Green synthesis of fluorescent carbon dots from watermelon peel waste for sensing applications

Abstract Carbon dots (CDs) are versatile nanomaterials valued for their fluorescence, biocompatibility, and potential in bioimaging and drug delivery. Current synthesis methods, such as hydrothermal or microwave techniques, often require specialized equipment and energy-intensive processes, limiting their accessibility. This study presents an efficient, sustainable approach to synthesizing CDs from watermelon peel, an abundant waste biomass, using a round-bottom flask. Watermelon peel was sun-dried, crushed, and boiled with distilled water (1:10 w/v) for 5 h, followed by centrifugation. The resulting CDs exhibited blue fluorescence under a fluorometer, indicative of small particle sizes (<10 nm), and a UV-vis absorption peak at 250 nm, consistent with π-π* transitions of conjugated C=C and C=O bonds. This method leverages simple equipment and a renewable precursor, offering a cost-effective, eco-friendly alternative to conventional techniques. The CDs’ optical properties suggest suitability for biomedical applications, though further optimization (e.g., quantum yield, size distribution) is needed. This work highlights the potential of waste-derived CDs, contributing to sustainable nanotechnology development.