Facile colorimetric detection of Hg2+ based on anti-aggregation of silver nanoparticles

This paper describes an investigation of a facile colorimetric sensor for Hg(2+) in aqueous solution based on the anti-aggregation of silver nanoparticles (AgNPs). In the absence of Hg(2+), the addition of 6-Thioguanine to AgNPs solution led to the aggregation of AgNPs, resulting in a color change from yellow to brown with a red shift of absorption spectra. However, the presence of Hg(2+) inhibited the 6-Thioguanine-induced aggregation of AgNPs accompanying with a color change from brown to yellow. Under the optimal conditions, the ratio between the absorbance at 530 nm and 394 nm (A530/A394) was linearly proportional to the Hg(2+) concentration in a range from 0 to 333 nM with a detection limit of 4 nM. Other environmentally relevant metal ions did not interfere with the detection of Hg(2+). The proposed method was simple, cost-effective and rapid without any complicated modifying step. It was successfully applied to detect Hg(2+) in environmental water samples.