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In pH 5.5 2-( N-morpholino)-ethanosulfonic acid buffer solution containing 0.25 M NaCl at 80 °C, the single-stranded substrate DNA hybridizes with the enzyme DNA to form double-stranded DNA (dsDNA). The substrate chain of dsDNA could be cracked catalytically by UO to produce a short single-stranded DNA (ssDNA) that adsorbed on the nanogold (NG) surface to form a stable nanogold-ssDNA conjugate and then further combine with rhodamine 6G (RhG) to form a NG-ssDNA-RhG conjugate that can be monitored by the surface-enhanced resonance Raman scattering (SERRS) spectral technique at 1,360 cm. Under the selected conditions, the increased SERRS intensity Δ I was linear to UO concentration in the range of 5-125 nmol/L, with a detection limit of 1.6 nmol/L. Using a 0.5-μmol/L Hg as enhancer, a 2.5-100-nmol/L UO can be determined. [ABSTRACT FROM AUTHOR]

Single-strand deoxyribonucleic acid (ssDNA) were used to modified nanogold particle to obtain a aptamer-nanogold probe (NGssDNA) for Hg(II). The probe is not aggregated in high concentration of NaCl. In the pH 7.0 Na2HPO4-NaH2PO4 buffer solution and in the presence of high concentration of NaCl, NGssDNA interact with Hg(II) to form stable double-strand T-Hg(II)-T mismatches and to release nanogold particles from the probe. The released nanogold particles aggregated to form bigger clusters which leaded the resonance scattering (RS) intensity at 540 nm enhanced linearly with the concentration of Hg2+ in the range of 0.39–1666.7 nM, with detection of 0.1 nM. This simple, rapid, and sensitive aptamer-nanogold RS assay was applied to determination of Hg2+ in wastewater, with satisfactory results. [ABSTRACT FROM AUTHOR]

In the medium of H2SO4 and in the presence of TiO2+, gold nanoparticles in size of 10 nm exhibited a weak surface plasmon resonance scattering (SPRS) peak at 775 nm. Upon addition of trace H2O2, the yellow complex [TiO(H2O2)]2+ formed that cause the gold nanoparticles aggregations to form bigger gold nanoparticle clusters in size of about 900 nm, and the SPRS intensity at 775 nm ( I) enhanced greatly. The enhanced intensity Δ I was linear to the H2O2 concentration in the range of 0.025–48.7 μg/mL, with a detection limit of 0.014 μg/mL H2O2. This SPRS method was applied to determining H2O2 in water samples with satisfactory results. [ABSTRACT FROM AUTHOR]