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Sensors, Volume 6, Issue 10 (October 2006), Pages 1161-1427

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Research

Jump to: Review

Open AccessArticle A New Overpotential — Capacitance Mechanism for H2 Electrode
Sensors 2006, 6(10), 1187-1198; doi:10.3390/s6101187
Received: 22 July 2006 / Accepted: 28 September 2006 / Published: 1 October 2006
Cited by 3 | PDF Full-text (308 KB) | HTML Full-text | XML Full-text
Abstract
The H2 electrode is commonly assumed to be a half-cell, 2 H+ 2e == H2, andexplained by the Nernst equation. We cannot assume that the H+ is easily reduced to H2 inan H2 saturated solution, [...] Read more.
The H2 electrode is commonly assumed to be a half-cell, 2 H+ 2e == H2, andexplained by the Nernst equation. We cannot assume that the H+ is easily reduced to H2 inan H2 saturated solution, and H2 becoming oxidized to H+ in a strongly acid solution againstthe equilibrium principle. How can the H2 gas is involved from a basic solution where thereis practically no H+ ions? Another equilibrium has been postulated, H2 (soln) = 2H(adsorbed on metal) = 2 H 2e. This paper reports the results of studying the H2 electrodeusing various techniques, such as adsorption, bubbling with H2, and N2, charging,discharging, and recharging, replacing the salt bridge with a conducting wire, etc. Aninteresting overpotential was observed that bubbling H2 into the solution caused a suddenchange of potential to more negative without changing the solution pH. The H2 may bereplaced by N2 to give a similar calibration curve without the overpotential. The resultscontradict the redox mechanism. When the Pt is separated by H2 coating, it cannot act as acatalyst in the solution. Our results seem to explain the H2 electrode mechanism as thecombination of its overpotential and capacitance potential. Bubbling of H2 or N2 onlyremoves interfering gases such as O2 and CO2. Since neither H2 nor N2 is involved in thepotential development, it is improper to call the H2 or N2 electrode. A term of pH / OH Ptelectrode, like the pH / OH glass electrode, is suggested. Full article
Open AccessArticle Application of an IR Thermographic Device for the Detection of a Simulated Defect in a Pipe
Sensors 2006, 6(10), 1199-1208; doi:10.3390/s6101199
Received: 23 June 2006 / Accepted: 2 October 2006 / Published: 4 October 2006
Cited by 6 | PDF Full-text (85 KB) | HTML Full-text | XML Full-text
Abstract
An infrared (IR) temperature sensor module developed for the detection ofdefects in a metal plate is modified for defect detection in a pipe. A module giving closesensor arrangement and maintaining a constant distance between sensor and measuredobject is developed and utilized in [...] Read more.
An infrared (IR) temperature sensor module developed for the detection ofdefects in a metal plate is modified for defect detection in a pipe. A module giving closesensor arrangement and maintaining a constant distance between sensor and measuredobject is developed and utilized in the present modification of the IR thermographic device.The defect detection performance is experimentally investigated, and the measuredtemperature is compared with the computed temperature distribution and with a previousexperimental result. The outcome of this experiment indicates that detection of a simulateddefect is readily obtainable, and the measured temperature distribution is better for defectdetection than with the previously utilized device. The comparison of standard deviations ofdifferent sensors clearly indicates an improvement in the location of defects in this study.Also, the measured temperature distribution is comparable to the one calculated using a heatconduction equation. The device developed for defect detection here is suitable forimplementation in chemical processes, where most vessels and piping systems arecylindrical in shape. Full article
Open AccessArticle Monitoring the Freshness of Moroccan Sardines with a Neural-Network Based Electronic Nose
Sensors 2006, 6(10), 1209-1223; doi:10.3390/s6101209
Received: 15 July 2006 / Accepted: 3 October 2006 / Published: 5 October 2006
Cited by 20 | PDF Full-text (207 KB) | HTML Full-text | XML Full-text
Abstract
An electronic nose was developed and used as a rapid technique to classify thefreshness of sardine samples according to the number of days spent under cold storage (4 ±1°C, in air). The volatile compounds present in the headspace of weighted sardine sampleswere [...] Read more.
An electronic nose was developed and used as a rapid technique to classify thefreshness of sardine samples according to the number of days spent under cold storage (4 ±1°C, in air). The volatile compounds present in the headspace of weighted sardine sampleswere introduced into a sensor chamber and the response signals of the sensors wererecorded as a function of time. Commercially available gas sensors based on metal oxidesemiconductors were used and both static and dynamic features from the sensorconductance response were input to the pattern recognition engine. Data analysis wasperformed by three different pattern recognition methods such as probabilistic neuralnetworks (PNN), fuzzy ARTMAP neural networks (FANN) and support vector machines(SVM). The objective of this study was to find, among these three pattern recognitionmethods, the most suitable one for accurately identifying the days of cold storage undergoneby sardine samples. The results show that the electronic nose can monitor the freshness ofsardine samples stored at 4°C, and that the best classification and prediction are obtainedwith SVM neural network. The SVM approach shows improved classificationperformances, reducing the amount of misclassified samples down to 3.75 %. Full article
Open AccessArticle Flow-through Bulk Optode for Spectrophotometric Determination of Thiocyanate and Its Application to Water and Saliva Analysis
Sensors 2006, 6(10), 1224-1233; doi:10.3390/s6101224
Received: 23 June 2006 / Accepted: 3 October 2006 / Published: 9 October 2006
Cited by 6 | PDF Full-text (144 KB) | HTML Full-text | XML Full-text
Abstract
A flow-through spectrophotometric bulk optode for the flow-injectiondetermination of thiocyanate is described. As active constituents, the optode incorporatesthe lipophilized pH indicator 5-octadecanoyloxy-2-(4-nitrophenylazo)phenol andmethyltridodecyl ammonium chloride, dissolved in a plasticized poly(vinyl)chloridemembrane entrapped in a cellulose support. The optode is applied, in conjunction with [...] Read more.
A flow-through spectrophotometric bulk optode for the flow-injectiondetermination of thiocyanate is described. As active constituents, the optode incorporatesthe lipophilized pH indicator 5-octadecanoyloxy-2-(4-nitrophenylazo)phenol andmethyltridodecyl ammonium chloride, dissolved in a plasticized poly(vinyl)chloridemembrane entrapped in a cellulose support. The optode is applied, in conjunction with theflow injection technique, to the determination of thiocyanate at pH 7.5 (TRIS/H2SO4). Thesensor is readily regenerated with a 10-2 M NaOH carrier solution. The analyticalcharacteristics of this optode with respect to thiocyanate response time, dynamicmeasurement range, reproducibility and selectivity are discussed. The proposed FI methodis applied to the determination of thiocyanate in waters from different sources and in humansaliva samples in order to distinguish between smokers and non-smokers. Full article
(This article belongs to the Special Issue Sensors in Flow Analysis)
Open AccessArticle Studies on the Interaction Mechanism of 1,10-Phenanthroline Cobalt(II) Complex with DNA and Preparation of Electrochemical DNA Biosensor
Sensors 2006, 6(10), 1234-1244; doi:10.3390/s6101234
Received: 1 September 2006 / Accepted: 5 October 2006 / Published: 10 October 2006
Cited by 15 | PDF Full-text (277 KB) | HTML Full-text | XML Full-text
Abstract
Fluorescence spectroscopy and ultraviolet (UV) spectroscopy techniques coupled with cyclic voltammetry (CV) were used to study the interaction between salmon sperm DNA and 1,10-Phenanthroline cobalt(II) complex, [Co(phen)2(Cl)(H2O)]Cl·H2O, where phen = 1,10-phenanthroline. The interaction between [Co(phen)2 [...] Read more.
Fluorescence spectroscopy and ultraviolet (UV) spectroscopy techniques coupled with cyclic voltammetry (CV) were used to study the interaction between salmon sperm DNA and 1,10-Phenanthroline cobalt(II) complex, [Co(phen)2(Cl)(H2O)]Cl·H2O, where phen = 1,10-phenanthroline. The interaction between [Co(phen)2(Cl)(H2O)]+ and double-strand DNA (dsDNA) was identified to be intercalative mode. An electrochemical DNA biosensor was developed by covalent immobilization of probe single-strand DNA (ssDNA) related to human immunodeficiency virus (HIV) on the activated glassy carbon electrode (GCE). With [Co(phen)2(Cl)(H2O)]+ being the novel electrochemical hybridization indicator, the selectivity of ssDNA-modified electrode was investigated and selective detection of complementary ssDNA was achieved using differential pulse voltammetry (DPV). Full article
(This article belongs to the Special Issue Amperometric Sensors and Techniques for Neurochemical Monitoring)
Open AccessArticle Sub-Nanoliter Spectroscopic Gas Sensor
Sensors 2006, 6(10), 1308-1320; doi:10.3390/s6101308
Received: 31 August 2006 / Accepted: 9 October 2006 / Published: 11 October 2006
Cited by 11 | PDF Full-text (319 KB) | HTML Full-text | XML Full-text
Abstract
In this work, a new type of optical fiber based chemical sensor, the sub-nanolitersample cell (SNSC) based gas sensor, is described and compared to existing sensors designsin the literature. This novel SNSC gas sensor is shown to have the capability of gasdetection [...] Read more.
In this work, a new type of optical fiber based chemical sensor, the sub-nanolitersample cell (SNSC) based gas sensor, is described and compared to existing sensors designsin the literature. This novel SNSC gas sensor is shown to have the capability of gasdetection with a cell volume in the sub-nanoliter range. Experimental results for variousconfigurations of the sensor design are presented which demonstrate the capabilities of theminiature gas sensor. Full article
(This article belongs to the Special Issue Gas Sensors)
Open AccessArticle Development of Multichannel Artificial Lipid-Polymer Membrane Sensor for Phytomedicine Application
Sensors 2006, 6(10), 1333-1344; doi:10.3390/s6101333
Received: 10 March 2006 / Revised: 6 October 2006 / Accepted: 16 October 2006 / Published: 17 October 2006
Cited by 9 | PDF Full-text (114 KB) | HTML Full-text | XML Full-text
Abstract
Quality control of herbal medicines remain a challenging issue towardsintegrating phytomedicine into the primary health care system. As medicinal plants is acomplicated system of mixtures, a rapid and cost-effective evaluation method tocharacterize the chemical fingerprint of the plant without performing laborious samplepreparation [...] Read more.
Quality control of herbal medicines remain a challenging issue towardsintegrating phytomedicine into the primary health care system. As medicinal plants is acomplicated system of mixtures, a rapid and cost-effective evaluation method tocharacterize the chemical fingerprint of the plant without performing laborious samplepreparation procedure is reported. A novel research methodology based on an in-housefabricated multichannel sensor incorporating an array of artificial lipid-polymer membraneas a fingerprinting device for quality evaluation of a highly sought after herbal medicine inthe Asean Region namely Eurycoma longifolia (Tongkat Ali). The sensor array is based onthe principle of the bioelectronic tongue that mimics the human gustatory system throughthe incorporation of artificial lipid material as sensing element. The eight non-specificsensors have partially overlapping selectivity and cross-sensitivity towards the targetedanalyte. Hence, electrical potential response represented by radar plot is used to characterizeextracts from different parts of plant, age, batch-to-batch variation and mode of extraction ofE. longifolia through the obtained potentiometric fingerprint profile. Classification modelwas also developed classifying various E. longifolia extracts with the aid of chemometricpattern recognition tools namely hierarchical cluster analysis (HCA) and principalcomponent analysis (PCA). The sensor seems to be a promising analytical device for qualitycontrol based on potentiometric fingerprint analysis of phytomedicine. Full article
Open AccessArticle Sensor for Injection Rate Measurements
Sensors 2006, 6(10), 1367-1382; doi:10.3390/s6101367
Received: 17 June 2006 / Accepted: 10 October 2006 / Published: 23 October 2006
Cited by 7 | PDF Full-text (243 KB) | HTML Full-text | XML Full-text
Abstract
A vast majority of the medium and high speed Diesel engines are equipped withmulti-hole injection nozzles nowadays. Inaccuracies in workmanship and changinghydraulic conditions in the nozzles result in differences in injection rates between individualinjection nozzle holes. The new deformational measuring method described [...] Read more.
A vast majority of the medium and high speed Diesel engines are equipped withmulti-hole injection nozzles nowadays. Inaccuracies in workmanship and changinghydraulic conditions in the nozzles result in differences in injection rates between individualinjection nozzle holes. The new deformational measuring method described in the paperallows injection rate measurement in each injection nozzle hole. The differences in injectionrates lead to uneven thermal loads of Diesel engine combustion chambers. All today knownmeasuring method, such as Bosch and Zeuch give accurate results of the injection rate indiesel single-hole nozzles. With multihole nozzles they tell us nothing about possibledifferences in injection rates between individual holes of the nozzle. At deformationalmeasuring method, the criterion of the injected fuel is expressed by the deformation ofmembrane occurring due to the collision of the pressure wave against the membrane. Thepressure wave is generated by the injection of the fuel into the measuring space. For eachhole of the nozzle the measuring device must have a measuring space of its own into whichfuel is injected as well as its measuring membrane and its own fuel outlet. Duringmeasurements procedure the measuring space must be filled with fuel to maintain anoverpressure of 5 kPa. Fuel escaping from the measuring device is conducted into thegraduated cylinders for measuring the volumetric flow through each hole of the nozzle.Themembrane deformation is assessed by strain gauges. They are glued to the membrane andforming the full Wheatstone’s bridge. We devoted special attention to the membrane shapeand temperature compensation of the strain gauges. Full article
Open AccessArticle ZnO:Al Thin Film Gas Sensor for Detection of Ethanol Vapor
Sensors 2006, 6(10), 1420-1427; doi:10.3390/s6101420
Received: 31 July 2006 / Accepted: 27 October 2006 / Published: 30 October 2006
Cited by 71 | PDF Full-text (208 KB) | HTML Full-text | XML Full-text
Abstract
The ZnO:Al thin films were prepared by RF magnetron sputtering on Si substrateusing Pt as interdigitated electrodes. The structure was characterized by XRD and SEManalyses, and the ethanol vapor gas sensing as well as electrical properties have beeninvestigated and discussed. The gas [...] Read more.
The ZnO:Al thin films were prepared by RF magnetron sputtering on Si substrateusing Pt as interdigitated electrodes. The structure was characterized by XRD and SEManalyses, and the ethanol vapor gas sensing as well as electrical properties have beeninvestigated and discussed. The gas sensing results show that the sensitivity for detecting400 ppm ethanol vapor was ~20 at an operating temperature of 250°C. The high sensitivity,fast recovery, and reliability suggest that ZnO:Al thin film prepared by RF magnetronsputtering can be used for ethanol vapor gas sensing. Full article
(This article belongs to the Special Issue Gas Sensors)

Review

Jump to: Research

Open AccessReview Trends in Flow-based Biosensing Systems for Pesticide Assessment
Sensors 2006, 6(10), 1161-1186; doi:10.3390/s6101161
Received: 29 July 2006 / Accepted: 29 September 2006 / Published: 1 October 2006
Cited by 38 | PDF Full-text (464 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This review gives a survey on the state of the art of pesticide detection usingflow-based biosensing systems for sample screening. Although immunosensor systems havebeen proposed as powerful pesticide monitoring tools, this review is mainly focused onenzyme-based biosensors, as they are the most [...] Read more.
This review gives a survey on the state of the art of pesticide detection usingflow-based biosensing systems for sample screening. Although immunosensor systems havebeen proposed as powerful pesticide monitoring tools, this review is mainly focused onenzyme-based biosensors, as they are the most commonly employed when using a flowsystem. Among the different detection methods able to be integrated into flow-injectionanalysis (FIA) systems, the electrochemical ones will be treated in more detail, due to theirhigh sensitivity, simple sample pretreatment, easy operational procedures and real-timedetection. During the last decade, new trends have been emerging in order to increase theenzyme stability, the sensitivity and selectivity of the measurements, and to lower thedetection limits. These approaches are based on (i) the design of novel matrices for enzymeimmobilisation, (ii) new manifold configurations of the FIA system, sometimes includingminiaturisation or lab-on-chip protocols thanks to micromachining technology, (iii) the useof cholinesterase enzymes either from various commercial sources or genetically modifiedwith the aim of being more sensitive, (iv) the incorporation of other highly specificenzymes, such as organophosphate hydrolase (OPH) or parathion hydrolase (PH) and (v) thecombination of different electrochemical methods of detection. This article discusses thesenovel strategies and their advantages and limitations. Full article
(This article belongs to the Special Issue Sensors in Flow Analysis)
Open AccessReview Recent Development in Optical Chemical Sensors Coupling with Flow Injection Analysis
Sensors 2006, 6(10), 1245-1307; doi:10.3390/s6101245
Received: 4 May 2006 / Accepted: 5 October 2006 / Published: 10 October 2006
Cited by 18 | PDF Full-text (326 KB) | HTML Full-text | XML Full-text
Abstract
Optical techniques for chemical analysis are well established and sensors based on thesetechniques are now attracting considerable attention because of their importance in applications suchas environmental monitoring, biomedical sensing, and industrial process control. On the other hand,flow injection analysis (FIA) is advisable [...] Read more.
Optical techniques for chemical analysis are well established and sensors based on thesetechniques are now attracting considerable attention because of their importance in applications suchas environmental monitoring, biomedical sensing, and industrial process control. On the other hand,flow injection analysis (FIA) is advisable for the rapid analysis of microliter volume samples and canbe interfaced directly to the chemical process. The FIA has become a widespread automatic analyticalmethod for more reasons; mainly due to the simplicity and low cost of the setups, their versatility, andease of assembling. In this paper, an overview of flow injection determinations by using opticalchemical sensors is provided, and instrumentation, sensor design, and applications are discussed. Thiswork summarizes the most relevant manuscripts from 1980 to date referred to analysis using opticalchemical sensors in FIA. Full article
(This article belongs to the Special Issue Sensors in Flow Analysis)
Open AccessReview Gas/Liquid and Liquid/Liquid Solvent Extraction in Flow Analysis with the Chromatomembrane Cell
Sensors 2006, 6(10), 1321-1332; doi:10.3390/s6101321
Received: 15 July 2006 / Accepted: 15 October 2006 / Published: 17 October 2006
Cited by 4 | PDF Full-text (92 KB) | HTML Full-text | XML Full-text
Abstract
Since twelve years the Chromatomembrane Cell has been proposed as a new andversatile device for extraxtion procedures in the flow based analysis. In the meantime aremarkable number of papers was submitted dealing with applications of the novel methodto all the conceivable varieties [...] Read more.
Since twelve years the Chromatomembrane Cell has been proposed as a new andversatile device for extraxtion procedures in the flow based analysis. In the meantime aremarkable number of papers was submitted dealing with applications of the novel methodto all the conceivable varieties of flow injection and sequential injection analysis. Thedevice supports important analytical procedures such as sampling, sample preparation, andpreconcentration each being combined with a phase transfer of the analyte. TheChromatomembrane Cell can be coupled to most of the modern detectors which workcomputer aided in the laboratories of today. Centrepiece of the cell is a block made frombiporous hydrophobic PTFE, inside which polar (in the macropores) and nonpolar (in themicropores) solvents come into a close contact with each other and might flowindependently with different flow rates. Microporous PTFE membranes prevent polarphases from their flowthrough into directions which are reserved for nonpolar fluids only.Thus, a strict control over the fluxes can be established at the analysts request. Especially,that PTFE block offers outstanding possibilities as a sampling unit for air monitoring. Full article
(This article belongs to the Special Issue Sensors in Flow Analysis)
Open AccessReview Surface Science Studies of Gas Sensing Materials: SnO2
Sensors 2006, 6(10), 1345-1366; doi:10.3390/s6101345
Received: 26 September 2006 / Accepted: 16 October 2006 / Published: 17 October 2006
Cited by 76 | PDF Full-text (1040 KB) | HTML Full-text | XML Full-text
Abstract
This review is an attempt to give an overview on how surface science studies cancontribute to a fundamental understanding of metal oxide gas sensors. In here tin dioxide isused as a model system for metal oxide gas sensor materials and we review [...] Read more.
This review is an attempt to give an overview on how surface science studies cancontribute to a fundamental understanding of metal oxide gas sensors. In here tin dioxide isused as a model system for metal oxide gas sensor materials and we review surface sciencestudies of single crystal SnO2. The composition, structure, electronic and chemicalproperties of the (110) and (101) surfaces is described. The influence of compositionalchanges as a function of the oxygen chemical potential on the electronic surface structureand the chemical properties is emphasized on the example of the (101) surface. The surfacechemical properties are discussed on the example of water adsorption. It is shown thechemical and gas sensing properties depend strongly on the surface composition. Full article
(This article belongs to the Special Issue Gas Sensors)
Open AccessReview Recent Electrochemical and Optical Sensors in Flow-Based Analysis
Sensors 2006, 6(10), 1383-1410; doi:10.3390/s6101383
Received: 8 August 2006 / Accepted: 9 October 2006 / Published: 24 October 2006
Cited by 18 | PDF Full-text (336 KB) | HTML Full-text | XML Full-text
Abstract
Some recent analytical sensors based on electrochemical and optical detectioncoupled with different flow techniques have been chosen in this overview. A briefdescription of fundamental concepts and applications of each flow technique, such as flowinjection analysis (FIA), sequential injection analysis (SIA), all injection [...] Read more.
Some recent analytical sensors based on electrochemical and optical detectioncoupled with different flow techniques have been chosen in this overview. A briefdescription of fundamental concepts and applications of each flow technique, such as flowinjection analysis (FIA), sequential injection analysis (SIA), all injection analysis (AIA),batch injection analysis (BIA), multicommutated FIA (MCFIA), multisyringe FIA(MSFIA), and multipumped FIA (MPFIA) were reviewed. Full article
(This article belongs to the Special Issue Sensors in Flow Analysis)
Open AccessReview Photoacoustic Spectroscopy with Quantum Cascade Lasers for Trace Gas Detection
Sensors 2006, 6(10), 1411-1419; doi:10.3390/s6101411
Received: 4 October 2006 / Accepted: 25 October 2006 / Published: 27 October 2006
Cited by 12 | PDF Full-text (76 KB) | HTML Full-text | XML Full-text
Abstract
Various applications, such as pollution monitoring, toxic-gas detection, noninvasive medical diagnostics and industrial process control, require sensitive and selectivedetection of gas traces with concentrations in the parts in 109 (ppb) and sub-ppb range.The recent development of quantum-cascade lasers (QCLs) has given [...] Read more.
Various applications, such as pollution monitoring, toxic-gas detection, noninvasive medical diagnostics and industrial process control, require sensitive and selectivedetection of gas traces with concentrations in the parts in 109 (ppb) and sub-ppb range.The recent development of quantum-cascade lasers (QCLs) has given a new aspect toinfrared laser-based trace gas sensors. In particular, single mode distributed feedback QCLsare attractive spectroscopic sources because of their excellent properties in terms of narrowlinewidth, average power and room temperature operation. In combination with these lasersources, photoacoustic spectroscopy offers the advantage of high sensitivity and selectivity,compact sensor platform, fast time-response and user friendly operation. This paper reportsrecent developments on quantum cascade laser-based photoacoustic spectroscopy for tracegas detection. In particular, different applications of a photoacoustic trace gas sensoremploying a longitudinal resonant cell with a detection limit on the order of hundred ppb ofozone and ammonia are discussed. We also report two QC laser-based photoacousticsensors for the detection of nitric oxide, for environmental pollution monitoring andmedical diagnostics, and hexamethyldisilazane, for applications in semiconductormanufacturing process. Full article
(This article belongs to the Special Issue Gas Sensors)

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