Laser irradiation-induced two-photon photolysis of sulfates for photoluminescent sulfur quantum dots†

Recently, sulfur quantum dots (SQDs) have gained great research interest because of their excellent optical properties and low toxicity, thus inspiring researchers to make efforts to explore a simpler and faster approach for the synthesis of SQDs. Herein, a facile and green bottom-up strategy is first proposed to prepare SQDs via 532 nm laser irradiation of a sulfate-containing solution without any extra additives. The reduction of sulfates to elemental sulfur under visible light is demonstrated for the first time. Furthermore, fluorescence characterization combined with density functional theory calculations revealed that the two-photon dissociation of sulfates plays a critical role in the formation of SQDs under laser irradiation. The nucleation mechanisms of self-assembling of sulfur element were revealed by molecular dynamics.