Ag<sup>+</sup>-Cl<sup>-</sup>-多取代荧光素体系的RRS和RNLS光谱及其分析应用
摘要
In pH 3.2~5.7 acetate (HAc-NaAc) buffer solution, AgCl forms by the reaction of Ag<sup>+</sup> with Cl<sup>- </sup>can bind with excessive Ag<sup>+ </sup>to form a [AgCl·Ag]<sup>+ </sup>cation. The cation further reacts with Polysubstituted fluorescein dyes (eosin B, eosin Y, tiger red, phloxine and ethyl eosin) anion (HL<sup>-</sup>) to form ion-association complexes [(AgCl·Ag)HL] by virtue of electrostatic attraction and hydrophobic force. Then the complexes draw close to each other and further aggregate to produce [(AgCl·Ag)HL]<italic><sub>n</sub></italic> nanoparticles with an average diameter of 20 nm due to the extrusion action of water and Van der Waals force. As a result, the spectra of absorption and fluorescence are changed a little, but resonance Rayleigh scattering (RRS) and resonance non-linear scattering (RNLS) such as frequency doubling scattering (FDS) and second-order scattering (SOS) are enhanced greatly. The sensitivity of Ag<sup>+</sup>-Cl<sup>-</sup>-eosin B system is the highest among six systems. Its maximum wavelengths of RRS, FDS and SOS are located at 315, 350 and 560 nm, respectively. The increments of three scattering intensity (ΔI<sub>RRS</sub>, ΔI<sub>FDS </sub>and ΔI<sub>SOS</sub>) are directly proportional to the concentration of Cl<sup>-</sup> in certain ranges, and three scattering methods can be applied to the determination of Cl<sup>-</sup>. Among them, the FDS method has the highest sensitivity, and followed by the RRS method. Take the eosin B system with the highest sensitivity as an example, the linear ranges and the detection limits for Cl<sup>-</sup> of the three methods (RRS, FDS and SOS) are 0.005-1.22 mg/mL, 0.004-2.92 mg/mL, 0.01-1.94 mg/mL and 1.50 ng/mL, 1.20 ng/mL, 3.90 ng/mL, respectively. In this paper, the formation of [(AgCl·Ag)HL]<italic><sub>n</sub></italic> nanoparticles, the enhancement of scattering intensity, the optimum conditions and the influencing factors have been investigated. Meanwhile, the effects of