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7133 KiB

Open AccessArticle

Sensing Characteristics of Flame-Spray-Made Pt/ZnO Thick Films as H₂Gas Sensor

by Nittaya Tamaekong, Chaikarn Liewhiran, Anurat Wisitsoraat and Sukon Phanichphant

Sensors 2009, 9(9), 6652-6669; https://doi.org/10.3390/s90906652 - 26 Aug 2009

Cited by 72 | Viewed by 13991

Abstract

Hydrogen sensing of thick films of nanoparticles of pristine, 0.2, 1.0 and 2.0 atomic percentage of Pt concentration doped ZnO were investigated. ZnO nanoparticles doped with 0.2–2.0 at.% Pt were successfully produced in a single step by flame spray pyrolysis (FSP) technique using [...] Read more.

Hydrogen sensing of thick films of nanoparticles of pristine, 0.2, 1.0 and 2.0 atomic percentage of Pt concentration doped ZnO were investigated. ZnO nanoparticles doped with 0.2–2.0 at.% Pt were successfully produced in a single step by flame spray pyrolysis (FSP) technique using zinc naphthenate and platinum(II) acetylacetonate as precursors dissolved in xylene. The particle properties were analyzed by XRD, BET, SEM and TEM. Under the 5/5 (precursor/oxygen) flame condition, ZnO nanoparticles and nanorods were observed. The crystallite sizes of ZnO spheroidal and hexagonal particles were found to be ranging from 5 to 20 nm while ZnO nanorods were seen to be 5–20 nm wide and 20–40 nm long. ZnO nanoparticles paste composed of ethyl cellulose and terpineol as binder and solvent respectively was coated on Al₂O₃ substrate interdigitated with gold electrodes to form thin films by spin coating technique. The thin film morphology was analyzed by SEM technique. The gas sensing properties toward hydrogen (H₂) was found that the 0.2 at.% Pt/ZnO sensing film showed an optimum H₂ sensitivity of ~164 at hydrogen concentration in air of 1 volume% at 300 °C and a low hydrogen detection limit of 50 ppm at 300 °C operating temperature. Full article

(This article belongs to the Special Issue Gas Sensors)

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200 KiB

Open AccessArticle

Studies of the Cataluminescence of Benzene Homologues onNanosized γ–Al₂O₃/Eu₂O₃ and the Development of a Gas Sensorfor Benzene Homologue Vapors

by Jieshan Lu, Xiaoan Cao, Canying Pan, Lianfeng Yang, Guangbo Lai, Jianling Chen and Cuiqin Wu

Sensors 2006, 6(12), 1827-1836; https://doi.org/10.3390/s6121827 - 26 Dec 2006

Cited by 16 | Viewed by 11900

Abstract

The cataluminescence (CTL) of benzene and the benzene homologues tolueneand xylene on nanosized γ–Al₂O₃ doped with Eu₂O₃ (γ–Al₂O₃/Eu₂O₃) was studied and asensor of determining these gases was designed. The [...] Read more.

The cataluminescence (CTL) of benzene and the benzene homologues tolueneand xylene on nanosized γ–Al₂O₃ doped with Eu₂O₃ (γ–Al₂O₃/Eu₂O₃) was studied and asensor of determining these gases was designed. The proposed sensor showed highsensitivity and selectivity at an optimal temperature of 432 ºC, a wavelength of 425 nm anda flow rate of 400 mL/min. Quantitative analysis was performed at the optimal conditions.The linear ranges of CTL intensity versus concentration of the benzene homologues were asfollows: benzene 2.4~5000 mL/m³, toluene 4.0~5000 mL/m³ and xylene 6.8~5000 mL/m³,with detection limits (3σ) of 1.8 mL/m³, 3.0 mL/m³ and 3.4 mL/m³ for each one,respectively. The response time of this system was less than 3 s. The coexistence of othergases, such as SO₂, CO and NH₃, caused interference at levels around 11.7%, 5.8% and8.9% respectively. The technique is a convenient and fast way of determining the vapors ofbenzene homologues in air. Full article

(This article belongs to the Special Issue Gas Sensors)

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1204 KiB

Open AccessArticle

Characterizing Clutter in the Context of Detecting Weak Gaseous Plumes in Hyperspectral Imagery

by Tom Burr, Bernie Foy, Herb Fry and Brian McVey

Sensors 2006, 6(11), 1587-1615; https://doi.org/10.3390/s6111587 - 23 Nov 2006

Cited by 17 | Viewed by 8666

Abstract

Weak gaseous plume detection in hyperspectral imagery requires thatbackground clutter consisting of a mixture of components such as water, grass, and asphaltbe well characterized. The appropriate characterization depends on analysis goals.Although we almost never see clutter as a single-component multivariate Gaussian(SCMG), alternatives such [...] Read more.

Weak gaseous plume detection in hyperspectral imagery requires thatbackground clutter consisting of a mixture of components such as water, grass, and asphaltbe well characterized. The appropriate characterization depends on analysis goals.Although we almost never see clutter as a single-component multivariate Gaussian(SCMG), alternatives such as various mixture distributions that have been proposed mightnot be necessary for modeling clutter in the context of plume detection when the chemicaltargets that could be present are known at least approximately. Our goal is to show to whatextent the generalized least squares (GLS) approach applied to real data to look for evidenceof known chemical targets leads to chemical concentration estimates and to chemicalprobability estimates (arising from repeated application of the GLS approach) that aresimilar to corresponding estimates arising from simulated SCMG data. In some cases,approximations to decision thresholds or confidence estimates based on assuming the clutterhas a SCMG distribution will not be sufficiently accurate. Therefore, we also describe astrategy that uses a scene-specific reference distribution to estimate decision thresholds forplume detection and associated confidence measures. Full article

(This article belongs to the Special Issue Gas Sensors)

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451 KiB

Open AccessArticle

Wet Chemical Synthesis and Screening of Thick Porous Oxide Films for Resistive Gas Sensing Applications

by Gerald Frenzer, Andreas Frantzen, Daniel Sanders, Ulrich Simon and Wilhelm F. Maier

Sensors 2006, 6(11), 1568-1586; https://doi.org/10.3390/s6111568 - 15 Nov 2006

Cited by 16 | Viewed by 11010

Abstract

A method of wet chemical synthesis suitable for high throughput and combinatorial applications has been developed for the synthesis of porous resistive thick-film gas sensors. This method is based on the robot-controlled application of unstable metal oxide suspensions on an array of 64 [...] Read more.

A method of wet chemical synthesis suitable for high throughput and combinatorial applications has been developed for the synthesis of porous resistive thick-film gas sensors. This method is based on the robot-controlled application of unstable metal oxide suspensions on an array of 64 inter-digital electrodes positioned on an Al₂O₃ substrate. SnO₂, WO₃, ZrO₂, TiO₂, CeO₂, In₂O₃ and Bi₂O₃ were chosen as base oxides, and were optimised by doping or mixed oxide formation. The parallel synthesis of mixed oxide sensors is illustrated by representative examples. The electrical characteristics and the sensor performance of the films were measured by high-throughput impedance spectroscopy while supplying various test gases (H₂, CO, NO, NO₂, propene). Data collection, data mining techniques applied and the best potential sensor materials discovered are presented. Full article

(This article belongs to the Special Issue Gas Sensors)

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208 KiB

Open AccessArticle

ZnO:Al Thin Film Gas Sensor for Detection of Ethanol Vapor

by Shih Min Chou, Lay Gaik Teoh, Wei Hao Lai, Yen Hsun Su and Min Hsiung Hon

Sensors 2006, 6(10), 1420-1427; https://doi.org/10.3390/s6101420 - 30 Oct 2006

Cited by 134 | Viewed by 18281

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 sensing [...] 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)

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319 KiB

Open AccessArticle

Sub-Nanoliter Spectroscopic Gas Sensor

by Bassam Alfeeli, Gary Pickrell and Anbo Wang

Sensors 2006, 6(10), 1308-1320; https://doi.org/10.3390/s6101308 - 11 Oct 2006

Cited by 17 | Viewed by 9382

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 with [...] 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)

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52 KiB

Open AccessArticle

Biasing Voltage Dependence of Sensitivity of Electron Beam Evaporated SnO2 Thin Film CO Sensor

by Sardar M. Ayub Durrani

Sensors 2006, 6(9), 1153-1160; https://doi.org/10.3390/s6091153 - 26 Sep 2006

Cited by 20 | Viewed by 8713

Abstract

Thin films of tin oxide were deposited by electron beam evaporation. The effectsof the sensor biasing voltage and film thickness on the CO-sensing of tin oxide thin filmswere investigated. The films were characterized using X-ray diffraction and X-rayphotoelectron spectroscopy All the films were [...] Read more.

Thin films of tin oxide were deposited by electron beam evaporation. The effectsof the sensor biasing voltage and film thickness on the CO-sensing of tin oxide thin filmswere investigated. The films were characterized using X-ray diffraction and X-rayphotoelectron spectroscopy All the films were found to be amorphous. The current-voltagecharacteristic of the sensor in air has shown that semiconductor-metal interface formsSchottky barrier. It was found that the CO-sensing properties depend on the sensor biasingvoltage and film thickness. For lower biasing voltages the sensitivity was much higher thanfor the higher voltages. It was found that the sensitivity of the films to CO increased withthe film thickness. Full article

(This article belongs to the Special Issue Gas Sensors)

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290 KiB

Open AccessArticle

Development of an In-Fiber Nanocavity Towards Detection of Volatile Organic Gases

by Cesar Elosua, Ignacio R. Matias, Candido Bariain and Francisco J. Arregui

Sensors 2006, 6(6), 578-592; https://doi.org/10.3390/s6060578 - 16 Jun 2006

Cited by 32 | Viewed by 9523

Abstract

A fiber optic sensor for Volatile Organic Compounds (VOCs) detection has beendeveloped and characterized for some organic gasses. The sensor is based on a novelvapochromic material, which is able to change its optical properties in presence of organicvapors in a reversely way. A [...] Read more.

A fiber optic sensor for Volatile Organic Compounds (VOCs) detection has beendeveloped and characterized for some organic gasses. The sensor is based on a novelvapochromic material, which is able to change its optical properties in presence of organicvapors in a reversely way. A nano Fabry Perot is constructed onto a cleaved ended opticalfiber pigtail by Electrostatic Self Assembly method (ESA), doping this structure with thevapochromic material. Employing a reflection scheme, a change in the intensity modulatedreflected signal at 850 nm have been registered. The response of the sensor has beenevaluated for five different VOCs, and a deeper study has been made for vapors of threedifferent alcohols. Full article

(This article belongs to the Special Issue Gas Sensors)

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436 KiB

Open AccessArticle

Micro Semiconductor CO Sensors Based on Indium-Doped Tin Dioxide Nanocrystalline Powders

by Il Jin Kim, Sang Do Han, Chi Hwan Han, Jihye Gwak, Hi Doek Lee and Jin Suk Wang

Sensors 2006, 6(5), 526-535; https://doi.org/10.3390/s6050526 - 10 May 2006

Cited by 15 | Viewed by 11059

Abstract

The precursors of SnO₂ or In₂O₃/SnO₂ nanocrystlline powders have been prepared bythe sol-precipitation method. The precursors were calcined at different temperatures to prepareSnO₂ or In₂O₃/SnO₂ nanocrystalline powders with different particle sizes. [...] Read more.

The precursors of SnO₂ or In₂O₃/SnO₂ nanocrystlline powders have been prepared bythe sol-precipitation method. The precursors were calcined at different temperatures to prepareSnO₂ or In₂O₃/SnO₂ nanocrystalline powders with different particle sizes. The nanocrystalliteswere examined by differential thermal analysis (DTA), X-ray diffraction (XRD) andtransmission electron microscopy (TEM). And then thick film CO sensors were fabricated usingprepared SnO₂ or In₂O₃/SnO₂ nanocrystlline powders loaded with PdO_x. The composition thatgave the highest sensitivity for CO was in the weight% ratio of 5 wt.% In₂O₃/SnO₂:PdO_x as99:1(wt %). The composite material was found sensitive against CO at the working temperature200 °C. It was found that the sensors based on In₂O₃/SnO₂ nanocrystalline system exhibitedvery short response time to CO at ppm level. These characteristics make the sensor to be apromising candidate for detecting low concentrations of CO. Full article

(This article belongs to the Special Issue Gas Sensors)

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153 KiB

Open AccessArticle

Enhancement of H₂-sensing Properties of F-doped SnO₂ Sensorby Surface Modification with SiO₂

by Chi-Hwan Han, Sang-Do Han and S. P. Khatkar

Sensors 2006, 6(5), 492-502; https://doi.org/10.3390/s6050492 - 9 May 2006

Cited by 34 | Viewed by 11301

Abstract

Effects of surface chemical modification with sodium silicate on the gas-sensingproperties of F-doped SnO₂ gas sensor designed and fabricated employing micro-electromechanical system (MEMS) technology were investigated. Gas sensing properties of thesensor were checked against combustible gases like H₂, CO, CH [...] Read more.

Effects of surface chemical modification with sodium silicate on the gas-sensingproperties of F-doped SnO₂ gas sensor designed and fabricated employing micro-electromechanical system (MEMS) technology were investigated. Gas sensing properties of thesensor were checked against combustible gases like H₂, CO, CH₄ and C₃H₈ at a heatervoltage of 0.7 V. The H₂ sensitivity of the surface modified F-doped SnO₂ micro sensormarkedly increased and reached S = 175 which was found to be about 40 times more thanthat of unmodified sensor (S = ~ 4.2). The increase in the sensitivity is discussed in terms ofincreased resistivity and reduced permeation of gaseous oxygen into the underlying sensinglayer due to the surface modification of the sensor. The present micro-hydrogen sensor withenhanced sensitivity due to SiO₂ incorporation is a low energy consuming portable sensormodule that can be mass-produced using MEMS technology at low cost. Full article

(This article belongs to the Special Issue Gas Sensors)

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119 KiB

Open AccessArticle

CNT Sensors for Detecting Gases with Low Adsorption Energy by Ionization

by Seongjeen Kim

Sensors 2006, 6(5), 503-513; https://doi.org/10.3390/s6050503 - 5 May 2006

Cited by 64 | Viewed by 11631

Abstract

In case of typical chemical gas sensors reacted by gas adsorption on surface of anactive layer, it is difficult to detect some gases which have low chemical adsorption energylike inert gases. In this paper, we report a gas sensor using carbon nanotube(CNT) array [...] Read more.

In case of typical chemical gas sensors reacted by gas adsorption on surface of anactive layer, it is difficult to detect some gases which have low chemical adsorption energylike inert gases. In this paper, we report a gas sensor using carbon nanotube(CNT) array aselectron emitters for the purpose of detecting these gases. Specifically, sensors werefabricated with applications of glass patterning by a sand-blast process and of anodicbonding between glass and silicon to improve the compactness of the structure and thereliability in process. The proposed sensor, based on an electrical discharge theory known asPaschen's law, worked by figuring the changes of dark discharge current and initialbreakdown voltage depending on the concentration and the identity of gases. In this work,air and Ar gases were examined and discussed. Full article

(This article belongs to the Special Issue Gas Sensors)

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Review

Jump to: Research

4803 KiB

Open AccessReview

Studying the Effect of Deposition Conditions on the Performance and Reliability of MEMS Gas Sensors

by Khaled Sadek and Walied Moussa

Sensors 2007, 7(3), 319-340; https://doi.org/10.3390/s7030319 - 14 Mar 2007

Cited by 12 | Viewed by 12366

Abstract

In this paper, the reliability of a micro-electro-mechanical system (MEMS)-based gas sensor has been investigated using Three Dimensional (3D) coupled multiphysics Finite Element (FE) analysis. The coupled field analysis involved a two-way sequential electro- thermal fields coupling and a one-way sequential thermal-structural fields [...] Read more.

In this paper, the reliability of a micro-electro-mechanical system (MEMS)-based gas sensor has been investigated using Three Dimensional (3D) coupled multiphysics Finite Element (FE) analysis. The coupled field analysis involved a two-way sequential electro- thermal fields coupling and a one-way sequential thermal-structural fields coupling. An automated substructuring code was developed to reduce the computational cost involved in simulating this complicated coupled multiphysics FE analysis by up to 76 percent. The substructured multiphysics model was then used to conduct a parametric study of the MEMS-based gas sensor performance in response to the variations expected in the thermal and mechanical characteristics of thin films layers composing the sensing MEMS device generated at various stages of the microfabrication process. Whenever possible, the appropriate deposition variables were correlated in the current work to the design parameters, with good accuracy, for optimum operation conditions of the gas sensor. This is used to establish a set of design rules, using linear and nonlinear empirical relations, which can be utilized in real-time at the design and development decision-making stages of similar gas sensors to enable the microfabrication of these sensors with reliable operation. Full article

(This article belongs to the Special Issue Gas Sensors)

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514 KiB

Open AccessReview

Gas Sensors Based on Conducting Polymers

by Hua Bai and Gaoquan Shi

Sensors 2007, 7(3), 267-307; https://doi.org/10.3390/s7030267 - 7 Mar 2007

Cited by 1342 | Viewed by 47882

Abstract

The gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of [...] Read more.

The gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of the gas sensors are also addressed. The disadvantages of the sensors and a brief prospect in this research field are discussed at the end of the review. Full article

(This article belongs to the Special Issue Gas Sensors)

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166 KiB

Open AccessReview

Zeolite-based Materials for Gas Sensors

by Xiaowen Xu, Jing Wang and Yingcai Long

Sensors 2006, 6(12), 1751-1764; https://doi.org/10.3390/s6121751 - 13 Dec 2006

Cited by 157 | Viewed by 16081

Abstract

This review of 53 references deals with the uses of zeolites and zeolite-basedmaterials for developing gas sensors. The potential of these materials is highlighted andavenues for further research are suggested. Full article

(This article belongs to the Special Issue Gas Sensors)

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420 KiB

Open AccessReview

Overview of Physical Models and Statistical Approaches for Weak Gaseous Plume Detection using Passive Infrared Hyperspectral Imagery

by Tom Burr and Nicolas Hengartner

Sensors 2006, 6(12), 1721-1750; https://doi.org/10.3390/s6121721 - 6 Dec 2006

Cited by 38 | Viewed by 10364

Abstract

The performance of weak gaseous plume-detection methods in hyperspectral long-wave infrared imagery depends on scene-specific conditions such at the ability to properly estimate atmospheric transmission, the accuracy of estimated chemical signatures, and background clutter. This paper reviews commonly-applied physical models in the context [...] Read more.

The performance of weak gaseous plume-detection methods in hyperspectral long-wave infrared imagery depends on scene-specific conditions such at the ability to properly estimate atmospheric transmission, the accuracy of estimated chemical signatures, and background clutter. This paper reviews commonly-applied physical models in the context of weak plume identification and quantification, identifies inherent error sources as well as those introduced by making simplifying assumptions, and indicates research areas. Full article

(This article belongs to the Special Issue Gas Sensors)

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10884 KiB

Open AccessReview

Airborne Chemical Sensing with Mobile Robots

by Achim J. Lilienthal, Amy Loutfi and Tom Duckett

Sensors 2006, 6(11), 1616-1678; https://doi.org/10.3390/s6111616 - 20 Nov 2006

Cited by 159 | Viewed by 15440

Abstract

Airborne chemical sensing with mobile robots has been an active research areasince the beginning of the 1990s. This article presents a review of research work in this field,including gas distribution mapping, trail guidance, and the different subtasks of gas sourcelocalisation. Due to the [...] Read more.

Airborne chemical sensing with mobile robots has been an active research areasince the beginning of the 1990s. This article presents a review of research work in this field,including gas distribution mapping, trail guidance, and the different subtasks of gas sourcelocalisation. Due to the difficulty of modelling gas distribution in a real world environmentwith currently available simulation techniques, we focus largely on experimental work and donot consider publications that are purely based on simulations. Full article

(This article belongs to the Special Issue Gas Sensors)

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1151 KiB

Open AccessReview

Volatile Organic Compound Optical Fiber Sensors: A Review

by Cesar Elosua, Ignacio R. Matias, Candido Bariain and Francisco J. Arregui

Sensors 2006, 6(11), 1440-1465; https://doi.org/10.3390/s6111440 - 1 Nov 2006

Cited by 171 | Viewed by 19291

Abstract

Volatile organic compound (VOC) detection is a topic of growing interest withapplications in diverse fields, ranging from environmental uses to the food or chemicalindustries. Optical fiber VOC sensors offering new and interesting properties whichovercame some of the inconveniences found on traditional gas sensors [...] Read more.

Volatile organic compound (VOC) detection is a topic of growing interest withapplications in diverse fields, ranging from environmental uses to the food or chemicalindustries. Optical fiber VOC sensors offering new and interesting properties whichovercame some of the inconveniences found on traditional gas sensors appeared over twodecades ago. Thanks to its minimum invasive nature and the advantages that optical fiberoffers such as light weight, passive nature, low attenuation and the possibility ofmultiplexing, among others, these sensors are a real alternative to electronic ones inelectrically noisy environments where electronic sensors cannot operate correctly. In thepresent work, a classification of these devices has been made according to the sensingmechanism and taking also into account the sensing materials or the different methods offabrication. In addition, some solutions already implemented for the detection of VOCsusing optical fiber sensors will be described with detail. Full article

(This article belongs to the Special Issue Gas Sensors)

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49 KiB

Open AccessReview

Application of Electronic Noses for Disease Diagnosis and Food Spoilage Detection

by Ida A. Casalinuovo, Donato Di Pierro, Massimiliano Coletta and Paolo Di Francesco

Sensors 2006, 6(11), 1428-1439; https://doi.org/10.3390/s6111428 - 1 Nov 2006

Cited by 141 | Viewed by 19766

Abstract

Over the last twenty years, newly developed chemical sensor systems (socalled“electronic noses") have odour analyses made possible. This paper describes theapplications of these systems for microbial detection in different fields such as medicineand the food industry, where fast detection methods are essential for [...] Read more.

Over the last twenty years, newly developed chemical sensor systems (socalled“electronic noses") have odour analyses made possible. This paper describes theapplications of these systems for microbial detection in different fields such as medicineand the food industry, where fast detection methods are essential for appropriatemanagement of health care. Several groups have employed different electronic noses forclassification and quantification of bacteria and fungi to obtain accurate medicaldiagnosis and food quality control. So far, detection and identification of bacterial andfungal volatiles have been achieved by use of e-noses offering different correctclassification percentages. The present review includes examples of bacterial and fungalspecies producing volatile compounds and correlated to infectious diseases or fooddeterioration. The results suggest the possibility of using this new technology both inmedical diagnostics and in food control management. Full article

(This article belongs to the Special Issue Gas Sensors)

76 KiB

Open AccessReview

Photoacoustic Spectroscopy with Quantum Cascade Lasers for Trace Gas Detection

by Angela Elia, Cinzia Di Franco, Pietro Mario Lugarà and Gaetano Scamarcio

Sensors 2006, 6(10), 1411-1419; https://doi.org/10.3390/s6101411 - 27 Oct 2006

Cited by 34 | Viewed by 11818

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 a [...] 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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1040 KiB

Open AccessReview

Surface Science Studies of Gas Sensing Materials: SnO₂

by Matthias Batzill

Sensors 2006, 6(10), 1345-1366; https://doi.org/10.3390/s6101345 - 17 Oct 2006

Cited by 200 | Viewed by 17623

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 surface [...] 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)

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995 KiB

Open AccessReview

Wide Bandgap Semiconductor Nanorod and Thin Film Gas Sensors

by Byoung Sam Kang, Hung-Ta Wang, Li- Chia Tien, Fan Ren, Brent P. Gila, David P. Norton, Cammy R. Abernathy, Jenshan Lin and Stepehn J. Pearton

Sensors 2006, 6(6), 643-666; https://doi.org/10.3390/s6060643 - 24 Jun 2006

Cited by 67 | Viewed by 15932

Abstract

In this review we discuss the advances in use of GaN and ZnO-based solid-statesensors for gas sensing applications. AlGaN/GaN high electron mobility transistors(HEMTs) show a strong dependence of source/drain current on the piezoelectricpolarization -induced two dimensional electron gas (2DEG). Furthermore, spontaneous andpiezoelectric polarization [...] Read more.

In this review we discuss the advances in use of GaN and ZnO-based solid-statesensors for gas sensing applications. AlGaN/GaN high electron mobility transistors(HEMTs) show a strong dependence of source/drain current on the piezoelectricpolarization -induced two dimensional electron gas (2DEG). Furthermore, spontaneous andpiezoelectric polarization induced surface and interface charges can be used to develop verysensitive but robust sensors for the detection of gases. Pt-gated GaN Schottky diodes and Sc₂O₃/AlGaN/GaN metal-oxide semiconductor diodes also show large change in forwardcurrents upon exposure to H₂ containing ambients. Of particular interest are methods fordetecting ethylene (C₂H₄), which offers problems because of its strong double bonds andhence the difficulty in dissociating it at modest temperatures. ZnO nanorods offer largesurface area, are bio-safe and offer excellent gas sensing characteristics. Full article

(This article belongs to the Special Issue Gas Sensors)

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