Amino-ended hyperbranched polyamide as template for tuning the morphology of self-assembled ZnS particles

Zinc sulfide (ZnS) is an important photocatalytic and photoelectric material. Considerable efforts have been devoted to developing processes for synthesis of wurtzite ZnS with controllable morphology and structure. Control over the crystal structure and preparation of sphalerite ZnS remains to be a challenge. Here we report controllable fabrication of self-assembled ZnS particles in a number of crystal structures and morphologies using an amino-ended hyperbranched polyamide as template. The parameters affecting the morphology of the self-assembled ZnS, including template content, reaction temperature and time, molar ratio between zinc acetate and dithizone, were discussed in detail. We obtained three types (spherical, cubical and flower-shaped) of ZnS self-assemblies by tuning the reaction temperature. Both the cubical and the flower-shaped self-assembled ZnS particles are identified as forms of cubic sphalerite structure and the spherical particles are identified as a hexagonal wurtzite structure. In the fabrication of spherical self-assembled ZnS particles, initial ZnS crystal particles form first, and this followed by the formation of ZnS nanorods due to aggregation of the ZnS crystal particles and self-assembly of ZnS nanorods. The microstructure, morphology and optical properties of the self-assembled ZnS particles were characterized using SEM, XRD, XPS, Raman, UV-vis absorption and photoluminescence spectroscopy.