An ultra-sensitive detection of Melamine in milk using Rare-earth doped Graphene Quantum Dots- Synthesis and Optical Spectroscopic approach

This work focuses on a rapid and sensitive spectroscopic approach for detecting melamine in food products based on rare-earth Terbium-doped Graphene Quantum Dots (Tb-GQDs) synthesized using microwave and simple chemical conjugation methods. Citric acid and diethylene triamine (DETA) are the precursors of synthesizing GQDs. Terbium, a rare earth element with exceptional fluorescence properties, is doped onto the surface of the GQD to obtain dual photoemission with a broad spectral window and to provide excellent photo-stable characteristics. The as-synthesized Tb-GQDs were characterized using various spectroscopic and microscopic techniques. The synthesized Tb-GQD were spherical with a size of around 6 nm, showing approximately a quantum yield of 52 %, concerning the Standard-Quinine sulfate quantum yield of 54 %. Further, Tb-doped GQDs act as a fluorescent probe, were used to detect and quantify the concentration of melamine (0--5 mu M) used as an adulterant in milk and milk products and obtained a maximum detection limit of 0.31 mu M. This work concludes that the reported dual emitting Tb-GQDs provide a sensitive and effective platform for detecting melamine in real-time samples, especially in milk, and show promising potential in food industries.