In Situ Colorimetric Recognition of Melamine Based on Thymine Derivative-Functionalized Gold Nanoparticle

A simple, fast, and convenient colorimetric sensing system is presented for melamine recognition in milk samples by thymine-derivative- (NT-) decorated gold nanoparticles (AuNPs), based on the complementary hydrogen bond between thymine and melamine, wherein the introduction of melamine causes a rapid and obvious red-to-blue color change. Therefore, the melamine content in milk can be qualitatively recognized by the naked eye and quantitatively measured by measuring absorbance. NT-AuNPs show excellent selectivity to melamine against any other tested molecules, anions, and metal ions, as well as very good sensitivity that can distinguish melamine-contaminated milk from safe milk with a limit of detection of 3.5 nM.