Flash photolysis Eosin

We have performed laser flash photolysis experiments in ethyl acetate/20% methanol under conditions in which triplet-triplet annihilation is not important. We achieve these conditions by using Eosin concentrations higher than 1 x 10 5 M and low pulse energies in order to obtain clean exponential decays for the triplet. Determination of the triplet lifetime at different Eosin and amine concentrations allows us to obtain the rate constants collected in Table 5. A summary of our observations is as follows ... 

Recently Fouassier and Chesneau [219] studied the photochemistry of the system Eosin-PDO-MDEA in aqueous acetonitrile using steady-state irradiation and laser flash photolysis. The photopolymerization of methyl methacrylate (MMA) sensitized by the photoreduction of Eosin is investigated in acetronitrile to understand the mechanism of initiation and the enhancement in the rate of polymerization caused by the presence of PDO, 3. Rates, quantum yields of photopolymerization, and number average molecular weights of the polymer are determined with MMA (7 M), Eosin (3 x 10 5 M), and MDEA (0.1 M) in the presence and in the absence of 2 x 10-3 M PDO. 

The decrease in the termination rate is attributed to the efficient capture of semireduced Eosin radical by diphenyliodonium. The rate constant of the reaction shown in Eq. (30) was determined by laser flash photolysis as 1 x 1010 M-1s-1. 

Ryan, M. A. Fitzgerald, E. C. Spider, M. T. Internal reflection flash photolysis study of the photochemistry of eosin at T102 semiconductor electrodes, J. Phys. Chem. 1989, 93, 6150. 

The theory of rotation effects on prolate luminescent molecules in solution and its experimental verification have been developed and compared. Generalized diffusion equations for the rotational motion of an asymmetric rigid motor have been used to given an expression for steady-state fluorescence depolarization. " The radiationless transition from the first excited singlet state of Eosin has been measured by optoacoustic relaxation, and the absolute fluorescence quantum yields of organic dyes in poly(vinyl alcohol) have also been measured by the photoacoustic method. The accuracy of the method has been discussed in the latter paper. Actinometry in flash photolysis experiments has been assisted by new measurements on the extinction coefficient of triplet benzophenone. Matrix-isolation fluorescence spectrometry has been used to detect polycyclic aromatic hydrocarbons from gas chromatography. ... 

SDS by flash photolysis and ESR shows that triplet eosin does not... 

The results obtained with the eosin dianion are similar to fluorescein. In this case, the R absorptions at 369 m/x (monoanion) and 405 m/x (dianion) agree exactly with the flash photolysis assignments (7, 10, 16), while the X monoanion band at 450 m/x is reasonably close to the flash photolysis spectra reported at 462 (10) and 456 m/x (16). The eosin OH adduct maximum is located near 600 m/x compared with 570 20 m/x for fluorescein (4, 5). The initial yields at pH 9.0 are G(R) =3.3 0.3 and G(X) = 2.0 0.3 (22). The smaller contribution of the OH addition path in eosin compared with fluorescein is consistent with the occupation of four of the six xanthene ring sites by bromine atoms. The only information available on erythrosin from pulse radiolysis locates the R dianion at 450 m/x and the X monoanion at 470 m/x (6). 

Using a combination of internal reflection spectroscopy and laser flash photolysis, Ryan et al. [66] recently observed the electron exchange with a single crystal Ti02 electrode for the singlet state, the triplet state and the cation radical of the dye Eosin Y. With a temporal resolution of 100 ns, the kinetics of the charge transfer are compared with those of the dye in solution and used to interpret the photoelectrochemistry of the dye at the electrode. Spectroscopic evidence revealed photocurrent production by the triplet state and a reduction of the eosin radical cation by electrons from the Ti02 conduction band and by hydroquinone. 

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