Materials, solar energy conversion systems

Until a recent x-ray diffraction study (17) provided direct evidence of the arrangement of the pigment species in the reaction center of the photosynthetic bacterium Rhodopseudomonas Viridis, a considerable amount of all evidence pertaining to the internal molecular architecture of plant or bacterial reaction centers was inferred from the results of in vitro spectroscopic experiments and from work on model systems (5, 18, 19). Aside from their use as indirect probes of the structure and function of plant and bacterial reaction centers, model studies have also provided insights into the development of potential biomimetic solar energy conversion systems. In this regard, the work of Netzel and co-workers (20-22) is particularly noteworthy, and in addition, is quite relevant to the material discussed at this conference. 

As described above, polymeric materials provide specific microenvironment in solution which contributes much to construct solar energy conversion systems. Macrohetero-geneous systems constructed from polymers are of great value especially from the practical point of view. 

Polymers are attracting much attention as functional materials to construct photochemical solar energy conversion systems. Polymers and molecular assemblies are of great value for a conversion system to realize the necessary one-directional electron flow. Colloids of polymer supported metal and polynuclear metal complex are especially effective as catalysts for water photolysis. Fixation and reduction of N2 or C02 are also attractive in solar energy utilization, although they were not described in this article. If the reduction products such as alcohols, hydrocarbons, and ammonia are to be used as fuels, water should be the electron source for the economical reduction. This is why water photolysis has to be studied first. 

The construction of solar energy conversion systems requires the combination of molecularly designed functional materials. Functional polymers play deciding roles for this purpose. 

C.G. Granqvist, Materials Science for Solar Energy Conversion Systems, C.G. Granqvist (Ed.), Pergamon, Oxford, 1991, p. 106. 

It appears highly justified just now that the research on renewable resources is dramatically increased, and that this is done within the scope of these raw materials being a part of solar energy conversion systems. Land use policies and improvements in the efficiency of the use of solar energy and nutrients for the production of organic materials also have to be brought into the picture. As a wood chemist I find it tragic that the ACS division that used to have "Wood in its name now has dropped it in favor of the textile application. 

Most of the efforts of researchers, working in the field of semiconductor colloids, are directed to the chemical modification of the system to make photoproduction reactions more efficient. EPR spectroscopy will certainly contribute to the development of new nanoscale materials which can effectively undergo charge separation for wide application in photocatalysis and solar energy conversion. 

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