Electron transfer quenching Stem-Volmer equation

In a solid phase, since the reaction components cannot move or move only slightly during a photoexcited state, the electron transfer shows a specific aspect entirely different from that in a homogenous solution, for which reaction takes place commonly by a dynamic mechanism. In a solid phase, on the contrary, electron transfer takes place usually by a static mechanism. Depending on the mobility of the components the mechanism can be partly dynamic. The mechanism can be determined by investigating the emission intensity and emission decay based on quenching of the emission by electron transfer. When the mechanism is dynamic, the reaction is expressed by the Stem-Volmer equation (Eq. (13-7)) [28], where Iq is the emission intensity in the absence of quencher (Q, here an electron acceptor or donor), / is that in the presence of Q (concentration [Q] mol dm" ), t is the corresponding lifetime of the exeited state determined by its emission decay, and ksv is the Stem-Volmer constant (Fig. 13-11 (a)). 

Still another example is an initiating system composed of 7-diethylamino-3 -(2 -N-methyl-benzimidazolyl)-coumarin and diphenyliodonium hexafluorophosphate. This composition initiates the polymerization of methyl methacrylate in visible light. After the dye absorbs flic light energy, quick electron transfer takes place from the dye to the iodonium salt to produce free radicals. " The light induced reaction is claimed to occur mainly through the excited singlet state of the coumarin and results in low sensitive to O2. The fluorescence of the coumarin compound was reported to be quenched efficiently by the iodonium salt. " The reaction was observed to be in accord with the Stem-Volmer equation. The influence of the concentration of coumarin on the polymerization rate of methyl methacrylate led to the conclusion that the free radicals from coumarin act mainly as chain terminators. ... 

Keywords Quenching Forster transfer Stem-Volmer equation Electron-transfer-quenching path Cathodic ECL Energy scavenging process... 

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