The Core-Shell Structure of CdSe-ZnS Quantum Dots Characterized by X-Ray Absorption Fine SpectroscopyReport as inadecuate




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Journal of Nanomaterials - Volume 2015 2015, Article ID 764712, 7 pages -

Research Article

College of Physics and Electronic Engineering, Henan Normal University, Henan 453007, China

Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China

Received 15 December 2014; Revised 9 February 2015; Accepted 17 February 2015

Academic Editor: Hsueh-Shih Chen

Copyright © 2015 Huijing Wei et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Understanding the chemical and physical properties of core-shell nanocrystal quantum dots QDs is key for their use in light-emission applications. In this paper, a single-step injection-free scalable synthetic method is applied to prepare high-quality core-shell QDs with emission wavelengths of 544 nm, 601 nm, and 634 nm. X-ray absorption fine structure spectra are used to determine the core-shell structure of CdSe-ZnS quantum dots. Moreover, theoretical XANES spectra calculated by FEFF.8.20 are used to determine the structure of Se and S compounds. The QD samples displayed nearly spherical shapes with diameters of approximately 3.4 ± 0.5 nm 634 nm, 4.5 ± 0.4 nm 601 nm, and 5.5 ± 0.5 nm 544 nm. With XANES results and MS calculations, it is indicated that sphalerite ZnS capped with organic sulfur ligands should be the shell structure. Wurtzite CdSe is the main core structure with a Cd-Se bond length of 2.3 Å without phase shift. This means that different emission wavelengths are only due to the crystal size with single-step injection-free synthesis. Therefore, single-step injection-free synthesis could generate a nearly ideal core-shell structure of CdSe-ZnS QDs capped with an organic sulfur ligand.





Author: Huijing Wei, Jing Zhou, Linjuan Zhang, Fang Wang, Jianqiang Wang, and Chan Jin

Source: https://www.hindawi.com/



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