The Effect of 4-Nitroaniline Concentration on Ag Nanoparticles for Detecting the Melamine Level in Milk

ABSTRACT Silver nanoparticles were prepared by reduction of AgNO3 in dilute aqueous solutions of 4-nitroaniline. The effect of 4-nitroaniline concentration on Ag nanoparticles was investigated, and the sensitivity and selectivity of the prepared Ag nanoparticles solution on the presence of melamine in milk were studied. A color change from yellow to blue was observed with increasing melamine concentration. The characterization methods used were transmission electron microscopy (TEM) and ultraviolet-visible (UV-Vis) spectroscopy. The TEM images indicated that the silver nanoparticles solution consisted of well-dispersed agglomerates of spherical-shaped Ag nanoparticles with an average size of about 32 nm. The plasmon absorption peak of the silver nanoparticles was found at 397 nm. In addition, it was revealed that a sensitive nonlinear correlation existed between the absorbance and the logarithm of melamine concentrations ranging from 50 to 10 ppm.