▎ 摘　　要

Fabrication of effective photocatalyst using semiconductors and graphene or reduced graphene oxide has been regarded as one of the most promising task to attenuate the environmental pollution. This paper reports the synthesis of different nanocomposites of reduced graphene oxide-cadmium sulfide (RGO-CdS) with varying weight ratio of RGO by simple reflux condensation reaction, during which the reduction of graphene oxide (GO) and formation of CdS nanoparticles occur simultaneously. The combination of CdS nanoparticles (NPs) with the optimum amount of RGO gives a noticeable effect on the properties of the synthesized hybrid nanocomposites, such as enhanced optical, photocatalytic properties. The microscopic studies proved that with the increasing RGO content in the nanocomposites, the particle size decreases and got different shapes. These nanocomposites have been investigated separately as nanocatalyst for the reduction of Cr(VI) to Cr(III) in the presence of visible light irradiation and the catalytic activity depends on the pH of the medium and also the particle size of the CdS NPs which are supported by the band gap energy derived from Tauc's equation. The significant increase in photocatalytic performance of the RGO-CdS nanocomposite was attributed to high electron conductivity of the CdS NPs and RGO surface which facilitates charge separation and prolongs the lifetime of photogenerated electron-hole pairs by decreasing the recombination rate. Antibacterial and antiprotozoal activities have been investigated to determine the efficiency of these RGO-CdS nanocomposites on different bacterial and protozoan strains.