Study On Photophysical Properties Of Fluorescein-dimer And Rhodamine Analogues

The excellent fluorescence properties, due to high extinction coefficient and high fluorescence quantum yield in aqueous solution, of fluorescein and rhodamine dyes have gained wide spread applications in chemistry and biological analysis. As a typical fluorescent material, fluorescein was first reported in 1987 by Bayer. Presently,the synthesis and fluorescence properties of the new fluorescein derivative to provide a theoretical basis for further applications. In this thesis, a series of fluorescein dimers were designed and synthesized based on fluorescein, then their fluorescence properities were investigated by UV-Vis spectra, fluorescence spectra and time-correlated single photon counting in different solvent containing sodium hydroxide. We found that the connection may exert a profound effect on the dyes properties of fluorescein.A series of fluorescein derivatives were designed and prepared by one-step synthetic route, and their photophysical properties were investigated in base condition.Depending on the concentrarion of sodium hydroxide, fluorescein and fluorescein dimer exist in solution in a variety of neutral and ionic forms. Compared to FL, both absorption and emission maxima of the fluorescein-dimer does not significantly move, but the fluorescence quantum yield and lifetime were quenching obviously.Analysing the effect of substituents on the photophysical properties of Acridine Red(AR), Pyronin Y(PYY), and Pyronin B(PYB) in aqueous and organic solvents,we found that the structural variation does not alter the rate constant of radiation process(kf) but does change the rate constant of non radiation process(kic)significantly. The phenyl in Rhodamine B or Rhodamine 6G shows only a slight effect on the fluorescence properties.