NSTI Nanotech 2009

PbSe semiconductor nanocrystals: size-dependent stability, composition, and molar extinction coefficient

Q. Dai, Y. Wang, R. Li, Y. Zhang, X. Li, D.J. Pellegrino, B. Zou, J. Seo, Y. Wang, W.W. Yu
Worcester Polytechnic Institute, US

Keywords: PbSe, size-dependent, stability, molar extinction coefficient

Abstract:

Infrared-emitting PbSe nanocrystals are of increasing interest in both fundamental research and technical application. However, the practical applications are limited by their poor stability. We firstly investigated the stability of PbSe nanocrystals under different conditions. Both absorption and luminescence spectra of PbSe nanocrystals were affected by particle size, particle concentration, and light exposure. The photoluminescence emission intensity of the PbSe nanocrystal solution under ultraviolet exposure in air increased first and then decreased slowly; without UV irradiation, the emission intensity monotonously decreased over time. Then we determined the atomic compositions and molar extinction coefficients of PbSe semiconductor nanocrystals by atomic absorption spectrometry, UV-Vis-NIR spectrophotometry, and TEM. The Pb/Se atomic ratio was found to be size-dependent with a systematic excess of Pb atoms in the PbSe nanocrystal system. We proposed a new computational approach to calculate the total number of Pb and Se atoms in different sized particles. This calculation played a key role on the accurate determination of the strongly size-dependent extinction coefficient, which followed a power law with an exponent of ~ 2.5.
 
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