Post on 12-Jan-2016
Engineering Spontaneous Emission in Hybrid Nanoscale Materials for
Optoelectronics and Bio-photonics
Arup Neogi
Department of Physics and Materials EngineeringUniversity of North Texas
Email: arup@unt.edu
Ultrafast and Nanoscale Photonics Group Arup Neogi, Department of Physics
Research AreasResearch Areas
1. Nanoscale Optoelectronic materials for efficient light emission2. Biophotonic materials; for hybrid molecular electronics and photonics
http://www.phys.unt.edu/research/photonic/website/
Funding:• National Science Foundation• US Department of Energy• Japan Soc. for Promotion of Sciences
Using subwavelength corrugated surface grating:• Momentum can be transferred to couple the light and plasmon modes• Directional Emission can be improved by using corrugated surfaces
Surface plasmons polariton coupling with directional emission
Change in radiative recombination lifetime in Qdots due to resonant exciton-surface plasmon coupling
Radiative recombination rate in strained quantum dots emission - observed above the SP emission energy
Energy Transfer in Quantum Dots entrapped in Hydrogel Microspheres
Arup Neogi, Zhibing Hu
Department of Physics
University of North Texas
Temperature induced changes in hydrogel
The NIPAM sample in water: Effect of temperature61
21 oC 35 oC1 cm 1 cm
The phase transition temperature (Tc) of PNIPAM is 34 °C.
below Tc, the hydrogel is hydrophilic and swells in water, while
above Tc it is hydrophobic and collapses into a small volume.
Change in scattering properties with particle size
200 250 300 350 4000.00
0.05
0.10
0.15
0.20
f(R
h)
Rh (nm)
Broken S-S bond PNIPAM microgels PNIPAM/ NCs microgels PNIPAM microgels
Variation of Particle size with chemistry Change in scattering properties with turbidity
Photoluminescence Spectrum of QDs embedded in GEL
UV
Sunlight
The image of PNIPAM/CdTe microgel
under sunlight
The PL image of PNIPAM/CdTe microgel
under UV lamp.
400 450 500 550 600 650 700 750 800
2000
4000
6000
8000
10000
Inte
nsi
ty
Wavelength (nm)
qd2 qd3 qd4
Electric Field Induced effects in PNIPA Gels
*Wu, J. et. al. Phys. Rev. Lett., 90, 48304 (2003) +Hu, Z. et. al. Advan. Mater. 13, 1708 (2001)
At room temperature
No electric field
3.5V/cm electric field
Hybrid Semiconductors for FRET based light emitters
Arup Neogi, Jianyou Li
University of North Texas, Denton, TX, USA
Terry Ishihara
Frontier Research Laboratory, RIKEN, Japan
Oligonucleotide based nanoscale photodetector
GaN
* MRS Best paper award 2005
SAGCs behave like wide-bandgap GaN semiconductors, with equivalent energy gap ~ 3.5 eV & electron e1ective mass ~ 2m* at 300 K; concentration ~ 3.33 x 10-2 M
280 300 320 340 360 380 400 420 440 4606.96
6.97
6.98
6.99
7.00
7.01
7.02
7.03
Ph
oto
cu
rre
nt
(a.u
.)
Wavelength (nm)
54 Device
Nanoscale Photodiode