Nitrogen and sulfur co-doped carbon dots synthesis via one step hydrothermal carbonization of green alga and their multifunctional applications

Carbon dots co-doped with nitrogen and sulfur (N/S-CDs) were prepared with the model bloom-forming green alga Dunaliella salina via a one-step hydrothermal reaction, i.e., no chemicals were required. The obtained N/S-CDs with average particle size about 3.2 +/- 0.5 nm exhibited great photostability, low toxicity, high water solubility, excitation-dependent emission, and enough fluorescent activity. According to the synergy effect of the co-doped nitrogen and sulfur atoms, N/S-CDs were used as multifunctional fluorescent probes for algal imaging, scavenging of 1, 1-diphenyl-2-picrylhydrazyl and hydroxyl radicals, selective detection of Fe(III), and visible light-induced photodegradation of methylene blue and methyl violet. In a word, harmful green alga blooms could be transformed into multifunctional N/S-CDs.