Optimized nitrogen-doping of carbon quantum dots from Banana Peel waste: A highly selective Fe2+sensor probe

This research explores into the eco-friendly synthesis of nitrogen-doped carbon quantum dots (NCQDs) utilizing discarded banana peel waste as a sustainable carbon source and ethylenediamine as a nitrogen dopant. The study aims on the critical gap in environmentally sustainable ion detection system by optimizing the fluorescent properties of CQDs for Fe2+ detection applications through nitrogen doping at an optimum ratio. Herein, we reported a facile one-step hydrothermal method to synthesize NCQDs with varying nitrogen dopant concentrations. The precursor material was characterized by thermal gravimetric analysis and Raman spectroscopy which exhibited a more amorphous carbon structure. Fourier-transform infrared spectroscopy and Proton nuclear magnetic resonance spectroscopy proves the successful bonding of nitrogen functional group to pristine CQDs. The obtained nitrogen-doped CQDs (NCQDs) exhibited precise size control, with an average size of 5.05 nm. Optical analysis showed that NCQDs with a nitrogen doping level of 1.25 % had the best photostability, brightness, and fluorescence stability. These NCQDs demonstrated high selectivity in detecting Fe2+ through a fluorescent quenching mechanism. These findings suggested that obtained NCQDs has potential as environmentally friendly fluorescence probes in the application water filtration systems and medical diagnostics, particularly in Fe2+ detection and sensing due to their high selectivity and efficient fluorescent properties.