The bifurcation point of the oxygen reduction reaction on Au-Pd nanoalloys.

The oxygen reduction reaction is of major importance in energy conversion and storage. Controlling electrocatalytic activity and its selectivity remains a challenge of modern electrochemistry. Here, first principles calculations and analysis of experimental data unravel the mechanism of this reaction on Au-Pd nanoalloys in acid media.

Nanoparticles and self-organisation: the emergence of hierarchical properties from the nanoparticle soup (i.e., the small is getting bigger). Concluding remarks for Faraday Discussion: Nanoparticle Synthesis and Assembly.

Some four years ago, one of the participants in this Discussion (Prof. Nicholas Kotov) predicted that: "within five years we shall see multiple examples of electronic, sensor, optical and other devices utilizing self-assembled superstructures" (N. A.

Structure and dielectric properties of electrochemically grown ZrO2 films.

The dielectric properties of electrochemically grown zirconium oxide films by anodisation of zirconium in 1.0 mol dm-3 phosphoric acid solution were investigated in a 3 to 30 V potential range with a view to inducing surface modifications for eventual use in biomedical and electronic applications. The oxide films grown at different potentials were characterised by Atomic Force Microscopy, X-ray photoelectron and Raman spectroscopies; the latter demonstrated the incorporation of phosphate ions into the passive films.

Quantized electron-transfer pathways at nanoparticle-redox centre hybrids.

Hexanethiolate gold monolayer-protected clusters (C6-MPCs) with an average core diameter of 1.8 nm and a capacitance of 0.6 aF are synthesised by a two-phase method.

O2 induced Cu surface segregation in Au-Cu alloys studied by angle resolved XPS and DFT modelling.

Surface segregation effects on polycrystalline Au-Cu alloys (Au(0.80)Cu(0.20), Au(0.

Single atom hot-spots at Au-Pd nanoalloys for electrocatalytic H2O2 production.

A novel strategy to direct the oxygen reduction reaction to preferentially produce H(2)O(2) is formulated and evaluated. The approach combines the inertness of Au nanoparticles toward oxidation, with the improved O(2) sticking probability of isolated transition metal "guest" atoms embedded in the Au "host". DFT modeling was employed to screen for the best alloy candidates.

Role of axially coordinated surface sites for electrochemically controlled carbon monoxide adsorption on single crystal copper electrodes.

The adsorption of CO on low index copper single crystals in electrochemical environments has been investigated. The results, analysed through a combination of in situ infrared spectroscopy, DFT and cyclic voltammetry, reveal a unique adsorption behaviour when compared to previous studies on copper and the more widely studied noble metal surfaces. By employing small, weakly specifically adsorbed electrolytes, it is shown that carbon monoxide is adsorbed over a much wider electrode potential range than previously reported.

Electrocatalytic oxygen reduction on functionalized gold nanoparticles incorporated in a hydrophobic environment.

The electrocatalytic properties of gold nanoparticles covalently capped with a monolayer film of 1,4-decylphenyl groups for oxygen reduction in an alkaline solution have been studied. Functionalized nanoparticles were adsorbed on a film of the same capping ligand previously grafted to a glassy carbon electrode. The molecular film-nanoparticle assembly was characterized by cyclic voltammetry and XPS.

Kinetics of electrocatalytic reduction of oxygen and hydrogen peroxide on dispersed gold nanoparticles.

The electrocatalytic properties of Au nanoparticles of mean size between 4.2 to 9.5 nm have been investigated for the oxygen reduction reaction (ORR).

Direct electron transfer to a metalloenzyme redox center coordinated to a monolayer-protected cluster.

A strategy for establishing electrical contact to the metal center of a redox metalloenzyme, galactose oxidase (GOase), by coordination of a linker attached to a monolayer-protected gold cluster is presented. The cluster-enzyme hybrid system was first prepared in solution and characterized by high-angle annular dark-field scanning transmission electron microscopy. Electrochemical communication between a gold electrode and GOase was achieved by first modifying the electrode surface with a biphenyl dithiol self-assembled monolayer followed by reaction with gold clusters capped with thioctic acid.

Electrochemical reduction of oxygen on nanoparticulate gold electrodeposited on a molecular template.

The reduction of oxygen on gold electrodeposited on an organic template has been investigated. The template consisted of reduced 4-nitrophenyl groups attached to glassy carbon (GC) by the electrochemical reduction of the corresponding diazonium compound. The electrode modified by this Au nanostructured film shows electrocatalytic properties for the oxygen reduction reaction (ORR) different from those of bulk Au, GC or GC grafted with 4-nitrophenyl groups.

All dressed up, but where to go? Concluding remarks for FD 140.

The aim of this meeting was to bring together experimentalists and theoreticians to discuss the interplay between recent developments in theoretical and computational tools with experimental results in electrocatalysis. Intense and rewarding discussions in aspects of very topical electrochemical research arose during the three days of this Faraday Discussion. A closer collaboration between experimentalists and theoreticians is a prerequisite for successful development of the field and this meeting definitely aided mutual understanding of these areas of research.

Photoswitching electron transport properties of an azobenzene containing thiol-SAM.

The influence of conformational and electrical properties of azobenzene molecules on the electron transfer barrier properties of their SAMs was studied by SECM and ellipsometry.

Dependence of the critical temperature on molecular parameters.

At the critical temperature the surface tension between coexisting liquid and vapor phases must be zero, and the repulsive contributions associated with cavity formation must exactly counterbalance those from interactions of a molecule in the cavity and the bulk. An expression for the critical temperature of pure fluids in terms of the parameters of scaled particle theory (SPT) has been obtained, and the calculated critical temperatures are compared with experimental data for a range of pure fluids. These include noble and diatomic gases, short and medium length hydrocarbons, aromatic compounds, halogenated compounds, oxygen-containing compounds, and water.

Optical switching of coupled plasmons of Ag-nanoparticles by photoisomerisation of an azobenzene ligand.

The optical switching of coupled plasmons of silver nanoparticles derivatised with a photoisomerisable azobenzene ligand is presented. It is shown that nanoparticle clusters, linked with an azobenzene dithiol molecule, display switchable optical properties. The photoisomerisation of the linker molecule was used to vary the separation between nanoparticles, which was monitored by changes in the UV-Vis-spectra of the plasmon band of adjacent nanoparticles.

Precision control of single-molecule electrical junctions.

There is much discussion of molecules as components for future electronic devices. However, the contacts, the local environment and the temperature can all affect their electrical properties. This sensitivity, particularly at the single-molecule level, may limit the use of molecules as active electrical components, and therefore it is important to design and evaluate molecular junctions with a robust and stable electrical response over a wide range of junction configurations and temperatures.

Quantum chemical modelling of the rate determining step for oxygen reduction on quinones.

Two inner-sphere electrocatalytic channels for quinone-mediated reduction of molecular oxygen to form hydrogen peroxide have been addressed by means of density functional theory. Each of the channels comprises an initial rate determining chemical step and a subsequent electrochemical reduction step by which peroxide is produced. The reduction mechanism was determined for 9,10-anthraquinone and 9,10-phenanthrenequinone and the quantum chemical results are compared with experimental results.

A combined top-down bottom-up approach for introducing nanoparticle networks into nanoelectrode gaps.

We report here on the fabrication of a three-dimensional array of nanoparticles which bridges the gap between lithographically defined gold electrode contacts separated by 20 nm. The nanoparticle assemblies are formed from about 5 nm gold nanoparticles and benzenedimethanethiol (BDMT) bridging ligands. These assemblies are introduced between the contacts using a layer-by-layer protocol with successive BDMT self-assembly being followed by nanoparticle adsorption until the gap is bridged.

Synthesis of metal nanoparticles stabilized by metal-carbon bonds.

A new method for the preparation of metal nanoparticles in organic media is proposed. This is based on the formation of metal-carbon bonds after reduction of the corresponding diazonium derivative of the capping ligand. The particles are very stable due to the strong metal-ligand covalent bond, and the proposed method appears to be an alternative for the preparation of monolayer-protected metal nanoparticles when the formation of metal-sulfur or metal-nitrogen bonds needs to be avoided.

Plasmon interactions between gold nanoparticles in aqueous solution with controlled spatial separation.

The effects of interparticle distance on the UV-visible absorption spectrum of gold nanocrystals aggregates in aqueous solution have been investigated. The aggregates were produced by ion-templated chelation of omega-mercaptocarboxylic acid ligands covalently attached to the nanoparticles surface. Variation of the ligand chain length provides control over the interparticle separation in the aggregates.

Thermal gating of the single molecule conductance of alkanedithiols.

The temperature dependence of the single molecule conductance (SMC) of alpha,omega-alkanedithiols has been investigated using a scanning tunnelling microscopy (STM) method. This is based on trapping molecules between a gold STM tip and a gold substrate and measuring directly the current across the molecule under different applied potentials. A pronounced temperature dependence of the conductance, which scales logarithmically with T(1), is observed in the temperature range between 293 and 353 K.

Quantum chemical modeling of the reduction of quinones.

A systematic study of the redox properties of six parent quinones has been carried out using quantum chemistry methods. The reduction of the ortho (o-) and para (p-) isomers of benzoquinone and naphthoquinone, 9,10- anthraquinone and 9,10-phenantrenequinone to the corresponding hydroquinones and semiquinone radicals was investigated at the B3LYP/6-311+G(d,p) level of theory. Thermodynamic functions in the gas-phase were calculated for all the reduction reactions.