ZnIn2S4 microspheres were synthesized via a hydrothermal method using zinc chloride (ZnCl2), indium chloride tetrahydrate (InCl3·4H2O) and L-cysteine (C3H7NO2S). The effect of hydrothermal temperatures (160 oC, 200 oC and 240 oC) on the crystallinity, morphology and optical properties of the synthesized powders was investigated. The synthesized products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). The results showed that the synthesized powders were pure ZnIn2S4 with a hexagonal structure. The ZnIn2S4 powders were microspheres with diameters of 8.3-9.5 μm, constructed from several nanosheets. These nanosheets interconnected with each other, forming a pore structure. With increasing hydrothermal temperature, the nanosheets increased in thickness and the width of the pores between the nanosheets expanded. The ZnIn2S4 powder synthesized at 240 oC exhibited stronger UV-Vis absorption and photoluminescence (PL) intensities than the other samples. The photocatalytic activity of the ZnIn2S4 photocatalyst was investigated by photodegradation of methylene blue under blue light irradiation; 97% of the methylene blue degraded within 210 min. Photostability of the ZnIn2S4 photocatalyst was also investigated.

Keywords: Zinc indium sulfide, Photocatalysts, Hydrothermal, Optical properties.