Hydrothermal synthesis of nitrogen-doped CQDs for detection of Cr6+ and removal of MB dye in wastewater

Research has demonstrated the feasibility of synthesizing nitrogen-doped carbon quantum dots (CQDs) without the passivation or oxidation chemicals. Given that lemon peels are a rich, renewable carbon source and a common agricultural waste and that these peels are readily available, we chose to use them to prepare fluorescent CQDs to detect metal ions. Synthesis of N-CQDs using biowastes appears to be an environmentally friendly, fast, and efficient method. N-CQDs are preferred for sensing applications due to their various characteristic properties. N-CQDs are important for fluorescent sensors since they produce strong fluorescence emissions. In addition, since N-CQDs have high water solubility, they can work without any problems in biological and environmental sensing in aqueous solutions. The surface composition of N-CQDs was determined by Fourier transform infrared (FTIR) analysis and electronic transitions by UV–visible (UV-Vis) analysis. The morphology and average size of N-CQDs were determined by transmission electron microscope (TEM). In TEM analysis, the average particle size of the nanoparticles was determined to be 5.96 nm. N-CQDs were tested for heavy metal determination and exhibited a low detection limit of 19.37 µM for Cr⁶⁺. N-CQD exhibited 85.73 % photocatalytic activity for the degradation of methylene blue (MB) under visible light. The development of lemon peel-based N-CQDs has significant potential in environmental protection through the treatment of wastewater contaminated with MB dyes and the detection of Cr⁶⁺ metal ions.