COMPOSITE DENDRIMER MATERIALS - MINT Center · Center for Materials for Information Technology an...

Center for Materials for Information Technologyan NSF Materials Science and Engineering Center

COMPOSITE DENDRIMER MATERIALS

Shane Street (UA, Chemistry)Mark Weaver (UA, MtE)

John Barnard (Pitt, Mat. Sci.)[email protected]


Areas of Research

� Dendrimer-mediated Ultrathin Films� Dendrimer-mediated overlayer film growth; morphology� Nanomechanical behavior of metal/dendrimer composites� Adhesion and hardness issues

� Dendrimer-mediated Synthesis of Nanoparticles and Patterned Nanostructures� Microcontact printing� Metal/dendrimer composite structures� Metallic nanoparticles


Dendrimers as Functional ComponentsStarburst PAMAM Dendrimers

Repeated UnitsN- (CH2)2 -N

(CH2)2 - CO -NH - (CH2)2-N

(CH2)2 - CO -NH - (CH2)2-NCore

Dendrimers are 3d, highly branched, macromoleculeswith a core/repeat unit/terminal shell structure.

Generally classified by generation, e.g., G4: -NH2 terminated64 endgroupsMW ~ 14000


Dendrimer Adlayers and Interfacial Interactions

~3-2

0 nm

Typical Samples Schematic


Dendrimer-Mediated Film Morphology10 nm Co 10 nm Cr 10 nm Au 10 nm Cu1 µm x 1 µm

scan size

Bare Si

G8


Dendrimer-mediated Overlayer Film Growth

� Increase in squareness� Decrease in magnetic

moment� Influence is on ordering in

overlayer Co?

Influence of morphology of the Cu seed layer on magneticproperties of an overlayer (Co)


Molecular Interlayers and Abrasive Wear�AFM image of residual impressionleft by diamond scratch tip

�Impression made in thick Cu film

�Blunted Berkovitch shape

�Scratches carried out in face-forward mode

�Velocity: 1 micron/second

Si

15 nm Cu

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15 nm Cuvs

Constant load (4 mN) nanoscratches, 100 µm long.


SEM Images of Nanoscratch Events4 mN constant load, Berkovitch tip (face forward)

15 nm Cu/Si 15 nm Cu/G8/Si

Plowing Irregular cutting


Nanomechanical Behavior: Critical Load

� Increase normal load to failure in ramped load scratch� A general result: Ti, Cu. CNx? TiB2?� Influence of adhesion? Grain size or hardness?


Dendrimer Adlayers and Interfacial Interactions

� The presence of the dendrimer monolayer influences the morphology, nanomechanical properties and chemical composition of overlayer metal ultrathin films (growth modes, grain size, chemical composition of the interface, resistivity of the thin film)

� Improve overlayer magnetic materials properties (Grain size control?)

� Distinguish between hardness, and adhesion effects in nanomechanical properties? Does adlayer improve “hard coatings” adhesion or fracture resistance?


Formation of Metal Nanoparticles within PAMAM dendrimers

The dendrimer monolayer can attract metal ions to its interior. Subsequent reduction, e.g., Cu2+ to Cu0 (metal).

(Zhao, M.; Crooks, R. M. Adv. Mater. 1999, 11, 217-220.)


UV Irradiation of Co(II)/G4-OH System

hν+

CoCl2aqueous

Dendrimer aqueous

Mixed

Amine-coordinated

Co2+We have shown that the reduction ofCo ions can be carried out photochemically


TEM image of Acicular Co Nanoparticles

The resulting particlesare acicular, metallic,and magnetic

Dr. M. Shamsuzzoha


Acicular Co Nanoparticles

-5000 -4000 -3000 -2000 -1000 0 1000 2000 3000 4000 5000-1.0x10-5

-5.0x10-6

0.0

5.0x10-6

1.0x10-5

HC = 300.6Oe

M (e

mu)

H (Oe)

Magnetic Hysteresis Loop of Co Nanoparticles

The Co particles produced are relatively monodisperse, acicular, magnetic, and apparently metallic.

(0001)hcp Co with stacking faults

TEM Image of Single Co Nanoparticle

Zhang et al. manuscript in preparation


Patterning Surfaces Using Microcontact Printing

� Microcontact printing (µCP) is a means of forming chemical patterns on surfaces.

� A polydimethylsiloxane (PDMS) stamp is used. The stamp is treated with the chemical �ink� which is subsequently transferred to the substrate.

Preparation of stamp

Inking of stamp

Contact withsubstrate

Patterned ink remains


Dendrimer Multilayer PatterningAFM Image of Patterned G4 Dendrimer Multilayer

Unusually stable dendrimer multilayers can be patterned using microcontact printing techniques.

Arrington et al. Langmuir 18 (2002) 7788-7791


Metallized Polymeric Structures via Photoreduction

Cu plating solution

hυ

Dendrimer adlayer(variable thickness)atop silicon substrate

Conductivity? Materials Properties?


Metallized Polymeric Structures via Photoreduction

� G4.5 monolayer in CuSO4 plating solution

� Copper appears to be metallic rather than Cu2+

� Increase in metal content as a function of irradiation time

Cu 2p XPS: G4.5/Cu(plating solution)


Dendrimer Assisted NanoTransfer Printing10

0 µm

x 1

00 µ

m

~ 20 nm Co features printed onto a dendrimer monolayer mediated Sisubstrate

Au

AuM

Possible multilayerstructure transfer?

Dendrimer monolayers can allow direct printing of metal structures


Dendrimer Patterning and Functional Nanostructures

� Dendrimer mono- and multilayers can be patterned by printing.� Metal ions can be reduced under UV irradiation in the presence

of the dendrimer. � Interdendrimer particles Co particles produced are relatively

monodisperse, acicular, magnetic, and apparently metallic.� Functional nanopatterned multilayer structures?� Shape, size selectivity in magnetic nanoparticles?

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