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Solar conversion of water into the storable energy carrier H2 can be achieved through photoelectrochemical water splitting using light adsorbing anodes and cathodes bearing O2 and H2 evolving catalysts, respectively. Herein a novel photocathode nanohybrid system is reported. This photocathode consists of a dye-sensitized p-type nickel oxide (NiO) with a perylene-based chromophore (PCA) and a tetra-adamantane modified cobaloxime reduction catalyst (Co) that photo-reduces aqueous protons to H2. An original supramolecular approach was employed, using β-cyclodextrin functionalized gold nanoparticles (β-CD-AuNPs) to link the alkane chain of the PCA dye to the adamantane moieties of the cobaloxime catalyst (Co). This new architecture was investigated by photoelectrochemical measurements and via femtosecond-transient absorption spectroscopy. The results show that irradiation of the complete NiO‖PCA‖β-CD-AuNPs‖Co electrode leads to ultrafast hole injection into NiO (π = 3 ps) from the excited dye, followed by rapid reduction of the catalyst, and finally H2 evolution. [ABSTRACT FROM AUTHOR]

The activation of carbon dioxide by three different Mo-diimine complexes [Mo(CO)4(L)] (L=bipyridine (bpy), 1,10-phenantroline (phen) or pyridylindolizine (py-indz)) has been investigated by electrochemistry and spectroelectrochemistry. Under an inert atmosphere, monoreduction of the complexes is ligandcentered and leads to tetracarbonyl [Mo(CO)4(L)]*- species, whereas double reduction induces CO release. Under CO2, [Mo(CO)4(L)] complexes undergo unexpected coupled chemicalelectrochemical reactions at the first reduction step, leading to the formation of reduced CO2 derivatives. The experimental results obtained from IR, NIR and UV-Vis spectroelectrochemistry, as well as DFT calculations, demonstrate an electron-transfer reaction whose rate is ligand-dependent. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (RGO) was covalently functionalized by the in situ generation and reduction of anthraquinone diazonium salt. Deposition on multi-wall carbon nanotube (MWCNT) electrodes prevents the aggregation of RGO nanosheets and allows the stable deposition of modified graphene, accompanied with excellent electron transfer properties. Laccases were immobilized on the nanostructured electrode by the interaction between the anthraquinone moiety and the laccase hydrophobic pocket located near the T1 copper center. The MWCNT/f-RGO electrode exhibits efficient bioelectrocatalytic oxygen reduction, with current densities of up to 0.9 mA cm−2. [ABSTRACT FROM AUTHOR]

Solar conversion of water into the storable energy carrier H 2 can be achieved through photoelectrochemical water splitting using light adsorbing anodes and cathodes bearing O 2 and H 2 evolving catalysts, respectively. Herein a novel photocathode nanohybrid system is reported. This photocathode consists of a dye-sensitized p-type nickel oxide (NiO) with a perylene-based chromophore ( PCA ) and a tetra-adamantane modified cobaloxime reduction catalyst ( Co ) that photo-reduces aqueous protons to H 2 . An original supramolecular approach was employed, using β-cyclodextrin functionalized gold nanoparticles ( β-CD-AuNPs ) to link the alkane chain of the PCA dye to the adamantane moieties of the cobaloxime catalyst ( Co ). This new architecture was investigated by photoelectrochemical measurements and via femtosecond-transient absorption spectroscopy. The results show that irradiation of the complete NiO| PCA|β-CD-AuNPs|Co electrode leads to ultrafast hole injection into NiO (π = 3 ps) from the excited dye, followed by rapid reduction of the catalyst, and finally H 2 evolution.

A facile surface amide-coupling method was examined to attach dye and catalyst molecules to silatrane-decorated NiO electrodes. Using this method, electrodes with a push-pull dye were assembled and characterized by photoelectrochemistry and transient absorption spectroscopy. The dye-sensitized electrodes exhibited hole injection into NiO and good photoelectrochemical stability in water, highlighting the stability of the silatrane anchoring group and the amide linkage. The amide-coupling protocol was further applied to electrodes that contain a molecular proton reduction catalyst for use in photocathode architectures. Evidence for catalyst reduction was observed during photoelectrochemical measurements and via femtosecond-transient absorption spectroscopy demonstrating the possibility for application in photocathodes.

The chemistry of Fe 2 (μ-SH) 2 (CO) 4 (PPh 3 ) 2 (2 HH ) is described with attention to S-S coupling reactions. Produced by the reduction of Fe 2 (μ-S 2 )(CO) 4 (PPh 3 ) 2 (2), 2 HH is an analogue of Fe 2 (μ-SH) 2 (CO) 6 (1 HH ), which exhibits well-behaved S-centered redox. Both 2 HH and the related 2 MeH exist as isomers that differ with respect to the stereochemistry of the μ-SR ligands (R = H, Me). Compounds 2 HH , 2 MeH , and 2 protonate to give rare examples of Fe-SH and Fe-S 2 hydrides. Salts of [H2] + , [H2 HH ] + , and [H2 MeH ] + were characterized crystallographically. Complex 2 HH reduces O 2 , H 2 O 2 , (PhCO 2 ) 2 , and Ph 2 N 2 , giving 2. Related reactions involving 1 HH gave uncharacterizable polymers. The differing behaviors of 2 HH and 1 HH reflect stabilization of the ferrous intermediates by the PPh 3 ligands. When independently generated by the reaction of 2 HH with 2,2,6,6-tetramethyl-1-piperidinyloxy, 2* quantitatively converts to 2 or, in the presence of C 2 H 4 , is trapped as the ethanedithiolate Fe 2 (μ-S 2 C 2 H 4 )(CO) 4 (PPh 3 ) 2 . Evidence is presented that the Hieber-Gruber synthesis of 1 involves polysulfido intermediates [Fe 2 (μ-S n ) 2 (CO) 6 ] 2- ( n > 1). Two relevant experiments are as follows: (i) protonation of [Fe 4 (μ-S) 2 (μ-S 2 )CO) 12 ] 2- gives 1 and 1 HH , and (ii) oxidation of 1 HH by sulfur gives 1.

We report the controlled orientation of bilirubin oxidases (BOD) from Myrothecium verrucaria on multiwalled carbon nanotubes (MWCNTs) functionalised by electrografting of 6-carboxynaphthalenediazonium and 4-(2-aminoethyl)benzenediazonium salts. On negatively charged naphthoate-modified MWCNTs, a high-potential (0.44 V vs. SCE) oxygen reduction electrocatalysis is observed, occurring via the T1 copper centre. On positively charged ammonium-modified MWCNTs, a low-potential (0.15 V) oxygen reduction electrocatalysis is observed, occurring through a partially oxidised state of the T2/T3 trinuclear copper cluster. Finally, chemically modified naphthoate MWCNTs exhibit high bioelectrocatalytic current densities of 3.9 mA cm(-2) under air at gas-diffusion electrode., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The efficient immobilization and orientation of bilirubin oxidase from Myrothecium verrucaria on multi-walled carbon nanotube electrodes by using π-stacked porphyrins as a direct electron-transfer promoter is reported. By comparing the use of different types of porphyrin, the rational effect of the porphyrin structure on both the immobilization and orientation of the enzyme is demonstrated. The best performances were obtained for protoporphyrin IX, which is the natural precursor of bilirubin. These electrodes exhibit full orientation of the enzyme, as confirmed by the observable non-catalytic redox system corresponding to the T1 copper center associated with pure Nernstian electrocatalytic behavior with high catalytic currents of almost 5 mA cm(-2) at neutral pH., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A series of redox-labeled L-tyrosinamide (L-Tym) derivatives was prepared and the nature of the functional group and the chain length of the spacer were systematically varied in a step-by-step affinity optimization process of the tracer for the L-Tym aptamer. The choice of the labeling position on L-Tym proved to be crucial for the molecular recognition event, which could be monitored by cyclic voltammetry and is based on the different diffusion rates of free and bound targets in solution. From this screening approach an efficient electroactive tracer emerged. Comparable dissociation constants Kd were obtained for the unlabeled and labeled targets in direct or competitive binding assays. The enantiomeric tracer was prepared and its enantioselective recognition by the corresponding anti-D-Tym aptamer was demonstrated. The access to both enantiomeric tracer molecules opens the door for the development of one-pot determination of the enantiomeric excess when using different labels with well-separated redox potentials for each enantiomer., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An efficient way of immobilizing and wiring a large amount of laccase on non-covalently-functionalized multi-walled carbon nanotube (MWCNT) electrodes is reported. 1-(2-anthraquinonylaminomethyl)pyrene and 1-[bis(2-anthraquinonyl)aminomethyl]pyrene were synthesized and studied for their capability to non-covalently functionalize MWCNT electrodes and immobilize and orientate laccase on the nanostructured electrodes. This led to high-performance biocathodes for oxygen reduction by direct electron transfer with maximum current densities of (1±0.2) mA cm(-2). The performance of the resulting bioelectrodes could be doubled simply by using the bis-anthraquinone compound. The bioelectrodes show excellent stability over weeks and can thus be envisioned in enzymatic biofuel cells., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)