Colorimetric detection of Hg2+ ions in aqueous media using CA–Au NPs

Abstract Based on the selective interaction between Hg 2+ ions and cyanuric acid (CA) and the anti-aggregation of CA stabilized gold nanoparticles (CA–Au NPs), a simple colorimetric method was developed for detecting Hg 2+ ions. In a medium of pH 7.4 tris–HCl buffer containing 8 × 10 −3 M NaCl, the CA–Au NPs solution was red, which was due to CA adsorbed onto the surface of Au NPs, stabilizing Au NPs against aggregation. When CA–Hg II –CA complex was formed in the presence of Hg 2+ , the stability of CA–Au NPs reduced, and then aggregation of Au NPs occurred. Consequently, the color of the solution changed from red to blue and could easily be measured with a common spectrophotometer. The aggregation of Au NPs was also validated using transmission electron microscopy (TEM). The controlled experiment showed that other ions including Ba 2+ , Ca 2+ , Zn 2+ , Cd 2+ , Co 2+ , Mn 2+ , Cu 2+ , Mg 2+ , and Ni 2+ ions did not induce any distinct spectral changes, which constituted a Hg 2+ -selective sensor. A dynamic range of 1.6–16 × 10 −6  M Hg 2+ ions was observed at the optimized reaction condition. This method provides a potentially useful tool for Hg 2+ detection.