Aggregation-induced superior peroxidase-like activity of Cu2−xSe nanoparticles for melamine detection

A novel method for sensitive melamine detection based on the aggregation-induced superior peroxidase-like activity of Cu2−xSe capped by sodium polystyrene sulfonate (PSS) (Cu2−xSe@PSS) nanoparticles has been developed. In the presence of melamine, Cu2−xSe@PSS nanoparticles aggregated and exhibited impressive peroxidase-like activity which can accelerate the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to its blue product (oxidized TMB) with H2O2. The enhancement of the absorbance intensity of oxidized TMB at 650 nm showed a good linear relationship with the addition of melamine ranging from 4.7 nM to 29.7 μM. And the detection limit for melamine was as low as 1.2 nM, which was far below the safety limits of melamine ingestion (20 mM in the USA and EU; 8 mM in infant formula in China). Control experiments suggested that the enhancement in the peroxidase-like activity of aggregation for Cu2−xSe@PSS in comparison to its disperse nanoparticles resulted from the ˙OH or O2˙− radical generated.