Methyl viologen indicator

Methyl viologen (l,T-dimethyl-4,4 -bipyridylium dichloride, MV " ) promotes photoanodic dissolution in aerated CdS solution Figure 8 shows how the rate of dissolution depends on the concentration. The colloid has a weak fluorescence at 620 nm which is quenched by. The curves for fluorescence and dissolution in Fig. 8 are symmetric, which indicates that the two processes have a common intermediate that reacts with M. These effects are explained by the following mechanism ... 

Photoinduced ET at liquid-liquid interfaces has been widely recognized as a model system for natural photosynthesis and heterogeneous photocatalysis [114-119]. One of the key aspects of photochemical reactions in these systems is that the efficiency of product separation can be enhanced by differences in solvation energy, diminishing the probability of a back electron-transfer process (see Fig. 11). For instance, Brugger and Gratzel reported that the efficiency of the photoreduction of the amphiphilic methyl viologen by Ru(bpy)3+ is effectively enhanced in the presence of cationic micelles formed by cetyltrimethylammonium chloride [120]. Flash photolysis studies indicated that while the kinetics of the photoinduced reaction,... 

Figure 5.5 Activition of an [NiFe] hydrogenase such as that from D.gigas, by incubation with H2, as measured by different assay methods.These are production of H2 with the low-potential donor methyl viologen consumption of H2 with the high-potential acceptor dlchlorolndophenol and Isotope exchange of H2 with H2O. The proportions of the enzyme in three different states, unready, ready and active, are indicated by the shading.

Figure 1. Representative polarographic traces that depict inhibition by energy transfer inhibitors and allelochemicals of ADP-stimulated electron transport in isolated spinach thylakoids and circumvention of the inhibition by an uncoupler (FCCP, 2 pM). Trace A chlorotributyltin (TBT, 1 pM) trace B phlorizin (400 pM) trace C DCCD (20 pM) trace D quercetin (200 pM) trace E naringenin (1 mM). Water served as electron donor and methyl viologen as electron acceptor. Rates of oxygen utilization, that resulted from the autooxidation of methyl viologen, expressed as pmol 0 consumed/mg Chi h, are indicated parenthet ically.

It may not be surprising that a,/ -dihydroxyalkyl radicals are able to achieve one-electron reduction of oxidants such as benzoquinone or methyl viologen, with the rate constants strongly dependent on the nature of the substituents, whereby reducing power of the radical and its rate of dehydration are correlated with each other [66]. This indicates that the push-component might be more important than the pull-component. 

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