Aqueous Synthesis of Mn-Doped ZnInS/ZnS Core/Shell Quantum Dots with Enhanced Optical Properties and Sensitivity for Priority Pollutants

The development of less toxic nanoparticles capable of producing and selectively sensing organic pollutants remains a significant challenge in biological and environmental applications. In this study, ZnInS/ZnS quantum dots (QDs) were synthesized via an aqueous-phase doping approach to integrate manganese (Mn) and enhance the singlet oxygen quantum yield (SOQY). The as-synthesized QDs displayed an average particle size of 7.40 nm, prolonged photoluminescence lifetimes, and tunable emission characteristics. Introduction of Mn into the host QDs enhanced the absolute quantum yield by up to twofold at the optimal concentrations, while the increased concentrations resulted in reduced luminescence due to increased non-radiative recombination. The surface chemistry of stabilizing agents further improved the formation of singlet oxygen. Thioglycolic acid (TGA)- and gelatin-capped QDs generated higher SOQY than QDs capped with citrate and TGA. Furthermore, as-synthesized Mn-doped QDs detected different organic pollutants such as trinitrophenol (TNP), dichlorophenol (DCP), naphthalene (NP), phenanthrene (PH), and pyrene (PY). Among these pollutants, TNP showed quenching behavior, while the others showed enhancement behavior. The QDs detected 620 µM of TNP following a linear Stern–Volmer relationship. These results show the potential of water-soluble Mn–ZnInS/ZnS QDs as multifunctional nanoprobes for phototherapy and environmental sensing applications.