Location control of electron donors and acceptors in photoinduced charge separation across surfactant interfaces

Abstract

The efficiency of photoinduced charge separation across surfactant interfaces of micelles and vesicles depends in part on the location of electron donors and acceptors relative to the interface. Achievement and assessment of control of such location by the addition of pendant alkyl chains to donors and acceptors are reviewed. The net photo-ionization efficiency can be measured by electron spin resonance of radical ions in frozen surfactant solutions. Assessment of relative locations of radical ions with respect to a surfactant interface has been achieved by analysis of electron spin-echo modulation with deuterated water at the interface. Alkylmethylviologen electron acceptors are shown to be particularly useful for location control of photo-ionization efficiency in vesicles and less so in micelles. Electron donors investigated for location control include alkylated ruthenium tris(bipyridyl) species and alkylphenothiazine sulphonate derivatives. Photoinduced conversion of alkylmethylviologen radical ion to surfactant radicals is shown to enhance the net photo-ionization efficiency. Comparative photo-ionization efficiency results in vesicles, micelles and reverse micelles reveal structural aspects of effective location control by pendant alkyl chains.