Electronic absorption spectroscopy of cobalt ions in diluted magnetic semiconductor quantum dots: Demonstration of an isocrystalline core/shell synthetic method
Electronic absorption spectroscopy of cobalt ions in diluted magnetic semiconductor quantum dots: Demonstration of an isocrystalline core/shell synthetic method
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DOI：
10.1021/ja0115215
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发表时间：
2001-12-12
影响因子：
15
通讯作者：
Gamelin, DR
中科院分区：
文献类型：
--
作者：
Radovanovic, PV;Gamelin, DR
本文报道了用配体场电子吸收光谱探测稀释磁性半导体量子点中Co2+掺杂离子的方法。研究发现，用标准的倒胶束共沉淀法制备Co2+掺杂CdS （Co2+:CdS）量子点时，掺杂离子主要结合在纳米晶体表面。这些Co2+:CdS纳米晶体对于表面结合的Co2+的溶剂化是不稳定的，并且随时间的吸收测量允许识别两种涉及溶剂-钴配位的瞬态表面结合中间体。与采用相同方法制备的Co2+:ZnS量子点相比，Co2+的离子半径（0.74埃）与Cd2+（0.97埃）之间存在较大的不匹配，这是导致cd纳米晶体生长过程中Co2+离子被排斥的原因。开发了一种等晶核/壳制备方法，通过将表面结合离子封装在额外的CdS层下，可以合成内部掺杂的Co2+:CdS量子点。
This paper reports the application of ligand-field electronic absorption spectroscopy to probe Co2+ dopant ions in diluted magnetic semiconductor quantum dots. It is found that standard inverted micelle coprecipitation methods for preparing Co2+-doped CdS (Co2+:CdS) quantum dots yield dopant ions predominantly bound to the nanocrystal surfaces. These Co2+:CdS nanocrystals are unstable with respect to solvation of surface-bound Co2+, and time-dependent absorption measurements allow identification of two transient surface-bound intermediates involving solvent-cobalt coordination. Comparison with Co2+:ZnS quantum dots prepared by the same methods, which show nearly isotropic dopant distribution, indicates that the large mismatch between the ionic radii of Co2+ (0.74 Angstrom) and Cd2+ (0.97 Angstrom) is responsible for exclusion of Co2+ ions during CdS nanocrystal growth. An isocrystalline core/shell preparative method is developed that allows synthesis of internally doped Co2+:CdS quantum dots through encapsulation of surface-bound ions beneath additional layers of CdS.