS2 NP unique optical properties, a hybrid
AuNP core and MoS2 shell would be a unique, stable and interesting hybrid nanomaterial. In this
work we present a synthesis of AuNPs coated by MoS2 single-layer. i.e. a core-shell nanostructure
(Au@MoS2).
86
G-3
Chemical Bath Deposition of Nano-Columnar PbSe Thin Films for
SWIR Detection
Maayan Perez1,2 ,Tzvi Templeman1,2*, Nitzan Maman 1,4, Amir Tal1,3, Sucheta Sengupta1, Hadar Manis
Levy1,3, Michael Shandalov5, Eyal Yahel5, Iris Visoly-Fisher1,4, Gabby Sarusi1,3 and Yuval Golan1,2 1Ilse Katz Institute for Nano-scale Science and Technology, Ben Gurion University of the Negev, Israel
2Department of Materials Engineering, Ben Gurion University of the Negev, Israel
3Department of ElectroOptics Engineering, Ben Gurion University of the Negev, Israel
4Department of Solar Energy and Environmental Physics, Swiss Institute for Dryland Environmental and Energy Research, Jacob Blaustein Institutes for Desert
Research, Ben Gurion University of the Negev, Israel
5Department of Physics, Nuclear Research Center Negev, P.O. Box 9001 Beer Sheva, Israel
Nano-columnar PbSe thin films have been investigated in order to determine their potential as
SWIR absorber material for upconversion night vision devices. The films were deposited on
GaAs(100) substrates using chemical bath deposition and studied using XRD, SEM, CSAFM,
optical absorption and PL.
PbSe is a narrow gap semiconductor with a direct forbidden band of 0.28 eV. Due to its
exceptionally large Bohr radius, combined with the nano-columnar film morphology, a tunable 2D
quantum confinement is achieved. Moreover, columnar boundaries showed insulating behavior
while grain interior shows good conduction along the z direction, which is advantageous for the
use of these films in the upconversion device.
Average film column width is controlled through growth solution parameters, specifically
temperature and pH, thus band gap tuning is achieved. Reducing solution pH, to a certain degree,
results in decreased column width and in blue shifting of the band gap energy, a wanted outcome
since the energy band gap required for SWIR is around 0.8 eV. Further reduction of the solution
pH leads to a growth transition towards cluster mechanism, hence disrupting the columnar
morphology. The pH value that was achieved without transitioning to cluster mechanism was
about 13.5, with corresponding energy gap of 0.55 eV, hence- the blue shift was insufficient and
an additional reduction of the pH was necessary. Introduction of trisodium citrate (Na3C6H5O7),
which acts as a co-complexing agent, allows for substantial reduction of the solution pH while
maintaining nano-columnar microstructures.
87
G-4
Enantioselective mesoporous carbon based on chiral ionic liquids
Sapir Shekef*, and Yitzhak Mastai
Department of Chemistry and Institute for Nanotechnology and Advanced Materials, Bar-Ilan
University, Ramat Gan 5290002, Israel
E-mail: [email protected]
Our group recently described the synthesis of chiral mesoporous carbonaceous materials (CIL-
C) based on the carbonization of chiral ionic liquids (ILs). In this poster, we are expand our
research and report the synthesis of new set of chiral mesoporous carbons materials, based on set
of chiral ionic liquids with new counter ion- 1-Butyl-1-methyl-pyrrolidinium-bis-
(trifluoromethylsulphonyl)-imide (NTF2) . In our study, we chose to use chiral ionic liquids
based on natural amino acids (Tyrosine, Phenylalanine, and Proline) as precursors for the
preparation of the chiral mesoporous carbons. In this work we have developed a new chemical
process that led to a new effective way for the preparation of chiral mesoporous carbon with high
yields (as shown in Figure 1).
Furthermore, we demonstrate the chiral nature of those mesoporous carbons by employing
various analytical techniques such as circular dichroism spectroscopy (CD), electrochemical
chronoamperometry (step potential) technique. Furthermore we examined the use of our chiral carbons
as enantioselective catalyst for the steroselective Aldol reaction.
Figure 1: a. HR-SEM images of a. Tyrions+BF-4 and b. Proline+BF-
4
References
[1] Fuchs, I.; Fechler, N.; Antonietti, M.; Mastai, Y. Enantioselective Nanoporous Carbon Based on Chiral Ionic
Liquids. Angew. Chem., Int. Ed. 2016, 55 (1), 408–412.
88
G-5
The effect of high pressure during spark plasma sintering (SPS) on the
microstructure of MgAl2O4
M. Sokol*, S. Kalabukhov and N. Frage
Department of Materials Engineering, Ben-Gurion University of the Negev,
Beer-Sheva, Israel
Corresponding author. E-mail address: [email protected]
HPSPS (up to 1GPa) technique was applied for fabricating polycrystalline magnesium aluminate
spinel (PMAS) at relatively low temperatures with short sintering time. The experimental results
on densification of PMAS indicate a strong effect of the applied pressure on the microstructure
and allows fabrication of nanostructured ceramics. Densification by SPS under high uniaxial
pressure has raised some fundamental questions related to the microstructure evolution,
densification and grain growth kinetics. The present work focuses on the understanding of
sintering behavior during HPSPS process, mainly on the stress induced grain growth mechanism.
The PMAS specimens fabricated by this low cost and time-saving approach display a good
combination of optical and mechanical properties; comparable with the best results reported in
literature for conventional fabrication processes.
89
G-6
Refractive index change due to electronic process and its application in sensing
and modulation
Tom Weiss1, *Rafi Shikler1
1Optoelectronic Organic Semiconductor Devices Laboratory (OOSDL)
Ben-Gurion University of the Negev, Dept. of Electrical and Computer Eng.,
Beer-Sheva 8410501, Israel P.O.B. 653
Corresponding author E-mail address: [email protected]
We present a novel Mach-Zehnder based design of a device that may act either as active modulator
or as sensor. The unique design offered allows for prominent phase accumulation larger than
expected considering physical device dimensions due to serpentine like path optimizing optical
path per surface. We demonstrate feasibility through loss simulations resulting from bend
radiation, reflection and absorption. We offer a coupling mechanism avoiding misalignment
between light-source and device altogether through a V-groove anisotropic etching allowing for
fixation of fiber source over substrate to perfectly align source with device input, since the latter
is fabricated according to the primer. The type of modulation\detection is determined according to
choice of active layer in the cladding, but may be of electro, magneto, thermos-optic or pressure
in nature. The mechanism is of a change in refractive index resulting from a polarization based
change due to electronic response to external source. The modulation is based on interference
between 2 identical beams propagating in different optical paths, determined by the type of active
layer and strength of modulation field. The physical length of the active layer allows for highly
sensitive detection or low voltage modulation, which lifts restraints over modulation and detection
rates. Relying on electronic processes allows for reaction times in the scale of 10−15𝑠𝑒𝑐 for
reorientation due to external sources and thus creating a polarization based effect. Polymers have
further advantages in that regard due to unique polarization characteristics, which by pooling
(thermally of electrically induced) incises the strength of our desired effects. The device will first
be examined as a single mode device, but can later be used in multimode operation as well once
effects of modulation over different modes is understood, with bend-modes serving a challenge in
that regard. Polymers tend to have wider transmittance bandwidths presenting further advantages
in modulation and in operation in general.
90
G-7
Carbon Nanotubes- Polythiophene Polymer and Fullerene Polythiophene:
From challenge of dispersion to incorporation in electrospunfiber.
Céline Bouniouxa, Ron Avrahamib, Gleb Vasilyevb, Nilesh Patilb, Alex Shames Eyal Zussmanb, Eugene
Katzc , Rachel Yerushalmi – Rozend, e
The process of spinning fibber of Polythiophene polymer-CNT and Polythiophene-Fullerene have
been challenging in the prospect of functional photo-active materials. Herein, we report two essential
advancements in the fabrication of functional fibber. First, we report a Single-step electrospinning of P3OT-
MWCNT, the processes as compared to previously reported host-guest or coreshell strategies for production
of conjugated-polymers fibbers allowed the procedure to be more suitable for commercial application.
Rheological characterization of the dispersions and structural analysis of the resulting in fibber indicate that
well dispersed CNT improve the spinnability of the polymer and enhance the crystallinity. In the second
step, we report that the incorporation of Fullerene provide the unusually light dependence of the phase of
the polaron of both PCBM and Polythiophene relative to the film plane in the fibber. This phenomena is
registered by the LESR spectra external magnetic field angular dependences.
a) Department of Materials Science and Engineering Faculty of Engineering & University
Center for Nano Science and Nanotechnology Tel Aviv University, Tel-Aviv, 69978,
Israel
b) Department of Mechanical Engineering, Technion, Haifa 32000, Israel
c) Department of Solar Energy and Environmental Physics, Jacob Blaustein Institutes for
Desert Research, Ben-Gurion University of the Negev, Sede Boker Campus 84990, Israel d) Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105,
Israel
e) The Ilze Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the
Negev, Beer-Sheva 84105, Israel
Corresponding email: [email protected]
91
G-8
Material Research Society (MRS) Tel Aviv University Chapter
Activity Report 2016
Demonstrations in the fields of Nanotechnology, Material Science and
Chemistry
Noah Metoki
a Biomaterials and Corrosion Lab, School of Mechanical Engineering & The Materials and
Nanotechnologies Program, Tel Aviv University, Ramat Aviv 62204, Israel.
The material research society (MRS) chapter in Tel-Aviv University is presenting its activity report.
The chapter was engaged with a lot of activity towards the community, and advancing scientific thinking
in young kids (ages 6-18).
The first project is exposing high school students to the applications of chemistry and nano-science, by
synthesizing with them in a short demonstration gold nanoparticles which are used as a detector for ionic
solutions. This project has been very successful, and we have reached hundreds of students in the past year.
The second project is the "Chemical garden". An experiment designed for smaller children,
demonstrating growth of crystals against gravity. These demonstrations will be starting over the summer in
kindergartens. The in situ growth of metal ion crystals inside sodium silicate solutions is overtaking.
Combined with the demonstration and explanation of the assumed mechanism, basic concepts in since, like
gravity and surface tension are demonstrated. The comparison to the experiment performs in space by Illan
Ramon, makes this experiment more appealing to young crowds.
Last but not least, we have recently responded to a request of our own undergraduate students to present
the abilities of applied research by showing the SEM and its abilities.
We invite you to come visit our poster and be a part of our enthusiastic vision! helping mold the next
generation of scientists.
92
ME-1
Scanning Tunneling Microscopy and Spectroscopy of Novel Silver-Containing
DNA Molecules
Natalie Fardian Melamed†, Gennady Eidelshtein‡, Roman Zhuravel†, Dvir Rotem†, Alexander B.
Kotlyar‡, and Danny Porath†*
†Institute of Chemistry and Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem
* Corresponding author. E-mail: [email protected]
‡Department of Biochemistry, Tel Aviv University
The quest for a suitable molecule to pave the way to molecular nano-electronics has been met with
obstacles for over a decade. Candidate molecules such as carbon nanotubes lack the appealing trait
of self-assembly, while DNA lacks the desirable feature of conductivity. Silver-containing
poly(G)-poly(C) DNA (E-DNA1) molecules were recently reported as promising candidates for
molecular electronics, owing to the selectivity of their metallization, their uniform structure, their
stability, their resistance to deformation, and their most possible conductivity. Here we present an
elaborate temperature dependent high-resolution morphology characterization of these unique
molecules, alongside a detailed depiction of their electronic level structure. Our findings were
acquired by use of an ultra-high vacuum (UHV) scanning tunneling microscope (STM). The
energy levels found for E-DNA indicate a novel, truly hybrid metal-molecule structure. These
findings2 add substantially to our knowledge about E-DNA molecules, leading to a further
understanding of these molecules’ conductive properties, bringing about their attractiveness as
nanowires.
Kalisman‐Levi , Gutkin V, Basmanov D, Klinov D, Rotem D,Melamed N‐FardianEidelshtein G, 1.
Containing DNA Molecules.‐Silver Y, Porath D, Kotlyar A. Synthesis and Properties of Novel
. 2016.Advanced Materials
, Eidelshtein G, Zhuravel R, Rotem D, Kotlyar A, Porath D. ScanningMelamed N-Fardian 2.
Tunneling Microscopy and Spectroscopy of Novel Silver-Containing DNA Molecules. (In
Preparation).
93
ME-2
Fabrication and characterization of MEH-PPV short channel
organic thin film transistors
Roy Goldman and Shachar Richter
Department of Materials Science and Engineering, Tel Aviv University, Tel-Aviv, Israel 6997801
We developed a process flow for the fabrication of a short channel OTFT and used these devices
to study the behavior of short channel MEH-PPV OTFT's. Three approaches have been
examined: A process for the fabrication of a bottom gate-coplanar short channel OTFT, and two
different processes for the fabrication of top-gate staggered structures with corbino shape. The
fabrication of the bottom-gate-coplanar device (type1) was successful. Devices with channel
lengths down to 450nm were fabricated and the channel length is tuned by a wet etch process of
the Gold electrodes. For the top-gate-staggered corbino devices (Type2 & Type3), we could not
integrate successfully the gate dielectric. In order to study the behavior of a bottom-gate-
coplanar short channel MEH-PPV OTFT, devices with channel lengths of 2400nm, 950nm and
450nm were fabricated and the output characteristics of these devices were measured. Devices
with channel lengths of 950nm and 430nm showed super-linear behavior and no saturation
regime was observed for all the 3 devices. Since the output characteristics of these devices
deviates from those of the conventional long channel devices, we cannot calculate the mobility
based on the transfer characteristics as usually done. Instead, the measured output plots were
fitted to a model suggested by Locci et al [86] for short channel OTFT's that take into account
the space charge limited current at the depletion region near the drain, and dependency of the
mobility in the longitudinal field. By fitting the plots to the model, the zero field mobility μ0 and
dependency factor γ in the longitudinal field were extracted. The extracted μ0 decreases as the
channel length decreases although it should be an intrinsic property of the material and its
morphology. A possible explanation for this result is that the model doesn’t take into account the
contact resistance which becomes significant compare to the channel resistance at these channel
lengths, and as a result the extracted mobility values effectively contain the parasitic low
conductivity of the contacts. Another possible explanation is that the morphology of the MEH-
PPV at the channel is related to the channel length.
94
ME-3
Tuning the Mechanisms of Electron Transport in Protein-Based Junctions
Ben Kayser*, M. Sheves, D. Cahen
Dept. of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel
In molecular electronics, electron transport mechanisms after often distinguished by length- and
temperature-dependence. Tunneling mechanisms are coherent processes and are generally
described as temperature-independent with a strong length-dependence whereas thermally-
activated sequential hopping is temperature-dependent with only a weak length-dependence.
Ascribing a particular mechanism to a process, given only length- and/or temperature-
dependence, is inherently unclear. Molecule-electrode (strong/weak) coupling, thermal
broadening of molecular levels and positioning of the molecular HOMO-LUMO levels in far/near
resonance could all contribute to a length or temperature effect. Given that most measurements
until now don’t include an electrostatic gate, interpretation of length- and temperature-
dependence alone is somewhat inconclusive.
A third terminal allows for the molecule’s energy levels to be shifted relative to the Fermi levels
of the electrodes, bringing it into (or into close proximity of) the resonance bias window. Control
over a molecule’s energy level positioning could give insight into the (possible) overlapping
contribution of electron transport mechanisms. By carrying out temperature- and gate-
dependent I-V measurements a conductance map can be generated to describe the contribution
of current in different regimes. Although this has been recently done for the first time with short
molecules1 (albeit with low junction yield, using break-junction techniques) it remains elusive in
the longer molecule regime that would necessitate hopping-like transport.
Studying the transition (or overlap) of multiple electron transport regimes will have great
implications on how we understand molecular signatures.
(1) Garrigues, A. R.; Wang, L.; del Barco, E.; Nijhuis, C. A. Electrostatic control
over temperature-dependent tunnelling across a single-molecule junction. Nature
communications 2016, 7.
95
ME-4
Chemical Bath Deposition of PbS for Infrared Absorbers
Olga Korchev Khina*1, Bhavana Gupta2, Iris Visoly-Fisher2
1Dept. of Materials Eng., 2Dept. of Solar Energy and Environmental Physics, Swiss Inst. for
Dryland Environmental and Energy Research, Blaustein Inst. for Desert Research
Ben-Gurion University of the Negev, Sede Boqer Campus 8499000, Israel
[email protected], [email protected], [email protected]
Infrared (IR) photosensors currently in use typically require high-energy production processes
(temperature, vacuum) and cryogenic cooling for operation. PbS is a semiconductor with high
absorption coefficient and a small bandgap that can be increased via decreasing the crystal size
beyond the Bohr radius. Consequently, IR absorbers made of PbS are expected to have a large
signal-to-noise ratio, can be used at room temperature for night and thermal imaging, and
efficiently harvest the IR portion of the solar spectrum. In this work, we focused on forming
homogenous PbS thin-films on flat and nano-wire (NW) structured Indium-Tin-Oxide (ITO)
substrates, for light absorption in the IR range. This was attained using the chemical bath
deposition method, which is an inexpensive, simple and environment-friendly growth technique.
We determined the conditions for PbS deposition – temperature, growth time and solution
concentrations – that provided complete, homogenous and adherent film coverage. We
characterized the resulting films using Scanning Electron Microscopy, Energy Dispersive X-ray
Spectroscopy, Ultra-Violet and Visible Spectroscopy, and electrical measurements. We
established that four-hour long deposition at room temperature lead to a complete coverage of a
bulk-like PbS film on ITO substrates. In the second part of this work, PbS was deposited on
CuSCN NW arrays towards the development of IR harvesting photocathodes for solar fuel
production by photoelectrolysis. Utilizing solar IR radiation, in addition to visible and ultraviolet
ones, is expected to improve the efficiency of solar water splitting.
96
ME-5
Analysis of Charge Accumulation in Pentacene Based Organic Transistors Using Kelvin Probe Force Microscope and Electrical Measurements
Roi Pinhas and Rafi Shikler*
P.O.B. 653 Beer-Sheva 8410501 Israel
e-mail: [email protected]
This research focuses on the switching behavior of an organic thin film transistor (TFT) based on
pentacene. Switching behavior is one of the important aspects of digital computation. One would
like to have fast switching that does not depend on the previous history of the device. Instead we
observed that in organic TFT the “on” switching depends on the time the transistor was in an “off”
state. We show that when the transistor is switched on an overshoot in the drain current takes place.
The amplitude of the overshoot depends on the duration the transistor was in the “off” state. We
present six cycles but this phenomenon is repeatable of the course of six months. We demonstrate
using Kelvin probe force microscope (KPFM) that this overshoot results from a discharge behavior
of a capacitor that was charged during the “off” state at the source-channel interface. We further
show that the time behavior of the current can be explained based on the stretched exponent model
that was also used to describe similar behavior in a-Si TFT.
97
ME-6
The electric and thermoelectric properties of different DNA sequences
Haim Rozler1* and Dr. Yonatan Dubi1,2
1Department of Chemistry and 2The Ilse Katz Center for Nanoscale
Science and Technology, Ben-Gurion University of the Negev,
Beer-Sheva 84105 Israel
E-mail: [email protected]
DNA has recently attracted considerable attention in the molecular electronics and
spintronics fields for its potential to transport charge in molecular electronics
applications. Recent experiments demonstrated the capability of using DNA-based
single-molecule junctions for electronic rectification and thermoelectric energy
conversion. A clear dependence between the DNA sequence and its electronic and
thermoelectric properties was observed.
In our work, we calculated the rectification and thermoelectric properties of
different DNA sequences containing 5 base pairs at 300 K, in search for the optimal
configuration for both cases. We find a maximal Seebeck coefficient and ZT values
reaching ~50 mV/K and ~0.1. The “optimal” sequences include a guanine base
contacting at least to one of the electrodes. A possible explanation is that the
HOMO orbital energy of the guanine base is the closest to the electrodes’ Fermi
energy, leading to efficient charge transport along the DNA chain.
98
ME-7
Electrical Characterization of 1D Molecular Structures
Avigail Stern1, Gideon I. Livshitz1, Dvir Rotem1, Suzanna Azoubel1, Shlomo Magdassi1, Genady
Eidelshtein2, Alexander Kotlyar2, Danny Porath1*
1Institute of Chemistry and The Harvey M. Krueger Center for Nanoscience and Nanotechnology, The Hebrew University of
Jerusalem, 91904 Israel
2Department of Biochemistry and Molecular Biology and the Center of Nanoscience and Nanotechnology, Tel Aviv University,
Israel
*Corresponding Author: [email protected]
Charge transport through 1D polymers is intriguing, but extremely challenging to research.
Detailed research of the mechanism of such transport has been detained, mainly due to shortage of
reliable charge transport measurements through such molecules. In order to supply this shortage a
reliable measurement setup, that is suitable for measurement of molecules tens to hundreds of
nanometers long, is required.
Recently, a new measurement setup was developed in our lab that answers this requirement. This
setup involves a stationary gold electrode that is evaporated over the molecules of interest and a
conductive AFM tip serving as a second mobile electrode that contacts single molecules protruding
from the gold electrode. We demonstrate the efficiency of this setup with two different types of
1D structures. The first is single-walled carbon nanotube junctions in a carbon nanotube network.
For these structures we demonstrated the effect of HNO3 treatment on individual junctions,
showing that the HNO3 improves the conductivity of each of the junctions. The second type of
structure was gold coated DNA, for which we showed that the thicker the gold coating is, the
longer the length of the molecule that is conductive.
99
ME-8
Proton "Hole" Conduction in Self-Assembled Cyclic Peptide Nanotubes
Subhasish Roy1, Ohad Silberbush1, Moran Amit1 and Nurit Ashkenasy*1, 2
1Department of Materials Engineering, Ben Gurion University of the Negev, Beer- Sheva-8410501,
Israel, 2The Ilse Katz Institute for Nanoscale Science & Technology, Ben Gurion University of the Negev,
Beer- Sheva-8410501, Israel, [email protected]
The quest for the development of environmental friendly materials has accelerated research into the
structure, chemistry and functionality of biomaterials. Such materials may serve for preparing devices for
renewable energy applications. Owing to chemical diversity, ease of synthesis and unique propensity to
self-assemble to form nanofibrils and nanotubes, peptides are particularly attractive for the development of
proton exchange membrane for energy conversion and storage devices. Incorporating free amine side chains
into the peptide sequences can be used to promote "proton hole" conduction. The effect of different basic
amino acids on proton conduction of alternating D,L α-cyclic peptide self-assembled nanotubes will be
presented here.
We designed and synthesized cyclic alternating D,L-alpha- octapeptides containing phenylalanine in their
four L-amino acid positions, and one of the natural basic amino acids in their four D-positions, (Fig. 1).
These alternating D,L α-cyclic peptides were found to undergo self-assembly to form nanotubes at water-
acetonitrile mixture at room temperature. Current-voltage measurements show an exponential dependence
of the conductance through these peptide nanotubes on the relative humidity. Upon changing the electrode
from gold to PdHx a huge enhancement of conductance is observed due to enhanced proton injection into
the peptide-based nanotubes. Impedance spectroscopy measurements also support the observed
conductance trends. These observations demonstrate that proton transport dominates the conduction.
Interestingly, the conductivity of c(KF)4 is higher than that of the other two peptides. Moreover, c(KF)4
shows efficient conduction at higher temperatures, in the range of 100-140 ̊C, indicating that the nanotubes
may be used for high temperature fuel cell construction. These findings present the promises endorsed in
using peptide as building blocks for the development of future generations of biocompatible proton-
conducting materials.
100
ME-9
Towards electrical transport measurements through single DNA molecules
Roman Zhuravel1, Haichao Huang1, Haya Dachlika1, Avigail Slutzkin1, Dvir Rotem1, Shalom
Wind2 and Danny Porath*1
1 Institute of Chemistry and The Harvey M. Krueger Center for Nanoscience and Nanotechnology, The Hebrew
University of Jerusalem, Israel
2 Department of Applied Physics and Applied Mathematics Center for Electron Transport in Molecular
Nanostructures, Columbia University, New York, USA
The field of Nano-electronics concentrates a lot of interest from technological and scientific
point of view. The technological interest is obvious as the semi-conductor industry approaches the
nanometric scales and seeks for further device miniaturization. It raises many scientific questions
and challenges, one of them is understanding the charge transport in single molecules. While
charge transport in the solid state has been widely researched, for large single molecules many
fundamental questions remain unsolved.
DNA is a good model molecule for many polymeric systems and its structure suggests the
possibility for significant charge transport. Charge migration along DNA molecules has attracted
scientific interest for over half a century. However, due to the many free parameters concerning
these experiments, a variety of results were achieved triggering an ongoing scientific debate on the
DNA molecule conductivity. Our goal in this research is to eliminate as many degrees of
freedom as possible.
We create dimers of gold nanoparticles bridged by exactly one DNA molecule. Each
nanoparticle is connected to the DNA trough one thiol. This system is very well-defined with
minimum number of unknown parameters. The dimer is brought to a small gap between pointing
electrodes by dielectrophoresis for further electrical characterization. Our system enables precise
measurements with very good control of many environmental parameters such as temperature,
atmosphere etc. These measurements have already generated promising preliminary results.
101
ME-10
Proton and Electron Conduction in Self-assembled Amyloid β-Based Peptide
Nanostructures
Moran Amit,a,* Nurit Ashkenasya,b
aDepartment of Materials Engineering and bThe Ilse Katz Institute for Nanoscale Science and
Technology, Ben-Gurion University of the Negev, Beer-Sheva, Israel
Inspired by the efficacy of charge transport in natural systems, the possibility of using peptides
- short man-made proteins - as electronic materials, seems to be very attractive. Synthesis
flexibility together with the ability of peptides to self-assemble into nanometric structures enables
exploiting the advantages of both natural and synthetic organic materials. However, there are still
open questions regarding charge transport phenomena in peptide nanostructures and the factors
affecting them.
This research sheds light on the nature of charge transport in fibrous networks of amyloid β-
based peptides, and the structural and environmental conditions that affect it. We demonstrate that
the electronic conduction of the peptide nanostructures is improved by introducing non-natural
amino acids or side chains to the peptide sequence.1,2 Furthermore, we show that in similar to
natural systems, both proton and electron charge carriers exist in these systems.3 The effects of
self-assembly conditions on the resulting morphology, and hence, the charge conduction are
discussed. Particularly, we show that the finer and more homogenous the peptide fiber morphology
is, the higher are both the conductance and its dependence on the relative humidity.1,3 Finally, we
show that proton blocking electrodes as Au and Pd could still be used to extract proton current.
This process could be improved by the use of AC voltage or the hydrogenation of the Pd electrodes.
This research proves that by precise control of the peptide sequence, the procedure parameters
used for the self-assembly, and the design of the electrodes, peptide fibrils can serve as a novel
class of nano-materials in bioelectric applications.
References: 1 Moran Amit, Ge Cheng, Ian W. Hamley, and Nurit Ashkenasy, Soft Matter 2012, 8, 8690. 2 Moran Amit and Nurit Ashkenasy, Isr. J. Chem. 2014, 54, 703. 3 Moran Amit, Sagi Appel, Rotem Cohen, Ge Cheng, Ian W. Hamley, and Nurit Ashkenasy, Adv. Funct. Mater. 2014,
24, 5873.
102
ME-11
Permanent top contact protein junction’s
Jerry A. Fereiro1*, Sabyasachi. Mukhopadhyay1, David. Cahen1, Mordechai Sheves 2 1
Weizmann Institute of Science, Dept., of Materials and Interfaces1, Organic Chemistry 2. Keywords:
Bioelectronics, Proteins- junctions, electron transport mechanism(s).
Bio-electronics is the investigation of single (layers of) bio-molecules as elements of an electronic circuit.
Interest in bioelectronics, i.e., exploring the possibility of using biomolecules as part of electronic circuits
has, in the past couple of decades, joined forces with the fundamental scientific pursuit of achieving basic
understanding on natural phenomena involving charge transport such as photosynthesis and respiration
(1). In biomolecules, proteins enjoy particular attention due to their natural diversity in structure and
function. Surprisingly, it was found that proteins can be quite efficient electronic conductors, comparable
to conjugated organic molecules of the types used in organic electronics as described in selected
references below (2,3).
We study the electron transport (ETp) characteristics of OTG-BR Protein monolayers modified on highly
doped p++ Si surface with thermally deposited lead(Pb) as permanent top contact to complete the Nano-
fabricated cross junction device. The well established procedure to modify the Si surface with proteins
has been used, here the bottom will serve as one of the contacts. The initial experiments involve the
fabrication of the protein devices (see figure above) and then use the fabricated junctions for studying the
electron transport mechanism. Solid state variable temperature measurements (i-vT), measurement was
carried out for understanding the electron transport mechanism. The results obtained from this experiment
compared with the number of other soft top contact methods, available in the group such as LOFO and
Hg drop remain consistent. Surface analysis measurements has been carried out at each step of modifying
the Si surface with the protein monolayer.
A special advantage of “hybrid” devices combining molecular and silicon components which I hope to
pursue is chemical analysis, in which the protein component binds with a chemical or biological agent to
change the electronic properties of the underlying silicon.
References: (1) Giese, B. Long-distance electron transfer through DNA. Annu. Rev. Biochem. 71,
5170(2002). (2) Amdursky, N. et al. Electronic transport via Proteins. Adv. Mater. 26, 7142-7161 (2014).
(3) Sepunaru, L. et al. Solid-state electron transport across Azurin: from a temperatureindependent to a
temperature-activated mechanism. J. Am. Chem. Soc. 133, 24212423(2011).
103
ME-12
Integrating Proteins into Electronics
Sabyasachi Mukhopadhyay,1,2* Sidney R. Cohen,3 Israel Pecht,4 Mordechai Sheves2
and David Cahen1
Department of 1Materials and Interfaces, 2Organic Chemistry, 3Chemical Research Support Unit
and 4Immunology
Weizmann Institute of Science, Rehovot, Israel
E-mail: [email protected]
Molecular electronics is advancing toward the goal of functional molecular devices suitable for niche
applications. We are investigating proteins as potential building blocks for future optoelectronic devices,
based on our results showing of efficient electronic conduction significantly higher than for which is non-
conjugated organic molecules. We address several questions, such as: “How general is the electron transport
behavior across proteins? What mechanisms enable efficient conduction across large bio-molecules?” To
answer these questions we have measured and analyzed electron-transport and optoelectronic performance
at micro- and nano-scales for Halorhodopsin and Bacteriorhodopsin proteins, and consider the influence of
cofactors and protein-electrode interaction. We found that electron transport through monomeric
bacteriorhodopsin protein (bR) occurs through a tunneling process and that the protein does not denature
between 80K and 380K. The resistance decreases with force up to 40 nN. At the lowest applied force (6
nN), green light (562nm) illumination leads to a decrease in resistance of 25% on average, showing that bR
remains photo-active in the bound, solid-state configuration. This photoconductivity effect increases both
as a function of temperature, humidity and applied force. In Halorhodopsin (phR), electrode-bactrioruberin
coupling facilitates efficient temperature independent current flow across the contacting interfaces by
tunneling via superexchange between the protein terminals that contact the electrodes. Such a scenario is
consistent with the temperature-dependent ETp of apo(ruberin)-phR monolayer, where bacterioruberin was
chemically oxidized, eliminating its conjugation. Taken together the present results suggest that ETp in phR
is cooperatively affected by both retinal and bacterioruberin. Efficient bio-photovoltaic and bio-transistors
employing different hetero-protein complexes could be achieved via solid state protein-electronic devices.
References:
1. S. Mukhopadhyay, S. R. Cohen, D. Marchak, N. Friedman, I. Pecht, M. Sheves and D. Cahen, ACS Nano
8 (8), 7714-7722 (2014).
2. S. Mukhopadhyay, S. Dutta, I. Pecht, M. Sheves and D. Cahen, J. Am. Chem. Soc. 137 (35), 11226-
11229 (2015).
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Solid State Electron Transport via Myoglobin Protein and the role of substrate-
protein coupling in such systems1
David Cahen Sheves,, Israel Pecht, Mordechai Sara Raichlin
Depts. of †Materials and Interfaces, ‡Organic Chem., §Immunology, Weizmann Inst. of Science, Rehovot 76100
Corresponding author: Sara Raichlin
Phone: +972-8-934-2340
Integrating proteins into electronic junctions is a challenging research task, which combines nano-science
and -technology, biophysics and bio-electrochemistry, but which allows us to learn about electron transport
through biomolecules. A potentially practical future goal may be the use of proteins as building blocks to
develop multi-functional electronic devices for applications, such as biomedical ones, biofuel cells and
biosensing devices.
The current density that can flow at a given voltage across a protein is a key parameter which does not only
depend on the specific protein, but also on the protein / contact interface. To unravel and understand those
factors we examined the effects of protein modifications on ETp, and Myoglobin, Mb, an oxygen carrier in
the vertebrate’s muscles, is a protein that aloows such experiments. Mb consists of a Hemin prosthetic
group which has Fe at its center. First, the concept of proteins secondary structure preservation in the dry
state was proven. In addition, the involvement of the Heme site in the ETp path was measured by using
Myoglobin derivatives (WT, Apo and Fe-free Mb) as well as the importance of the Hemin coupling to the
surface by electrically wiring the protein to the surface.1 At last, the role of types of contacts on the resulted
ETp in various devices configurations was examined as well as the comparison between the protein-
substrate coupling performance on highly doped Si and Au substrate. Such experiments are starting to allow
us to draw conclusions about which substrate show the best protein-substrate coupling and by doing that to
optimize control over ETp and its mechanism, across the proteins.
1 Raichlin, S.; Pecht, I.; Sheves, M.; Cahen, D. Angew. Chemie Int'l. Ed. 2015, 54, 12379.
105
NF-1
Heterogeneous sub-20nm nano-arrays by nanoimprint lithography
Yossi Keydar *, Mark Schvartzman
Department of Materials Engineering, Ben-Gurion University of the Negev,
Beer-Sheva 8410501 [email protected]
Nanoimprint lithography (NIL) is enables high-throughput and ultra-high resolution. Yet,
it can pattern only one material. To produce heterogeneous nonpatterns, multiple steps of
lithography and pattern transfer are required. Furthermore, alignment between different
lithographic layers, which is usually done optically, is limited by diffraction , and precludes layer
registration at the nanoscale.
Here, we demonstrate a novel approach for nanoimprint of heterogeneous nanopatterns in
single lithographic step, which enables nanoscale registration between layers. An array of
nanoimprinted 20-nm dots in thermal resist (PMMA) was covered by angle-deposited hard Ti
mask. The pattern was transferred by O2 plasma, sequential evaporation of two different metals,
and liftoff. The resulting nonpattern consists of pairs of two metals, whose overlapping or
separation is controlled by the deposition angles (Fig1). Larger spacing between the dots can be
achieved by a deposition of a sacrificial layer and its etching (Fig 2).
Our novel approach enables various applications, including heterogeneous hybridized
plasmonic nano-arrays, complex metamaterials, and heterogeneous platforms for molecular
functionalization. In particular, we to orthogonally functionalize these heterogeneous arrays with
different ligands for cellular transmembrane receptors. This will allow next-generation molecular
–scale biomimetic devices for the study and regulation of crosstalk between different signaling
pathways in stem cells and immune cells
figure 3 deposition
angles
figure 2 pairs of separated dots achieved by a deposition of a sacrificial layer
106
NF-2
Imprinting chirality in silica nanotubes by N-stearoyl-serine template
Gila Levi,1* Yosef Scolnik,2 and Yitzhak Mastai1
1Department of Chemistry and Institute for Nanotechnology and Advanced Materials, Bar-Ilan
University, Ramat Gan 5290002, Israel
2IYAR, The Israeli Institute for Advanced Research
E-mail: [email protected]
Chiral inorganic porous materials are of high interest for many chiral applications, such as chiral
separations and asymmetric synthesis. Various methods have been developed for the preparation of
chiral mesoporous silicas (CMS), mostly based on the chiral template approach.1, 2
In this article, we describe the synthesis of imprinted chiral silica nanotubes based on the use of a chiral
N-stearoyl L-serine (C18Ser) anionic surfactant as the chiral template. The resulting chiral silica nanotube
structures were characterized by electronic microscopy and nitrogen isotherms that proved the formation
of well-ordered silica nanotubes. A C18Ser surfactant template was used for the preparation of the silica
nanotubes, due to its effective molecular organization within the silica network. After chemical extraction
of the chiral template, the enantioselectivity feature of the silica nanotubes was confirmed by selective
adsorption of the enantiomers using circular dichroism (CD) and isothermal titration calorimetry (ITC)
measurements. Although these measurements show a relatively low chiral selectivity of the silica
nanotubes (ca. 6% enantiomeric excess), the system described here offers new approaches for the
application of chiral porous materials in chirality.
Figure 1. a. ESEM and b. HR-TEM images of the As-SiO2-C18Ser. References
(1) Gabashvili, A.; Medina, D. D.; Gedanken, A.; Mastai, Y. J. Phys. Chem B. 2007, 111 (38), 11105-11110.
(2) Fireman-Shoresh, S.; Popov, I.; Avnir, D.; Marx, S. J. Am. Chem. Soc. 2005, 127 (8), 2650-2655.
a b
107
NF-3
Microstructures formation using Standing Surface Acoustic Waves
Haim Sazan*1, Michael Layani2, Silvia Piperno1, Shlomo Magdassi2, Hagay Shpaisman1
1The Nanotechnology Institute, Chemistry Department, Bar-Ilan University, Ramat-Gan, Israel
2Casali Institute for Applied Chemistry, Institute of Chemistry, The Hebrew University of
Jerusalem, Jerusalem 91904, Israel
In this research, I study how standing surface acoustic waves (SSAWs) affect the formation
of structures from suspended nanoparticle solutions and control chemical reactions. Recently,
SSAWs were used to selectively promote coalescence and to create ordered colloidal crystals and
metamaterials. SSAWs could be used to create new microstructures – metallic, polymeric and
hybrid (organic-inorganic) materials and to control surface reactions. Under the exposure of
SSAWs, nanoparticles in a microfluidic channel would be forced towards pressure nodes (for
particles with a positive acoustic contrast factor in the medium). If the acoustic force pushing them
together is stronger than the electrostatic forces arising from their charges, coalescence and partial
fusion could occur. When the system partly fuses, we predict that microstructures will be formed
following the contour of the nodes.
I investigate the formation of microstructures by silver nanoparticles sintering. These
nanoparticles can be sintered at room temperature with exposure to chloride ions. Streaming the
silver suspended nanoparticles with chloride ions solution under the SSAWs field could sinter the
particles in a micro-fiber shape.
Another project is controlling chemical reaction, such as crystallization growth of titanium
oxide, by SSAWs exposure. As opposed to the silver nanoparticles sintering where the
nanoparticles are being arranged instantly by the acoustic waves and then the stabilizer is removed
to form nano/microstructures, here crystals grow along the pressure nodes lines.
Email: [email protected]
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NF-4
Magneto-Lithography, a Simple and Inexpensive Method for High-Throughput, Surface patterning
Amos Bardea1* and Alex Yoffe2
1.) Faculty of Engineering, Holon Institute of Technology (HIT), Holon, Israel.
(e-mail: [email protected])
2.) Department of Chemical Research Support, Weizmann Institute of Science, Rehovot,
Israel.
Magneto-lithography (ML) is based on patterning magnetic field on a substrate, using
paramagnetic or diamagnetic masks that defines the shape and strength of the magnetic field. We
demonstrate the use of various methods of ML for common microelectronic processes such as
etching and deposition. In principle, high resolution can be obtained by applying simple and
inexpensive tools. Hence, ML has the potential to become the method of choice in the future, both
in the microelectronic industry as well as for chemical patterning of surfaces. The first step in ML
is to pattern the magnetic field strength on the substrate, using a permanent magnetic field applied
perpendicular to the substrate and paramagnetic (or diamagnetic) masks that define the spatial
distribution and shape of the magnetic field on the substrate. The second component in ML is
assembly of ferromagnetic nanoparticles (NPs) onto the substrate in a pattern defined by the field
induced by the mask. After processing, namely, either deposition or etching, the NPs are washed
away.
The ML technique was shown in the past to provide a simple and fast way for chemical and
biomaterial patterning of surfaces. The technique is much simpler and less expensive to apply than
common photolithography. ML does not depend on the surface topography and planarity and that
it can be used for patterning non-flat and the inside surfaces of a closed volume. ML method opens
up new possibilities in high-throughput surface patterning.
109
NF-5
Inversion Schottkey Diode as Working Mechanism of High Voltage CH3NH3PbBr3(Cl)-Based Solar Cells
Michael Kulbak, Nir Kedem, David Cahen* and Garry hodes*
Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel 7610001
* [email protected], *[email protected]
The working mechanism of high Voc ( >1.3 V), single junction, methylamonium lead tri-bromide
(MAPbBr3)nhalide perovskite (HaP) based solar cells is studied in detail. Single junction high Voc
devices are of interest for solar spectrum splitting and driving photo-electrochemical reactions for
energy storage applications. Resolving the working mechanism of HaP based devices as well as
measuring critical parameters such as excited minority carrier diffusion length and space charge
region width (SCR) are of great importance for our basic understanding of the device physics as
well as any future improvement of performance. For this study, devices are prepared as thin film
devices, i.e. a layered stack of Glass/FTO/TiO2/MAPbBr3/HTL/Metal electrode, where HTL
stands for Hole Transport Layer and the metal was interchanged between Pb, Au and Pt. The metal
electrodes were selected for their WF with WFPb = 4.25 eV, WFAu = 5.1 eV and WFPt = 5.6 eV
In continue to previous work1, where we find MAPbBr3 based devices to be a pn-junction device,
we now track he formation of the junction and the contribution of each of the layers to formation
of the Voc. Using light response in Kelvin Probe measurements, J-V measurements, and Electron
Beam Induced Current we find that the metal electrode work function (WF), and not the selective
contacts, is the most important parameter for the formation of the built in voltage. Without the
metal electrode, or using the low WF Pb electrode, a very low photo-response is indicated.
Furthermore, with increase of the metal WF, a shorter SCR and lower minority carrier diffusion
length are found, both indicating higher doping of the HaP. We therefore postulate that the high
WF metal inverts the HaP film from slightly n- to p-type and facilitates the formation of the pn-
junction. This study suggests that interface engineering such as WF modification or high WF and
highly doped selective contacts would be required in order to retain high Voc when using low cost
and low WF metal electrodes in future technology.
1Kedem et al., Light-Induced Increase of Electron Diffusion Length in a p–n Junction Type CH3NH3PbBr3 Perovskite
Solar Cell, J. Phys. Chem. Lett., 2015, 6 (13), pp 2469–2476
110
NF-6
Tuneable light-emitting carbon-dot/polymer flexible films for white light
application
Dr. Susanta Kumar Bhunia,1 Dr. Rafi Shikler,2 Prof. Raz Jelinek*1,3
1 Department of Chemistry, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
2 Department of Electrical and Computer Engineering, Ben Gurion University of the Negev, Beer
Sheva 84015, Israel
3 Ilse Katz Institute for Nanotechnology, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
Carbon dots (C-dots) constitute newly discovered fluorescent nanoparticles exhibiting great
promise as bioimaging agents and as well as potential luminescent sources in light-emitting
devices and photonic systems and as substitutes for inorganic semiconductor quantum dots due to
their biocompatibility and less cytotoxicity. C-dots are quasi-spherical nanoscale (<10 nm)
particles and have attracted significant research interest due to their unique structural and
photophysical properties and applications in nano-biotechnology and solid state illumination
device. Moreover, C-dots are chemically stable and display broad excitation/emission spectral
ranges and low photobleaching, which are favorable characteristics for bioimaging, lighting
industry and optical technologies.
We present a simple strategy for the fabrication of flexible transparent films exhibiting
tuneable light emission through one-pot synthesis of polymer matrixes with embedded carbon dots
assembled in situ. Importantly, different luminescence colours (interestingly white light) were
produced simply by preparing C-dot/polymer films using carbon precursors that yielded C-dots
exhibiting distinct fluorescence emission profiles.
UV excitation
Different carbon dot fluorescent film
111
NF-7
Soft Thermal Nanoimprint Lithography
Liran Menachem , Mark Schvartzman*
Department of Materials Engineering, Ben-Gurion University of the Negev
Nanoimprint lithography (NIL) can be performed using two types of resists. In the UV
nanoimprint, a liquid UV curable resist film is embossed at the room temperature, and hardened by UV-
crosslinking. Such resists can be imprinted either by rigid or soft (elastomeric molds). In thermal
nanoimprint, a film of thermoplastic resist is embossed when heated above its glass transition
temperature. This type of nanoimprint is not compatible with soft molds, whose relief features would
deform while pressed against the highly viscous molten polymer. This limitation precludes many
application of thermal NIL, such as ultra-high resolution nanopatterning of curved surfaces.
In this work, we introduce a novel concept of hybrid Soft-Substrate-Rigid-Feature (SSRF) nano
imprint mold, which is based on soft substrate with rigid relief features.
The SSRF mold was fabricated by electron-beam lithography of Hydrogen Silsesquioxane (HSQ) on a
sacrificial substrate, followed by transferring the obtained HSQ features to elastomeric PDMS substrate.
Anti-adhesive coating, which is usually used for hard Si based molds, was successfully applied on SSRF
mold, and was shown to be essential for robust demolding after the imprint.
SSRF molds were used to imprint thin films of Polymethyl Benzacrylate – a thermal resist with
the glass transition temperature around 60 oC. This is, for the best of our knowledge, the first time that
a thermal NIL was done with soft elastomeric molds. Furthermore,tTo demonstrate the uniqueness of
our approach, we thermally imprinted PBMA films applied on lenses.. In summary, we demonstrate here
a novel concept of facile and robust mold for thermal nanoimprint lithography, which will pave a way to
the broad variety of applications impossible up today.
112
NF-8
MATRIX-ISOLATED NANOCOMPOSITES - ALUMINA-SILICON
FLOCCULANTS-COAGULANTS
Kudryavtsev P.1, Kudryavtsev N.2 1 Professor, HIT Holon Institute of Technology, 52 Golomb Street, POB 305 Holon 5810201,
Israel, e-mail: [email protected] 2 Polymate Ltd - Israel Research Center, POBox 73, Migdal HaEmek 10550, Israel, e-mail:
Aluminum-silicon flocculant-coagulant ASFC is one of the few binary compositions, composed of
only inorganic components: a coagulant - aluminum sulfate and an anionic flocculant - active silicic acid.
Action ASFC based on the reaction of the primary components ASFC - coagulant aluminum compound
and flocculant active silicic acid. Complex compounds are formed with higher flocculating ability. There
is a synergistic effect - an increase the efficiency of the impact, as a result of integration of individual
processes into a single system.
However, existing methods to date, allowed receiving such materials only in the form of solutions.
Thus, their lifetime is not more than 2-3 weeks. This factor is holding back the practical use of ASFC, in
industrial practice for wastewater treatment.
The task was solved with a processing of aluminum-silicon raw material with sulfuric acid,
separating the liquid phase from the solid and liquid phase dehydration. Processing of raw materials was
carried out with concentrated sulfuric acid under conditions effective to obtain a concentrated 20-30% or
more of an aqueous solution of flocculant-coagulant. Dehydration of the resulting solution to obtain a dry
product, carried out at a temperature below the boiling point of water by evaporation under vacuum, or by
dispersing in a high-temperature high-speed gas stream of coolant. The resulting product is dried and
separated from the coolant at a temperature below the boiling point of water.
These processing methods have allowed “freezing” and isolating the solid phase matrix components
produced flocculant-coagulant, which are in a nanodispersed state. Quick transfer of active ingredients in a
solid state can dramatically reduce the rate of diffusion processes and, thus, preserve the activity of the
material.
Experiments have shown that the material thus obtained can be stored for a long time. For some
samples were observed to preserve 90% of the activity for over 2 years. For effective water treatment the
reagent is required in much smaller quantities. An important feature is the use of powdered ASFC in water
treatment from oil.
113
NP-1
Continuous Formation of Hybrid Colloids by Optical Traps
Eitan Edri* & Erel Lassnoy**, Hagay Shpaismann
Chemistry Department, Institute for Nanotechnology and Advanced Materials
Bar-Ilan University, Israel
Recently we have demonstrated how optical traps can influence colloidal formation by coalescence
or partial fusion of nucleation seeds and oligomers during emulsion polymerization, leading to
control over size and shape of the colloids.
Here, we show how this approach could be further developed towards formation of organic/in-
organic hybrid microstructures. This is achieved by introducing optical traps to a heterogenic
environment of an organic monomer emulsion and a suspension of inorganic nanoparticles. Due
to the radiation pressure the nanoparticles are physically adsorbed on the surface of the growing
polymeric structure. Endless hybrid combinations could be designed as there is no a-priori
requirement on the chemical affinity between the organic matrix and inorganic nanoparticles.
Furthermore, we present a novel method that allows continuous controlled fabrication by optical
traps of colloids. We use the Holographic Optical Trapping (HOT) method to form multiple optical
traps inside a micro-fluidic device. As the emulsion/suspension flows through the micro-channel,
multiple colloids are formed at the location of the optical traps. Once the drag forces on a colloid
exceeds the trapping force it will leave the optical trap, and a new colloid will start forming. This
novel lab-on-chip approach will allow us to fabricate tailor made on demand colloidal suspensions.
114
NP-2
Fluorescent nanofibers for white light emission applications.
Michal Golan 1,2 Roman Nudelman1,2 , Shachar Richter*1,2
12Center for Nanoscience and nanotechnology
3 Department of Material Science and Engineering Faculty of Engineering
Tel- Aviv University, Tel-Aviv, Israel,
A significant fraction of the global electricity demand is for lighting, white light is in the most common use.
This days the widely used for a standard white light LED is composed of Blue Gallium Nitrogen (GaN) LED
(440-470nm emission) with a coating of red and green phosphors-based compound.
Phosphorous is a vital element for all living organisms, there are only 5 countries that control 90% of the
World's phosphate reserves, simultaneal there is increase growth rate in the phosphorus production from
year to year. Therefor studies number that the reserves of phosphate will be depleted within 50-120 years.
In this study we focus on the development of P-free White light-emitting coating. For this task we utilize
electrospinning technique to make light emitting fibers. These are composed of a PVA and a mixture of
different hydrophilic dyes and quantum dots. The properties of the fibers could be controlled by means
of the experimental parameters: applied voltage, needle-collector distance, needle diameter, flow rate
and compound blends concentrations.
115
NP-3
Sub-micron photoluminescence degradation study in F8BT/PFO by Near-field
scanning optical microscopy
Shiran Nabha-Barnea1,*, Nitzan Maman2, Iris Visoly-Fisher2, 3, Rafi Shikler1, 3
1Dept. of Electrical and Computer Eng., 2Dept. of Solar Energy and Environmental Physics,
Swiss Institute for Dryland Environmental and Energy Research, The Jacob Blaustein Institutes
for Desert Research, 3Ilse Katz Inst. For Nano-Science and Eng.,
Ben-Gurion University of the Negev, Be'er Sheva 8410501, Israel
*Corresponding author E-mail address: [email protected]
We have studied degradation processes of the photoluminescence (PL) on a sub-micron length-
scale in a polyfluorene blend, F8BT/PFO, phase-separated film using near-field scanning
microscopy (NSOM). We have visualized the time dependence of the spatial distribution of the
PL of blend compositions that do not exist macroscopically in equilibrium. The emission from
both the PFO-rich phase and the F8BT-rich phase was dominated by green fluorescence due to
efficient energy transfer from PFO to F8BT. In the initial NSOM scans, the topography and the
PL mapping were anti-correlated, as the emission was dominated by the lower-lying matrix phase,
identified as the PFO-rich phase. This behavior changed at longer illumination time, where the
emission was dominated by the higher-lying, protruding F8BT-rich phase, i.e., the topography and
PL were correlated. Using macroscopic investigation of the mechanisms that govern the PL
process, from absorption of light through energy transfer to PL, we could explain the time-
dependence of the spatial distribution of the PL: while the degradation of F8BT was driven by
photo-bleaching and the absorption remained almost unchanged, both faster absorption and photo-
bleaching processes dominate the degradation of PFO. Hence the efficiency of the energy transfer
from the PFO to the F8BT is hampered resulting in the observed contrast change. This implies that
energy transfer does not protect the PFO from degradation and does not improve its resistance to
oxidation, thus, as the concentration of the PFO increases in blend films, the degradation rate
gradually increased.
116
NP-4
Nonlinear Wave Mixing in Plasmonic Structures: A Transformation
Optics Approach
K. Nireekshan Reddy1, Antonio I. Fernandez-Dominguez2 and Yonatan Sivan1*
1) Unit of Electro-Optic Engineering, Ben-Gurion University, Beer-Sheva 8410501,Israel
2) Departamento de Fisica Teorica de la Materia Condensada, Universidad Autonoma de
Madrid, E-28049 Madrid, Spain.
Singular structures in plasmonics, for example, touching wires, crescent cylinders, etc., are well
known for enhancing the field in small volumes by several orders of magnitude. Recent studies
revealed that transformation optics can provide a very powerful analytical tool to solve these class
of problems. It was also pointed out that these class of structures can also be suitable candidates
for energy harvesting and field enhancements were calculated to be as high as 104 close to singular
points. We review some of the theoretical and the experimental results of the linear properties of
these structures.
Such high field enhancement would definitely invoke the nonlinear phenomenon. Our present
study analytically incorporates such nonlinear phenomenon from χ(2) materials initially focusing
on second-harmonic generation. We follow the route of conformal transformation optics but now
extending it to nonlinear materials. To the best of our knowledge there have been no reports on
such analytical techniques describing nonlinear optics at nanoscale. We identify the relations for
phase and amplitude matching for the second-harmonic fields. Our approach also connects with
the standard coupled-mode theory used in “macro-optics” structures such as waveguide to the
Green’s function approach which is extensively used in nano-optics. We identify the optimal
conditions for second-harmonic generation efficiency. This approach is the starting point to
understand various other nonlinear interactions such as three and four-wave mixing in singular
structures.
References:
[1] J. B. Pendry, A. Aubry, D. R. Smith, S. A. Maier,Transformation Optics and Subwavelength
Control of Light,” Science 337, 549 (2012).
117
NP-5
“Hybridization between Nano Cavities for Polarimetric Color Sorter at the Sub-Micron Scale”
Elad Segal a, Adam Weissman a, David Gachet b, and Adi Salomon a*
a Department of Chemistry, Institute of Nanotechnology and Advanced Materials, Bar-Ilan
University, Ramat-Gan 52900, Israel.
b Attolight AG, EPFL Innovation Park, Building D, 1015 Lausanne, Switzerland.
*Corresponding author E-mail: [email protected]
Color generation is commonly pigmentation-related and is spatially limited to tens of microns, two
orders of magnitude above the diffraction limit. Colors can also be generated with interference
devices such as photonic crystals and subwavelength plasmonic structures. The latter are suggested
as the next generation for color display, because they have the potential to reach the diffraction
limit resolution using advanced fabrication techniques. Furthermore, light can be efficiently
manipulated by such plasmonic structures followed by polarization for instance. Plasmonic
nanostructures such as hole arrays, grooves, disks, and slits have been shown to generate colors
efficiently, and have the potential to function as dynamic color pixels. Yet, their size is still limited
to several microns. Therefore, we exploit the plasmonic-hybridization of nano cavities milled in
metallic films which encounter mutual coupling. Following hybridization, new states are formed:
the ‘in-phase’ and ‘out of phase’ states, in analogy to molecular orbitals. The polarization state of
the incoming optical field modifies the charge distribution around the cavities, thus, one can
actively achieve the whole energy landscape of the optical range.
Herein, we report on such active, sub-micron plasmonic devices. To examine the whole structure
which acts as a unified entity, we utilize both optical far field microscopy, alongside
cathodoluminescene (CL) spectroscopy. The properties of these plasmonic devices are unique and
related to the interactions between the neighboring cavities. We present a thorough study of the
modes which give rise to the enhanced mutual coupling between these cavities. This examination
is possible due to spatial mapping of the photon emission for a given energy, which can easily be
obtained by CL - providing a direct way to probe the local electric field.
118
NP-6
Genetic Algorithms based Design of Spectral Response of Nanostructures for Super Resolved Microscopy Applications
Chen Tzur1, 2 and Zeev Zalevsky1,2
1Faculty of Engineering, Bar Ilan University, Ramat-Gan 5290002, Israel
2The Bar-Ilan Institute of Nanotechnology & Advanced Materials, Bar Ilan University, Ramat-
Gan 5290002, Israel
Author's mail: [email protected]
We present a way of designing the spectral response of plasmonic gold nanoparticles and
nanostructures with the use of machine learning algorithms in order to use the designed
nanostructures for wavelength multiplexing super resolved microscopy applications. Following
setting a specific desired spectral response, we design the geometry of our nanostructure using
genetic algorithm, thus affecting their plasmon resonance and optical properties. Our work
presents the description of the computational methods, simulation methods and physical effects
that take place in the design process. As an example we present the calculated results for the design
of two non-coupled nano dimers, each designed to have scattering peak in a specific wavelength,
e.g. two structures with orthogonal line-shapes. The use of machine learning is an advanced
approach in the world of nanophotonics and can contribute greatly in the fields of super resolution,
nanorobotics, communication and bio-sensing.
119
SE-1
Space Charge Region and Diffusion Length of CsPbBr3 Solar Cells
Michael Kulbak, Nir Kedem, Gary Hodes and David Cahen*
Department of Materials & Interfaces, Weizmann Institute of Science, Rehovot, 7610001, Israel.
High open-circuit voltage solar cells are important in spectral splitting systems to optimize the use
of high-energy photon photons and to drive a variety of electrochemical reactions. Hybrid organic-
inorganic lead halide perovskites with the generic structural formula AMX3 (where ‘A’ is a usually
an organic monovalent cation, ‘M’ is the divalent metal center and ‘X’ is a halide) have been
thoroughly studied in the last few years but still face stability issues. Among the possible solutions
replacing the organic moiety by cesium has gained increasing attention [1], [2]. While it has been
shown that high band gap (>2 eV) devices made from CsPbBr3 as an absorber layer can work
equally well as, and with better stability than devices based on CH3NH3PbBr3 [3], there are still
large gaps in our knowledge regarding how the inorganic halide perovskite photovoltaic devices
operate.
In this presentation we discuss what the working mechanisms of CsPbBr3-based devices are, by
comparing the Cs with the organic perovskite in terms of how free carriers are separated, the width
of the space charge region and the diffusion length as measured by Electron Induced Beam Current
(EBIC) under different conditions in the scanning electron microscope.
EBIC uses the electron beam to act as a light source equivalent (electrovoltaic, instead of
photovoltaic effect), generating electron-hole pairs in the junction area. If these pairs separate into
free carriers, and are collected at the contacts, we measure a current in real time and a current
collection efficiency image can be drawn.
References
[1] McMeekin, D. P.; et al., Science (2016), 351, 151–155.
[2] Kulbak, M.; Cahen, D.; Hodes, G., J. Phys. Chem. Lett. (2015), 6, 2452–2456.
[3] Kulbak, M.; Gupta, S.; Kedem, N.; Levine, I.; Bendikov, T.; Hodes, G.; Cahen, D., J. Phys.
Chem. Lett. (2016), 7, 167–172.
120
SE-2
Investigation of the Organic Solar Cell Power Loss Effect Caused by the
Transparent Anode Finite Conductivity
Dor Gotleyb1, *Rafi Shikler1
1Optoelectronic Organic Semiconductor Devices Laboratory (OOSDL)
Ben-Gurion University of the Negev, Dept. of Electrical and Computer Eng.,
Beer-Sheva 8410501, Israel P.O.B. 653
Corresponding author E-mail address: [email protected]
We examine the effect of the transparent anode on the efficiency of organic solar cells. In
specific we study the size dependence of the power loss over the anode due to its finite
conductivity. We simulated an organic solar cell with active material polymer:fullerene an
electron blocking layer of PEDOT:PSS and a transparent anode from ITO. Our unique approach
is to divide the two dimensional structure of the solar cells into two sub-domains. In the first
domain that contains the electro-optic active materials we solve the conventional equations,
namely, the Poisson and two continuity equations for the bulk heterojunction case. In the second
domain, representing the ITO, we solve just the Laplace equation with the boundary conditions
that match the two domains.
The matching is done by using the results of one domain as a boundary condition for the other.
The boundary for the active layer equations is the potential drop along the interface calculated
from the Laplace equation whereas the Laplace equation boundary arise from ohm's law with the
current across the interface calculated from the active layer equations. This matching process is
done iteratively until convergence is achieved.
We successfully established an innovative 2D simulation based on the fundamental physics of
charge transport in organic materials and ITO. The simulation which involves the entire device
domains reveals a significant loss in efficiency as the length of the cell increase. This effect of
efficiency loss is mainly an outcome of a reduced generated current in regions further away from
the contact.
121
SE-3
Cs2SnI6: an Air-stable, All-inorganic Absorber as an Alternative to Hybrid
Organic–inorganic Perovskites
Adi Kama, Shay Tirosh, Ronen Gottesman*, Arie Zaban*
Department of Chemistry, Institute for Nanotechnology & Advanced Materials, Bar-Ilan
University, Ramat Gan 52900, Israel.
Email: [email protected] ; [email protected]
Remarkable progress in the development of photovoltaic devices based on hybrid organic–
inorganic perovskites shows nowadays more than 20% power conversion efficiencies. However,
the AMX3 perovskites (A= Methylammonium, Formamidinium or their mix, M=Lead, and X=I,
Br, Cl) suffer from high instability and toxicity. Despite their contribution the materials' superior
qualities, stable and benign substitutes are required to replace the volatile organic as well as the
toxic lead cations. The ideal replacements should yield stable, environmentally-friendly,
inexpensive materials, with comparable properties to the organic and lead-containing perovskites.
The main focus of this research is to investigate the all-inorganic, lead-free Cs2SnI6 as an absorber
layer for photovoltaic devices. This air-stable perovskite has great potential due to its ideal low
bandgap and semiconducting properties, and is implemented and studied as a replacement to the
hybrid organic–inorganic perovskites in photovoltaic devices. Moreover, since the Cs2SnI6 is air-
stable, it can be synthesized in ambient conditions and the synthesis can be done using several
simple low cost methods.
122
SE-4
Use of steady-state photocarrier-grating to determine charge carrier diffusion
lengths of MAPbI3 films
Igal Levine1, Satyajit Gupta1, Gary Hodes1, Doron Azulay2, Oded Milo2, Isaac Balberg2* and David
Cahen1
1Dept. of Materials & Interfaces, Weizmann Inst. of Science, Rehovot 76100, Israel
2The Racah Institute, The Hebrew University, Jerusalem 91904, Israel
The diffusion length of photogenerated carriers in solar cells is of critical importance for
optimizing their design. This holds also for the design of halide perovskite-based cells, such as
those based on MAPbI3. In this work we use the Steady-State Photocarrier-Grating (SSPG)
technique, a well-established method, first developed by Ritter, Zeldov and Weiser at the
Technion in the mid 1980s. The method is based on the presence of a spatial sinusoidal
modulation in the photogeneration rate G of electronic charge carriers, which induces a so-called
photocarrier grating. We find that the obtained ambipolar diffusion lengths of the MAPbI3 films
are highly dependent on the route used for preparing the films. For films prepared using lead
acetate we find that the diffusion length is 200-400nm, while for films prepared using lead
chloride precursor, the diffusion length is much longer, in the order of or larger than 2 µm.
* Corresponding author email: [email protected] , [email protected]
123
SE-5
Are Photovoltaic Halide-Perovskites Ferroelectric?
Yevgeny Rakita, Elena Meirzadeh, Omri Bar-Eli, Hadar Kaslasi, Lior Ne’eman, Vyacheslav Kalchenko, Igor
Lubomirsky, Gary Hodes, Dan Oron ,David Ehre, and David Cahen
Halide perovskites (mainly methylammonium lead iodide (MAPbI3) and its bromide analog,
MAPbBr3) are the next wave of light-harvesting materials for solar cell applications, with the best
cells showing certified solar to electrical energy conversion efficiencies over 22 %. The origin for
such outstanding performance intrigues the scientific community for the last couple of years.
Ferroelectricity has repeatedly been suggested as a possible reason for some of the outstanding
properties, especially the low carrier recombination rate and high voltage efficiency. Classical
measurements to (dis)prove ferroelectricity require high electric fields, which may give rise to
experimental artifacts for these materials, because of possible ion migration and the materials’ low
formation energies.2 Since a necessary condition for a material to be ferroelectric is that it will
have a non-centrosymmetric and polar nature (point group), we examine these two prerequisite
conditions via careful Second-Harmonic-Generation (SHG) polar mapping and pyroelectricity
characterization (using the Chynoweth method1). These two experimental methods are more
accurate than X-ray- or neutron- diffraction methods, which are limited in explicitly determining
small deviations in (non-)centrosymmetric structures.
After reporting3 a clear conclusion on the non-ferroelectric nature of MAPbBr3 (which will be
presented as well), we continue our investigation on MAPbI3 and will report our most recent results
on it (which, so far, does show some differences with MAPbBr3 ).
1. Fan, Z. et al.; J. Phys. Chem. Lett. 6, 1155–1161 (2015).
2. Lubomirsky, I. & Stafsudd, O. ; Rev. Sci. Instrum. 83, 051101 (2012).
3. Rakita, Y. et al. ;APL Mat. 4, 051101 (2016)
124
SE-6
The Feasibility of Energy Extraction from Acidic Wastewater by Capacitive
Mixing with Molecular Sieving Carbon Cathode.
Barak Shapira, Eran Avraham and Doron Aurbach
Capacitive mixing is new emerging technique, for the production of renewable energy from
salinity differences. The method is based on the controlled mixing of two streams with different
salt concentrations that alternatively, are being in contact with pre-charged porous electrodes,
taking the advantage that modification at the electrical double layer of the electrodes takes place
as a cause of the changes at the solution salinity. In most publications, the renewable energy
resources are sea and river water. This work presented here aims at the demonstration of the
concept that energy extraction by capacitive mixing can take place where the energy resources
are acidic wastewater and seawater. This concept was proven by means of fabrication of proton
selective carbon cathode (meaning the negatively polarized electrode) achieved by carbonation
of cellulose filter paper followed by mild activation in concentrated nitric acid. Considerable
amount of energy extraction was demonstrated even when the concentration of the saline
solution was tenfold higher than the acidic solution.
Exchanged charge (C)
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. Re
f.
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-
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+
+
+
+
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125
SE-8
Polyoxometalates complexes of α-Fe2O3 cores in water
Dr. Biswarup Chakraborty and Prof. Ira A. Weinstock*
Department of Chemistry and Ilse Katz Institute for Nanoscale Science and Technology,
Ben-Gurion University of Negev, Israel Email: [email protected]
An unprecedented role for metal-oxide cluster-anions (polyoxometalates, or POMs) as covalently
coordinated inorganic ligands for individual hematite nanocrystals, gives isolable anionic clusters
uniquely positioned between molecular macroanions and traditional colloidal nanoparticles.[1]
Sodium salts of α-PW11O397- anions serve as pentadentate “capping” ligands for complexed Fe(III)
ions linked via their sixth coordination site to 3-5-nm α-Fe2O3 cores. Multiple spectroscopic
methods and analytical measurements confirm the presence of POM-capping ligands, [α-
PW11O39Fe-O-]n-, covalently bound to the surfaces of the hematite cores. Clear orange solutions
of these unique complexes are stable in water over a wide range of pH values (2.5-8), which spans
the isoelectric point of hematite (pH 5.3). Over this entire pH range, zeta-potential values (ξ),
remain nearly constant, ranging from -33 to -38 mV. Moreover, covalent attachment of the POM
anions allows for repeated precipitated (by added salt), and re-dissolution in water. Raman, FTIR,
EDS and XPS data show that numerous POMs are associated with each 3-4-nm hematite
nanocrystal, and high-resolution TEM, cryogenic-TEM, and HAADF-STEM images clearly reveal
the covalently bound POM ligands at the hematite surfaces. As a first step toward visible light
driven water splitting (currently underway) (Figure 1), differential-pulse voltammetry (DPV) was
used to reveal the reversible redox chemistry of the covalently attached POM ligands.
Figure 1. Visible light driven water splitting by the α-Fe2O3-POM hybrid.
References:
[1] M. Raula, G. Gan Or, M. Saganovich, O. Zeiri, Y. Wang, M. R. Chierotti, R. Gobetto, I. A. Weinstock, Angew. Chem. Int. Ed. 2015, 54,
12416-12421.
126
SE-9
CsSnBr3, a lead-free halide perovskite for long-term solar cell application
Satyajit Guptaa, Tatyana Bendikovb Gary Hodesa* and David Cahena*
Department of Materials & Interfacesa and Chemical Research Supportb,
Weizmann Institute of Science, Rehovot, 76100, Israel.
e-mail: [email protected], [email protected]
In the past few years, there is a tremendous interest and research effort on ‘Halide Perovskites (HaPs)’,
with general composition AMX3 (A: monovalent cation, primarily methyl ammonium (MA),
formamidinium (FA) or cesium (Cs); M: Pb; X: halogen-Br, Cl, I) Some specific compositions of
lead-based HaPs, demonstrated small cell power conversion efficiencies (PCE) over 22%, up from a
few % within ~5 years. However, lead, which is used in the most studied, widely perceived as toxic,
which will affect its widespread use. We explored a lead-free option, CsSnBr3 perovskite for opto-
electronic applications. The cubic perovskite phase of the as-synthesized CsSnBr3 was confirmed
using X-Ray diffraction (XRD) analysis; and, its optical absorption edge was analyzed using UV-
Visible spectroscopy, indicating a direct band-gap of 1.75 eV. The energetics (work function-WF and
top of the valence band-EVB) of the material (with and without SnF2 addition) was examined using
Ultraviolet photoelectron spectroscopy (UPS) on different substrates: dense titania (TiO2) and gold
(Au). An elemental composition of the CsSnBr3 was determined using X-ray photoelectron
spectroscopy (XPS) analysis, showing presence of Cs, Sn and Br on the surface. The time-dependent
XPS analysis revealed the fact that pristine CsSnBr3 is susceptible to beam-damage. However, addition
of ~20 mol% of SnF2 improves stability of the perovskite and for this material no beam damage was
observed.
Furthermore, the solar cells with CsSnBr3 were thoroughly optimized and tested using various ‘hole-
selective’ and ‘electron-selective’ contacts. The addition of SnF2 was confirmed to be beneficial for
obtaining good device performance, possibly due to filling of cation vacancies and/or reduction of
background carrier density and trap densities. The solar cells demonstrated efficiencies up to 2.1%,
JSC of ~9 mA cm-2, VOC of 0.41 V and fill factor (FF) of 58% under 1 sun (100 mW cm-2) illumination,
which are among the best reported. The non-encapsulated devices were observed to be highly unstable
during continuous illumination in ambient atmosphere (~10 min life-time), possibly due to the
oxidation of Sn2+ to Sn4+, as well as degradation due to moisture. However, they are highly stable in
the inert atmosphere with intense white LED illumination (intensity ≈2 sun) for 5 hr of continuous
illumination.
127
SE-10
NANOSTRUCTURED ORGANIC ALKALI-SOLUBLE SILICATE FOR
INDUSTRIAL APPLICATION
Kudryavtsev P.G.1, Figovsky O.L.2
1 Professor, HIT Holon Institute of Technology, 52 Golomb Street, POB 305 Holon 5810201,
Israel, e-mail: [email protected]
2 Professor, Polymate Ltd - Israel Research Center, POBox 73, Migdal HaEmek 10550, Israel,
e-mail: [email protected]
In this paper we analyzed the properties of the water-soluble high-modulus silicate systems,
and their technology for producing. We have shown how these systems are transformed, from
lower to higher oligomers, through the formation of the silica sol and the implementation of the
sol-gel process for these oligomers. We have conducted advanced research of various aspects of
the use of these materials as the binder. Modifiers have been proposed for making of hybrid
nanostructured composite materials by a sol-gel process. Have been shown of structuring
phenomena some aspects, synthesis and application of hybrid materials based on silica with grafted
polymers. Production of polymer concrete, which was nanostructuring of silicon dioxide serves as
an example of the application of silicate systems. It has been shown, the possibility of modifying
compositions using the nano structuring agents such as tetrafurfuryloxysilane, and an aqueous
dispersion of chlorosulfonated polyethylene and other polymers. In the present work are also
described methods of synthesis products for modifying a sol-gel process using polyurethanes. They
include applications of sols for producing of hybrid nanocomposites, monolithic blocks and fire-
resistant materials and technology for the production of new nanocomposite materials and acid-
resistant coating for protection aggressive environments.
It should be emphasized that even small changes in process parameters in the manufacture
of nanocomposite materials can have a significant impact on the final product. On the one hand,
this increases the complexity of the system and, on the other hand, offers an excellent opportunity
to develop their own, individual solutions of practical problems, which are often associated with
minimal changes in the composition and production technology.
128
SS-1
Thermostable Energetic Hybrid Coordination Surfaces Based on a Novell Graphene Oxide-Cu(II) Complex
Adva Cohen§, Yuzhang Yang‡, Qi-Long Yan§, Avital Shlomovich§, Natan Petrutik§, Larisa
Bursteinξ, Si-Ping Pang‡, Michael Gozin§*
§ School of Chemistry, Faculty of Exact Science, Tel Aviv University, Tel Aviv, 69978, Israel.
ξ Wolfson Applied Materials Research Center, Tel Aviv University, Tel Aviv, 69978, Israel. ‡School of Material Science & Engineering, Beijing Institute of Technology, Beijing 100081, China
*Michael Gozin: [email protected]
A new group of 3D high energetic coordination polymers (ECPs) based on graphene oxide copper(II)
complex have been synthesized using 5,5’-azo-1,2,3,4-tetrazole (TEZ) and 4,4’-azo-1,2,4-triazole (ATRZ)
as linking ligands. The chemical structure of the new energetic surfaces ware studied using various
techniques. The sensitivity and detonation performances of these ECPs were also determined. It has been
shown that these energetic nanomaterials are insensitive and highly thermostable, due to high heat
dissipation capacity of GO sheets. To be more specific, the decomposition temperature has increase
significantly due to the formation of the coordination polymer. In particular, the GO-TEZ-Cu(II) CP with
low sensitivity (Im = 21 J) has a comparable detonation performance to that of RDX. Also, the novel
GO/Cu(II)/ATRZ composite exhibits the highest density (2.85 g cm-3), thermal stability (Tp= 456 °C) and
insensitivity (impact energy, Im > 98 J). This material has a detonation velocity of 7082 m s-1, which is
slightly higher than that of its parent ATRZ-Cu(II) MOF and one of the top thermostable compounds HNS
(Tp = 316 °C; 7000 m s-1).
The SEM images of (a) GO with 1-5 layers, (b) GO-Cu(II)-ATRZ CP, (c) GO-Cu(II)-TEZ CP, (f) GO/Cu(II)/TEZ composite, and (g)
GO/Cu(II)/ATRZ composite; the EDS spectra showing elemental analysis on the surface of the samples (d) GO-Cu(II)-ATRZ CP and (e) GO-
Cu(II)-TEZ CP as examples; the mechanical mixtures of GO layers with Cu(II)-TEZ complex (h), Cu(II)-ATRZ MOF (i) and the pure ATRZ
MOF crystals (j).
129
SS-2
Graphene Quantum Dots Produced by Microfluidization
Matat Buzaglo*, Michael Shtein and Oren Regev
Department of Chemical Engineering and Ilse Katz Institute for Meso and Nanoscale Science and
Technology, Ben-Gurion University of the Negev, Beer-Sheva, Israel
The unique physical properties of graphene quantum dots, including their controllable photoluminescence,
flexible structure, biocompatibility and photostability, make them highly desirable for novel applications,
such as flexible photovoltaics and bioimaging.
However, the commercialization of these next–generation quantum dots is limited because their production
is highly complex and costly. Here, we present for a first time, a purely mechanical method for top-down
fabrication of graphene quantum dots.
During a microfluidizer-based “top-down” fabrication, millimeter-sized graphite flakes are fragmented into
zero-dimensional nano-sized dots due to high shear rates (>107 sec-1) generated by pressurizing the
graphite-aqueous suspension through micro-sized channels. The as-prepared GQDs are non-functionalized
and exhibit excitation-independent photoluminescence.
This facile, environmentally friendly, and scalable method provides an ideal framework for substantial
progress toward large-scale production and commercialization of GQDs-based applications.
References
[1] Buzaglo, M.; Shtein, M.; Regev, O., Graphene Quantum Dots Produced by Microfluidization.
Chemistry of Materials, 28 (2016), 21-24
Figures
Figure 4 - Typical flow profile within the channel with maximal flow speed of 400m/s. The graphite flakes are
exfoliated into graphene sheets and further fragmented into nanosized graphene quantum dots.
130
SS-3
The electronic structure of transition-metal silicide nanostructures:
experiment and theory
M. Dascalu 1, R. Levi1, Y. Camus1, F. Cesura1, J. K. Tripathi1, I. Goldfarb1,2, O. Dieguez1
1Department of Materials Science and Engineering, Faculty of Engineering, Tel Aviv University, Ramat
Aviv, Tel Aviv 6997801, Israel
2Research Center for Nanoscience and Nanotechnology, Tel Aviv University, Ramat Aviv, Tel Aviv
6997801, Israel
We fabricated self-assembled three-dimensional alpha-FeSi2 nano islands and two-dimensional NiSi2 ultra-
thin films, using solid phase epitaxy and reactive deposition of a few monolayers of Fe or Ni on vicinal
Si(111) surfaces. We then investigated the structural, electronic and magnetic properties of these materials
using scanning tunneling microscopy, scanning tunneling spectroscopy, and superconducting quantum
interference device magnetometry. We also used density-functional theory calculations to help understand
our experimental results. In particular, we found that the alpha-FeSi2 nanoislands show a band gap of 0.5
eV, a distinctively different result than that of than Han et al [ref1] and Cao et al [ref2] , who reported
metallic character for these nanoislands. Regarding the NiSi2 films, we found a band gap that is much larger
than the 0.1 eV reported for the bulk material [ref3]. Both systems show 2x2 reconstructions. We used
energetic and kinetic considerations to understand the electronic and morphological nature of these
structures.
Refrences:
[1] Nannan Han, Hongsheng Liu, and Jijun Zhao. Journal of Superconductivity and Novel Magnetism,
28(6):1755–1758, January 2015.
[2] Guixin Cao, D.J. Singh, X.-G. Zhang, German Samolyuk, Liang Qiao, Chad Parish, Ke Jin, Yanwen
Zhang, Hangwen Guo, Siwei Tang, Wen- bin Wang, Jieyu Yi, Claudia Cantoni, Wolter Siemons, E.
Andrew Payzant, Michael Biegalski, T.Z. Ward, David Mandrus, G.M. Stocks,
and Zheng Gai. Physical Review Letters, 114(14):147202 April 2015
[3] O. Bisi and C. Calandra. Journal of Physics C: Solid State Physics, 14(35):5479, 1981.
131
SS-4
Chiral Templating of Alumina Nanofilms by Atomic Layer Deposition Process
Ortal Lidor-Shalev1*, Yacov Carmiel2, Ronen Gottesman3, Shay Tirosh4, and
Yitzhak Mastai5 Department of Chemistry, Bar-Ilan Institute of Nanotechnology and
Advanced Materials (BINA), Bar-Ilan University, Ramat Gan, 5290002, Israel.
*e-mail: [email protected]
In the past decades, chirality at the nanoscale has received a great attention
due to the potential use of chiral nanoscale systems for various applications, such as
enantioselective chemical synthesis and separation of chiral compound s.
In the presented work, we describe the synthesis of new chiral metal -oxide
nanofilms and surfaces, based on the chiral templating of cellulose microfibers by
atomic layer deposition (ALD) process. The overall preparation pathway of the new
type of chiral metal-oxide surfaces is shown below (a). The ALD process is performed
to deposit nanofilms of metal-oxide (e.g. alumina) onto assembled cellulose
microfibers, followed by the chemical extraction of the templating cellulose.
The chiral metal-oxide nanofilms preserve the helical morphology of the chiral
templating microfibers (b). The chiral nature of the nanofilms was characterized by
circular dichroism (CD) adsorption, chiral high-performance liquid chromatography
(HPLC), quartz crystal microbalance (QCM) analysis, and cyclic voltammetry (CV)
measurements.
(a) (b)
1 µm
132
SS-5
Nitrogen oxide interaction with CVD fabricated vanadium dioxide films:towards state-to-state study of molecule interaction with catalytic surface
Anita Pilipody1, Artur Meling2, Bastian Krueger2, Tim Schaefer2, Vladimir Tsionsky3, Sergey
Cheskis1 Alec M. Wodtke2,4 and Igor Rahinov3
1. School of Chemistry, Tel Aviv University, Israel 2. Institute of Physical Chemistry, Georg-August University of Goettingen, Germany 3. Department of Natural Sciences, The Open University of Israel, Israel 4. Max Planck Institute for Biophysical Chemistry, Goettingen, Germany
Oxides of vanadium are widely used in catalytic protocols for pollution abatement
[1, 2] and synthetic fuel production [3, 4] and heterogeneous catalysis in general. In addition,
Vanadium oxide has some peculiar properties: Vanadium oxides exhibits a phase transition from
semi-conductor to a metal at 68 C. Simultaneously with the resistivity drop the reflectivity in the
IR wavelength is increased by several orders of magnitude. This process is called Mott transition
[5] and occurs due to change in the unit cell structure from monoclinic structure to tetragonal rutile
structure (see figure 1). At the rutile structure the distance between the V atoms is reduced, and
allows the electrons to move freely along the V-V chains. This unusual properties origin form Mott
transition could be used as thermo-electric switches, optical switches, thermal windows and super-
capacitors
Scattering experiments explore the energy exchange between the different degrees of freedom of
the molecule and the surface. Scattering of gas molecules from insulator and from metal surface
are well established [6]. One of the great motivations in this project is to perform scattering
experiments from surface with switchable conductivity.
Vanadium dioxide films were grown in hot wall, horizontal, low pressure MOCVD built-in-house
apparatus. The CVD fabrication of 1-3 µm thick VO2 films employed sublimation of Vanadyl
acetylacetonate (VO(acac)2) at ~150-190oC and its subsequent reaction with O2 at CVD chamber.
The product The dependence of film morphology and resistance properties on CVD reactor
temperature, precursor sublimation temperature and the substrate position along the reaction axis
was tested. The X-ray Diffraction of (XRD) indicates that the predominant phase in the CVD
fabricated samples is monoclinic Vanadium Dioxide. Scanning Electron Microscopy (SEM)
analysis reveals grain sizes in the range of 0.5-2 µm. Four probe resistance measurements indicate
resistance drop of 3-4 orders of magnitude across the insulator-to-metal transition. Here presented
preliminary results of NO molecule scattering from the resulting VO2 thin films.
References:
1. F. Gilardoni and J. Weber, A.B., International Journal of Quantum Chemistry, 1997. 61.
2. H. Randall, R.D., A. Renken, Applied Catalysis B: Environmental, 1998. 17.
3. L. C. Caero, E.H., F. Pedraza, F. Murrieta, Catalysis Today, 2005. 107-108.
4. K. Otsuka, A.M., S. Takenaka, I. Yamanaka, International Journal of Hydrogen Energy, 2001. 26.
5. Mott, A.Z.a.N.F., Phys. Rev. B, 1975. 11.
6. Y.Huang, C.T.R., Daniel J. Auerbach, Alec M. Wodtke, Vibrational Promotion of Electron
Transfer. SCIENCE, 2000. 290(6).
133
SS-6
X-Ray Photoelectron Spectroscopy of Nd doped CeO2
Lee Shelly, Yuval Mordekovitz and Dr. Shmuel Hayun
Department of materials science and the Ilse Katz Institute for Nanoscale Science and
Technology, Ben-Gurion University of the Negev, P. 0. Box 653, Beer-Sheva 8410501, Israel.
CeO2 is an attractive material for various applications due to its physical, chemical and electrical
properties. For example, CeO2 is a basic component in oxidative catalysis as well as sensors and fuel cell
technology, where catalytically active surfaces and high ionic conductivity, well-known for CeO2, are
essential. These applications are based on the easily formed oxygen vacancies in the fluorite structure of
ceria due to the variable oxidation state of Ce ions (+3 and +4). Doping ceria with aliovalent cations to
some extent may increase the oxygen vacancies while maintaining the cubic fluorite structure. These
ceria-based materials found to have high ionic conductivity and enhance catalytically active surface. In
the present work, the effect of neodymium on the formation of Ce3+ in nanoparticles of CeO2 was
investigated using X-ray photoelectron spectroscopy. The overall oxygen vacancies increased with the
neodymium addition while the Ce3+ concentration was reduced. Nevertheless, the amount of OH
species found at the surface increased with larger neodymium content.
134
SS-6
Steps at Interfaces in SrTiO3 and Their Role in Kinetic Processes
Hadas Sternlicht1, Wolfgang Rheinheimer2, Alex Mehlmann1, Avner Rothchild1, Michael J.
Hoffmann2 and Wayne D. Kaplan*1
1Department of Materials Science and Engineering, Technion – Israel Institute of Technology,
Haifa 32000, Israel.
2Karlsruhe Institute of Technology, Institute of Applied Materials, Karlsruhe, Germany.
The kinetics of grain boundary (GB) motion can be determined experimentally. In SrTiO3
annealed under an oxidizing atmosphere, the GB mobility was found to decrease with an
increase in temperature (in the temperature range of 1350-1425°C), deviating from the expected
Arrhenius behavior. While GB mobility can be measured, the mechanism by which a GB moves
has not yet been determined at the atomistic level in general polycrystalline systems. According
to the terrace ledge kink (TLK) and disconnection models, GBs were described as stepped planes
which move by step-motion along the boundary plane during grain growth. Steps at GBs can
have both a step and dislocation character (called disconnections). Such steps were previously
described to play a role in crystal growth. The present work focuses on the atomistic mechanism
by which GBs migrate, using high resolution transmission electron microscopy (HRTEM) and
SrTiO3 as a model system, following the TLK and disconnections theories.
Both steps and dislocations were visible along general GBs in SrTiO3 annealed under an
oxidizing atmosphere. The steps were found to be aligned mainly parallel to {001} and {110}
type planes. The dislocation component of the disconnections was found to have an edge
component mainly parallel to the same crystallographic planes. The atomistic terminations along
the boundaries were found to vary. In addition, motion of the steps parallel to {001} and {110}
type planes was recorded during in-situ HRTEM experiments along surfaces of grains in
polycrystalline SrTiO3 annealed under an oxidizing atmosphere.
Thus, the consistent appearance of certain types of steps along interfaces in SrTiO3 annealed
under an oxidizing atmosphere was noted. These steps appeared in both in-situ and ex-situ
experiments, indicating their role in kinetic processes such as grain and crystal growth.
135
SS-7
Doping and Alloying Made Simple: How to Maximize the Potential of Transition Metal Dichalcogenides
Oren E. Meiron1, Houben Lothar2, Maya Bar-Sadan1*
1Ben Gurion University of the Negev, the chemistry department, Beer Sheba, Israel
2 Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel
*Corresponding author: [email protected]
Transition metal dichalcogenides (TMDs) are trending as promising materials for a large verity of
applications such as photocatalysis, photonics, photovoltaic devices, thin layer transistors, super capacitors
and many others. Precise control over morphology and composition of the TMDs is crucial and should be
tailored for each specific application. Traditional solid state techniques such as chemical vapour deposition
(CVD) or chemical vapour transport (CVT), while simple and well established for producing flat, single or
few layers TMDs, become inefficient when required to produce large scale, homogeneous constructs with
complicated morphologies.
We have shown that colloidal synthesis can be used to produce TMD alloys as well as to dope TMDs with
other atoms, thus obtaining control over their electronic and catalytic properties. Choosing to focus on
photocatalysis, we produce thin edge nanoflowers of Mo(SxSe1-x)2 alloys as well as Fe-doped MoS2 and
MoSe2 as model systems to show the versatility of the method. Various analytical methods were used to
determine the formation mechanism, composition and structure of the products as well as their
electrochemical and photocatalytic performance. We were able to determine that for this specific approach,
the formation mechanism initiates from the precipitation of amorphous homogeneous substance. It then
crystallizes into curled and tangled sheets of the appropriate TMD enabling the production of homogeneous
alloys or doped constructs.
Electrochemical and hydrogen production measurements showed that Fe-doped MoS2 and MoSe2 have
superior performance to pure MoS2 and MoSe2 when the Fe is homogeneously distributed in the nanoflower
structure. By successfully modifying the electronic and catalytic properties of TMDs using colloidal
synthesis we have opened the door for additional tuning and optimization of TMDs for other applications
such as photonics, super capacitors or batteries.
136
SS-8
Surface properties of oriented -Fe2O3 thin films
correlated with their photo-electrochemical behavior
Bhavana Gupta1, Daniel A. Grave2, Hen Dotan2, Avner Rothschild2 and Iris Visoly-Fisher1
1Department of Solar Energy and Environmental Physics, Swiss Institute for Dryland
Environmental and Energy Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion
University of the Negev, Sede Boqer campus, Israel
2Materials Science and Engineering Department, Technion - Israel Institute of Technology,
Haifa, Israel
Hematite (a-Fe2O3) is one of the important anodic materials for energy conversion via solar to fuel
conversion by water photo-electrochemical oxidation. The conversion efficiency is known to be
improved by tailoring the particle size, doping and surface modification. Herein we studied the
effect of the crystallographic surface orientation on the electrode/electrolyte interface reaction .
We studied the photo-electrochemical performance of three oriented Sn-doped α-Fe2O3 thin films
(oriented at C-plane (001), A-plane (110), and M-plane (100)) grown by pulsed laser deposition
on oriented sapphire substrates, and correlated it with surface properties including the surface
potential/work function and current sensing mapping. It was observed that the plane with highest
work function (M-(100)) and better electrical conductance was more efficient towards photo-
electrochemical water oxidation. All films showed post-reaction increase in surface potential /
decrease in work function. The surface morphology was also found to depend on the orientation;
M-(100) and C-(001) oriented films were found to be smoother than A-(110) films. The
morphology and surface properties were found to change following electrochemical -oxidation in
alkaline medium, with the changes depending on the films' orientation; Surface agglomeration was
observed for C-(001), while M-(100) became smoother and the morphology of A-(110) was almost
unchanged. These changes can help understand the water oxidation reaction mechanism at the
hematite surface.
137
SS-9
Near Surface Polarity characterization of crystals by XPS, Pyroelectricity and
Molecular Dynamics simulations
Elena Meirzadeh1, Liel Sapir2, Hagai Cohen3, David Ehre1, Meir Lahav1, Daniel Harries3 and
Igor Lubomirsky1*
*[email protected] 1Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel
2Institute of Chemistry and The Fritz Haber Research Center, The Hebrew University, Jerusalem
91904, Israel 3Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100,
Israel
Pyroelectricity is a property of polar materials, encountering surface charge under temperature changes.
This property was confined exclusively for the polar directions of the ten polar crystalline classes [1, 2].
However, in contrast to the generally accepted symmetry restrictions, we found that non-polar crystals of
amino acids exhibit surface pyroelectricity at specific crystal faces [3, 4].
Conventional pyroelectric measurements are frequently challenging, due to the typically rapid charge
compensation by adsorbed moieties, as well as various difficulties arising as a result of contacts
introduction. In particular, surface pyroelectric measurements are extremely sensitive to the above
difficulties and, therefore, they require complementary measuring techniques. Here we exploit the recent
chemically resolved electrical measurements (CREM) [5] based on x-ray photoelectron spectroscopy
(XPS), to measure in a non-contact mode [6] and, importantly, under ultra-high vacuum, the bulk and
surface pyroelectricity of pure (non-polar) and L-threonine doped (polar) α-glycine crystals [7].
Combined with Atomic Force Microscopy (AFM) studies, the pyroelectric measurements provide
information on various types of crystal surface reconstructions. Molecular Dynamics simulations provide
the structure of the near surface hydrated glycine molecules of the crystal at the molecular level.
References
1) Lang, S.B. Pyroelectricity: From ancient curiosity to modern imaging tool. Physics Today 58, 31 (2005).
2) Kittel, C. Introduction to solid state physics. (Wiley, 2005).
3) S. Piperno, E. Meirzadeh, E. Mishuk, D. Ehre, S. Cohen, M. Eisenstein, M. Lahav, I. Lubomirsky, Angew.
Chem. Int. Edit. 52, 6513 (2013).
4) E. Mishuk, I. Weissbuch, M. Lahav, I. Lubomirsky, Cryst. Growth Des. 14, 3839 (2014).
5) H. Cohen, Appl. Phys. Lett. 85, 1271 (2004).
6) D. Ehre, H. Cohen, Appl. Phys. Lett. 103, 052901 (2013).
7) E. Meirzadeh, Liel Sapir, David Ehre, Meir Lahav, Daniel Harries and Igor Lubomirsky, Ready to submit for
publication.
138
T-1
Origin and structure of polar domains in doped molecular crystals
E. Meirzadeh1, I. Azuri1,*, D. Ehre1, A. M. Rappe2, M. Lahav1, L. Kronik1, I. Lubomirsky1
1Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel. 2The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania,
Philadelphia, PA 19104-6323, USA.
Doping is a primary tool for the modification of the properties of materials. Occlusion of guest
molecules in crystals generally reduces their symmetry by the creation of polar domains, which
engender polarization and pyroelectricity in the doped crystals. Here we describe a molecular-level
determination of the structure of such polar domains, as created by low dopant concentrations
(<0.5%). The approach comprises crystal engineering, pyroelectric measurements, and dispersion
corrected density functional theory (DFT) calculations of the doped crystals, using neutron
diffraction data of the host at different temperatures. This approach is illustrated using
centrosymmetric α-glycine crystals doped with minute amounts of different L-amino acids. The
experimentally determined pyroelectric coefficients are rationalized by the structure and
polarization calculations, thus providing strong support for the local and global understanding
concerning how different dopants influence the properties of molecular crystals.
139
T-2
PFC and Triglyme for Li–Air Batteries: A Molecular Dynamics Study
Natalia Kuritz1, Michael Murat1, Moran Balaish2, Yair Ein-Eli2, and Amir Natan1*
1Department of Physical Electronics, Tel-Aviv University, Israel
2Department of Materials Science, Technion, Israel
In recent years significant effort has been devoted to vehicle electrification. Development of a better
electrochemical storage for this purpose became a key research challenge. Rechargeable systems, and in
particular Li-air batteries were recognized as appealing candidates for this application. Choosing an
appropriate electrolyte, whose properties optimize the electro-chemical cell, is a central aspect of the battery
design.
In this work, we present an all-atom molecular dynamics (MD) study of triglyme and per-
fluorinated carbons (PFCs) using classical atomistic force fields. Triglyme is a typical solvent used
in non-aqueous Li–air battery cells. PFCs were recently reported to increase oxygen availability
in such cells. We show that O2 diffusion in two specific PFC molecules (C6F14 and C8F18) is
significantly faster than in triglyme. Furthermore, by starting with two very different initial
configurations for our MD simulation, we demonstrate that C8F18 and triglyme do not mix. The
mutual solubility of these molecules is evaluated. Finally, we show that the solubility of O2 in
C8F18 is considerably higher than in triglyme.
140
T-3
Optimal Nanomaterial Concentration: Harnessing Percolation Theory Towards
Enhanced Performance
Roey Nadiv1*, Michael Shtein 2 and Oren Regev 1, 2
1Department of Chemical Engineering and 2Ilse Katz Institute for Meso and Nanoscale Science and
Technology, Ben-Gurion University of the Negev, Beer-Sheva, Israel
*Corresponding author email: [email protected]
Successful exploitation of nanocomposite depends largely on the development of models and experimental
techniques 1-4 capable of predicting the optimal nanomaterial concertation (ONC) at which a maximal
reinforcement is achieved. Within this scenario, we present a simple approach to identify the ONC based
on the premise that it is typically located in close proximity to the rheological percolation threshold, and
thus an abrupt increase in matrix viscosity may be used as an indicator of the ONC. This premise is validated
by detailed rheological and fractography studies of numerous composites with various nanomaterials
(graphene nanoribbons 1 carbon or tungsten disulfide nanotubes 2-3). The correlation between in-situ
viscosity, the rheological percolation threshold and nanocomposite surface structure indicated the utility of
the method.
References:
1. Nadiv, R.; Shtein, M.; Buzaglo, M.; Peretz-Damari, S.; Kovalchuk, A.; Wang, T.; Tour, J. M.; Regev,
O., Graphene nanoribbon – Polymer composites: The critical role of edge functionalization. Carbon 2016,
99, 444-450.
2. Shtein, M.; Nadiv, R.; Lachman, N.; Daniel Wagner, H.; Regev ,O., Fracture behavior of nanotube–
polymer composites: Insights on surface roughness and failure mechanism. Compos. Sci. Technol. 2013,
87 (0), 157-163.
3. Nadiv, R.; Shtein, M.; Peled, A.; Regev, O., WS2 nanotube – Reinforced cement: Dispersion matters
.Constr Build Mater 2015, 98, 112-118.
4. Ma, P.-C.; Siddiqui, N. A.; Marom, G.; Kim, J.-K., Dispersion and functionalization of carbon
nanotubes for polymer-based nanocomposites: A review. Composites Part A 2010, 41 (10), 1345-1367.
141
T-4
Modeling the adsorption processes at electrode material surfaces for Li-air and
Na-air batteries
Keren Raz1, Diana Golodnitsky1*, and Amir Natan2*
1 – School of Chemistry, Tel-Aviv University, Israel 69978
2- Department of Physical Electronics, Tel-Aviv University, Israel 69978
Rechargeable lithium-air and sodium-air batteries are very attractive because they offer very high
theoretical energy densities with the potential to power the electric vehicles and to reduce the use
of oil. The design of these batteries involves complicated optimization of electrolytes and electrode
materials. Li2O2 or Na2O2 and other intermediates and products are formed either at the electrode
surface or in solution during the discharge process. One approach to model the product formation
at the electrode is to simulate the adsorption and assembling of molecules at the electrode surface.
At some stage, single molecules can cluster and finally crystalize at the surface to form crystalline
Li2O2 or Na2O2 compounds, this can be modeled by simulating a "perfect" interface of the
crystalline electrode and the crystalline peroxides and superoxides.
In this work we analyze, with Density Functional Theory (DFT) simulations, the adsorption
properties of different-coverage Li2O2, Na2O2 and NaO2 compounds at different clean surfaces of
titanium-carbide (TiC). We also repeat this analysis for the adsorption of alkali metal peroxide and
superoxide molecules at the oxidized TiC surface. Finally we model the "perfect" interface
between TiC planes and crystalline forms of Li2O2, Na2O2 and NaO2. For the latter problem we
have implemented a surface matching procedure according to the Zur & McGill algorithm (Journal
of applied physics 55.2 (1984): 378-386). We demonstrate the results of applying this algorithm
for TiC/MxOy interfaces and calculate the adsorption energies for the perfect crystal. We
summarize with some conclusions from the comparison of different molecules and surfaces and
analyze the differences between the Li and Na cases.
142
T-5
Predicting Device Performance Using Genetic Algorithms and Principle
Component Analysis
Elana Borvick, Assaf Y. Anderson*, David A. Keller, Maayan Priel, Hanna-Noa Barad, Adam
Ginsburg, Kevin J. Rietwyk and Arie Zaban*
Department of Chemistry and Center for Nanotechnology and Advanced Materials,
Bar Ilan University, Ramat Gan
Data mining in combination with high-throughput material science is a developing field that has
already been used to better visualize data, to cluster data into groups and analyze spectrums. It was
shown that these algorithms can help us gain a broader understanding of our data and accelerate
the process of analyzing our data.
Using high-throughput fabrication and screening, a large amount of data is generated in a short
amount of time. In our research we use high-throughput combinatorial methods in order to study
metal oxides and their performance in photovoltaic devices. We apply data mining algorithms to
the generated data in order to gain a better understanding of the results, find various relationships
in the data and visualize it, in order to predict photovoltaic performance of the libraries.
In this study we fabricated libraries of Fe2O3 using radio-frequency (RF) sputtering, we used a
static mask which divides each library in to six parts, every part with different deposition
parameters. This gives us libraries with high variance of deposition parameters, which include
length of deposition, the power used for deposition, amount of oxygen in chamber, etc. The
libraries were measured using optical and current-voltage high-throughput scanning methods. We
then apply genetic algorithms to the obtained results to find out how the different deposition
parameters affect the thickness of the layer and the photovoltaic performance of the samples. In
addition, we use principle component analysis (PCA) to help visualize the trends in the libraries.
Using these algorithms we gain a better understanding of our materials and are able to predict
structural and photovoltaic properties.
