Taken together, we suppose that two steps are involved in the specific inhibition of Hg2+. Firstly, Ag+ was reduced to zero-valent silver and formed AgNPs; secondly, Hg2+ was adsorbed on the surface of the as-formed AgNPs and thus changed the surface properties of AgNPs, decreasing the cata-
lytic ability of AgNPs. Attributed to the high affinity of Hg to Ag/Au,23,31 the specificity of Hg2+ of this proposed method can be explained.
Optimization of the sensing system
The reaction conditions were optimized to establish the optimum analytical conditions. We used the changes of fluor-escence, that is, F0 − F, as a criterion to optimize the detection conditions, where F0 and F are the fluorescence intensities at 563 nm in the absence and presence of Hg2+, respectively.
Effect of time
The effect of time on Ag+ autocatalytical reaction was studied, and the experimental results in Fig. 5A indicate that the fluor-escence increased gradually and reached about 90% of the maximum when the reaction time reached 10 min, which means that the oxidation reaction was almost complete in 10 min. For this reason, the optimum time for the proposed system was set as 10 min.
Effect of the concentration of Ag+
The effect of the concentration of Ag+ was studied in the range from 48 to 192 μM. The result is shown in Fig. 5B. It was