Light-energy conversion

Recently, new insight into detailed mechanisms of photochemical processes in donor-acceptor pairs (DA) has emerged. To study the role of bridge energy levels on electron transfer rates, a series of rod-like donor-bridge-acceptor (D-B-A) molecules in which a 4-aminonaphthalene-l,8-imide (ANI) electron donor is linked to a 1,8 4,5-naphthalenediimide acceptor (NI) via the 1,4 positions on a phenyl bridge was 

The transient Q-band EPR experiments provide direct evidence for sequential electron transfer from the primary to the secondary radical pair of the triplet channel in a triad consisting of a zinc-9-desoxo-meso-methylpyrochlorophyllide donor (ZC), a pyromellitimide primary acceptor (PI), and a naphthalene-1,8 4,5-diimide secondary acceptor oriented in a liquid crystal (Heinen et al., 2002). At room temperature this process occurs with an exponential time constant of tT = 50 + 1 ns. In the singlet-initiated channel, the intramolecular electron-transfer rates are too fast for direct EPR detection. The species decay with a time constant of tS = 36 1 ns by charge recombination to the singlet ground state. 

To investigate the effect of a protein on electron transfer and the energy conversion, the dual probes (R ) were incorporated to the hydrophobic pocket obovin serum albumin (Rubtsova et al., 1993 Vogel et al., 1994 Likhtenshtein, 1996 Lozinsky et al., 2001). Experimental temperature dependence on the rate constant of photoreduction kpr was found to be similar to that in the above-mentioned solvent. Values estimated from experiments of parameters of local molecular dynamics with the correlation frequency at 

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The rate of H2 production by one unit of photobioreactor s volume is not useful for estimation of strain capabilities or for measurements of efficiency of light energy conversion. However, it is useful unit of measurements for optimization of hydrogen production by particular photobioreactor. From practical point of view it does not matter how much cells are in the photobioreactor or how much hydrogen is produced by one unit of illuminated surface. The rate of hydrogen production by the whole photobioreactor is of first importance. For a comparison of different photobioreactors it is better to express rate of hydrogen photoproduction per unit of its volume. So, it is practical unit for estimation of actual hydrogen photoproduction. 

J. Miyake, S. Kawamura (1987) Efficiency of light energy conversion to hydrogen by the photosynthetic bacterium Rhodobacter sphaeroides. Int. J. Hydr. Energy., 3 147-149... 

The efficiency of light energy conversion to H2 by the AhupL mutant at its highest H2... 

Another important phytotoxic atmospheric pollutant that has been studied with respect to its inhibitory effects on plant photosynthesis is peroxyacetyl nitrate (PAN). This phytotoxicant applied for 30 min at 1 ppm depressed the incorporation of 1 C02 into intact pinto bean leaves, but only after visible tissue injury started to develop (20). From companion studies on isolated chloroplasts, it was concluded that PAN-induced inhibition was probably associated with the carboxylating reaction or the chloroplast light-energy conversion system leading to assimilative power. The inhibition appeared to result in a quantitative reduction (but not a qualitative change) in the early products of photosynthesis. 

Miyake J, Miyake M, Asada Y (1999) Biotechnological hydrogen production research for efficient light energy conversion. J Biotechnol 70 89-101... 

Much of the work on the photoreduction of carbon dioxide centres on the use of transition metal catalysts to produce formic acid and carbon monoxide. A large number of these catalysts are metalloporphyrins and phthalocyanines. These include cobalt porphyrins and iron porphyrins, in which the metal in the porphyrin is first of all photochemically reduced from M(ii) to M(o), the latter reacting rapidly with CO to produce formic acid and CO. ° Because the M(o) is oxidised in the process to M(ii) the process is catalytic with high percentage conversion rates. However, there is a problem with light energy conversion and the major issue of porphyrin stability. 

The pristine and doped poly-phenylene sulfide may be used for light energy conversion to the electrical one. The efficiency coefficient is of the order 0.01-0.2% for various lightwaves, fill factor 0.07-0.20. The characteristics are better than ones for doped TNF PVC. 

The present chapter deals with the principles and recent advances in the investigation of light energy conversion systems based on semiconductor/liquid... 

Light use efficiency (the efficiency of light energy conversion) is usually expressed in models as the slope of regression of the gross amount of dry matter produced upon the cumulative amount of intercepted light. Light use efficiency depends on canopy architecture, the chemical nature of dry matter produced, and other factors. 

Abstract. Recent synthetic, spectroscopic and photopysical work related to the problem of light energy conversion is reported. In particular, new isocyano Ru(II) bipyridine photosensitizers are described, and a number of polynuclear complexes are discussed in which intramolecular transport of electronic charge and excitation energy can be studied. 

Electronic and structural changes of the semiconductor surfaces may influence light energy conversion yields or catalytic enhancements of desired reactions to chemical fuels. The involved processes are up till now not really understood on a molecular level. 

Sayama K, Mukasa K, Abe R, Abe Y, Arakawa H (2002) Photo-catalytic water splitting system into H2 and 02 under visible light irradiation mimicking a Z-scheme mechanism in photosynthesis. Solar Light Energy Conversion Team, Photoreaction Control Research Center, Advanced Industrial Science and Technology (AIST), Ibaraki, Japan... 

Light energy conversion and water-oxidation systems in photosynthesis... 

The key step of the process is the water splitting under absorption of light quanta of relative low energy. Here we will focus mainly on the latter process which appears to be one of the most enigmatic reactions in chemistry and photochemistry and will only briefly consider the light energy conversion reaction centers of PS I and PS II. 

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