Selective synthesis of cubic and hexagonal phase of CuInS2 nanocrystals by microwave irradiation

Abstract

Metastable cubic zincblende and hexagonal wurtzite CuInS₂ nanocrystals were successfully synthesized by a facile microwave radiation method. The morphology, structure and phase composition of the as-prepared products were examined, and the results demonstrated that high-purity and uniform CuInS₂ nanocrystals were obtained. Further investigation revealed a structural evolution process from cubic zincblende to hexagonal wurtzite with increasing volume ratio of ethylenediamine and ethanol from 1 : 30 to 1 : 1 at 160 °C. In addition, the optical absorption properties of samples were also studied. It was found that the as-synthesized cubic and hexagonal CuInS₂ nanocrystals had band gaps of 1.503 and 1.470 eV, respectively. Thanks to the superior optical absorption properties for visible light, CuInS₂ nanocrystals may have potential applications in various nanostructured optoelectronic devices. The possible formation mechanism of the product, namely “phase transformation”, was systematically studied.