Abstract
We have developed a simple method for the selective colorimetric detection of aqueous mercuric (Hg2+), silver (Ag+), and lead (Pb2+) ions by using label-free gold nanoparticles (Au NPs) and alkanethiols. The degree of alkanethiol-induced aggregation of the Au NPs decreases in the order of 6-mercaptohexanol (6-MH) ∼ 4-mercaptobutanol (4-MB) > 11-mercaptoundecanol (11-MU) > 2-mercaptoethanol (2-ME). The specific and strong interactions of these alkanethiols with Au NPs and heavy metal ions enabled us to develop label-free assays for the sensitive and selective detection of Hg2+ ions using the 4-MB/Au NPs probe, as well as Ag+ and Pb2+ ions using the 2-ME/Au NPs probe. The presence of strong Hg2+-S bonds alleviated the extent of 4-MB-induced aggregation of the Au NPs, resulting in a declining ratio of the extinction coefficients at 650 to 520 nm (Ex650/520, a measure of the molar ratio of the aggregated to the dispersed Au NPs) of the Au NP solution. In contrast, the presence of Ag+, Cu2+, and Pb2+ ions led ...
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