Highly porous ZnS microspheres for superior photoactivity after Au and Pt deposition and thermal treatment

This work highlights the enhanced photocatalytic activity of porous ZnS microspheres after Au and Pt deposition and heat treatment at 500 °C for 2 h. Microporous ZnS particles of size 2–5 μm with large surface area 173.14 m2 g−1 and pore volume 0.0212 cm3 g−1 were prepared by refluxing under an alkaline medium. Photoluminescence of ZnS at 437 nm attributed to sulfur or zinc vacancies were quenched to 30% and 49%, respectively, after 1 wt% Au and Pt loading. SEM images revealed that each ZnS microparticle consist of several smaller ZnS spheres of size 2.13 nm as calculated by Scherrerʹs equation. The rate of photooxidation of 4-nitrophenol (10 μM) under UV (125 W Hg arc–10.4 mW/cm2) irradiation has been significantly improved by Au and Pt deposition followed by sintering due to better electron capturing capacity of deposited metals and growth of crystalline ZnS phase with less surface defects.