Detection of Hg2+ in Water by Modified Gold Nanoparticles: A Rapid Method and Its Mechanistic Basis

A new sensor was developed to detect Hg2+ ions; different volume ratios of chloroauric acid and sodium citrate were used, which were 1.0, 0.8 and 0.5. Three kinds of gold nanoparticles (AuNPs) with sizes of 18 nm, 25 nm and 32 nm were synthesized in this way. The functional modification with succinimide and glutarimide was performed on these three sizes of AuNPs. Hg2+ was detected by colorimetric detection of AuNPs modified with succinimide and glutarimide. Research shows that, because a complex structure was formed by a coordination reaction with Hg2+, the aggregation of AuNPs occurred, the color changed from red to purple, and the characteristic absorption peak of the UV–visible absorption spectrum was redshifted. The best visual detection limit is 5 μmol/L, showing good selectivity and broad applicability; it was found that the material was specific to the detection of Hg2+. The novelty of this study lies in the use of simple imide-containing modifiers and the systematic comparison of particle-size-dependent colorimetric responses of modified AuNPs toward Hg2+. These results offer a promising approach for tracking and monitoring Hg2+ contamination in aquatic environments.