Sulfur precursor and citric acid effect on SnS nanoparticles and their influence on the photodegradation activity of selected organic compounds.

Semiconductor nanoparticle-mediated photocatalysis is an attractive option for water decontamination, being the semiconductors as SnS with a bandgap in the visible region, the most promising materials. In the present work, we evaluated the influence of important parameters in the photocatalytic application of SnS nanoparticles. Our results show that the presence of citric acid (used as a capping agent) restricts the formation of hexagonal nanoparticles. We also demonstrated that using thioacetamide as a sulfur source results in smaller nanoparticles than thiourea, 24.0 nm and 616 nm respectively. Moreover, small hexagonal nanoparticles play a key role in the photocatalytic activity of SnS nanoparticles. Compared with TiO performance, SnS nanoparticles exhibited faster kinetics for methyl orange (MO) degradation, Kapp = 0.0102 min, and 0.029 min, respectively. We proved that SnS is capable of breaking the azo bond of methyl orange by direct reduction. Furthermore, our analyses indicate that SnS nanoparticles do not degrade atrazine and imazapic, but the photocatalytic route of metribuzin competed with photolysis, resulting in a particular transformation product that was not obtained with light irradiation only. We demonstrated that SnS nanoparticles have high bond selectivity for azo breaking. Furthermore, they represent an advance for the development of designed materials (such as heterostructures), where the properties of SnS can be tuned.