Pumpkin-waste-derived copper quantum dots: green synthesis, underlying mechanism, and multifunctional applications in catalysis, antioxidants, and bioimaging

Abstract

Agricultural waste poses a significant challenge and opportunity for sustainable nanotechnology. This study presents a novel, eco-friendly, and cost-effective green synthesis of copper quantum dots (CuQDs) utilizing pumpkin waste extract. Our mechanistic investigations using LC-MS revealed a three-phase process (reduction, nucleation, and stabilization) driven by synergistic phytochemical interactions, providing key insights into CuQDs formation. The synthesized CuQDs exhibit rich optical properties, including strong fluorescence emission and a narrow size distribution (4 ± 0.4 nm). These CuQDs demonstrated significant catalytic efficiency, achieving 90% degradation of crystal violet and 96% of methylene blue within 3 min, alongside notable antioxidant activity. These functionalities are directly correlated with the elucidated mechanistic insights, where phytochemicals not only facilitate synthesis but also impart inherent bioactivity. Furthermore, CuQDs exhibited robust tissue-specific accumulation and bright fluorescence in zebrafish embryos, highlighting their potential for real-time bioimaging. Biocompatibility assessments confirmed minimal toxicity, with normal embryonic development and hatching rates, and environmental safety was validated through seed germination experiments. This green synthesis method offers a superior, sustainable alternative to conventional approaches by eliminating toxic chemicals and energy-intensive processes, thereby advancing environmentally responsible nanomaterial production.