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

This paper presents a facile synthesis of a luminescent carbon dot from a plant source (Brassica oleracea) and subsequent chemical modification of carbon dots with ionic liquid. The ionic liquid-modified carbon dot (ILCD) shows intense blue luminescence, which was remarkably quenched in the presence of dichromate ions. The decrease in intensity is mainly indexed to the inner filter effect. Under optimized conditions, a broad linear range of 1–750 μM was observed for the detection of Cr(VI) with a lower limit of detection of 0.5 μM. Further, the ILCD-incorporated mesoporous SiO2-TiO2 (ILCD@SiO2-TiO2) was successfully used for the adsorption as well as the detoxification of Cr(VI) under sunlight. The removal efficiency of dichromate from aqueous solution is 82% as verified by the atomic absorption spectroscopy technique. Importantly, ILCD@SiO2-TiO2 can be used for the reduction of Cr(VI) under solar light with a reduction efficiency of 98% and can be reusable up to the fifth cycle with a reduction efficiency of 79%. Due to low cost and green synthesis, this ILCD and ILCD@SiO2-TiO2 can be used for on-field detection and production of Cr(VI) free water in a pilot scale.