Fluorescent detection of melamine in real samples using green-synthesized N-CQDs: A sustainable approach

Melamine, a nitrogen-rich industrial compound, is often illegally added to food products-especially dairy, to artificially inflate protein content, posing serious health risks such as kidney damage upon long-term exposure. This study aims to develop a fluorescence-based sensor for the sensitive detection of melamine. Nitrogen-doped carbon quantum dots (N-CQDs) were synthesized using Murraya koenigii leaves via a green, microwave-assisted method. Resulting N-CQDs exhibited a high fluorescence-quantum-yield of 30 %, and their structural and optical characteristics were thoroughly analysed using appropriate techniques. Detection mechanism is based on dynamic fluorescence quenching, allowing for highly responsive melamine-sensing with a low detection limit of 0.385 μM. When applied to real samples like water and milk, sensor demonstrated excellent performance, achieving recovery rates between 96.8 % and 101.8 % with low relative standard deviations (0.70 %-4.34 %). Results suggest that developed sensor is a promising tool for rapid, green, and sensitive detection of melamine in food safety and environmental monitoring.