Microwave‐Driven Fabrication of Blue Fluorescent Undoped and Nitrogen‐Doped Carbon Quantum Dots From Ficus religiosa for Efficient Visible‐Light Photocatalytic Degradation of Cationic Dyes: A Parametric Optimization Study

Malachite green (MG), a persistent aquatic pollutant, poses serious risks to water bodies and requires efficient degradation strategies. The use of bare or undoped carbon quantum dots (UCQDs) has been shown to be an effective approach for degrading such pollutants. In this study, we explored the enhancement of photocatalytic performance in UCQDs through modification with nitrogen‐doped carbon quantum dots (N‐CQDs). These both CQDs were synthesized via a one‐step microwave‐assisted treatment of Ficus religiosa leaf powder and urea. The resulting N‐CQDs were obtained by carbonizing the UCQDs with urea at 800 W. Compared with UCQDs, which were produced solely from leaf powder, the N‐CQDs exhibited significantly improved degradation efficiency, with nitrogen content increasing from 1.5% to 5.5%. Under optimized conditions, the degradation rate of MG using N‐CQDs reached 94.84%. Free radical scavenging experiments revealed the key active species involved in the photocatalytic process. The study confirmed the participation of h + , •O 2 − , and •OH radicals, with the order of their contribution to MG degradation determined as •OH > •O 2 − > h + . The kinetics of photocatalytic degradation were examined as well. The MG dye molecule's degradation pathway was determined by the radical scavenging experiment. On account of these findings, the photocatalytic mechanism, which forms h + , • O 2 − , and • OH by electron transition and transfer, was speculated on, yielding several significant implications for the utilization of the photocatalytic technique in the treatment of wastewater.