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Engineering Spontaneous Emission in Hybrid Nanoscale Materials for
Optoelectronics and Bio-photonics
Arup Neogi
Department of Physics and Materials EngineeringUniversity of North Texas
Email: [email protected]
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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
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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
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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
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Energy Transfer in Quantum Dots entrapped in Hydrogel Microspheres
Arup Neogi, Zhibing Hu
Department of Physics
University of North Texas
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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.
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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
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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
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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
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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
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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