Controllable synthesis of colloidal CuInS2 nanocrystals with tunable structures and its nonlinear optical properties

Abstract

Monodisperse CuInS2 nanocrystals (CIS NCs) with wurtzite (hexagonal) and chalcopyrite (tetragonal) structures have been obtained via a facile route of thermal decomposition of metal–thiolate. The morphologies of the nanocrystals were tuned from pyramid-shaped to nanospheres by varying the concentrations of oleylamine (OLA). The band gaps of the nanocrystals ranged from 2.73eV to 2.65eV when reaction time changed. Furthermore, the third-order optical nonlinearities of WZ–CIS NCs in n-Hexane were studied by Z-scan at a wavelength of 770nm. By increasing the concentration of OLA, the value of the third-order nonlinear-index coefficient γ, the nonlinear absorption coefficient β and nonlinear susceptibility χ(3) became larger.