Electrochemical Behavior and Multilayer Assembly Films with Fine Functional Activities of the Sandwich‐Type Polyoxometallate [Sb2W20Fe2O70(H2O)6]8−

The iron‐substituted sandwich‐type polyoxometalate (POM), comprised of the main group element Sb(III) as the central heteroatom, [Sb₂W₂₀Fe₂O₇₀(H₂O)₆]^8? (Sb₂W₂₀Fe₂), is one of the Krebs‐type derivatives. For the first time, the POMs' redox electrochemistry has been elucidated under acidic conditions employing cyclic voltammetry. It exhibited what is believed to be a bielectronic redox couple associated with the two Fe(III) centers followed by four‐electron and two‐electron redox processes, respectively, with these being attributed to redox processes of the tungsten‐oxo framework. The oxidized form of this POM was found to be stable from pH 1.5 to pH 6. Release of the iron centers from the complex, namely demetallization, was observed upon reduction of the Fe(III) sites at room temperature, with an influence of the solution pH being observed. Through the technique of layer‐by‐layer (LBL) assembly, the POM was successfully immobilized on both quartz and glassy carbon electrode (GCE) surfaces by alternate deposition with the polyelectrolyte poly(diallydimethylammonium chloride) (PDDA). Thus‐prepared multilayer films have been characterized by cyclic voltammetry (CV), UV‐vis spectroscopy (UV‐vis) and XPS. The electrocatalytic activities of the multilayer films containing Sb₂W₂₀Fe₂ have been investigated towards the reduction of NO₃^? and IO₃^?. With an increase in the number of Sb₂W₂₀Fe₂ monolayers within the assembly, the catalytic current towards the reduction of IO₃^? was enhanced.     

β‐Methylumbelliferone Surface Modification and Permeability Investigations at PENTEL™ Graphite Electrodes

Electrochemical and micro‐imaging analysis of a commercial graphite‐composite material is presented following electro‐oxidation with β‐methylumbelliferone. Charge‐transfer surface modification was observed for the graphite electrode, presumed to have arisen from adsorbed interfacial umbelliferone moieties. The molecular permeability of the new surface towards a range of similar, yet size‐variable (23 ų–136 ų) molecular redox probes is discussed. Red‐shift fluorescence in confocal microscopy offers further support for the presence of a surface‐bound umbelliferone layer. An SEM‐platinum profiling technique was used as an imaging tool to map the umbelliferone surface and size‐distribution of electro‐active sites.     

Apparent inter-channel interference in dual-electrode electrochemical detection.

During the course of routine high-performance liquid chromatographic analyses of brain catecholamines using dual-electrode electrochemical detection, we encountered an unusual negative peak in the lower-voltage channel. Subsequent investigations suggested that this peak was caused by tyrosine which produced a positive peak in the higher-voltage channel. Our investigations indicate that compounds that generate a peak in one channel appear to be responsible for complex peaks in a second channel set at a lower voltage, close to or below that necessary for oxidation. The complex peaks are biphasic; a sharp negative peak coinciding with the positive peak on the higher-voltage channel, followed by a positive peak. This effect was not specific for tyrosine, but was observed on the lower-voltage channel with all compounds tested that produced signals on the high-voltage channel. The cause of the problem is unknown, but it appears to be an artifact of the electrical coupling of the two electrode channels in a dual-channel system.     

Intensity modulated radiation therapy treatment plan optimization

In this paper, we provide an overview of the state-of-the-art of optimization models for static radiation therapy treatment planning, focusing in particular on intensity modulated radiation therapy (IMRT) by (i) establishing a novel connection between risk management and radiation therapy treatment planning, and (ii) unifying and contrasting two different modeling approaches. In addition, we discussion recent and ongoing technological developments which show that this area of research is a lively and promising one that can continue to help patients by improving the clinical practice of radiation therapy. This invited paper is discussed in the comments available at: , , , , . This work was supported by the National Science Foundation under grant no. DMI-0457394/CMMI-0852727.     

trans-Sodium crocetinate and diffusion enhancement

trans-Sodium crocetinate (TSC) increases the diffusion coefficient of glucose through water by about 25-30%. This is the same percentage increase that TSC causes in the diffusivity of oxygen through water. TSC is also found to induce order in the surrounding water structure through increased hydrogen bonding of the water molecules, and molecular simulations suggest that the increase in diffusivity occurs only in these ordered regions.     

Electrochemical Sensing of NADH and Glutamate Based on Meldola Blue in 1,2‐Diaminobenzene and 3,4‐Ethylenedioxythiophene Polymer Films

The redox mediator Meldola blue (MB) was entrapped into two polymers, poly‐1,2‐diaminobenzene (p‐DAB) and poly‐3,4‐ethylenedioxythiophene (p‐EDOT) by potential cycling and films were applied to NADH oxidation with subsequent glutamate detection using immobilized glutamate dehydrogenase. Both polymer films were tested for electrocatalysis of NADH using amperometry at E_app=0.1 V vs. Ag/AgCl and similar response characteristics were obtained with sensitivity values of 6.1 nA μM^?1, linear range up to 0.5 mM (R²=0.9972) and LOD of 50 μM. Subsequent amperometric determination of glutamate resulted in sensitivity 0.7 nA μM^?1, linearity 0–100 μM and detection limit of 2 μM glutamate.