Green synthesis of carbon dots from Ocimum sanctum for effective fluorescent sensing of Pb2+ ions and live cell imaging

A simple, rapid and cost-effective approach is developed to synthesize fluorescent carbon dots (CDs) using the leaves of Ocimum sanctum as a carbon source for the first time. The as-synthesized CDs possess high stability in aqueous solution and exhibit strong fluorescence with quantum yield of 9.3%. We have explored the use of such CDs as a fluorescent sensor for Pb2+ ions detection, which is based on Pb2+ ions induced fluorescence quenching of CDs. More significantly the resultant CDs has excellent selectivity and sensitivity towards Pb2+ ions with a limit of detection (LOD) 0.59 nM and linear detection range of 0.01–1.0 μM. The practical use of synthesized CDs for detection of Pb2+ ions is demonstrated in triple negative breast cancer cells (MDA-MB 468 cells) and real water samples successfully. Moreover, the CDs are also possessing low cytotoxicity to exhibit excellent fluorescent probe for multicolour cellular imaging.