Colloidal photocatalysts, formation

It is possible that colloidal photochemistry will provide a new approach to prebiotic syntheses. The work described previously on redox reactions at colloidal ZnS semiconductor particles has been carried on successfully by S. T. Martin and co-workers, who studied reduction of CO2 to formate under UV irradiation in the aqueous phase. ZnS acts as a photocatalyst in the presence of a sulphur hole scavenger oxidation of formate to CO2 occurs in the absence of a hole scavenger. The quantum efficiency for the formate synthesis is 10% at pH 6.3 acetate and propionate were also formed. The authors assume that the primeval ocean contained semiconducting particles, at the surface of which photochemical syntheses could take place (Zhang et al 2007). 

Wang, C.Y., R. Pagel, D.W. Bahnemann and J.K. Dohrmann (2004a). Quantum yield of formaldehyde formation in the presence of colloidal Ti02-based photocatalysts Effect of intermittent illumination, platinization, and deoxygenation. Journal of Physical Chemistry B, 108(37), 14082-14092. 

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