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Sensing Devices (sensing + device)
Selected AbstractsA micron-sized nanoporous multifunction sensing devicePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2009L. Moreno i Codinachs Abstract In this work, a capacitive sensor based on Anodic Aluminium Oxide (AAO) porous structures has been developed. In some cases, the pores have been also conformally coated with a high chemical pure SiO2 by means of Atomic Layer Deposition (ALD). Temperature measurements have been done in DI water obtaining a response of 5 nF/°C. pH measurements have been performed and the responses obtained are between 0.2 and 1 nF/pH. The reproducibility of the sensors has been found to be high and a larger hysteresis effect has been observed in the samples with alumina pores rather than in the SiO2 ones. The hysteresis seems to be related to the charging of the oxide upon application of a voltage. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Glucose sensors: a review of current and emerging technologyDIABETIC MEDICINE, Issue 3 2009N. S. Oliver Abstract Glucose monitoring technology has been used in the management of diabetes for three decades. Traditional devices use enzymatic methods to measure glucose concentration and provide point sample information. More recently continuous glucose monitoring devices have become available providing more detailed data on glucose excursions. In future applications the continuous glucose sensor may become a critical component of the closed loop insulin delivery system and, as such, must be selective, rapid, predictable and acceptable for continuous patient use. Many potential sensing modalities are being pursued including optical and transdermal techniques. This review aims to summarize existing technology, the methods for assessing glucose sensing devices and provide an overview of emergent sensing modalities. [source] Application of Nanoparticles in Electrochemical Sensors and BiosensorsELECTROANALYSIS, Issue 4 2006Xiliang Luo Abstract The unique chemical and physical properties of nanoparticles make them extremely suitable for designing new and improved sensing devices, especially electrochemical sensors and biosensors. Many kinds of nanoparticles, such as metal, oxide and semiconductor nanoparticles have been used for constructing electrochemical sensors and biosensors, and these nanoparticles play different roles in different sensing systems. The important functions provided by nanoparticles include the immobilization of biomolecules, the catalysis of electrochemical reactions, the enhancement of electron transfer between electrode surfaces and proteins, labeling of biomolecules and even acting as reactant. This minireview addresses recent advances in nanoparticle-based electrochemical sensors and biosensors, and summarizes the main functions of nanoparticles in these sensor systems. [source] Diagnostic Implications of Uric Acid in Electroanalytical MeasurementsELECTROANALYSIS, Issue 14 2005Abstract Urate has a long history in clinical analysis and has served as an important diagnostic in a number of contexts. The increasing interest in metabolic syndrome has led to urate being used in combination with a number of other biomarkers in the assessment of cardiovascular risk. The traditional view of urate as principally an interferent in electrochemical measurement is now gradually being replaced with the realization that its measurement could serve as an invaluable secondary (if not primary) marker when monitoring conditions such as diabetes and heart disease. Rather than attempting to wholly exclude urate electrochemistry, many strategies are being developed that can integrate the urate signal within the device architecture such that a range of biomarkers can be sequentially assessed. The present review has sought to rationalize the clinical importance that urate measurements could hold in future diagnostic applications , particularly within near patient testing contexts. The technologies harnessed for its detection and also those previously employed for its removal are reviewed with the aim of highlighting how the seemingly contrasting approaches are evolving to aid the development of new sensing devices for clinical analysis. [source] Carbon-Nanotube Based Electrochemical Biosensors: A ReviewELECTROANALYSIS, Issue 1 2005Joseph Wang Abstract This review addresses recent advances in carbon-nanotubes (CNT) based electrochemical biosensors. The unique chemical and physical properties of CNT have paved the way to new and improved sensing devices, in general, and electrochemical biosensors, in particular. CNT-based electrochemical transducers offer substantial improvements in the performance of amperometric enzyme electrodes, immunosensors and nucleic-acid sensing devices. The greatly enhanced electrochemical reactivity of hydrogen peroxide and NADH at CNT-modified electrodes makes these nanomaterials extremely attractive for numerous oxidase- and dehydrogenase-based amperometric biosensors. Aligned CNT "forests" can act as molecular wires to allow efficient electron transfer between the underlying electrode and the redox centers of enzymes. Bioaffinity devices utilizing enzyme tags can greatly benefit from the enhanced response of the biocatalytic-reaction product at the CNT transducer and from CNT amplification platforms carrying multiple tags. Common designs of CNT-based biosensors are discussed, along with practical examples of such devices. The successful realization of CNT-based biosensors requires proper control of their chemical and physical properties, as well as their functionalization and surface immobilization. [source] Synthesis and Physicochemical Characterization of meso -Functionalized Corroles: Precursors of Organic,Inorganic Hybrid MaterialsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2005Jean-Michel Barbe Abstract Cobalt(III) corroles exhibit an infinite selectivity for the coordination of carbon monoxide towards dioxygen and dinitrogen. This peculiar property thus allows their use as sensing devices for CO detection. Here are described the syntheses and physico-chemical characterization of meso mono-, bis- and tris(triethoxysilyl)-functionalized corroles, precursors of organic,inorganic materials. The corrole ring formation was achieved in every case using the "2+1" method involving the reaction of two equivalents of an encumbered dipyrromethane with one equivalent of an aromatic aldehyde in the presence of a catalytic amount of trifluoroacetic acid. The functionalization of the corrole by triethoxysilyl chains was carried out by a condensation reaction of an isocyanate, bearing a triethoxysilyl termination, either on an amino or hydroxy group. Each final compound and intermediate were characterized by various physico-chemical techniques such as 1H NMR, UV/Vis, MALDI/TOF or EI mass spectrometry and elemental analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Densely Packed Arrays of Ultra-High-Aspect-Ratio Silicon Nanowires Fabricated using Block-Copolymer Lithography and Metal-Assisted EtchingADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Shih-Wei Chang Abstract Metal-assisted etching is used in conjunction with block-copolymer lithography to create ordered and densely-packed arrays of high-aspect-ratio single-crystal silicon nanowires with uniform crystallographic orientations. Nanowires with diameters and spacings down to 19,nm and 10,nm, respectively, are created as either continuous carpets or as carpets within trenches. Wires with aspect ratios up to 220 are fabricated, and capillary-induced clustering of wires is eliminated through post-etching critical point drying. The wires are single crystals with ,100, axis directions. The distribution of wire diameters is narrow and closely follows the size distribution of the block copolymer, with a standard deviation of 3.12,nm for wires of mean diameters 22.06,nm. Wire arrays formed in carpets and in channels have hexagonal order with good fidelity to the block copolymer pattern. Fabrication of wires in topographic features demonstrates the ability to accurately control wire placement. Wire arrays made using this new process will have applications in the creation of arrays of photonic and sensing devices. [source] Fluorimetric Nerve Gas Sensing Based on Pyrene Imines Incorporated into Films and Sub-Micrometer FibersADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Jeremy M. Rathfon Abstract The chemical sensing of nerve gas agents has become an increasingly important goal due to the 1995 terrorist attack in a Tokyo subway as well as national security concerns in regard to world affairs. Chemical detection needs to be sensitive and selective while being facile, portable, and timely. In this paper, a sensing approach using a pyrene imine molecule is presented that is fluorimetric in response. The detection of a chloro-Sarin surrogate is measured at 5 ppmv in less than 1 second and is highly selective towards halogenated organophosphates. The pyrene imine molecule is incorporated into polystyrene films as well as micrometer and sub-micrometer fibers. Using both a direct drawing approach and electrospinning, micrometer and nanofibers can be easily manufactured. Applications for functional sensing micrometer and nanofibers are envisioned for optical devices and photonics in addition to solution and airflow sensing devices. [source] Gas Sensors: Room-Temperature Gas Sensing Based on Electron Transfer between Discrete Tin Oxide Nanocrystals and Multiwalled Carbon Nanotubes (Adv. Mater.ADVANCED MATERIALS, Issue 24 200924/2009) Hybrid nanostructures consisting of multiwalled carbon nanotubes (CNTs) uniformly coated with SnO2 nanocrystals can be used as a novel gas sensing platform, exhibiting high sensitivity to low-concentration gases (NO2, H2, and CO) at room temperature, report Junhong Chen and co-workers on p. 2487. The hybrid nanomaterial provides a new opportunity to engineer sensing devices through electronic transfer between the nanocrystals and the CNT. [source] Laplacian Electrograms and the Interpretation of Complex Ventricular Activation Patterns During Ventricular FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2000PH.D., RUBEN CORONEL M.D. Laplacian Electrograms and Ventricular Fihrillation. Introduction. During ventricular fibrillation (VF) interpretation of a local electrogram and determination of the local activation moment are hampered by remote activity or intervening repolarization waves. Successful defibrillation depends on critical timing of the shock relative to local activation. We tested the applicabillity of Laplacian electrograms for detection of the moment of local activation during VF. Methods and Results. From isolated perfased porcine infact heart, 247 local unipolar electrograms were recorded simultaneously (13 × 19 matrix, interelectrode distance 0.3 mm) from the left ventricular wall during sinus rhythm, following pacing or during VF, Activation maps were constructed based on local unipolar electrograms, and Laplacian electrograms were calculated from local electrograms ane its eight neighbors. The Laplacian electrogram displayed a sharp R/S complex with local activation iodicted by the moment of zero crossing without interference from remote activity or repolarization waves. Its amplitude increased with decreasing interelectrode distance, Following epicardial stimulation, Laplacian amplitude was significantly larger than during complexes with different morphology. Collision of wavefronts was associated with entirely positive Laplacian waveforms; "focal" appearancce of acitivity was associated with an entirely negative waveform. Activation block in the activation maps was correlated with the appearance of substanined episodes of negativity or positivity in the Laplacian electrogram (depending on the location of the recording site relative to the line of block). Conclusion. Laplacian electrograms allow detection of the moment of local activation without interference from remote activity or repolarization, especially during complex arrhythmias. The technique applied toe automatic sensing devices, such its the internal defibrillator, may optimize defibrtilation success. (J Cardiovasc Electrophysiol, Vol. 11, pp. 1119-1128, October 2000) [source] Metallic Li in carbonaceous nanotubes grown by metalorganic chemical vapor deposition from a metalorganic precursorAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2008Mahua Das Abstract Metallic Li in carbonaceous nanostructures was obtained in high concentration (as much as 33.4%) through metalorganic chemical vapor deposition involving certain lithium,aminoalkyl moieties, which are formed in situ, by decomposition of a precursor containing both cobalt and lithium. The bimetallic complex containing both lithium and cobalt was characterized by IR spectroscopy, mass spectroscopy, nuclear magnetic resonance spectroscopy, elemental analysis and thermogravimetric analysis. X-ray photoelectron spectroscopy measurements performed on the as-grown films demonstrate that lithium can be stable in metallic form in such a film. Results of X-ray photoelectron spectroscopic analysis of the as-grown films are presented as direct evidence of the formation and stabilization of metallic lithium in carbon nanotubes. Carbon nanotubes, encapsulating metallic lithium, can potentially act as a miniaturized nanobattery. Such a battery would be potentially useful in the next generation of communication and remote sensing devices, where a pulse of current is required for their operation. In addition, with metallic lithium, having an effective nuclear magnetic moment, such materials can be envisioned to show potential applications in devices based on nuclear magnetic resonances. Copyright © 2008 John Wiley & Sons, Ltd. [source] Analysis of Dopamine and Tyrosinase Activity on Ion-Sensitive Field-Effect Transistor (ISFET) DevicesCHEMISTRY - A EUROPEAN JOURNAL, Issue 26 2007Ronit Freeman Abstract Dopamine (1) and tyrosinase (TR) activities were analyzed by using chemically modified ion-sensitive field-effect transistor (ISFET) devices. In one configuration, a phenylboronic acid functionalized ISFET was used to analyze 1 or TR. The formation of the boronate,1 complex on the surface of the gate altered the electrical potential associated with the gate, and thus enabled 1 to be analyzed with a detection limit of 7×10,5,M. Similarly, the TR-induced formation of 1, and its association with the boronic acid ligand allowed a quantitative assay of TR to be performed. In another configuration, the surface of the ISFET gate was modified with tyramine or 1 to form functional surfaces for analyzing TR activities. The TR-induced oxidation of the tyramine- or 1 -functionalized ISFETs resulted in the formation of the redox-active dopaquinone units. The control of the gate potential by the redox-active dopaquinone units allowed a quantitative assay of TR to be performed. The dopaquinone-functionalized ISFETs could be regenerated to give the 1 -modified sensing devices by treatment with ascorbic acid. [source] Vertically Aligned Antimony Nanowires as Solid-State pH SensorsCHEMPHYSCHEM, Issue 1 2007Pai-Chun Chang Antimony pH nanoelectrodes based on Sb nanowire arrays are fabricated by a template-assisted electrodeposition technique (see picture). Based on their highly linear response to hydrogen ion (H+) concentration, the Sb nanowire array demonstrates excellent characteristics for pH detection and offers the possibility of use in nanoscale solid-state sensing devices for biological systems. [source] | ||||||||||||||||