Formation of low density hydrous iron oxide via conformal transformation of MIL-53(Fe).

Hydrous iron oxide materials with a predefined shape, photo-electrochemical activity, low density (estimated to be 0.32 g cm(-3)), and high fractal porosity (BET ca. 117 m(2) g(-1)) are formed via internal hydrolytic transformation of the crystalline metal-organic framework MIL-53(Fe) in dilute aqueous hydroxide.

Plasmon resonance scattering spectroscopy at the single-nanoparticle level: real-time monitoring of a click reaction.

A method based on plasmon resonance Rayleigh scattering (PRRS) spectroscopy and dark-field microscopy (DFM) was established for the real-time monitoring of a click reaction at the single-nanoparticle level. Click reactions on the surface of single gold nanoparticles (GNPs) result in interparticle coupling, which leads to a red-shift of the λmax (Δλmax =43 nm) in the PRRS spectra and a color change of the single gold nanoparticles in DFM (from green to orange).

A model for efficient, semiconductor-free solar cells via supersensitized electron transfer cascades in photogalvanic devices.

A mathematical model for a photosynthesis-inspired regenerative photogalvanic device, for transient rather than exclusively steady-state conditions, based on molecular electrochemistry rather than electron transfer processes involving semiconductors, is considered within this work and which is adapted from an experimental system previously developed (J. E. Halls and J. D. Wadhawan, Energy Environ. Sci., 2012, 5, 6541). Computational simulations suggest that pragmatically achievable systems behave as middle-of-the-range photo-rechargeable electrochemical capacitors for light-to-electrical energy storage; in contrast the system performance as a light-to-electrical energy convertor (viz., solar cell), for cells constructed from electrochemically reversible redox couples with fast photo-induced electron transfer reactions is critically dependent on the concentration of the supersensitiser; maximum power conversion efficiency of ca. 6.5% under 500 nm light, 2.4 mW cm(-2) intensity for typical experimental parameters, neglecting Ohmic losses, and employing galvanostatic discharge, with a power conversion efficiency that is capable of being increased by a factor of five (to ca. 34%) when the supersensitizer concentration increases by an order of magnitude (from 5.0 to 50.0 mM). Under an AM 2.0 solar spectrum, numerical simulations suggest that one potentially pragmatically achievable embodiment of this regenerative system is able to perform with a solar-to-electrical power conversion efficiency of 4.5% - an attractive realistic single cell value.

Nano-TiO(2)-flavin adenine dinucleotide film redox processes in contact to humidified gas | salt electrolyte.

Redox processes in nano-TiO(2)-flavin adenine dinucleotide (TiO(2)-FAD) layer-by-layer assembled films on ITO substrate electrodes are investigated and compared in contact to aqueous electrolyte media (for dilute and saturated electrolyte) and in contact to solid humidified salt electrolyte (for extreme salt levels and different types of salts). Under these unusual conditions an aqueous microphase present at the gas | salt | electrode interface allows voltammograms to be obtained and redox processes to be analysed. It is demonstrated that the 2-electron 2-proton reduction of FAD can be used as reporter redox system to determine local pH at the electrode | gas | salt interface as pH 15, 12, 7 for contacts to K(3)PO(4), K(2)HPO(4), and KH(2)PO(4), respectively. Exposure to gases such as carbon dioxide is shown to lead to unexpected changes in surface pH. In the future, bio-electrochemical microphase processes under halophilic conditions could be useful for air-quality and rapid gas sensing devices.

Metal-organic frameworks post-synthetically modified with ferrocenyl groups: framework effects on redox processes and surface conduction.

Metal-organic framework (MOF) materials based on zinc(II) and aluminium(III) dicarboxylate frameworks with covalently attached ferrocene functional redox groups were synthesised by post-synthetic modification and investigated by voltammetry in aqueous and non-aqueous media. In the voltammetry experiments, ferrocene oxidation occurs in all cases, but chemically reversible and stable ferrocene oxidation without decay of the voltammetric response requires a "mild" dichloroethane solvent environment. The voltammetric response in this case is identified as "surface-confined" with fast surface-hopping of electrons and without affecting the bulk of MOF microcrystals. In aqueous media a more complex pH-dependent multi-stage redox process is observed associated with chemically irreversible bulk oxidation and disintegration of the MOF framework. A characteristic 30 mV per pH unit dependence of redox potentials is observed attributed to a "framework effect": the hydroxide-driven MOF framework dissolution.

Electrochemical estimation of diffusion anisotropy of N,N,N',N'-tetramethyl-para-phenylenediamine within the normal hexagonal lyotropic mesophase of Triton X 100/light water: when can the effects of cross-pseudophase electron transfer be neglected for partitioned reagents?

The H(1) lyotropic liquid crystalline phase of Triton X 100 with aqueous 0.1 M potassium chloride is examined as a medium in which to determine the axiosymmetric anisotropy in the diffusion flux of N,N,N',N'-tetramethyl-para-phenylenediamine using electrochemical methods (voltammetry and potential step chronoamperometry) at both planar electrodes and two-dimensional flux microdisk electrodes. Comparison of experiment with theory suggests the ratio of anisotropic diffusion coefficients in the directions tangential and perpendicular to the electrode surface varies over two orders of magnitude (from 0.04 to 3.3) with increasing concentration of the redox analyte. This is understood through the occurrence of a long-range charge transfer across the pseudophase | pseudophase boundary interface, occurring as a result of differential diffusivities of the redox probe within the surfactant and aqueous subphases. These data and their dependence on the analyte concentration empower, in a proof-of-concept, the estimation of the partition equilibrium constant (K(P)); the value estimated for the small electroactive-drug mimetic considered is log K(P) = 2.01 ± 0.05 (at 294 ± 2 K) and is in agreement with that envisaged for its partition between n-octanol and water. It is suggested that only measurements at low analyte loadings allow for interphase electron transfers to be neglected, since then percolation effects appear to dominate the Faradaic current.