An aptamer was modified using a gold nanoparticle (AuNP) to form a stable aptamer-AuNP probe that was not aggregated in the pH 7.2 2-4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) buffer solution in the presence of NaCl. The Ag + reacted with the aptamer-AuNP probe to form a hairpin structure complex of Ag + -aptamer and released the AuNPs that were aggregated to large particles, which led to a resonance Rayleigh scattering (RRS) peak at 596 nm enhancement. The enhanced value DI 596 nm varies linearly with the Ag + concentration in the range 6.7-133.3 6 10 28 M. The probe in the aptamer reaction solution has a strong catalytic effect on the Cu 2 O particle reaction of Fehling reagent and glucose, and the particle products exhibited a strong RRS peak at 610 nm. However, catalysis of AuNP aggregation is very weak, which means it can not be removed from the aptamer reaction solution. When the concentration of Ag + increased, the RRS peak intensity at 610 nm decreased. The decreased value DI 610 nm is linear to the Ag + concentration in the range of 3.3-666.7 6 10 29 M. Thus, two new RRS methods were proposed for the detection of Ag + , with high sensitivity, good selectivity and simplicity. A highly sensitive resonance Rayleigh scattering method was proposed for trace Ag + sensing using the aptamer-modified nanogold as a probe.

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In an aggregated gold nanoparticle (AuNP) sol substrate, rhodamine S (RhS) exhibited a surface-enhanced Raman scattering (SERS) peak at 1503 cm À1 . Based on the ozone oxidization and RhS-I 3 particle reactions, 1.56-62.5 nmol L À1 of O 3 can be determined by SERS, with a detection limit of 0.9 nmol L À1 .

The ozone in an air sample was trapped by H3 BO3 -LK solution to produce iodine (I2) that interacted with excess I(-) to form I3(-). In pH 4.0 acetate buffer solutions, the I3(-) reacted with acridine red to form acridine red-I3 ion association particles that resulted in the fluorescence peak decreased at 553 nm. The decreased value ΔF553 nm is linear to the O3 concentration in the range 0.08-53.3 × 10(-6) mol/L, with a detection limit of 4 × 10(-8) mol/L. This fluorescence method was used to determine ozone in air samples, and the results were in agreement with that of indigo carmine spectrophotometry.