Resonance scattering spectral detection of trace Hg2+ using aptamer-modified nanogold as probe and nanocatalyst.

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 Hg(2+). In the presence of NaCl, Hg(2+) interacts with AussDNA to form very stable double-strand T-Hg(2+)-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 Hg(2+) can be detected rapidly by the aptamer-modified nanogold RS assay, with a detection limit of 0.7 nM Hg(2+). If the large nanogold clusters were removed by membrane filtration, the excess AussDNA in the filtrate solution exhibits a catalytic effect on the new Cu(2)O particle reaction between NH(2)OH and Cu(2+)-EDTA complex at 60 degrees C. The excess AussDNA decreased with the addition of Hg(2+), which led the Cu(2)O particle RS intensity at 602 nm to decrease. The decreased RS intensity (DeltaI(602nm)) had a linear response to Hg(2+) concentration in the range of 0.1-400 nM, with a detection limit of 0.03 nM Hg(2+). This aptamer-modified nanogold catalytic RS method was applied for the detection of Hg(2+) in water samples, with sensitivity, selectivity, and simplicity.