Physical and chemical studies of chlorophyll in microemulsions. Progress report [report]

1980 unpublished
We,. havj? been conducting studies designed to provide fundamental information on both the nature of photoreactions in microemulsions and the utility of these media as solvents for absorbers of solar energy. As a.test system, we investigated the photoreduction of absorbed dye (principally methyl red) sensitized by chlorophylla in an anionic mineral oil in water microemulsion. Using ascorbate as the water soluble reducing agent and pigment concentrations of up to eight per drop (lOmM), the
more » ... p (lOmM), the reaction exhibits a pseudo zero order dependence on methyl red. T.he effect of sensitizer, ascorbate concentration and light intensity on the quantum yield was examined, as well as the effect of varying the microemulsion charge type, product catalysis; and the use of synthetic porphyrin sensitizers. In microemulsions containing up to eight chlorophyll molecules per microdroplet, the quantum yield remains constant over five orders of magnitude concentration. The intrinsic quantum yield is independent of droplet surface charge, but is dependent on pH. One of the products of the chemical reduction of methyl .red, N,N-dimethyl-p-phenylened.iamine (DMPD3 ;--increases the limiting quantum yield two to three .fold. Synth'eti-c~~.ponphyri~nsp~kia~e P-been .~f.ound' :to. 'act assensitizers, and a : . .. number of tetrapyridyl porphin derivatives containing one to four carbon chains of varying length have been made and examined. The results show that the quantum yield increases with Increasing chain length for the monoalkyl compounds, and also indicate the possble involvement of a sensitizer orientation effect. The transport of oil soluble electroactive species in nonionic microemulsions have been found to exhibit percdlation behavior, which has potential photogalvanic applioations.
doi:10.2172/6890397 fatcat:5wsvzke4mjeqfkllph4nal4tza