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Size-Dependent Composition and Molar Extinction Coefficient of PbSe Semiconductor Nanocrystals

2009; American Chemical Society; Volume: 3; Issue: 6 Linguagem: Inglês

10.1021/nn9001616

1936-086X

Quanqin Dai, Yingnan Wang, Xinbi Li, Yù Zhang, Donald J. Pellegrino, Muxun Zhao, Bo Zou, Jaetae Seo, Yiding Wang, William W. Yu,

Nanocluster Synthesis and Applications

Atomic compositions and molar extinction coefficients of PbSe semiconductor nanocrystals were determined by atomic absorption spectrometry, UV-vis-NIR spectrophotometry, and transmission electron microscopy. The Pb/Se atomic ratio was found to be size-dependent with a systematic excess of Pb atoms in the PbSe nanocrystal system. Experimental results indicated that the individual PbSe nanocrystal was nonstoichiometric, consisting of a PbSe core and an extra layer of Pb atoms. For these nonstoichiometric PbSe semiconductor nanocrystals, 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 approximately 2.5.