[DNAzyme cracking-nanogold resonance Rayleigh scattering spectral method for the determination of trace Cu2+]

In the condition of pH 7.0 HEPES buffer solution and 0.19 mol x L(-1) NaCl, the substrate strand DNA (SS) and the enzyme strand DNA (ES) hybridized into a double-stranded DNA (dsDNA) at 80 degrees C. The substrate chain of dsDNA could be cracked by Cu2+, and the released single-stranded DNA (ssDNA) were adsorbed on the nanogold(NG) surface to produce a stable NGssDNA conjugate. The unprotected NG was aggregated to form NG aggregation (NGA) that exhibited a resonance Rayleigh scattering (RRS) peak at 627 nm. When the Cu2+ was added, the NGssDNA increased, and the NGA decreased that caused the RRS intensity decreasing at 627 nm, and the solution color changed from blue to red. The decreased RS intensity deltaI was linear with the Cu2+ was added, the NGssDNA increased, and the NGA decreased that caused the RRS intensity decreasing at 627 nm, the solution color changed from blue to red. The decreased RS intensity deltaI was linear to the Cu2+ concentration in the range of 15-1 250 nmol x L(-1), with a regression equation of deltaI = 0.17c-2.3, coefficient of 0.989 5 and a detection limit of 8 nmol x L(-1) Cu2+. In addition, the influence of foreign substances on the determination of 0.75 micromol x L(-1) Cu2+ was considered. The results show that 3 micro mol x L(-1) Ca2+, Pb2+ and Hg2+, 2 micromol x L(-1) Fe2+, 1 micromol x L(-1) Sn2+, 4 micromol x L(-1) Al3+, 12 micromol x L(-1) Mn2+, 4 micromol x L(-1) Co2+ and Ni2+ did not interfered with the determination. This indicates that this method has good selectivity. This new, rapid, sensitive, selective RRS method was applied to the determination of Cu2+ in water, with satisfactory results.