Resonance Scattering Spectral Detection of Trace Hg2+ Using Aptamer-Modified Nanogold as Probe and Nanocatalyst

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Abstract
Single-strand DNA (ssDNA) was used to modify 10 nm nanogold to obtain an aptamer-modified nanogold resonance scattering (RS) probe (AussDNA) for detection of Hg2+. In the presence of NaCl, Hg2+ interacts with AussDNA to form very stable double-strand T−Hg2+−T mismatches and release nanogold particles that aggregate to large nanogold clusters causing the RS intensity at 540 nm to be enhanced linearly. On those grounds, 1.3−1667 nM Hg2+ can be detected rapidly by the aptamer-modified nanogold RS assay, with a detection limit of 0.7 nM Hg2+. If the large nanogold clusters were removed by membrane filtration, the excess AussDNA in the filtrate solution exhibits a catalytic effect on the new Cu2O particle reaction between NH2OH and Cu2+−EDTA complex at 60 °C. The excess AussDNA decreased with the addition of Hg2+, which led the Cu2O particle RS intensity at 602 nm to decrease. The decreased RS intensity (ΔI602nm) had a linear response to Hg2+ concentration in the range of 0.1−400 nM, with a detection limit of 0.03 nM Hg2+. This aptamer-modified nanogold catalytic RS method was applied for the detection of Hg2+ in water samples, with sensitivity, selectivity, and simplicity.

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