Fluorescence spectroscopy excitation transfer

Discussion of topics corresponding to proton transfer occurring in the excited state are included under Fluorescence Spectroscopy and Excited... 

VIIL Fluorescence Spectroscopy and Excited State Proton Transfer... 

Photosensitization of diaryliodonium salts by anthracene occurs by a photoredox reaction in which an electron is transferred from an excited singlet or triplet state of the anthracene to the diaryliodonium initiator.13"15,17 The lifetimes of the anthracene singlet and triplet states are on the order of nanoseconds and microseconds respectively, and the bimolecular electron transfer reactions between the anthracene and the initiator are limited by the rate of diffusion of reactants, which in turn depends upon the system viscosity. In this contribution, we have studied the effects of viscosity on the rate of the photosensitization reaction of diaryliodonium salts by anthracene. Using steady-state fluorescence spectroscopy, we have characterized the photosensitization rate in propanol/glycerol solutions of varying viscosities. The results were analyzed using numerical solutions of the photophysical kinetic equations in conjunction with the mathematical relationships provided by the Smoluchowski16 theory for the rate constants of the diffusion-controlled bimolecular reactions. 

Time-resolved fluorescence spectroscopy is widely used as a research tool in biochemistry and biophysics. These uses of fluorescence have resulted in extensive knowledge of the structure and dynamics of biological macromolecules. This information has been gained by studies of phenomena that affect the excited state, such as the local environment, quenching processes, and energy transfer. 

Generation of M in solution includes one-electron transfer and should be accompanied with ion pair formation, e.g., M -M, M -anion, etc. in any processes. Absorption spectroscopy of M are not sufficiently sensitive to distinguish ion pair from free ion, while fluorescence spectroscopy is enough sensitive. The delay time (10-1000 nsec) decreased rapidly during PR-LFP of TMB in DCE... 

Steady-state fluorescence spectroscopy has also been used to study solvation processes in supercritical fluids. For example, Okada et al. (29) and Kajimoto and co-workers (30) studied intramolecular excited-state complexation (exciplex) and charge-transfer formation, respectively, in supercritical CHF3. In the latter studies, the observed spectral shift was more than expected based on the McRae theory (56,57), this was attributed to cluster formation. In other studies, Brennecke and Eckert (5,31,44,45) examined the fluorescence of pyrene in supercritical CO2, C2HSteady-state emission spectra were used to show density augmentation near the critical point. Additional studies investigated the formation of the pyrene excimer (i.e., the reaction of excited- and ground-state pyrene monomers to form the excited-state dimer). These authors concluded that the observance of the pyrene excimer in the supercritical fluid medium was a consequence of increased solute-solute interactions. 

Picosecond time-resolved total internal reflection fluorescence spectroscopy was applied to analyze the proton-transfer reaction of INpOH in water-sapphire interface layers [206], The rate constant of the proton-transfer reaction from excited neutral species became slow in the interface layer as compared with that in the bulk aqueous solution and decreased smoothly with increasing penetration depth in the interfacial layer up to 100 nm. The anomaly was interpreted in terms of rotational fluctuations of water aggregates in the interface layer. 

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