Green synthesis of carbon dots from Calotropis procera leaves for trace level identification of isoprothiolane

Carbon nanocrystals play a crucial role in developing drug delivery and bioimaging systems because of their biocompatible nature, unique surface functionalities, and optical characteristics. In this study, we focused on the one-pot simple and convenient synthesis of carbon dots (CDs) from Calotropis procera leaves through hydrothermal carbonization. The synthesized CDs exhibit tremendous excitation-dependent emission spectra with a high quantum yield of 71.95% and do not require any surface modifications to enhance their fluorescence. The CDs show a robust emission peak at 416 nm. The exact size and stability (long-lasting in aqueous solution) of the fluorescent probe were characterized by transmission electron microscopy, UV-vis absorption, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. We obtained results indicating that the emission peak of CDs was significantly decreased with the addition of isoprothiolane. Moreover, the fluorescence intensity of the probe was not hampered vastly under different pH conditions. The detection limit for isoprothiolane was found to be 11.58 nM (3.36 ppb), and the CD-based fluorescence approach was applied to detect isoprothiolane pesticide in fruit and rice samples.