Water-Soluble Ag–Sn–S Nanocrystals Partially Coated with ZnS Shells for Photocatalytic Degradation of Organic Dyes

Water-soluble nonrare metal Ag–Sn–S nanocrystals (ATS NCs) were green synthesized at room temperature using the interfacial nucleation mechanism. Interfacial acids regulate the concentration of hydroxide ions outside the complex, the sulfur sources attack the cations at the complex interface, and the sulfur sources form covalent bonds to complete crystal nucleation and growth at room temperature. The band gap of ATS NCs synthesized by the interface nucleation mechanism is 2.32∼2.59 eV, which gives it a higher redox ability and very high photocatalytic degradation rate. A total of 0.8 mg of Ag2SnS3 NCs can achieve photocatalytic degradation of more than 99% of MO (1 mg) under visible light (λ > 420 nm) in 2 min with a photocatalytic rate constant of 2.1247 min–1. Interfacial regulation of acid protonation on the surface of ATS NCs produced more defect states, which was conducive to trapping holes (h+), promoting their transfer to organic pollutants, and improving the photocatalytic oxidation degradation efficiency. Active species of trapping experiments showing photocatalytic degradation of active species as h+, ·O2–, and ·OH do not act as active species for MO degradation in this system. ATS NCs have ultra-high photocatalytic activity and further improve their photocatalytic efficiency by partially coated ZnS shells. Finally, we present the mechanism of photocatalytic degradation of ATS NCs and analyze the possible applications of ATS NCs. Due to its unique advantages of direct synthesis in organic pollutants at room temperature, it is expected to achieve a breakthrough in the practical treatment of large-scale industrial wastewater.