Green Synthesis of Carbon Dots for Rapid Selective Detection and Photoreduction of Cr(VI) under Sunlight

This paper presents a facile synthesis of a luminescentcarbondot from a plant source (Brassica oleracea) and subsequent chemical modification of carbon dots with ionicliquid. The ionic liquid-modified carbon dot (ILCD) shows intenseblue luminescence, which was remarkably quenched in the presence ofdichromate ions. The decrease in intensity is mainly indexed to theinner filter effect. Under optimized conditions, a broad linear rangeof 1-750 & mu;M was observed for the detection of Cr(VI)with a lower limit of detection of 0.5 & mu;M. Further, the ILCD-incorporatedmesoporous SiO2-TiO2 (ILCD@SiO2-TiO2) was successfully used for the adsorption as well as thedetoxification of Cr(VI) under sunlight. The removal efficiency ofdichromate from aqueous solution is 82% as verified by the atomicabsorption spectroscopy technique. Importantly, ILCD@SiO2-TiO2 can be used for the reduction of Cr(VI) under solarlight with a reduction efficiency of 98% and can be reusable up tothe fifth cycle with a reduction efficiency of 79%. Due to low costand green synthesis, this ILCD and ILCD@SiO2-TiO2 can be used for on-field detection and production of Cr(VI) freewater in a pilot scale.