Bandgap engineering and plasmonically enhanced sun light photocatalyis in Au/Cd_1-xZn_xS nanocomposites

Metal nanoparticles-decorated semiconductor nanomaterials generally hold a series of advantages especially enhanced electron-hole pair lifetime and thus exhibit superior solar energy conversions. In this study, we report a facile solution processing of Au-decorated Cd1-xZnxS, where x = 0, 0.25, 0.5, 0.75, and 1, nanocomposites and their enhanced photocatalytic activity against methylene blue (MB) dye degradations. The Au/CdZnS nanocomposites were investigated for their structural, morphological, optical, and photocatalytic properties. The XRD patterns indicated that the crystalline sizes of CdZnS are found to fall within 1-3 nm. The electron microscopic images publicized that the average particle size of Cd0.25Zn0.75S is 5 nm. The bandgap values of pristine CdS, pristine ZnS, Cd0.75Zn0.25S, Cd0.5Zn0.5S, and Cd0.25Zn0.75S are 2.21 eV, 3.4 eV, 2.29 eV, 2.31 eV, and 2.53 eV, respectively. The optical band gap of the Cd1-xZnxS nanomaterials have got reduced for Au incorporation due to the occurrence of red shift and the enhanced visible region absorption for the incorporation of Au. The visible light photocatalytic effect of the nanocomposites has been evaluated with MB dye degradation reaction under sunlight light exposure. The Au-decorated Cd0.25Zn0.75S nanocompound had exhibited 97% of photocatalytic degradation of MB dye molecules which is 20% higher than the bare Cd0.25Zn0.75S nanocompound.