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The voltammetry at three micro-mesh electrodes is explored. It is found that at sufficiently short experimental durations, the micro-mesh working electrode first behaves as an ensemble of microband electrodes, then follows the behaviour anticipated for an array of diffusion-independent micro-ring electrodes of the same perimeter as individual grid-squares within the mesh. During prolonged electrolysis, the micro-mesh electrode follows that behaviour anticipated theoretically for a cubically-packed partially-blocked electrode. Application of the micro-mesh electrode for the electrochemical determination of carbon dioxide in DMSO electrolyte solutions is further illustrated.

Magnetic resonance imaging (MRI) is a noninvasive technique that can be used to visualize mixing processes in optically opaque systems in up to three dimensions. Here, MRI has been used for the first time to obtain both cross-sectional velocity and concentration maps of flow through an optically opaque Y-shaped microfluidic sensor. Images of 23 [micro]m x 23 [micro]m resolution were obtained for a channel of rectangular cross section (250 [micro]m x 500 [micro]m) fed by two square inlets (250 [micro]m x 250 [micro]m). Both miscible and immiscible liquid systems have been studied. These include a system in which the coupling of flow and mass transfer has been observed, as the diffusion of the analyte perturbs local hydrodynamics. MRI has been shown to be a versatile tool for the study of mixing processes in a microfluidic system via the multidimensional spatial resolution of flow and mass transfer.

A novel microfluidic approach for the quantification of reaction kinetics is presented. A three-dimensional finite difference numerical simulation was developed in order to extract quantitative kinetic information from fluorescence lifetime imaging experimental data. This approach was first utilized for the study of a fluorescence quenching reaction within a microchannel; the lifetime of a fluoro-phore was used to map the diffusion of a quencher across the microchannel. The approach was then applied to a more complex chemical reaction between a fluorescent amine and an acid chloride, via numerical simulation the bimolecular rate constant for this reaction was obtained.

The cyclic voltammetry response of partially blocked electrodes was modeled finite difference simulations and a method presented for determining currents at electrode surfaces, which have a well-defined geometric blocking pattern. The comparison of theory with experiment suggested that the modeling of hexagonally distributed blocking systems was superior to that of the cubically arranged ones.

A hydrodynamic system based on the channel flow cell for voltammetric detection of ions at the liquid/liquid interface is reported. The current response for tetraethy-lammonium ion transfer across a membrane-supported liquid/liquid interface is shown to be consistent with existing theory for both the flow rate and voltage scan rate dependence of such processes, with no calibration factors or other adjustable parameters required. The analytical utility of such a device is discussed with specific regard to in situ measurements in flow systems.

The design, fabrication and characterization of a new generation of electrochemical electron spin resonance (ESR) flow cell with narrow, but well-defined channel dimensions, suitable for in situ simultaneous hydrodynamic electrochemical ESR is reported. The signal intensity is measured as a function of flow rate and the behavior is validated using 3-dimensional numerical modeling of the hydrodynamic flow profile.

The general transient response of a PBE for which the blocks are distributed across an electrode surface at random intervals is characterized. A method is also presented for the determination of currents at electrode surfaces that have an unstructured blocking pattern.

DNA templated gold wires (AuWs) were fabricated on Pt sputtered ITO (Pt/ITO) substrates using ‘scribing’ or ‘writing’ method to be used as a modified counter electrode (CE) in Dye sensitized solar cells. The gold nanoparticles (AuNPs) bind to DNA in aqueous solution due to the polyanionic nature of DNA. When a scribe is made on the dropcasted Au-DNA solution, the diffusion of Au-DNA complex occurs towards the edges of the scribe due to the coffee ring effect. Capillary force induces evaporation of water that also forces the Au-DNA complex to migrate towards the scribed edges. Meanwhile, the AuNPs are reduced on the surface of DNA to form active seed for nucleation and growth of AuWs. DNA molecules act as a scaffold to arrange the nanoparticles into well-connected submicron to nanoscale wires. The cyclic voltammetry measurements showed that AuWs/Pt/ITO CE exhibited better electro-catalytic activity and higher conductivity than conventional Pt/ITO CE due to the synergistic effect of Pt and AuWs network on ITO. The DSSC fabricated using TiO2 photoanode, N719 dye, I3−/I− electrolyte and AuWs/Pt/ITO CE showed a 36% increase in efficiency as compared to the cells made under same parameters but using conventional (Pt/ITO) CE. [ABSTRACT FROM AUTHOR]