Herring sperm DNA (hsDNA) was used to modify 10 nm nanogold to obtain a resonance scattering (RS) spectral probe (AuhsDNA) for Hg^2＋. In the medium of pH 7.0 Tris-HCl-0.017 mol/L NaCl, Hg^2＋ interacted with AuhsDNA to form stable Hg^2＋-hsDNA complex and larger nanogold clusters, which could be removed by membrane filtration. The excess AuhsDNA in the filtration solution exhibited catalytic effect on the Fehling reagent-glucose reaction to form Cu₂O particles that exhibit the strongest RS peak at 580 nm. With addition of Hg^2＋, the excess AuhsDNA in the filtration solution decreased accordingly, and the RS intensity at 580 nm decreased. The decreased RS intensity (ΔI_{580 nm}) was linear to Hg^2＋concentration in the range of 1～833 nmol/L, with regression equation of ΔI_{580 nm}＝＋0.9, coefficient of 0.9990 and detection limit of 0.3 nmol/L. The proposed method was applied to detect Hg^2＋ in water samples with satisfactory results.

Key words: Hg^2＋, herring sperm DNA modified nanogold probe, nanocatalysis, resonance scattering