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THE ASUNSKIS RESEARCH GROUP

NANOMATERIALS

Semiconducting nanocrystals have widespread application as: Photovoltaics, Thermoelectrics, Nanoelectronics, Biological Imaging and Catalytic Materials. The interest in these materials are due to their size tunable properties such as the changes in bandgap emission with differences in nanocrystal size.

Through a series of reactions using different surfactant molecules and different reaction temperatures, we have been able to grow CdSe nanocrystals of different size that emit at the many colors of the visible spectrum under UV-illumination. Changes in crystal size from 2-6 nm in the same material can have dramatic effects on the physical properties of the nanocrystal.

Nanocrystals emitting light in a variety of colors.

COLLOIDAL SYNTHESIS

The lab set-up for colloidal synthesis.

The goal of this research is to grow and characterize different semiconductor nanocrystals by using high temperature syntheses with a variety of surfactants and solvents. Materials of interest include CdS, CdSe, PbS and PbSe. Students in this research frequently use a vacuum/gas manifold (right)for nanocrystal synthesis as well as a nitrogen filled glovebox (below) for sample preparation and processing.

A student using the nitrogen filled glovebox for sample preparation and processing.

MATERIALS ANALYSIS

CdSe Nanocrystals and Wavelength charts.

Absorption and fluorescence spectra are collected at BHSU. The band gap absorption for these two CdSe nanocrystal solutions is well defined at 510 and 565 nm for the green and orange emitting CdSe, respectively. The photoluminescence spectra for the green and orange CdSe have a narrow gaussian distribution indicating a monodisperse nanocrystal size distribution.

Transmission Electron Microscopy, TEM, collected at South Dakota School of Mines and Technology to measure the exact sizes and size distribution of the nanocrystal solutions. Pictured here are the 4.5 nm orange emitting CdSe nanocrystals verifying the monodisperse size nature of the synthesized nanocrystals.

4.5 nm orange emitting CdSe nanocrystals.

MORE TO COME...