Photoluminescence-tunable carbon dots from synergy effect of sulfur doping and water engineering

Multiple-color-emissive carbon dots (CDs) is one of the hotspots due to its potential in multi-fields. However, the exploring of efficient synthetic strategies and emission mechanisms still remain challenging. Herein, we report a facile solvothermal route to prepare CDs with tunable photoluminescence (PL) from green to red via a novel PL-tuning strategy of sulfur doping and water engineering. By detailed characterizations and comparison, it is demonstrated that the S doping can significantly increase the content of graphitic nitrogen, resulting in the fluorescence shifting from green to yellow; on the other hand, water engineering is able to yield carboxyl group and enhance surface oxidation degree, which can further facilitate the PL shifting from yellow to red. Owning to multicolor emissions and S doping, the prepared PL-tunable CDs present versatility in various applications including fluorescent films, light-emitting diodes (LED), bioimaging probe and highly sensitive Fe3+ detector.