Fruit Peel-Derived Carbon Quantum Dots: A Sustainable Fluorescent Probe for Detecting Melamine and Toxic Contaminants in Milk and Dairy Products

The detection of toxic contaminants, such as melamine, heavy metals, antibiotics, and mycotoxins, in milk and dairy products is critical for ensuring food safety and public health. Conventional detection methods, while accurate, are often expensive, time-consuming, and require sophisticated instrumentation. In recent years, carbon quantum dots (CQDs) derived from fruit peels have emerged as a sustainable, cost-effective, and eco-friendly alternative for sensing applications. Fruit peels, such as orange, banana, and pomegranate, serve as excellent carbon sources for synthesizing CQDs through green chemistry approaches like hydrothermal carbonization and microwave-assisted synthesis. These CQDs exhibit exceptional optical properties, including strong photoluminescence, high quantum yield, and tunable surface chemistry, making them ideal fluorescent probes for contaminant detection. The interaction between CQDs and target analytes, such as melamine, results in measurable changes in fluorescence intensity, enabling sensitive and selective detection. Recent studies have demonstrated the successful application of fruit peel-derived CQDs for detecting melamine in milk with detection limits as low as 10 nM, as well as heavy metals, antibiotics, and mycotoxins. Despite their potential, challenges such as standardization, matrix interference, and scalability remain. This review highlights the synthesis, properties, and applications of fruit peel-derived CQDs as sustainable fluorescent probes, emphasizing their role in advancing food safety and environmental monitoring. Future research should focus on multifunctional CQDs, portable sensing devices, and integration with advanced data analysis techniques to enhance their practical applicability.