The Interaction Between TiO₂and A Few Kinds Of Dyes’ Ground State, Excited State

As a kind of organic photosensitizer dyes applied to sensitize semiconductormaterials, Xanthenes and phthalocyanines play an important role in the field ofphotoelectric functional conversion. PET is the initial process of DSSC andDye-sensitized TiO₂Photocatalysis. The key to improve the PET rate is to chose thehigh-performance sensitizing dyes since the PET rate directly affects thephotoelectric conversion efficiency of DSSC and the photocatalytic efficiency ofdye-sensitized TiO₂.This paper proves that the mixture of TiO₂colloid with fluorescein under anacidic condition actually forms protonated fluorescein rather than composite,through measuring the UV-visible absorption spectroscopy of fluorescein underdifferent pH value condition. The nano-TiO₂colloid prepared with sol-gel methodunder neutral condition is uniformly mixed with fluorescein and halogenatedfluorescein, respectively. Measure the photophysical properties of above fluorescein,such as UV-visible absorption spectroscopy, fluorescein spectroscopy, fluorescencelifetime and so on, before and after they are mixed with TiO₂. Conclusion is drawnon the base of the photophysical results, which these dyes actually form compositewith nano-TiO₂. Moreover with the increment of halogen atomic number, someproperties have changed.Study on the nano-TiO₂photocatalytic degradation of different phthalocyanines,（tetrasulfonated zinc phthalocyanine, tetrasulfonated aluminum phthalocyanine,tetrasulfonated copper phthalocyanine, tetrasulfonated hollow phthalocyanine）, werespectively calculate the photocatalytic degradation rate and get the sequencingresults（CuPcS₄>H₂PcS₄>ZnPcS4>AlPcS₄）. The different forms in water caused bythe center element in the phthalocyanines have great impact on the photocatalyticdegradation among these four phthalocyanines. The first two excist as aggregation inwater, and the latter two single molecule. The change of absorbancy hints that twopathways are exposed in the photocatalytic degradation progress during the dark processing and photochemical reaction. The sharp decrease of absorbancy for firsttwo is mainly caused by their physical absorption during the dark processing,whereas by sensitization-photocatalytic degradation reaction during thephotochemical reaction. And the latter two only result from sensitizationphotocatalytic.