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

Based on the selective interaction between Hg2+ 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 Hg2+ 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–HgII–CA complex was formed in the presence of Hg2+, 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 Ba2+, Ca2+, Zn2+, Cd2+, Co2+, Mn2+, Cu2+, Mg2+, and Ni2+ ions did not induce any distinct spectral changes, which constituted a Hg2+-selective sensor. A dynamic range of 1.6–16 × 10−6 M Hg2+ ions was observed at the optimized reaction condition. This method provides a potentially useful tool for Hg2+ detection.

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► We developed a colorimetric method for detecting Hg2+ ions using Au NPs and CA.
► The experiment validated the selective interaction between CA and Hg2+ ions.
► The experiment validated the anti-aggregation of CA–Au NPs induced by NaCl.
► We also evaluated the sensitivity and selectivity of the sensor of Hg2+ ions.
► The use of a highly stable and commercially available CA as Hg2+ acceptor avoids any other labeling or modification steps.