Search

A mesoporous atomic layer deposition (ALD) double-shell electrode, Al2O3 (insulating core)//ALD ZnO | ALD TiO2, on a fluorine-doped tin oxide (FTO) conducting substrate was explored for a photoanode assembly, FTO//Al2O3 (insulating core)//ALD ZnO | ALD TiO2 | –chromophore–catalyst, for light-driven water oxidation. Photocurrent densities at photoanodes based on mesoporous ALD double-shell (ALD ZnO | ALD TiO2 |) and ALD single-shell (ALD ZnO | , ALD TiO2 |) electrodes were investigated for O2 evaluation by a generator–collector dual working electrode configuration. The high photocurrent densities obtained based on the mesoporous ALD ZnO | ALD TiO2 photoanode for O2 evolution arise from a significant barrier to back electron transfer (BET) by the optimized tunneling barrier in the structure with the built-in electric field at the ALD ZnO | ALD TiO2 interface. The charge recombination is thus largely decreased. In the films, BET following injection has been investigated through kinetic nanosecond transient absorption spectra, and the results of energy band analysis are used to derive insight into the internal electronic structure of the electrodes. [ABSTRACT FROM AUTHOR]

Gibbons are small arboreal apes that display an accelerated rate of evolutionary chromosomal rearrangement and occupy a key node in the primate phylogeny between Old World monkeys and great apes. Here we present the assembly and analysis of a northern white-cheeked gibbon (Nomascus leucogenys) genome. We describe the propensity for a gibbon-specific retrotransposon (LAVA) to insert into chromosome segregation genes and alter transcription by providing a premature termination site, suggesting a possible molecular mechanism for the genome plasticity of the gibbon lineage. We further show that the gibbon genera (Nomascus, Hylobates, Hoolock and Symphalangus) experienced a near-instantaneous radiation ~5 million years ago, coincident with major geographical changes in southeast Asia that caused cycles of habitat compression and expansion. Finally, we identify signatures of positive selection in genes important for forelimb development (TBX5) and connective tissues (COL1A1) that may have been involved in the adaptation of gibbons to their arboreal habitat. The genome of the gibbon, a tree-dwelling ape from Asia positioned between Old World monkeys and the great apes, is presented, providing insights into the evolutionary history of gibbon species and their accelerated karyotypes, as well as evidence for selection of genes such as those for forelimb development and connective tissue that may be important for locomotion through trees. Gibbon genome reflects the high life The many species of gibbons are small, tree-living apes from Southeast Asia, most of them listed as 'endangered' or 'critically endangered' on the IUCN list. In their presentation of the genome of the northern white-cheeked gibbon (Nomascus leucogenys) , Lucia Carbone and colleagues provide intriguing insights into the biology and evolutionary history of a group that straddles the divide between Old World monkeys and the great apes. The authors investigate how a novel gibbon-specific retrotransposon might be the source of gibbons' genome plasticity. Rapid karyotype evolution combined with multiple episodes of climate and environmental change might explain the almost instantaneous divergence of the four gibbon genera. Positive selection on genes involved in forelimb development and connective tissue might have been related to gibbons' unique mode of locomotion in the tropical canopy., Author(s): Lucia Carbone [sup.1] [sup.2] [sup.3] [sup.4] , R. Alan Harris [sup.5] , Sante Gnerre [sup.6] , Krishna R. Veeramah [sup.7] [sup.8] , Belen Lorente-Galdos [sup.9] , John Huddleston [sup.10] [...]

Light-driven water oxidation occurs in oxygenic photosynthesis in photosystem II and provides redox equivalents directed to photosystem I, in which carbon dioxide is reduced. Water oxidation is also essential in artificial photosynthesis and solar fuel-forming reactions, such as water splitting into hydrogen and oxygen (2 [H.sub.2]O + 4 hv [right arrow] [O.sub.2] + 2 [H.sub.2]) or water reduction of C[O.sub.2] to methanol (2 [H.sub.2]O + C[O.sub.2] + 6 hv [right arrow] C[H.sub.3]OH + 3/2 [O.sub.2]), or hydrocarbons, which could provide clean, renewable energy. The 'blue ruthenium dimer,' cis, cis-[[[(bpy).sub.2]([H.sub.2]O)[Ru.sup.III]O [Ru.sup.III](O[H.sub.2])[(bpy).sub.2]].sup.4+], was the first well characterized molecule to catalyze water oxidation. On the basis of recent insight into the mechanism, we have devised a strategy for enhancing catalytic rates by using kinetically facile electron-transfer mediators. Rate enhancements by factors of up to [approximately equal to] 30 have been obtained, and preliminary electrochemical experiments have demonstrated that mediator-assisted electro-catalytic water oxidation is also attainable. catalysis | redox mediator | electron transfer

The article explains the mechanism behind the numerous reactions that involve the proton-coupled electron transfer (PCET). PCET can also be easily induced in a reaction by making changes in the pH values.

Synthetic approaches based on sequential covalent bond formation, derivatization of preformed polymers, and stepwise polypeptide synthesis are used to prepare molecular assembly for artificial photosynthesis. Progress is made for metal polypyridyl complex assemblies based on sol-gels, electropolymerized thin films and chemical adsorption to thin films of metal oxide nanoparticles.

The oxidation of benzaldehyde and several of its derivatives to their carboxylic acids by cis-[Ru(super IV)(bpy)(sub 2)(py)(O)(super 2+)(Ru(super IV)=O2, bpy is 2,2'-bipyridine), cis-[Ru(super III)-OH(super 2+), and [Ru(super IV)(tpy)(bpy)(O)](super 2+)(tpy is 2,2':6'2''-terpydine) in acetonitrile and water is investigated. A benzoate intermediate is observed as an intermediate with [Ru(super IV)(tpy)(bpy)(O)](super 2+) as the oxidant.

A demonstration of the stepwise double addition to the nitrido ligand bound in trans-[Os(super IV)(tpy)(CL)2(N)]PF6(trans-[Os(super VI) triple bond N](super +) is presented. The reactions exhibit new derivatiztion of the nitrido ligand on Os(super VI) equivalent N with its implied synthetic utility.

An alternate approach for preparing stable sol-gel composites of Ru(II) and Os(II) polypyridyl complexes is described. There is a propensity for sol-gel immobilized species to leach out of conventional sol-gels when exposed to solvents such as acetonitrile or water.

Photocurrent measurements are made on nanocrystalline TiO2 surfaces derivatized by adsorption of a catalyst precursor or chromophore, and on surfaces containing both complexes. The experiments are carried out with the I(sub 3)(super -)/I(super -) or quinone/hydroquinone (Q/H2Q) relays in propylene carbonate, propylene carbonate-water mixtures, and acetonitrile-water mixtures.

Temperature-dependent excited state lifetime measurements were performed on four different Ru(II)-based dppz compounds in protic and aprotic solvents. Photophysics of light-switch compounds is explored through a systematic variation of the equilibrium energetics.

The kinetics of reduction of benzoquinone (Q) to hydroquinone ([H.sup.2]Q) by the Os(IV) hydrazido (trans-[Os.sup.IV](tpy)[(Cl).sub.2](N(H)N[(C[H.sub.2]).sub.4]O)]P[F.sub.6] = [1]P[F.sub.6], tpy = 2,2':6',2'-terpyridine), sulfilimido (trans-[[Os.sup.IV](tpy)[(CI).sub.2] (NS(H)-4-[C.sub.5][H.sub.4]Me)]P[F.sub.6] = [2]P[F.sub.6]), and phosphoraniminato (trans-[[Os.sup.IV](Tp[(CI).sub.2][(NP(H)(Et).sub.2])] = [3], [Tp.sup.-] = tris(pyrazolyl)-borate) complexes have been studied in 1:1 (vol/vol) C[H.sub.3]CN/[H.sub.2]O and C[H.sub.3]CN/[D.sub.2]O (1.0 M in N[H.sub.4]P[F.sub.6]/KN[O.sub.3] at 25.0 [+ or -] 0.1 [degress] C). The reactions are first order in both [Q] and Os(IV) complex and occur by parallel pH-independent ([k.sub.1]) and pH-dependent ([k.sub.2]) pathways that can be separated by pH-dependent measurements. Saturation kinetics are observed for the acid-independent pathway, consistent with formation of a H-bonded intermediate ([K.sub.A]) followed by a redox step ([k.sub.red]). For the pH-independent pathway, [k.sub.1]([H.sub.2]O)/ [k.sub.1]([D.sub.2]O) kinetic isotope effects are 455 [+ or -] 8 for [[1.sup.+]], 198 [+ or -] 6 for [[2.sup.+]], and 178 [+ or -] 5 for [3]. These results provide an example of colossal kinetic isotope effects for proton-coupled electron transfer reactions involving nitrogen, sulfur, and phosphorus as proton-donor atoms.