Alkaline Extraction and Characterization of Carbon Quantum Dots Synthesized from Coconut Husk

This research introduces an environmentally friendly and sustainable approach for producing carbon quantum dots (CQDs) from coconut husk, an abundant lignocellulosic agricultural by-product. The husk was pre-treated using 2% sodium hydroxide (NaOH) to remove lignin and hemicellulose, thereby enhancing cellulose availability for nanomaterial synthesis. The treated biomass was utilized to synthesize carbon quantum dots without any doping (UCQDs) via a hydrothermal process. The resulting UCQDs were characterized by zeta potential analysis, which revealed an average surface charge of –25.2 mV, indicating moderate colloidal stability. Particle size and electrophoretic mobility measurements further confirmed nanoscale dispersion with reproducible charge behaviour. The photocatalytic performance was assessed using methylene blue (MB) as a representative contaminant under white light exposure. UCQDs achieved 76.5% degradation within 180 minutes, while nitrogen-doped CQDs (NCQDs) exhibited superior performance, reaching 94% degradation in 150 minutes. Additionally, NCQDs maintained high photocatalytic efficiency across a broad pH range, demonstrating their robustness for diverse wastewater conditions. These results highlight the promise of coconut husk-based CQDs, especially NCQDs, as an economical option and eco-friendly nanomaterials for environmental remediation applications.