| Cyanine dyes bear the merits of large molar absorbability and high fluorescence quantum yield,and a better sensitivity and selectivity would be obtained if the measurement performed in near-IR region, a region of little interference from background. Furthermore, cyanine is sensitive to environment and its spectra may be varied with the change of microenvironment, which makes it very suitable for many analytical missions. In fact, cyanine has been already become one of the most important probes in fluorescence analysis field. In this thesis, I would continue to develop the application of cyanine in the fields of environmental and biological assays on the basis of previous work of predecessor. The thesis is consists of five chapters. In chapter 1, classifications, various qualities and application of cyanine were firstly summarized. Emphasis was focused on aggregation qualities of cyanines and their recent research progress in the fields of surfactant system and biological system. Then, the research proposal for this thesis is presented. In chapter 2, the spectral behaviors of cyanine I in the presence of surfactants were studied,and the mechanisms of spectral changes were also discussed. Firstly, the absorption changes of cyanine I in anionic surfactants was investigated. The hydrophobic cyanine I showed a moderately strong absorption peak at 700nm. When an amount of anionic surfactant sodium dodecyl benzenesulfonate (SDBS) added, the near-infrared absorption decreased. Moreover, the decreased absorption is proportional to the concentration of SDBS. Based on the absorption changes observed above, a new spectrophotometric method without a procedure of solvent extraction was developed for the determination of SDBS. Secondly, we studied the fluorescence changes of cyanine I in anionic surfactants. Spectra showed that cyanine I has two fluorescence emission maximum at 583nm (with excitation maximum 265nm) and 800nm (with excitation maximum 765nm), respectively. In present of anionic surfactant SDBS, the fluorescence at 583nm enhanced noticeably, while the fluorescence at 800nm quenched dramatically. The extents of fluorescence quenching and enhancing of cyanine I, under optimum conditions, are both proportional to the concentration of SDBS with a good linear relationship according to our observation. Based on the facts, two new fluorescence methods without solvent extraction were developed for the determination of SDBS. Researches show spectra changes of cyanine I are due to the formation of dye premicellar aggregates facilitated by SDBS. Compared with extraction–spectrophotometric method, in addition to high sensitivity and good reproducibility, the three methods for determination of anionic surfactant SDBS significantly simplify the analytical procedure and avoid the toxicity of organic solvent. At the same time, two methods are of low interference due to the measurement performed in the near-infrared region. In chapter 3, the interactions of cationic cyanine II with nucleic acids was studied by means of spectral technique. The fluorescence quenching of cyanine II in the presence of nucleic acids was studied. A near-infrared (NIR) fluorescence quenching method was proposed for the determination of nucleic acids, in which Triton X-100 with proper concentration was employed to improve the stability of this system. The quenching mechanism of fluorescence was also discussed. In chapter 4, the cyanine II-poly-glutamate-proteins ternary ion-association equilibrium system in acidic media was investigated. The cationic cyanine II could not be directly employed to determine proteins due to the lack of evident interaction between cyanine and proteins. However, cyanine II could intensely interact with opposite charged poly-glutamate and form ion-association. Free cationic cyanine II was highly fluorescent in solution, but its fluorescence almost completely quenched in the presence of negatively charged polymers-poly-glutamate. From the absorption blue-shift (from 696 to 628 nm) and fluorescence quenching, we inferred that two d...
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