Light-driven process

The strong interaction of the 13 /I" redox system with the metal dichalcogenide materials was recently exploited (31) to bring about the visible light-driven process representeiTby equation (10). In 50% by weight H2SO4 the reaction as written... 

The general approach of graded radiation exposure can also be used to examine light driven processes such as photopolymerization [19]. For example, Lin-Gibson and coworkers used this library technique to examine structure-property relationships in photopolymerized dimethacrylate networks [38] and to screen the mechanical and biocompatibility performance of photopolymerized dental resins [39]. In another set of recent studies, Johnson and coworkers combined graded light exposure with temperature and composition gradients to map and model the photopolymerization kinetics of acrylates, thiolenes and a series of co-monomer systems [40 2]. 

So far we have considered the importance of light-driven processes for the supply of energy in more or less indirect ways. The direct conversion of the energy of light into electricity or hydrogen gas does not exist in nature, but it is the aim of current research which will be described in section 6.6. 

A major challenge for research in future, the control of chemical reactions as stated by the Pimentel Report, can be approached by various methods light-driven processes are among the most important ones. Without interaction of the diverse scientific disciplines, recent progress in photochemistry, as well as future developments would scarcely be possible. This is particularily true for the study of electron transfer processes. Herein lies a challenge for science and economy and the special fascination of this topic — at least for the guest editor. 

This chapter focuses on the progress and challenges in the field of photocatalysis as applied towards the water splitting reaction (Eq. 1.). More specifically, homogeneous molecule based systems that mimic the natural photosynthetic system are examined for their potential to drive reaction 1. A number of molecules, including porphyrins, metalloporphyrins and phthalocyanines,17 transition metal complexes of Ru, Os, Re, Rh, Pt, Cu,811 and acridine and flavin derivatives,1214 have been examined as the chormophores and sensitizers for light driven processes. 

Coordination chemistry will continue to strengthen its role as a central expertise and discipline for materials science. It is critical to the development of new materials for nanoscience and nanotechnology. In materials science, light-driven processes are of enormous importance and processes based on molecular-level phenomena may provide the basis for photonics and information storage in the future. In catalysis, the use of metals will grow, particularly when control of asymmetric processes is mastered. 

Photosynthesis is a light driven process in which carbon dioxide and water are converted into sugar and dioxygen ... 

The [Ru(bpy)3] photocatalyst was also applied in the following novel visible-light driven processes (i) synthesis of indazolo[2,3-a]quinoline derivatives from 2-(2-nitrophenyl)-l,2,3,4-tetra-hydroquinolines (ii) azido- and amino-trifluoromethylation of alkenes (iii) reduction of nitro compounds to oximes (iv) generation of aryl radicals by visible-light photocatalytic reduction of sulfonium salts. ... 

The light dependence of photochemical recovery was studied at photon flux densities of 6, 36, 120 and 300 pmol m s. No difference in the rate of recovery was observed at these light levels (data not shown). A photon flux densitiy of 6 pmol m s was below the light compensation point of photosynthesis in all measurements. Still that light level was enough to induce a rapid recovery. The recovery of the photochemical efficiency therefore seems to be a light activated rather than a light driven process. 

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