A highly selective nanogold-aptamer catalytic resonance scattering spectral assay for trace Hg2+ using HAuCl4-ascorbic acid as indicator reaction

Single strand DNA (ssDNA) was used to modify nanogold to obtain a nanogold-aptamer resonance scattering (RS) probe (NGssDNA) for Hg2+, based on the formation of stable thymine-Hg2+-thymine (T-Hg2+-T) mismatches and aggregation of the released nanogold particles. After removing the aggregated particles by filtrate membrane, the excess NGssDNA in the filtration solution exhibit catalytic effect on the gold particle reaction between HAuCl4 and ascorbic acid (AA) that appear as RS peak at 596 nm. When Hg2+ concentration increased, the RS intensity at 596 nm decreased. The decreased intensity is linear to Hg2+ concentration in the range of 0.00008–0.888 ng/mL Hg2+, with detection limit of 0.000034 ng/mL. The nanogold-aptamer catalytic RS assay was applied to determination of Hg2+ in water with satisfactory results.