Rapid and highly-sensitive melamine sensing based on the efficient inner filter effect of Ag nanoparticles on the fluorescence of eco-friendly ZnSe quantum dots

A very practical and competitive sensing strategy for melamine has been developed based on the efficient inner filter effect (IFE) of Ag nanoparticles (AgNPs) on the fluorescence of eco-friendly ZnSe quantum dots (QDs). The fluorescence emission of ZnSe QDs could be quenched significantly by AgNPs via IFE, which resulted in a fluorescence “off-state”. The presence of melamine could induce the aggregation of AgNPs and modulate the IFE process. Thus the IFE-decreased fluorescence could gradually recover in a melamine concentration-dependent way, thereby achieving the fluorescence “turn-on” sensing for melamine. The detection mechanism was clearly illustrated and the influences of various experimental conditions were also investigated. Under the optimal conditions, a decent linear relationship for melamine was obtained in the range from 1.0 to 36   μg   L −1 , and the detection limit was as low as 0.11   μg   L −1 . The IFE-based strategy was successfully applied for melamine analysis in raw milk and egg samples and satisfactory results have been achieved. Therefore, it is very promising to use this simple, rapid, sensitive and eco-friendly method for on-site and real-time screening of melamine.