N, S-codoped Carbon Dots for Nontoxic Cell Imaging and As a Sunlight-Active Photocatalytic Material for the Removal of Chromium

Nitrogen-sulfur codoped carbon dots (NSCD) were synthesized via a single-step microwave-assisted method having a fluorescence quantum yield of ∼12%. The NSCD has been proven to be nontoxic and utilized as a fluorescent imaging nanoprobe for cancer cells (HeLa cells) under UV and blue light excitation (in vitro environment). In addition to the long-known cell imaging application, these NSCD have been used as a sunlight active photomaterial for the removal of toxic hexavalent chromium as Cr(VI). The experimental results reveal that the sunlight active NSCD shows good potential toward the photocatalytic removal of Cr(VI) ions from the wastewater. For the environment and water purification purpose, three different wastewater samples were tested that are synthetic wastewater (up to 100 ppm), laboratory wastewater, and Cr(VI) ion-spiked industrial wastewater for the photocatalytic removal of Cr(VI). The biocompatible NSCD as a fluorescent imaging probe of cancer cells along with its fruitful utilization in photocatalysis under sunlight (compared to the dark condition) demonstrates the overall sustainability of the presented process.