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Room temperature ionic liquids (RTILs) have been applied to a microelectrode array and been demonstrated to form effective, membrane-free amperometric gas sensors. Determining the RTIL [[P.sub.6,6,6,14]][FAP] as the most appropriate choice for extended use, the amperomeWic quantification of oxygen has been demonstrated. The response of the sensor was quantified by beth cyclic voltammetry and chronoamperometry. A range of 02 contents (2-13% v/v) and RTIL layer thicknesses (from ca. 6 to 125 [micro]m) have been investigated. The combination of microelectrode array and RTIL, as well as the absence of membrane and volatile solvent, results in an elegant, easy to calibrate gas sensor with potential utility in standard and nonstandard conditions. 10.1021/ac1006359

Physicochemical changes and substantially modified electrochemical behavior have been reported when ionic liquids are degassed with nitrogen. In conventional experiments in aqueous and organic media, degassing with N2 is commonly used to remove the electroactive dissolved oxygen. However, in hydrophilic ionic liquid media, degassing with [N.sub.2] removes not only the dissolved oxygen but also a significant amount of the adventitious water present. Given the low viscosity of water, this in turn leads to a dramatic change of the viscosity of the degassed ionic liquid and hence mass transport properties that influence voltammetric responses. In the widely used and relatively viscous room temperature ionic liquid, 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) containing the redox probe tetracyanoquinodimethane (TCNQ) and 9% (v/v) deliberately added water, 1 h degassing with very dry [N.sub.2] under benchtop conditions results in a dramatic decrease of the TCNQ reduction current obtained under steady-state conditions at a 1 [micro]m diameter microdisc electrode. This is reflected by a change of diffusion coefficient of TCNQ ([D.sub.TCNQ]) from 2.6 x [10.sup.-7] to 4.6 x [10.sup.-8] [cm.sup.2][s.sup.-1]. Karl Fischer titration measurements show that almost complete removal of the deliberately added 9% water is achieved by degassing under benchtop conditions. However, displacement of oxygen by nitrogen in the ionic liquid solution results in the decrease of electrochemical reduction current by 6%, implying that dissolved gases need not be inert with respect to solvent properties. Oxygen removal by placing the [BMIMBF.sub.4] ionic liquid in a nitrogen-filled glovebox or in a vacuum cell also simultaneously leads to removal of water and alteration of voltammetric data. This study highlights that (i) important physicochemical differences may arise upon addition or removal of a solute from viscous ionic liquids; (ii) degassing with dry nitrogen removes water as well as oxygen from ionic liquids, which may have implications on the viscosity and structure of the medium; (iii) particular caution must be exercised when deoxygenation is applied in ionic liquid media as part of the protocol used in electrochemical experiments to remove oxygen; (iv) gases such as oxygen, argon, and nitrogen dissolved in ionic liquids need not be innocent with respect to the properties of an ionic liquid. The use of vacuum based techniques to eliminate all volatile solutes, including water and oxygen, is advocated. 10.1021/ac100378g

The fabrication, characterization, and use of arrays of ring-recessed disk microelectrodes are reported. These devices are operated in generator-collector mode with a disk acting as the generator and the ring as the collector. We report experiments and simulations relating to time-off-light experiments in which material electrogenerated at a disk is diffusionally transported to the ring. Analysis of the current transient measured at the latter when it is potentiostatted at a value to ensure diffusionally controlled 'collection' is shown to sensitively reflect the diffusion coefficients of the species forming the redox couple being driven at the generator electrode. The method is applied to the ferrocene/ferrocenium couple in the room temperature ionic liquid [[No.sub.6,2,2,2]][[NTf.sub.2]], and the results are found to agree with independent measurements. 10.1021/ac9017633

A new composite electrode has been fabricated using multiwall carbon nanotubes (MWCNT) and the ionic liquid n-octylpyridinum hexafluorophosphate (OPFP). This electrode shows very attractive electrochemical performances compared to other conventional electrodes using graphite and mineral oil, notably improved sensitivity and stability. One major advantage of this electrode compared to other electrodes using carbon nanotubes and other ionic liquids is its extremely low capacitance and background currents. A 10% (w/w) loading of MWCNT was selected as the optimal composition based on voltammetric results, as well as the stability of the background response in solution. The new composite electrode showed good activity toward hydrogen peroxide and NADH, with the possibility of fabricating a sensitive biosensor for glucose and alcohol using glucose oxidase and alcohol dehydrogenase, respectively, by simply incorporating the specific enzyme within the composite matrix. The marked electrode stability and antifouling features toward NADH oxidation was much higher for this composite compared to a bare glassy carbon electrode. While a loading of 2% MWCNT showed very poor electrochemical behavior, a large enhancement was observed upon gentle heating to 70[degrees]C, which gave a response similar to the optimum composition of 10%. The ease of preparation, low background current, high sensitivity, stability, and small loading of nanotubes using this composite can create new novel avenues and applications for fabricating robust sensors and biosensors for many important species.

Theory is presented to describe the voltammetric signals associated with the stripping phase of stripping voltammetry at solid electrodes. Three mathematical models are considered, and the importance of the hemispherical diffusion associated with electrochemical dissolution of particles in the micrometer range is investigated. Model A considers a 'monolayer' system where the coverage at a specific point cannot exceed a maximum value. Model B considers a thin layer of metal or metal oxide, but in contrast to model A, the maximum surface coverage is not restricted. Model C represents the stripping of a 'thick layer' where the deposition is also unrestricted.

The electrochemical oxidation of dissolved hydrogen gas is evaluated in a range of room-temperature ionic liquids (RTILs) on a platinum microdisk electrode. The results can be used for defining p[K.sub.a] in RTIL media and also in the amperometric sensing of [H.sub.2] gas.

Temperature-dependent electronic circular dichroism (CD) spectra are described for (R)-(+)-3-methylcyclopentanone (R3MCP) in various solvents. Optical rotation (OR) measurements for R3MCP in cyclohexane solution in the visible region have displayed excellent agreement with OR DFT calculations of the equatorial and axial methyl conformers.

We consider the transition to steady-state flow in the inlet region of a hydrodynamic channel cell and show that a microelectrode positioned within this inlet region allows chronoamperometric results to be recorded, from which information about the extent of the development of the flow profile may be deduced as well as information about the precise dimensions of the microfiuidic channel.

A method for the fabrication of metal nanowires is described. The advantage of this electrochemical decoration method is that it has allowed metal nanowires to be fabricated without the simultaneous formation of nanoparticles on the basal plane terraces.

Gold nanoparticles (~30-60 nm in diameter) were deposited onto the surface of glassy carbon microspheres (10-20 [micro]m) through electroless plating to produce bulk (i.e., gram) quantities of nanoparticle surface-modified microspheres. The gold nanoparticle-modified powder was then characterized by means of scanning electron microscopy and cyclic voltammetry. The voltammetric response of a macroelectrode consisting of a film of gold nanoparticle-modified glassy carbon microspheres, bound together and 'wired-up' using multiwalled carbon nanotubes (MWCNTs), was investigated. We demonstrate that by intelligently exploiting both nano- and microchemical architectures and wiring up the electroactive centers using MWCNTs in this way, we can obtain macroelectrode voltammetric behavior while only using ~1% by mass of the expensive gold material that would be required to construct the equivalent gold film macrodisk electrode. The potential utility of electrodes constructed using chemical architectures such as this was demonstrated by applying them to the analytical determination of arsenic(III) concentration. An optimized limit of detection of 2.5 ppb was obtained.

Experimental vibrational spectroscopy in conjunction with DFT quantum chemical calculations is applied to characterize two fluorofullerenes, C60F48 and C60F36. The study reveals that vibrational spectroscopy, supplemented with reliable theoretical modeling could provide a powerful structural tool to meet the challenges of the structure determination for fullerene derivatives when other method, such as X-ray or NMR are unable to provide unambiguous solutions to the problem.

The electrochemical oxidation of tris(4-bromophenyl)amine (TBPA) in the presence of 2,6-lutidine is examined in acetonitrile. Voltammetric and spectroscopic studies show that the electrogenerated triaryl aminium radical cation oxidizes 2,6-lutidine in an electrochemical mechanism and a homogeneous electron transfer equilibrium exists between electrogenerated species TBPA and 2,6-lutidine.

The stabilization of cyclic-O(sub 3) with transition metals is studied using density functional theory. It is found that it is possible to use one-photon coherent anti-Stroke Raman Spectroscopy (CARS) scheme to detect the formation of cyclic-O(sub 3) and cyclic-SO(sub 2) because of the vibrational and electronic state spacings.

We report the development of all-diamond microelectrochemical devices, namely, a microelectrode array (MEA), in which a periodic array structure with well-defined diameters, distance, and hexagonal unit cell pattern is micromachined using a combination of state-of-the-art microwave-induced plasma growth and laser ablation shaping techniques to prepare and coat a patterned boron-doped diamond (BDD) substrate with an intrinsic diamond insulating layer. The active BDD element can be tuned to between 10 and 50 [micro]m in diameter with a 10 times diameter center-to-center distance between two adjacent conducting elements, which are exactly coplanar to the dielectric surroundings. This type of device should enable applications in harsh conditions such as high temperature, high pressure, and resistive media under dynamic flow regimes.

The synthesis of some simple compounds containing the 3-methylene-2-vinyltetrahydropyran systems, a unique feature of the liverwort metabolite, hodgsonox, is reported. The synthetic strategy focused on the creation of an acrolein substituted in the alpha-position with a three-carbon chain bearing a terminal electrophilic site, addition of a vinyl group, and cyclization.

We present a simple cost-effective design for an HOPG electrode that is well suited to voltammetric experiments accompanied by surface analysis. The utility of the electrode is demonstrated by an AFM study on the morphology of electrodeposited MoO2 nanowires. The design can be applied to a wide range of electrode materials.