Multifunctional CDs as photoinitiators: Detection and reduction for Cr(VI)

In the realm of sensing, carbon dots (CDs) have exhibited remarkable fluorescence characteristics. In the field of catalysis, CDs can function concurrently as electron donors and acceptors and have substantial electron or hole transport capacities. In this study, both merits were integrated into one, and a one-step hydrothermal approach was used to create multifunctional CDs. On the one hand, CDs are employed as a fluorescence probe with good sensitivity and selectivity to detect Cr(VI). On the other hand, CDs exhibit strong photoreduction capabilities for Cr(VI) in the absence of any external cocatalysts or photosensitizers when acting as photoinitiators. The results show that Cr(VI) quenches the CDs fluorescence as a result of the combined effects of static quenching and the inner filter effect. At the same time, under the condition of illumination, the inner filter effect encourages the CDs electrons to move from the valence band to the conduction band, resulting in electron hole pairs. With the help of electrons' reducing power, Cr(VI) can be rapidly and effectively converted to Cr(III). The findings of this study suggest that CDs are a satisfying bi-functional carbon-based material with significant potential for the treatment of industrial wastewater.