Synthesis, characterization, and photocatalytic activity of ZnS and Mn-doped ZnS nanostructures

Semiconductor quantum dots such as zinc sulfide have interesting potential applications, due to their size-dependent optical properties. These nanostructures can be used for applications in agriculture, environmental chemistry, and fluorescence microscopy. The great rise in nanotechnology has sparked the scientific community's interest in nanomaterials for the use of photodegradation in aquatic bodies. Quantum Dots (QDs) such as ZnS nanoparticles (NPs) can absorb electromagnetic radiation and generate subsequently reactive oxygen species (ROS) directly in aqueous phase. The presence of ROS in aquatic environments can be used to destroy organic contaminants by photocatalysis. Previous studies had evidenced that the presence of impurities (i.e. copper, manganese, nickel) in the crystalline structures of QDs can enhance their optical properties and consequently their catalytic capacity. Because of this, the present investigation was focused on generating water stable ZnS nanoparticles with catalytic properties. In this work, we have synthesized pure and doped ZnS nanoparticles using a reflux method. The morphology of these QDs was characterized by transmission electron microscopy (TEM). We also studied the photocatalytic properties of these nanostructures. A red shift was observed in the photoluminescence peak of pure ZnS nanoparticles when they were doped with heavy metals. Pure ZnS NPs and Mn-doped ZnS NPs showed luminescent peaks at 444 nm and 596 nm, respectively. Photodegradation studies were evaluated in the presence of organic dyes like Tropaeolin O (TO) and different concentrations of quantum dots (250 ppm and 500 ppm). The photodegradation of TO was dependent on the QDs concentration and exposure time. The destruction of organic dyes in the presence of photo-excited ZnS nanoparticles is envisioned as a fast and clean technology. The destruction of organic dyes in the presence of photo-excited ZnS nanoparticles is envisioned as a fast and clean technology.