A simple and green
colorimetric sensing assay strategy for highly
efficient determination of melamine has been fabricated, which is
based on the redox reaction of gallic acid with Ag
+
. Monodispersed
Ag nanoparticles (AgNPs) were obtained using gallic acid as a reducing
and stabilizing agent. However, the aggregate behavior of AgNPs was
observed, while the melamine was present in the reaction medium. As
a result, the color of the solution changed from vivid yellow to brown,
and the density of the color was quantitatively correlated with the
melamine concentration. The aggregation of AgNPs could be attributable
to the formation of hydrogen bonds between melamine and gallic acid.
The designed sensor exhibited a good detection limit of 0.099 μM
(0.012 ppm), which was much lower than the safety limit in China (1.0
ppm) and EU (2.0 ppm). Additionally, the sensing assay displayed good
selectivity toward melamine over other coexisting substances. Consequently,
the proposed colorimetric sensor was successfully used for the determination
of melamine detection in raw milk samples.