Evaluation of a simple disposable microband electrode device for amperometric gas sensing

We report a simple and facile methodology for constructing Pt (6.3 mm x 50 mu m) and Cu (6.3 mm x 30 mu m) annular microband electrodes for use in room temperature ionic liquids (RTILs) and propose their use for amperometric gas sensing. The suitability of microband electrodes for use in electrochemical analysis was examined in experiments on two systems. The first system studied to validate the electrochemical responses of the annular microband electrode was decamethylferrocene (DmFc), as a stable internal reference probe commonly used in ionic liquids, in [Pmim][NTf2], where the diffusion coefficients of DmFc and DmFc(+) and the standard electron rate constant for the DmFc/DmFc(+) couple were determined through fitting chronoamperometric and cyclic voltammetric responses with relevant simulations. These values are independently compared with those collected from a commercially available Pt microdisc electrode with excellent agreement. The second system focuses on O-2 reduction in [Pmim][NTf2], which is used as a model for gas sensing. The diffusion coefficients of O-2 and O-2(-) and the electron transfer rate constant were again obtained using chronoamperometry and cyclic voltammetry, along with simulations. Results determined from the microbands are again consistent to those evaluated from the Pt microdisc electrode when compared these results from home-made microband and commercially available microdisc electrodes. These observations indicate that the fabricated annular microband electrodes are suitable for quantitative measurements. Further the successful use of the Cu electrodes in the O-2 system suggests a cheap disposable sensor for gas detection. (C) 2013 Elsevier B.V. All rights reserved.

Epitaxial ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 thin films on La0.7Sr0.3MnO3 bottom electrode

Epitaxial (001)-oriented 0.7Pb(Mg_0.33Nb_0.67)O₃-0.3PbTiO₃ (PMN-PT) thin films were deposited by pulsed laser deposition on vicinal SrTiO₃ (001) substrates using La_0.7Sr_0.3MnO₃ as bottom electrode. Detailed microstructural investigations of these films were carried out using X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM). Polarization-field hysteresis curves were measured at room temperature. Spontaneous polarization P s , remnant polarization P r and coercive voltage V c were found to be 25 μC/cm², 15 μC/cm² and 0.81 V, respectively. Field dependent dielectric constant measurements exhibited butterfly shaped curves, indicating the true ferroelectric nature of these films at room temperature. The dielectric constant and the dielectric loss at 100 kHz were found to be 238 and 0.14, respectively. The local piezoelectric properties of PMN-PT films were investigated by piezoelectric force microscopy and were found to exhibit a local piezoelectric coefficient of 7.8 pm/V.

Influence of the interfacing with an electrically inhomogeneous bottom electrode on the ferroelectric properties of epitaxial PbTiO3

The influence of an electrically inhomogeneous epitaxial bottom layer on the ferroelectric and electrical properties has been explored in epitaxial PbTiO3 (PTO)/La0.7Sr0.3MnO3 (LSMO) submicron structures using atomic force microscopy. The submicron LSMO-dot structures underneath the ferroelectric PTO film allow exploring gradual changes in material properties. The LSMO interfacial layer influences significantly both electrical and ferroelectric properties of the upper PTO layer. The obtained results show that the as-grown polarization state of an epitaxial ferroelectric layer is strongly influenced by the properties of the layer on top of which it is deposited. (C) 2013 AIP Publishing LLC.

Electrowetting movement of an aqueous droplet between two three-dimensional electrode surfaces

In an effort to develop a novel electronic paper image display technology based on the electrowetting principle, a 3-D electrowetting cell is designed and fabricated, which consists of two 3-D bent electrodes, each having a horizontal surface made of gold and a vertical surface made of indium tin oxide (ITO) glass as a color display window, a layer of dielectric material on the 3-D electrodes, and a highly fluorinated hydrophobic layer on the surface of the dielectric layer. Results of this work show that an electrowetting-induced motion of an aqueous droplet in immiscible oils can be achieved reversibly across the boundary of the horizontal and vertical surfaces of the 3-D electrode surface. It is also shown that the droplet can maintain its wetting state on a vertical sidewall electrode free of a power supplier when the voltage is removed. This phenomenon may form the basis for color contrast modulation applications, where a power-free image display is required, such as electronic paper display technology in the future. (C) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3100201]

DEPENDENCE OF LIGHT OUTPUT FROM NOMINALLY SMOOTH AL-OX-AU TUNNEL-JUNCTIONS ON ELECTRODE MORPHOLOGY

The light output from nominally smooth Al-Ox-Au tunnel junctions is observed to be substantially independent of the deposition rate of the Au film electrode. Films deposited quickly (2 nm s-1) and those deposited slowly (0.16 nm s-1) have similar spectral dependences and intensities. (This is in contrast to roughened films where those deposited quickly give out less light, especially towards the blue end of the spectrum.) The behaviour can be interpreted in terms of the ratio l(ph)/l(em) where l(ph) and l(em) are the mean free paths of surface plasmons between external photon emissions and internal electromagnetic absorptions respectively. Once l(ph)/l(em) exceeds 100, as it does on smooth films, grain size has little further effect on the spectral shape of the light output. In fast-deposited films there are two compensating effects on the output intensity: grain boundary scattering decreases it and greater surface roughness increases it.

Wireless Rotating Disk Electrode (wRDE) for assessing Heterogeneous Water Oxidation Catalysts (WOCs)

A novel method for assessing the activity of a powdered water oxidation catalyst (WOC) is described, utilising an easily-prepared wireless rotating disc electrode of the WOC, thereby allowing its activity to be probed, via the observed kinetics of water oxidation by Ce(IV) ions, and so provide invaluable electrochemical information.