Exploration of biological activities of green N-Carbon Quantum Dots and photocatalytic studies of ZnO@N-CQDs

In this work, we have exemplified the highly fluorescent Nitrogen-doped Carbon Quantum Dots (N-CQDs) via a simple and greener hydrothermal approach from Cucumis maderaspatanus and ZnO@N-CQDs to explore biological and photocatalytic activity. To confirm their optical and morphological properties UV-visible Spectroscopy (UV-VIS), Fourier Transform Infra-Red Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) were undertaken where spherical uniform distribution of N-CQDs was found in TEM, graphitic carbon peak was observed for N-CQDs and hexagonal wurtzite structure was found for ZnO@N-CQDs in XRD, UV-DRS showed 3.07eV for ZnO@N-CQDs. The presence of all the functional groups was found in both N-CQDs and ZnO@N-CQDs by FT-IR analysis. Nitrogen-doped Carbon Quantum Dots (N-CQDs) were found to be very biocompatible since they showed better cytotoxicity, in vitro bio-imaging, and fluorescent ink application. In the case of photocatalytic degradation, about 70% of methylene blue dye was degraded by ZnO@N-CQDs within 60 minutes. Therefore, the N-CQDs and ZnO@N-CQDs, synthesized in this study, demonstrate enhanced suitability as materials for both biological and environmental applications.