Interfacial systems, photosensitized electron

Control of Photosensitized Electron Transfer Reactions in Organized Interfacial Systems... 

The separation of photoproducts formed in photosensitized electron transfer reactions is essential for efficient energy conversion and storage. The organization of the components involved in the photo-induced process in interfacial systems leads to efficient compartmentalization of the products. Several Interfaclal systems, e.g., lipid bllayer membranes (vesicles), water-in-oil mlcroemulslons and a solid SIO2 colloidal Interface, have been designed to accomplish this goal. 

Since these interfaces are usually constructed of charged detergents a diffuse electrical double layer is produced and the interfacial boundary can be characterized by a surface potential. Consequently, electrostatic as well as hydrophilic and hydrophobic interactions of the interfacial system can be designed. In this report we will review our achievements in organizing photosensitized electron transfer reactions in different microenvironments such as bilayer membranes and water-in-oil microemulsions.In addition, a novel solid-liquid interface, provided by colloidal Si02 particles in an aqueous medium will be discussed as a means of controlling photosensitized electron transfer reactions. 

Similar to the molecular photosensitizers described above, solid semiconductor materials can absorb photons and convert light into electrical energy capable of reducing C02. In solution, a semiconductor will absorb light, and the electric field created at the solid-liquid interface effects the separation of photo-excited electron-hole pairs. The electrons can then carry out an interfacial reduction reaction at one site, while the holes can perform an interfacial oxidation at a separate site. In the following sections, details will be provided of the reduction of C02 at both bulk semiconductor electrodes that resemble their metal electrode counterparts, and semiconductor powders and colloids that approach the molecular length scale. Further information on semiconductor systems for C02 reduction is available in several excellent reviews [8, 44, 104, 105],... 

FIG. 11 Schematic view of the designed photocatalytic systems with (a) transmembrane and (b) interfacial electron transfer, which is photosensitized by the CdS nanoparticles attached to the lipid membrane surface. Menaquinone (MQ) and heteropolyanions (HPA, SiWi20jo) are lipophilic molecular electron relays. Palladium particles are attached to CdS and operate as dark catalysts of hydrogen evolution from water. MV + methylviologen bication Gl glucose. 

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