Surface Defects Modulated Multicolor Emission from Sulfur Quantum Dots for LED Display

Sulfur quantum dots (SQDs) have recently drawn considerable attention due to their metal-free composition, low toxicity, and stable photoluminescence. However, effective approaches to extend SQDs emission into the long-wavelength region remain limited. In this study, we report a strategy for synthesizing emission-tunable SQDs through the use of thiol ligands. Sodium thiosulfate serves as the sulfur source, while various thiol reagents are employed to engineer the SQDs surface states. The formation of polysulfanyl radical surface defects arises from the reaction between thiol groups and sulfide ions, as made evident by electron paramagnetic resonance (EPR) analysis. Crucially, these surface defects, rather than particle size, govern band gap modulation. By selecting different thiol ligands, we successfully obtained SQDs emitting blue, green, and yellow fluorescence, with emission peaks tunable from approximately 400 to 580 nm. This sustainable and ecofriendly approach precisely adjusts emission wavelengths, creating a platform for designing application-specific SQDs, which greatly enhances their usability in fields such as sensing, optoelectronics, and biomedical imaging.