Preparation of size-controlled hexagonal CdS nanocrystallites and the characteristics of their surface structures

Abstract

Hexagonal CdS nanocrystallites have been easily prepared by reacting Cd²⁺ and S^2- (H₂S or Na₂S) in N,N-dimethylformamide (DMF) without adding any surface stabilizers. The mean diameter of the nanocrystallites can be rigorously controlled over the range 1.8–4.2 nm with keeping the hexagonal crystalline structure by varying the sulfur source (H₂S and Na₂S) and by regulating the preparation temperature. Use of Na₂S as a sulfur source produces smaller CdS nanocrystallites than use of H₂S. The size control and stability of CdS nanocrystallites are discussed in terms of the characteristics of the surface structures based on insitu Cd K-edge EXAFS analysis.