Fabrication and Calibration of an Ag Nanoparticles Sensor for Detecting the Melamine and NaCl Levels in Raw Milk

ABSTRACT A colorimetric, label-free, and aggregation-based Ag nanoparticles (AgNPs) probe was developed for the detection of melamine and NaCl. A color change from yellow to blue with increasing melamine concentration was observed. The plasmon absorbance of the formed AgNPs allowed quantitative detection of melamine. A sensitive nonlinear correlation existed between the absorbance and the logarithm of melamine concentration, ranging from 1000 to 0.25 ppm. Detection of NaCl at a concentration of 10 ppm in raw milk was also observed.