Colorimetric detection of mercury ions based on anti-aggregation of gold nanoparticles using 3, 5-dimethyl-1-thiocarboxamidepyrazole

Abstract

A colorimetric method based on the anti-aggregation of gold nanoparticles (AuNPs) for the rapid detection of mercury (II) ions in an aqueous medium is proposed. 3, 5-Dimethyl-1-thiocarboxamidepyrazole (Pzl) was synthesized that caused aggregation of AuNPs and induced a color change from red to blue. However, in the presence of Hg2+, the AuNPs remained in the dispersed state without changing color due to the resilient and preferable interactions between Pzl and mercury ions rather than AuNPs. The change in color of the solution containing AuNPs from red to blue was the consequence of the aggregation mechanism and the presence of mercury ions gave rise to the anti-aggregation mechanism among AuNPs. The sulphur and nitrogen-rich different binding sites of ligand Pzl led to the excellent properties of the signature binding of mercury ions. This admirable property imparted the selective and nanomolar sensitivity of the ligand for mercury ions over the other metal ions. The method can be effectively applied to estimate the mercury level in water samples with good accuracy. The experimental results were also corroborated by Density Functional Theory (DFT) calculations.