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

Monodisperse CuInS 2 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 2.73   eV to 2.65   eV 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 770   nm. 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.