Studies of dye-coated semiconductor electrodes

At large negative bias (-0.7V, for example), the reduction in the charge injection is accompanied by the appearance of the RUL3 emission at -0.7 V, as shown in the inset of figure 6. 

The initial absorption decrease occurs within the laser pulse, indicating that the charge injection step occurs extremely rapidly. The rate constant for back electron transfer spans several orders of magnitude and is determined by the potential applied to the membrane. The bleaching recovery shows a two component decay, a fast one (attributed to the back reaction referred to above) and a slow component (attributed to reduction of Ru L3 by the 

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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