Preparation and Optical Properties of CdS Nanocrystals Prepared by a Mechanical Alloying Process

Abstract

CdS nanocrystals have been successfully synthesized by a mechanical alloying process. The X-ray diffraction (XRD) pattern shows that the major phase of the product was wurtzite CdS compound after mechanical alloying of the elemental powders for 60 min. All the diffraction peaks from the elemental Cd and S powders disappeared completely in the XRD patterns of as-milled CdS nanocrystals ball milled for more than 10 h. High-resolution transmission electron microscopy (HRTEM) images confirmed the wurtzite structure of as-milled CdS nanocrystals. The as-milled CdS nanocrystals were subsequently capped with trioctylphosphine oxide/trioctylphosphine/nitric acid (TOPO/TOP/NA), which leads to the formation of yellow dispersion solution. The size of capped CdS nanocrystals ranges from 1.6 to 6.2 nm. The capped CdS nanocrystals show similar optical properties to those CdS nanocrystals prepared by the wet chemical process, the absorption peaks for the capped CdS nanocrystals locate within the range of 345 to 380 nm.