Exploration of Sulfur-Containing Nanoparticles: Synthesis, Microstructure Analysis, and Sensing Potential

In this work, three different sulfur sources such as sulfur powder, sodium sulfide, and sodium thiosulfate are selected to prepare sulfur-derived quantum dots (S-QDs), Na₂S-derived nanoparticles (NS-NPs), and Na₂S₂O₃^--derived QDs (NSO-QDs) in the presence of NaOH or assisted by hydrogen peroxide etching. The low sulfur percentage in the above three samples and the synthesis experiments in the presence of nitrogen/oxygen all support that poly(ethylene glycol) (PEG) plays an important role during the assembly process and the definition of sulfur dots is not accurate. For photophysical features, remarkable green quantum dots (S-QDs) possess an excitation-independent emission peak at 500 nm. But NS-NPs and NSO-QDs demonstrate observable shift tendency, and the evolution of emission profiles varies from 480 to 586 nm. NSO-QDs can be used as a fluorescent probe for highly selective and quantitative detection of Ni²⁺ in an aqueous solution in the presence of potential interfering ions with a low detection limit (0.18 μM) and a wide linear range (8-380 μM). Their reusability performance has also been demonstrated by employing dimethylglyoxime as the restoration reagent.