Home About us Contact
|
Home About us Contact | ||
|
|
||
Sensing Performance (sensing + performance)
Selected AbstractsHighly Stable Au Nanoparticles with Tunable Spacing and Their Potential Application in Surface Plasmon Resonance BiosensorsADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Shuyan Gao Abstract Colloidal Au-amplified surface plasmon resonance (SPR), like traditional SPR, is typically used to detect binding events on a thin noble metal film. The two major concerns in developing colloidal Au-amplified SPR lie in 1) the instability, manifested as a change in morphology following immersion in organic solvents and aqueous solutions, and 2) the uncontrollable interparticle distance, determining probe spacing and inducing steric hindrance between neighboring probe molecules. This may introduce uncertainties into such detecting techniques, degrade the sensitivity, and become the barricade hampering colloidal Au-based transducers from applications in sensing. In this paper, colloidal Au-amplified SPR transducers are produced by using ultrathin Au/Al2O3 nanocomposite films via a radio frequency magnetron co-sputtering method. Deposited Au/Al2O3 nanocomposite films exhibit superior stability, and average interparticle distances between Au nanoparticles with similar average sizes can be tuned by changing surface coverage. These characteristics are ascribed to the spacer function and rim confinement of dielectric Al2O3 and highlight their advantages for application in optimal nanoparticle-amplified SPR, especially when the probe size is smaller than the target molecule size. This importance is demonstrated here for the binding of protein (streptavidin) targets to the probe (biotin) surface. In this case, the dielectric matrix Al2O3 is a main contributor, behaving as a spacer, tuning the concentration of Au nanoparticles, and manipulating the average interparticle distance, and thus guaranteeing an appropriate number of biotin molecules and expected near-field coupling to obtain optimal sensing performance. [source] Fabrication of Free-Standing Titania-Based Gas Sensors by the Oxidation of Metallic Titanium FoilsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2000Pelagia I. Gouma A simple method for fabricating TiO2 -based sensors of CO(g) is demonstrated: the oxidation of Ti-bearing foils. Metallic foils (35 ,m thick) were converted into free-standing, porous rutile foils (60 ,m thick) by exposure to O2(g) at 800°,965°C. The oxidized foils contained thin (0.5,1 ,m thick), regularly spaced oxide layers oriented parallel to the external surface. The exposure of such porous foils to increasing concentrations of CO(g) resulted in a monotonic increase in the steady-state electrical resistance. Rutile foils sensitive to 50 ppm changes in CO(g) content with response times of a few minutes were produced. The effects of oxidation conditions and copper doping on sensing performance are discussed. [source] Excitation of the Intrinsic Conduction System Through His and Interventricular Septal PacingPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4 2006TIMOTHY G LASKE Background: Direct His bundle pacing results in rapid synchronous ventricular activation. However, clinical experiences with such pacing have been associated with long procedure times and compromised pacing and sensing performance. Methods: We evaluated myocardial activation sequences (AS) for pacing of the His bundle and peri-His region and assessed acute pacing performance using custom-designed plunge electrodes. Unipolar pacing was performed in isolated swine hearts (n = 10) using four quadripolar stimulation/sensing electrodes implanted into the interventricular septum and equally spaced between the membranous septum and the coronary sinus ostium (zones 1,4, respectively; electrode depth (ED) 1 = most distal, ED 4 = most proximal). Optimal pacing sites were defined as: pacing thresholds ,1.5 V, a P-R ratio of ,0.5, and ,50% occurrence of an intrinsic midseptal left ventricular (LV) endocardial electrical breakout (BO) and activation pattern. Results: Pacing thresholds improved with greater depth of electrode location within the septum (ED 1: 1.51 ± 0.8 V vs ED 4: 5.2 ± 3.8 V, P < 0.001), as did the P-R ratio (0.34 ± 0.6 vs 0.78 ± 1.0, P < 0.05). His potentials were only observed in zone 1 and 2 electrodes (0.12 and 0.02 mV, respectively). Only electrodes in zones 1 and 2 produced LV endocardial electrical BOs in the midseptal region that demonstrated an intrinsic-like endocardial AS. Depth 1 and 2 electrodes (11.75 and 8.75 mm, respectively) in zone 1 satisfied all three optimal pacing site requirements. Conclusions: This study has shown that LV activation patterns similar to sinus rhythm may be achieved without direct activation of the His bundle, while maintaining acceptable pacing and sensing performance. These data indicate that pacing systems designed to stimulate the tissues below the point at which the His bundle penetrates the central fibrous body may provide improved system efficiency and LV performance in comparison to both direct His bundle pacing and traditional pacing sites. [source] Porous Metal Oxides as Gas SensorsCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2007Michael Tiemann Dr. Abstract Semiconducting metal oxides are frequently used as gas-sensing materials. Apart from large surface-to-volume ratios, well-defined and uniform pore structures are particularly desired for improved sensing performance. This article addresses the role of some key structural aspects in porous gas sensors, such as grain size and agglomeration, pore size or crack-free film morphology. New synthesis concepts, for example, the utilisation of rigid matrices for structure replication, allow to control these parameters independently, providing the opportunity to create self-diagnostic sensors with enhanced sensitivity and reproducible selectivity. [source] Active Metal Electrode,Oxide Interface in Gas Sensor Operation Probed by In Situ and Time-Resolved X-Ray SpectroscopyCHEMPHYSCHEM, Issue 1 2010Aleksander Gurlo Dr. The feasibility of the in situ and operando methodology in studying the chemical and electronic phenomena associated with an active metal electrode,oxide interface in metal-oxide-based gas sensors (picture) is demonstrated. It is experimentally verified that the Pt electrodes in metal-oxide based gas sensors are partially oxidised and that the oxidised Pt electrodes contribute to overall sensing performance. [source] ,-Gallium Oxide as Oxygen Gas Sensors at a High TemperatureJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2007Marilena Bartic Resistive oxygen sensors based on gallium oxide were fabricated in order to analyze their sensing performances (as sensitivity, response, and recovery time) in an oxygen atmosphere at 1000°C. We prepared three types of sensors using a ,-Ga2O3 single crystal in a sandwich structure with Pt pad electrodes and ,-Ga2O3 polycrystalline thin films deposited by using both the sputtering technique and the chemical solution deposition method. For thin-film sensors, Pt interdigital electrodes were deposited on the surface of the films using the lift-off method. X-ray diffraction and atomic force microscopy investigations were performed to compare the structure and surface morphology of the samples. We achieved a response time of 10 s at 1000°C, while the sensitivity was 1.03 for the single crystal and 1.35,1.45 for thin films. The sensing properties depend on the preparation condition of Ga2O3 devices. [source] Effect of fabrication temperature on strain-sensing capacity of polypyrrole-coated conductive fabricsPOLYMER INTERNATIONAL, Issue 7 2007Joanna Tsang Abstract Textile strain sensors were made from polypyrrole-coated stretchable fabrics by a method of screen printing with chemical vapor deposition. The effect of polymerization temperature on the sensing performances was studied. It was found that polymerization at low temperature significantly improved the electrical conductivity, strain sensitivity and environmental stability of the fabric sensors. The conductive fabrics were characterized using X-ray diffraction, thermogravimetry, contact angle measurements, particle size analysis, scanning electron microscopy and scanning probe microscopy. Powders of pure polypyrrole prepared by the same fabrication method were characterized for a better understanding of the polypyrrole coating. Copyright © 2007 Society of Chemical Industry [source] | |||||||||||||