Sensitive and selective determination of 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 NO 2 − ions in aqueous samples.