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

•Monodisperse CIS NCs have been obtained via thermal decomposition of metal–thiolate.•The XRD pattern revealed that CIS NCs have chalcopyrite and wurtzite structures.•Pyramid-like (chalcopyrite) and nanospheres (wurtzite) were determined by TEM.•The third-order optical nonlinearity is investigated by using Z-scan technique.

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 2.73 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.