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Small; lithographically-defined and closely-spaced metallic features of dimensions and separation in the micrometer range are of strong interest as working and counter electrodes in compact electrochemical sensing devices. Such micro-electrode systems can be integrated with microfluidics and optical biosensors, such as surface plasmon waveguide biosensors, to enable multi-modal sensing strategies. We investigate lithographically-defined gold and platinum micro-electrodes experimentally, via cyclic voltammetry (CV) measurements obtained at various scan rates and concentrations of potassium ferricyanide as the redox species, in potassium nitrate as the supporting electrolyte. The magnitude of the double-layer capacitance is estimated using the voltammograms. Concentration curves for potassium ferricyanide are extracted from our CV measurements as a function of scan rate, and could be used as calibration curves from which an unknown concentration of potassium ferricyanide in the range of 0.5–5 mM can be determined. A blind test was done to confirm the validity of the calibration curve. The diffusion coefficient of potassium ferricyanide is also extracted from our CV measurements by fitting to the Randles–Sevcik equation (D = 4.18 × 10−10 m2/s). Our CV measurements were compared with measurements obtained using macroscopic commercial electrodes, yielding good agreement and verifying that the shape of our CV curves do not depend on micro-electrode geometry (only on area). We also compare our CV measurements with theoretical curves computed using the Butler–Volmer equation, achieving essentially perfect agreement while extracting the rate constant at zero potential for our redox species (ko = 10−6 m/s). Finally, we demonstrate the importance of burn-in to stabilize electrodes from the effects of electromigration and grain reorganization before use in CV measurements, by comparing with results obtained with as-deposited electrodes. Burn-in (or equivalently, annealing) of lithographic microelectrodes before use is of general importance to electrochemical sensing devices

The ab initio calculations based on the density functional theory (DFT) using the self-consistent fullpotential linearized augmented plane wave (FPLAPW) method were performed to study the electronic structure and magnetism of CoMnTiZ (Z = P, As, and Sb) quaternary Heusler compounds. The results showed that these compounds in the stable structure of Y I were true half-metallic (HM) ferromagnets. The minority (half-metallic) band gaps were found to be 0.60 (0.27) 0.36 (0.16), and 0.43 (0.10) eV for Z = P, As, and Sb, respectively. The characteristic of energy bands and origin of minority band gaps were also studied. The total magnetic moments of CoMnTiZ (Z = P, As, and Sb) compounds were obtained 1 μ B per formula unit, which were in agreement with Slater-Pauling rule (M tot = Z tot − 24). The CoMnTiZ (Z = P, As, and Sb) compounds maintained the HM character at ranges of 5. 43-5.91, 5.44-5.89, and 5.46-6.22Å, respectively, which makes them ideal candidates for spintronic applications.

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