Sensitive and selective determination of NO(2)(-) ion in aqueous samples using modified gold nanoparticle as a colorimetric probe

A sensitive and selective colorimetric method for determination of nitrite ion in aqueous samples was developed using 1-(2-mercaptoethyl)-1, 3, 5-triazinane-2, 4, 6-trione-functionalized gold nanoparticles (MTT-GNPs). The nitrite ion seems to be used as a "molecular bridge", which can form NH---N and NH---O hydrogen bonds with the MTT-GNPs, shorten the interparticle distance, and induce the aggregation of the MTT-GNPs. This aggregation results in a dramatic change from wine-red to purple-gray color. Therefore, the concentration of nitrite ion in environmental samples can be quantitatively detected using the MTT-GNPs sensor by the naked eyes or UV-vis spectrometer. Moreover, investigations have revealed the sensitivity of the detection could be clearly improved by modulating pH of the solution, which led to a more rapid color change in the optimized GNPs system. The absorption ratios (A790/A535) of the modified GNPs solution exhibited a linear correlation with nitrite ion concentrations and the limit of detection was 1 ppm. This cost effective sensing system allows for the rapid and facile determination of the concentration of [Formula: see text] ions in aqueous samples.