Green synthesis of highly fluorescent nitrogen - Doped carbon dots from Lantana camara berries for effective detection of lead(II) and bioimaging

Here, we developed a simple green approach for the synthesis of highly fluorescent nitrogen doped carbon dots (NCDs) using Lantana camara berries. Optical and physicochemical properties of as synthesized NCDs were extensively studied by using various analytical techniques. NCDs exhibited bright fluorescence with Quantum yield as high as 33.15%, which is stable to various effects like heat, pH, ionic strength and continuous irradiation. Furthermore, the NCDs presented highly selective and sensitive fluorescence response towards Pb2+ which explored their potential to serve as a label-free fluorescent probe for the effective detection of Pb2+. As developed NCDs based probe exhibited a great linear response (R-2 = 0.998) towards Pb2+ in the concentration range of 0-200 nM with a detection limit of 9.64 nM. The probe further presented high precision without any interference and was successfully applied for the detection of Pb2+ in the real water and human sera (serum and urine) samples. Cytotoxicity studies on both cancerous (human breast adenocarcinoma MCF-7) and normal (Human embryonic kidney HEK-293) cell lines revealed their excellent biocompatibility. With their low cytotoxicity, strong fluorescence and excitation-dependent emission, NCDs were successfully applied as multi-colour bioimaging agents and Pb2+ detection capabilities were further evaluated in live cells.