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Sensing Applications (sensing + application)
Selected AbstractsGraphene Solution-Gated Field-Effect Transistor Array for Sensing ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Markus Dankerl Abstract Graphene, with its unique combination of physical and electronic properties, holds great promise for biosensor and bioelectronic applications. In this respect, the development of graphene solution-gated field-effect transistor (SGFET) arrays capable of operation in aqueous environments will establish the real potential of graphene in this rapidly emerging field. Here, we report on a facile route for the scalable fabrication of such graphene transistor arrays and provide a comprehensive characterization of their operation in aqueous electrolytes. An on-chip structure for Hall-effect measurements allows the direct determination of charge carrier concentrations and mobilities under electrolyte gate control. The effect of the solution-gate potential on the electronic properties of graphene is explained using a model that considers the microscopic structure of water at the graphene/electrolyte interface. The graphene SGFETs exhibit a high transconductance and correspondingly high sensitivity, together with an effective gate noise as low as tens of ,V. Our study demonstrates that graphene SGFETs, with their facile technology, high transconductance, and low noise promise to far outperform state-of-the-art Si-based devices for biosensor and bioelectronic applications. [source] Precisely Defined Heterogeneous Conducting Polymer Nanowire Arrays , Fabrication and Chemical Sensing ApplicationsADVANCED MATERIALS, Issue 20 2009Yixuan Chen Heterogeneous conducting polymer nanostructures are fabricated using a newly developed method. Completely isolated nanowires of several conducting polymer materials can be fabricated side-by-side with perfect registry to each other on a rigid or flexible substrate. Results of a chemical sensing study using PPY and PEDOT nanowires are presented (see figure). [source] Sulphonic acids doped poly(N -ethyl aniline): A material for humidity sensing applicationPOLYMER ENGINEERING & SCIENCE, Issue 10 2007Milind V. Kulkarni Substituted polyaniline, poly(N- ethyl aniline) (PNEA), doped with camphor sulphonic acid (CSA) and p -toluene sulphonic acid (p -TSA), was synthesized by single-step chemical polymerization method using ammonium persulphate as an oxidizing agent. This is a single-step polymerization process to synthesize directly the conducting emeraldine salt phase of the polymer using CSA and p -toluene sulphonic acid as dopants. The synthesized polymers were characterized by UV,vis and FTIR spectroscopy, scanning electron microscopy, TGA/SDTA, DSC, and conductivity measurements. This single-step chemical synthesis method offers a polymer having very good physicochemical properties with good electrical conductivity. High temperature conductivity measurements show "thermal activated behavior." The change in resistance with respect to % relative humidity (% RH) is observed, when pressed pellets of the polymer were exposed to the broad range of humidity (ranging between 20 and 100% RH). POLYM. ENG. SCI., 47:1621,1629, 2007. © 2007 Society of Plastics Engineers [source] G-Quadruplex Aptamers with Peroxidase-Like DNAzyme Functions: Which Is the Best and How Does it Work?CHEMISTRY - AN ASIAN JOURNAL, Issue 6 2009Tao Li Abstract Select the best: Five G-quadruplex hemin-binding aptamers are compared to determine the best candidate for DNAzyme-based sensing application. The structural model and catalytic mechanism of the hemin,G-quadruplex complex are proposed to indicate how it works in a manner similar to the peroxidase. Some G-quadruplex DNA aptamers have been found to strongly bind hemin to form DNAzymes with peroxidase-like activity. To help determine the most suitable DNAzymes and to understand how they work, five previously reported G-quadruplex aptamers were compared for their binding affinity and then the potential catalytic mechanism of their corresponding hemin-G-quadruplex DNAzymes was explored. Among these aptamers, a G-quadruplex named AGRO100 was shown to possess the highest hemin-binding affinity and the best DNAzyme function. This means that AGRO100 is the most ideal candidate for DNAzyme-based analysis. Furthermore, we found the peroxidase-like activity of DNAzyme to be primarily dependent on the concentration of H2O2 and independent of that of the peroxidase substrate (that is, 2,2,-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt). Accordingly, a reaction mechanism for DNAzyme-catalyzed peroxidation is proposed. This study provides new insights into the G-quadruplex-based DNAzymes and will help us to further extend their applications in the analytical field. [source] Parallel heterogeneous CBIR system for efficient hyperspectral image retrieval using spectral mixture analysisCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 9 2010Antonio J. Plaza Abstract The purpose of content-based image retrieval (CBIR) is to retrieve, from real data stored in a database, information that is relevant to a query. In remote sensing applications, the wealth of spectral information provided by latest-generation (hyperspectral) instruments has quickly introduced the need for parallel CBIR systems able to effectively retrieve features of interest from ever-growing data archives. To address this need, this paper develops a new parallel CBIR system that has been specifically designed to be run on heterogeneous networks of computers (HNOCs). These platforms have soon become a standard computing architecture in remote sensing missions due to the distributed nature of data repositories. The proposed heterogeneous system first extracts an image feature vector able to characterize image content with sub-pixel precision using spectral mixture analysis concepts, and then uses the obtained feature as a search reference. The system is validated using a complex hyperspectral image database, and implemented on several networks of workstations and a Beowulf cluster at NASA's Goddard Space Flight Center. Our experimental results indicate that the proposed parallel system can efficiently retrieve hyperspectral images from complex image databases by efficiently adapting to the underlying parallel platform on which it is run, regardless of the heterogeneity in the compute nodes and communication links that form such parallel platform. Copyright © 2009 John Wiley & Sons, Ltd. [source] Nanowire-Based Electrochemical BiosensorsELECTROANALYSIS, Issue 6 2006Abstract We review recent advances in biosensors based on one-dimensional (1-D) nanostructure field-effect transistors (FET). Specifically, we address the fabrication, functionalization, assembly/alignment and sensing applications of FET based on carbon nanotubes, silicon nanowires and conducting polymer nanowires. The advantages and disadvantages of various fabrication, functionalization, and assembling procedures of these nanosensors are reviewed and discussed. We evaluate how they have been used for detection of various biological molecules and how such devices have enabled the achievement of high sensitivity and selectivity with low detection limits. Finally, we conclude by highlighting some of the challenges researchers face in the 1-D nanostructures research arena and also predict the direction toward which future research in this area might be directed. [source] Tuning the Composition and Nanostructure of Pt/Ir Films via Anodized Aluminum Oxide Templated Atomic Layer DepositionADVANCED FUNCTIONAL MATERIALS, Issue 18 2010David J. Comstock Abstract Nanostructured metal films have been widely studied for their roles in sensing, catalysis, and energy storage. In this work, the synthesis of compositionally controlled and nanostructured Pt/Ir films by atomic layer deposition (ALD) into porous anodized aluminum oxide templates is demonstrated. Templated ALD provides advantages over alternative synthesis techniques, including improved film uniformity and conformality as well as atomic-scale control over morphology and composition. Nanostructured Pt ALD films are demonstrated with morphological control provided by the Pt precursor exposure time and the number of ALD cycles. With these approaches, Pt films with enhanced surface areas, as characterized by roughness factors as large as 310, are reproducibly synthesized. Additionally, nanostructured PtIr alloy films of controlled composition and morphology are demonstrated by templated ALD, with compositions varying systematically from pure Pt to pure Ir. Lastly, the application of nanostructured Pt films to electrochemical sensing applications is demonstrated by the non-enzymatic sensing of glucose. [source] Tuning the Composition and Nanostructure of Pt/Ir Films via Anodized Aluminum Oxide Templated Atomic Layer DepositionADVANCED FUNCTIONAL MATERIALS, Issue 18 2010David J. Comstock Abstract Nanostructured metal films have been widely studied for their roles in sensing, catalysis, and energy storage. In this work, the synthesis of compositionally controlled and nanostructured Pt/Ir films by atomic layer deposition (ALD) into porous anodized aluminum oxide templates is demonstrated. Templated ALD provides advantages over alternative synthesis techniques, including improved film uniformity and conformality as well as atomic-scale control over morphology and composition. Nanostructured Pt ALD films are demonstrated with morphological control provided by the Pt precursor exposure time and the number of ALD cycles. With these approaches, Pt films with enhanced surface areas, as characterized by roughness factors as large as 310, are reproducibly synthesized. Additionally, nanostructured PtIr alloy films of controlled composition and morphology are demonstrated by templated ALD, with compositions varying systematically from pure Pt to pure Ir. Lastly, the application of nanostructured Pt films to electrochemical sensing applications is demonstrated by the non-enzymatic sensing of glucose. [source] A Reusable Interface Constructed by 3-Aminophenylboronic Acid-Functionalized Multiwalled Carbon Nanotubes for Cell Capture, Release, and CytosensingADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Xue Zhong Abstract A newly developed electrochemical cell sensor for the determination of K562 leukemia cells using 3-aminophenylboronic acid (APBA)-functionalized multiwalled carbon nanotubes (MWCNTs) films is demonstrated. The films are generated by the covalent coupling between the NH2 groups in APBA and the COOH group in the acid-oxidized MWCNTs. As a result of the sugar-specific affinity interactions, the K562 leukemia cells are firmly bound to the APBA-functionalized MWCNTs film via boronic acid groups. Compared to electropolymerized APBA films, the presence of MWCNTs not only provides abundant boronic acid domains for cell capture, their high electrical conductivity also makes the film suitable for electrochemical sensing applications. The resulting modified electrodes are tested as cell detection sensors. This work presents a promising platform for effective cell capture and constructing reusable cytosensors. [source] Shrink-Induced Nanowrinkles: Tunable Nanowrinkles on Shape Memory Polymer Sheets (Adv. Mater.ADVANCED MATERIALS, Issue 44 200944/2009) By leveraging the mismatch in stiffness between a stiff thin metal film and heat-induced shrinkage of prestressed polystyrene sheets, Michelle Khine and co-workers can rapidly and controllably create tunable nanowrinkles of various sizes and shapes for surface-enhanced sensing applications, as reported on p. 4472. Because the wrinkles are robustly embedded into the plastic, nanostructures can be integrated into microfluidic channels within minutes. Cover design by Libre Design. [source] Dielectric properties of pharmaceutical materials relevant to microwave processing: Effects of field frequency, material density, and moisture contentJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2010Paul W.S. Heng Abstract The rising popularity of microwaves for drying, material processing and quality sensing has fuelled the need for knowledge concerning dielectric properties of common pharmaceutical materials. This article represents one of the few reports on the density and moisture content dependence of the dielectric properties of primary pharmaceutical materials and their relevance to microwave-assisted processing. Dielectric constants and losses of 13 pharmaceutical materials were measured over a frequency range of 1,MHz,1,GHz at 23,±,1°C using a parallel-electrode measurement system. Effects of field frequency, material density and moisture content on dielectric properties were studied. Material dielectric properties varied considerably with frequency. At microwave frequencies, linear relationships were established between cube-root functions of the dielectric parameters ( and ) and density which enabled dielectric properties of materials at various densities to be estimated by regression. Moisture content was the main factor that contributed to the disparities in dielectric properties and heating capabilities of the materials in a laboratory microwave oven. The effectiveness of a single frequency density-independent dielectric function for moisture sensing applications was explored and found to be suitable within low ranges of moisture contents for a model material. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:941,957, 2010 [source] Multiwavelength source based on SOA and EDFA in a ring-cavity resonatorMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2009S. Shahi Abstract A multiwavelength source incorporating a semiconductor optical amplifier (SOA) and a erbium-doped fiber amplifier (EDFA) in a ring-cavity configuration was demonstrated. The multiwavelength source was able to generate more than 13 channels at ,27 dBm and above at a SOA bias current of 300 mA and 980-nm pump power of 92 mW. The number of wavelengths generated can be controlled by adjusting the birefringence of the ring cavity using the polarization controllers. The proposed laser has constant channel spacing of 0.8 nm, which is suitable for communication and sensing applications, and shows stable operation at room temperature. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 110,113, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23970 [source] Long-wavelength (, , 1.3 µm) InGaAlAs,InP vertical-cavity surface-emitting lasers for applications in optical communication and sensingPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 14 2006Markus-Christian Amann Abstract In this paper we present an overview of the properties and applications of long-wavelength vertical-cavity surface-emitting lasers (VCSELs) based on the InGaAlAs,InP material system. With respect to significant temperature sensitivity of active material gain as well as insufficient thermal conductivity of InP-based epitaxial compound layers, the effective thermal heat management appears as a major issue for application suitable device performance. In this context, the incorporation of a buried tunnel junction (BTJ) in connection with improved heat sinking resembles a breakthrough for long-wavelength VCSELs. With the utilization of n-type spreading layers and consequently ultralow series resistances, BTJ-VCSELs exhibit sharply reduced excess heat generation. Furthermore, the BTJ-approach enables self-aligned optical and current confinement. A hybrid dielectric stack with Au-coating yields an improved thermal heatsinking. The current status of BTJ-VCSELs encompasses a number of superior performance values. At 1.55 µm wavelength, this includes room temperature single- and multimode continuous wave (cw) output powers of more than 3 mW and 10 mW, respectively, laser operation for heat sink temperatures well exceeding 100 °C, and optical data transmission rates up to 10 Gbit/s. The versatility of compound layer composition enables arbitrary emission wavelengths within a broad range of 1.3 and 2 µm. With respect to sensing applications, BTJ-VCSELs appear as ideal components for optical detection of infrared active gases. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] AlGaN metal-semiconductor-metal structure for pressure sensing applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2006Z. Hassan Abstract We report on the effects of hydrostatic pressure on an Alx Ga1,xN metal-semiconductor-metal (MSM) structure with Ni Schottky contacts. Structural, optical, and electrical analysis of the Alx Ga1,xN film were carried out using atomic force microscopy (AFM), high resolution X-ray diffraction (HRXRD), Raman, UV-visible spectroscopy, and Hall effect measurements. The AlN mole fraction in this film was determined to be about 24%. Current-voltage (I-V) measurements of the MSM structure under hydrostatic pressure indicated a linear decrease of current with pressure. The decrease of the current under pressure was attributed to an increase in barrier height, tentatively attributed to a combination of piezoelectric and band structure effects. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Charge storage of electrospun fiber mats of poly(phenylene ether)/polystyrene blendsPOLYMER ENGINEERING & SCIENCE, Issue 12 2009Deliani Lovera Nonwoven fiber mats composed of poly(phenylene ether) (PPE) and polystyrene (PS) blends were prepared by electrospinning of PPE/PS solutions in a mixture of chloroform and hexafluoroisopropanol. The blends showed higher electrospinnability and led to thinner fibers (200 nm,1.3 ,m) than the pure components, because of a proper balance of electrical conductivity and interaction with the electrospinning solvent. The charge retention of the electrospun fibers was evaluated and related to the blend composition and the electret properties of the components. It was found that the nonwoven mats were able to retain up to 60% of the initial surface potential after several days of annealing at temperatures as high as 140°C, which is markedly higher than the charge retention of corona-charged compact films. The capability of the electrospinning technique, to inject charges into the bulk of the material and to orientate the dipoles of the PPE phase in the field direction at the same time, was related to the good surface potential stability of the PPE/PS electrospun fiber mats. The possibility of creating thin PPE/PS fibers with excellent charge retention capabilities makes these materials ideal candidates for electret filter and sensing applications. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Silver-Ion-Mediated DNAzyme Switch for the Ultrasensitive and Selective Colorimetric Detection of Aqueous Ag+ and CysteineCHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2009Tao Li Abstract Two states, two applications! An Ag+ -mediated DNAzyme switch has been designed to detect Ag+ and cysteine with high sensitivity and selectivity. In the closed state, Ag+ turns on the switch through the formation of cytosine,Ag+,cytosine base pairs, whereas adding cysteine turns off the open switch because it competitively binds to Ag+. This feature endows the DNAzyme switch with two sensing applications. [source] | ||||||||||||||||