Hydrogen-bonding-induced colorimetric detection of melamine by nonaggregation-based Au-NPs as a probe.

A colorimetric, label-free, and nonaggregation-based gold nanoparticles probe has been developed for the detection of melamine. Gold nanoparticles were generated using 3,5-dihydroxybenzoic acid as a reducer without adding gold nanoparticle seeds at room temperature. Upon the addition of melamine, the reducer 3,5-dihydroxybenzoic acid can interact with melamine through strong hydrogen-bonding interaction. Consequently, the formation of gold nanoparticles was interrupted by melamine since there was not enough reducer for the reduction of Au(3+) ion. And the color change from purple to yellowgreen with increasing melamine concentration was observed. The plasmon absorbance of the formed Au-NPs allows the quantitative detection of melamine. A sensitive linear correlation existed between the absorbance and the logarithm of melamine concentration ranging from 1x10(-9) M to 1x10(-5) M with a linear coefficiency of 0.993. The system has a high selectivity to melamine with a low detection limit of 8x10(-10) M.