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.