Development of FRET-based optical sensors using N-doped carbon dots for detection of chromium (VI) and manganese (VII) in water for a sustainable future

Carbon dots (CDs) synthesis has received much attention due to their considerable application potential. Natural compounds are efficient CD carbon precursors, exhibiting significant physical and chemical characteristics. In the present work, the hydrothermal method has successfully derived blue fluorescent N-doped carbon dots (NCDs) from Alstonia scholaris leaves and ethylenediamine. The synthesized NCDs were characterized by Fourier transform infrared (FTIR), Transmission Electron Microscopy (TEM), fluorescence and UV–vis analysis. It exhibits better chemical and physical properties with a relatively good quantum yield of 21%. As-synthesized NCDs were applied for the FRET-based detection of Cr6+ and Mn7+ ions in water samples to investigate their suitability as fluorescent probes. The detection limit was 0.173 µM and 0.394 µM for Cr6+ and Mn7+, respectively. This study has illustrated an environmentally friendly approach for the facile synthesis of blue fluorescent NCDs with remarkable potential for further utilization in sensing devices.