Photophysical Properties Of Perylene And Some Xanthene Dyes

As aromatic fluorescent dyes, fluorescein, rhodamine, fluorone and perylene arewidely applied in materials and life sciences because of their unique characters.Perylene nanocrystal, as a new type of organic nanocrystals, plays a more and moreimportant roal in organic light-emitting diodes, organic solar cell and other aspects.At present, about aromatic fluorescent dyes such as fluorescein, people’s attention ismainly placed on synthesis, application and changing their properties by revisingdyes. UV-Vis absorption, fluorescence emission and time-correlated single photoncounting were employed to examine the photophysical properties of fluoresceinderivatives and rhodamine derivatives in different solvent. We designed andsynthesized p-hydroxyphenylfluorone and explored the effect of the substituents atC-9on photophysical properties of fluorone. We reported hereby the necessaryconditions for the formation of perylene oligomers, which is closely related to thecrystal nuclei.Analysing the effect of substituents on the photophysical properties offluorescein dyes, we found that the modification may exert a profound effect on thedyes properties of the parent molecule, even if the fluorophore （xanthene ring）remains unchanged. Compared to fluorescein, the introduction of amino, a strongelectron donating group, or nitro, a strong withdrawing group, caused a substantialquenching of both the fluorescence quantum yield and lifetime. For dihalogenatedfluorescein, both absorption and emission maxima follow the trend FlBr2＜FlCl2＜FlI2, but for tetrahalogenated fluorecein, both absorption and emission maxima followthe trend FlCl4＜FlBr4＜FlI4. Φfof chlorinated dyes surpass brominated andiodinated dyes’s, and Φfof brominated and iodinated xanthene dyes is remarkablyless than unity.Analysing the effect of substituents on the photophysical properties ofrhodamine dyes, we found that the maximum absorption and emission wavelength ofalkylrhodamine esters, comparing with rhodamine, generate red shift and thefluorescence quanthum yield larger than rhodamine. It is indicated that the carbon-chain of ankylrhodamine esters have little influence on fluorescenceproperties. N substituted and stabilized both lead to the enlargement of the maximumabsorption and emission wavelength. The maximum absorption and emissionwavelength of the most rhodamine dyes generate red shift with the enhancing of thesolvent polarity.Depending on the concentrarion of sodium hydroxide, p-hydroxyphenyl-fluorone, phenylfluorone and methylfluorone exist in solution in a variety of neutraland ionic forms. Compared to the neutral form, the dissociation of1a-3a caused alittle reducing of both molar extinction coefficient and fluorescence quantum yield.For absorbing position and emission position C-9substituents have obvious effect,but Φfis slightly dependent on the substituents.The effect of water content and perylene concentration on the aggregation viafluorescence and absorption spectra were studied. The spectral behavior indicated thatfluorescent J-type perylene oligomer was formed even when the concentration in theorder μmol·L^-1. The aggregation number is9, while a large equilibrium constant wasobtained.