Paper Title
INVESTIGATION OF DOPING CONCENTRATION EFFECT ON PHOTOCATALYTIC ACTIVITY OF Sr/ZnS NANOPARTICLES

Abstract
Nanomaterials exhibit unusual physicochemical properties, which make them very interesting and increasingly sought after, especially semiconducting nanomaterials. Zinc sulfide (ZnS) nanoparticles (NPs) are of particular interest because of their wide band gap energy (39 meV). Tuning this band energy can influence and adjust their optical properties and make them more attractive in several fields such as antibacterial and photocatalytic activities. The aim of this work is to study the effect of Sr-doping concentration on the structural and optical properties of ZnSNPsand torevealing an improvement in theirphotocatalyticactivity.Strontium-doped ZnSNPs were synthesized through hydrothermal method andused Sr concentrations were 1.5, 5 and 9 wt%. The characterization by XRD demonstratedthe successful synthesis of ZnS NPs with two crystalline phases (cubic and hexagonal), without apparition of any XRD peaks related to Sr phases. The SEM images show that the NPs have great tendency to aggregate into spherical shapes. Spectroscopy analysis revealed vibration modes specific to ZnS materials on the Raman spectra at about 260 and 345 cm-1 and on Fourier-transform infrared spectra at 668.9 cm-1. The UV–Visible absorption spectra showed that NPs are almost transparent in the visible region and exhibit a strong absorption in the UV region. The maximum absorption is located at around 334 nm. A slight shift towards higher wavelengths is observed for the absorption edge of the whole of samples. This expresses a decrease in the band gap energy of Sr-doped ZnS NPs, which is a favorable factor for the improvement of photocatalytic performances. Finally, the methyl orange organic dye degradation rate increases with Sr concentration and reached75% in 60 minutes. Keywords - Sr-doped ZnS Nanoparticles, Hydrothermal synthesis, Phoyocatalytic activity, Methyl orange dye.