Betel leaf derived multicolor emitting carbon dots as a fluorescent probe for imaging mouse normal fibroblast and human thyroid cancer cells

Abstract A facile and eco-friendly approach was adapted for the preparation of multicolor emitting carbon dots (BL-MECDs) by hydrothermal method using betel leaves. BL-MECDs were synthesized at various reaction times-12 h, 24 h, 36 h, and 48 h at 200 °C. The reaction times were varied to find the optimum reaction condition to obtain BL-MECDs with excellent optical- and chemical properties. BL-MECDs were characterized by various analytical techniques. The surface morphology, degree of graphitization, and their composition were examined by field emission scanning electron microscope, Raman spectrum, and attenuated total reflection-Fourier transform infrared spectroscopy, respectively. The optical properties were evaluated via ultraviolet–visible and fluorescence spectroscopy techniques. The result suggests that BL-MECDs prepared at 36 h have enriched functional groups and excellent fluorescence emission with acceptable quantum yield (15%). Thus, BL-MECDs prepared at 36 h were utilized for further studies. X-ray photoelectron spectroscopy confirmed the existence of functional groups such as carboxyl, carbonyl, and hydroxyl groups. Moreover, the obtained BL-MECDs exhibited excellent prolonged stability and photostability even after 150 days of storage in atmospheric condition and by continuous irradiation of about 100 min with 365 nm UV-lamb, respectively. Further, BL-MECDs showed excellent biocompatibility and negligible cytotoxicity and thus explored for cell imaging for normal mouse fibroblast cell line (L929) and human anaplastic thyroid cancer cells line (SW1736). Cellular fluorescence imaging suggesting that BL-MECDs have great potential in bioimaging applications.