Visual Colorimetric Detection of Hg( II ) with Graphene Oxide Peroxidase-Like Activity

A new method for visual detection of trace He2+ ions was successfully established based on the single-stranded DNA (ssDNA) and T-Hg2+-T complex have different interaction with graphene oxide (GO), which owns mimetic enzyme catalytic performance. In NaAc-HAc buffer of pH 4. 0, ssDNA can be adsorbed on the GO surface, which will efficiently decrease the peroxidase-like activity of GO to catalyze the oxidation of peroxidase substrate TMB to form blue product in the presence of H2O2, which presented a characteristic absorbance at 652 nm. When Hg2+ ions exist, the ssDNA formed double-stranded DNA via thymine-He2+-thymine complex coordination structure, which hardly absorbed on the surface of GO for the interactionbetween dsDNA and GO is much weaker, the peroxidase mimetic activity of GO is not affected, accompanying with the color darkening and increase of absorbance at 652 nm. Under the optimal conditions, the absorbance versus He2+ concentration is linear in the range from 3. 26 X 10(-8) to 9. 0 X 10(-7) mol center dot L-1, which can make a calibration graph. The regression equation is Delta A = 41. 75c(mol center dot L-1) +0. 048 7, r=0. 997 3. The limit of detection is 9. 79 X 10(-9) mol center dot L-1. This method has the advantages of simplicity, cost saving and good specificity, thus can be applied for determinating mercury ion in the environment samples.