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Research Projects
Advanced Synthesis of Semiconductor Nanowires
The spontaneous self-assembly of II-IV stabilizer depleted
nanoparticles (NPs) into nanowires (NWs) is a complex process
that is only partially understood. My work examines the
mechanism governing the change in growth pattern of CdTe NWs by
varying the growth conditions. Specifically, we have studied
the changes in the growth of the NWs induced by the addition of
dimethyl sulfoxide (DMSO) to the NW growth solution. We propose
that after the initial step of formation of NP pearl necklace
assemblies, the recrystallization of these assemblies and their
subsequent growth into long NWs involves Ostwald ripening.
Addition of DMSO allows for improved control over the NW length
and diameter. As the DMSO concentration in the NW growth
solution is increased, the resulting NW length and diameter
increases. When DMSO concentrations are raised above 70%, there
is no NW formation, which is attributed to inhibition of the
formation of pearl necklace assemblies. DMSO influence on NW
morphology can be correlated with the effect of the added
organic solvent on electrostatic interactions between the
nanoparticles and mass exchange between the growing nuclei. We
are currently studying the effects of mixtures of NPs on the
growth of NWs.
Images: Dependence of CdTe NW (A) length, (B) diameter, and (C)
fluorescence wavelength on DMSO concentration in growth
solution. Each data point in (A) and (B) represents the average
of 20 NWs from 5 separate runs using AFM and Nanoscope IIIa
software.
Layer-by-Layer
Assembly of LED Thin Films
I am examining the use of semiconductor NPs for use in LEDs.
Specifically, this involves the incorporation of these NPs in
layer by layer (LBL) films. The films are tuned to have an UV
absorbance with a visible fluorescent emission.
Images: TGA-CdSe/ZnS
and PPPA, and DLHA-CdSe/ZnS and PDDA LBL films on glass
substrates. The left image is under normal lighting, and the
right image is with UV exposure.
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