Vectorially photoinduced electron-transfer processes across water-in-oil interfaces of microemulsions
Artificial photosynthetic devices are potential fuel sources. The basic idea in the design of such devices is a photosensitized electron-transfer that yields chemical species capable of reducing and oxidizing water to hydrogen and oxygen. A fundamental difficulty in effecting this transfer is the thermodynamically favored back reactions of the intermediary redox species. An interfacial model composed of a water-in-oil microemulsion is suggested to provide the separation of these redox species, thereby preventing back-reactions. This model is designed to accomplish the photodecomposition of water in two separate water-in-oil microemulsions coupled by a redox reaction. Phase-transfer of one of the redox products from the water-in-oil interface to the continuous organic phase is the principle by which separation is achieved. The oxidation and reduction sites of the general model have been constructed. One system includes the photosensitized oxidation of a donor, EDTA, solubilized in the water pool, benzylnicotinamide acts as a primary acceptor that mediates by the phase transfer principle the reduction of a secondary acceptor, dimethylamino-azobenzene, solubilized in the continuous organic phase. In system two, involving the photosensitized reduction of methyl viologen, by tris(2,2'bipyridine)Ru(2+), thioophenol is used as the donor and its oxidation product is phase transferred to the continuous organic phase. The photoinduced processes accomplished in the two systems proceed along an uphill gradient of free energy. Two water soluble zinc-porphyrins can substitute for the Ru(2+) complex in the second system. As the two Zn-porphyrins are oppositely charged, the effect of electrostatic interactions on the quantum yields of viologen reduction could be evaluated. The results suggest that the surface charge of the wateroil interface strongly influences the efficiency of electron-transfer.
- Research Organization:
- California Univ., Berkeley (USA). Lawrence Berkeley Lab.
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5140968
- Report Number(s):
- LBL-11232; CONF-8006111-1
- Resource Relation:
- 10. North Eastern regional meeting of the American Chemical Society, Potsdam, NY, USA, 29 Jun 1980
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
080106 -- Hydrogen-- Production-- Biosynthesis & Photochemical Processes
14 SOLAR ENERGY
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
AZINES
BIOMIMETIC PROCESSES
BIPYRIDINES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
COLLOIDS
COMPLEXES
CONVERSION
CRYOGENIC FLUIDS
DISPERSIONS
EFFICIENCY
ELECTRON TRANSFER
ELEMENTS
EMULSIONS
ENERGY CONVERSION
FLUIDS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROGEN
HYDROGEN COMPOUNDS
HYDROGEN PRODUCTION
INTERFACES
MICROEMULSIONS
NONMETALS
OILS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OTHER ORGANIC COMPOUNDS
OXIDATION
OXYGEN
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PORPHYRINS
PYRIDINES
REAGENTS
REDOX REACTIONS
REDUCTION
RUTHENIUM COMPLEXES
SENSITIZERS
SOLAR ENERGY CONVERSION
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
WATER
ZINC COMPLEXES