Gas Sensor

In various fruit storage applications precise and continuous ethylene detection is needed. The aim of this work is the development of a miniaturised mid-infrared filter spectrometer for ethylene detection at 10.6 µm wavelength. For this reason optical components and signal processing electronics were developed, tested and integrated in a compact measurement system. The present article describes the optical components, the integration of the optical system, electronics and results of gas measurements. Next to a Silicon-based macroporous IR-emitter, a miniaturised absorption cell and a detector module for the simultaneous measurement at four channels for ethylene, two interfering gases and the reference signal were integrated in the optical system. Optical filters were attached to fourfold thermopile-arrays by flipchip-technology. Silicon-based Fresnel multilenses were processed and attached to the cap of the detector housing. Because of the high reflection losses at the silicon-air surface the Fresnel lenses were coated with Antireflection layers made of Zinc sulphide. For the signal processing electronics a preamplification stage and a Lock-in-board has been developed. First ethylene measurements with the optical system with miniaturised gas cell, Silicon-based IR-emitter, a commercial thermopile detector and the self-developed system electronics showed a detection limit of smaller than 20ppm.

We present an optical gas sensor based on the classical nondispersive infrared technique using ultracompact photonic crystal gas cells. The ultracompact device is conceptually based on low group velocities inside a photonic crystal gas cell and low-reflectivity antireflection layers coupling light into the device. Experimentally, an enhancement of the CO2 infrared absorption by a factor of 2.6 to 3.5 as compared to an empty cell, due to slow light inside a 2D silicon photonic crystal gas cell, was observed; this is in excellent agreement with numerical simulations. We show that, theoretically, for an optimal design enhancement factors of up to 60 are possible in the region of slow light. However, the overall transmission of bulk photonic crystals, and thus the performance of the device, is limited by fluctuations of the pore diameter. Numerical estimates suggest that the positional variations and pore diameter fluctuations have to be well below 0.5% to allow for a reasonable transmi...

Recently, the research on olfactory sense in virtual reality has gradually expanded even though the technology is still premature. We have developed an olfactory display composed of multiple solenoid valves. In the present study, an extended olfactory display, where 32 component odors can be blended in any recipe, is described; the previous version has only 8 odor components. The size was unchanged even though the number of odor components was four times larger than that in the previous display. The complexity of blending was greatly reduced because of algorithm improvement. The blending method and the fundamental experiment using a QCM (quartz crystal microbalance) sensor are described here.

Volatile organic compounds (VOCs) released by plants are closely associated with plant metabolism and can serve as biomarkers for disease diagnosis. Huanglongbing (HLB), also known as citrus greening or yellow shoot disease, is a lethal threat to the multi-billion-dollar citrus industry. Early detection of HLB is vital for removal of susceptible citrus trees and containment of the disease. Gas sensors are applied to monitor the air quality or toxic gases owing to their low-cost fabrication, smooth operation, and possible miniaturization. Here, we report on the development, characterization, and application of electrical biosensor arrays based on single-walled carbon nanotubes (SWNTs) decorated with single-stranded DNA (ssDNA) for the detection of four VOCs—ethylhexanol, linalool, tetradecene, and phenylacetaldehyde—that serve as secondary biomarkers for detection of infected citrus trees during the asymptomatic stage. SWNTs were noncovalently functionalized with ssDNA using π–π inte...

Graphene with a large area was synthesized on Cu foils by chemical vapor deposition under ambient pressure. A 4 × 4 graphene film was transferred onto a 6 Si wafer with a thermally grown oxide film. Raman mapping indicates monolayer graphene dominates the transferred graphene film. Gas sensors were fabricated on a 4 mm × 3 mm size graphene film with a 1 nm palladium film deposited for hydrogen detection. Hydrogen in air with concentrations in 0.0025-1% (25-10,000 ppm) was used to test graphenebased gas sensors. The gas sensors based on palladium-decorated graphene films show high sensitivity, fast response and recovery, and can be used with multiple cycles. The mechanism of hydrogen detection is also discussed.

recommended by the European Agency for Safety and Health at Work (EU-OSHA) is 5 ppmv . The permissible exposure limit value for H 2 S is 10 ppmv, the Immediately Dangerous to Life and Health (IDLH) level is 300 ppmv and lethal concentrations are in the range of 2000 ppmv . In practice, concentrations ranging from sub-ppmv levels at low pressures to several per cents at atmospheric conditions need to be monitored. Despite a variety of online monitoring options for gaseous H 2 S, its reliable quantitative and selective determination still remains challenging in the field of chemical sensors . In the field of laser spectroscopy, the constant improvement of quantum cascade lasers (QCLs) has led to their application as reliable sources of coherent light ranging from the mid-infrared (MIR) to the terahertz spectral region for sensitive detection of molecular species on their fundamental vibrational, respectively, rotational bands . Due to their tailorable emission wavelength, high output power, compactness, narrow spectral linewidth, and wavelength tuneability, QCLs are optimal choices for spectroscopic applications. In addition, optical resonator designs are constantly improved over the years with the distributed feedback (DFB) [10] and the external cavity (EC) approach being the most prominent ones. A general aim with respect to the ongoing development of QCLs for sensing applications is to reduce the line width of the emitted radiation to a minimum while achieving a spectral coverage as large as possible. So far, EC-QCLs offer the largest tuning range which, depending on the employed gain medium, may cover up to several hundreds of wavenumbers. The external cavity design facilitates broadband spectral tuning by an external diffraction grating, while the selection of the emission wavelength takes place by changing the grating angle relative to the QCL chip.

Un ni iv ve er rs si it tá á d di i B Br re es sc ci ia a, , I It ta aly Sensors & Transducers Journal (ISSN 1726-5479) is a peer review international journal published monthly online by International Frequency Sensor Association (IFSA). Available in electronic and CD-ROM. S Se en ns so or rs s & & T Tr ra an ns sd du uc ce er rs s J Jo ou ur rn na al l C C o o n n t t e e n n t t s s Authors are encouraged to submit article in MS Word (doc) and Acrobat (pdf) formats by Abstract: A novel model-based nonlinear control strategy is proposed using an experimental pH neutralization process. The control strategy involves a non linear neural network (NN) model, in the context of internal model control (IMC). When integrated into the internal model control scheme, the resulting controller is shown to have favorable practical implications as well as superior performance. The designed model based online IMC controller was implemented to a laboratory scaled pH process in real time using dSPACE...

A methodology of fabrication of silicon micromachined structures is presented, that allows the integration of low power and robust substrates for gas sensor array systems. The structure is based on the combination of bulk micromachined wafers anodically bonded to structured glass substrates. The thermal isolation achieved allows on-chip integration of high and low temperature areas for gas sensing materials and CMOS electronics, respectively.

The paper discusses the mechanical and thermal behaviour of drop-coated micromachined gas sensors. A laboratory optimised micromachined hotplate has been developed and coated with SnO 2 sensing pastes by means of microdropping technology. Different drop dimensions and geometries have been investigated with regard to their in¯uence on the power consumption, the time response and the mechanical behaviour of the whole sensor. The analysis concerning the micro-drop in¯uence on the sensor operation has been completed by means of coupled thermo-mechanical FEM simulations. The obtained results have been discussed and contrasted with the performances provided by the not coated micro-hotplate. As a conclusion, design rules for the deposition technique of the sensing material are detailed.

In our earlier study, we reported that at 300 • C, a 2.0 wt.% CeO 2 -doped SnO 2 sensor is highly selective to ethanol in the presence of CO and CH 4 gases [F. Pourfayaz, A. Khodadadi, Y. Mortazavi, S.S. Mohajerzadeh, CeO 2 doped SnO 2 sensor selective to ethanol in presence of CO, LPG and CH 4 , Sens. Actuators B 108 (2005) 172-176]. In the present investigation, we report the influence of ambient air humidity on the ethanol selective SnO 2 sensor doped with 2.0 wt.% CeO 2 . Maximum response to ethanol occurs at 300 • C which decreases with the relative humidity. The relative humidity was changed from 0 to 80% for different ambient air temperatures of 30, 40 and 50 • C and the response of the sensor was monitored in a 250-450 • C temperature range. As the relative humidity in 50 • C air increased from 0 to 30%, a 15% reduction in the maximum response to ethanol was observed. A further increase in the relative humidity no longer reduced the response significantly. The presence of humidity improved the sensor response to both CO and CH 4 up to 350 • C after which the extent of improvement became smaller and at 450 • C was almost diminished. The sensor is shown to be quite selective to ethanol in the presence of humid air containing CO and CH 4 . The selectivity passes a maximum at 300 • C; however it declines at higher operating temperatures.

The design and development of a compact wireless gas sensor with a surface modified multiwalled carbon nanotube ( f -CNT) chemiresistor as the sensing element is presented in this paper. f -CNT/polymer composite sensing film is patterned on a printed circuit board and is integrated to the wireless system. The change in resistance of the CNT/polymer composite film due to exposure of different gases is utilized as the principle of this gas sensor. The response for different organic vapors are evaluated and it is observed that the f -CNT/PMMA composite film shows fast response and change in resistance of the order of 10 2 -10 3 due to its surface modification.

Recently, the interest in development of rapid, sensitive and selective smart gas sensors devices has increased for environment protection and healthcare uses. Substantial exploration has been carried out in the field of sensor technology. Nevertheless, there exist certain challenges. This chapter discusses the fundamentals of chemical gas sensors, sensor characteristics, gas sensing performance-enhancing methods, Factors influencing the performance of gas sensor, Ways to improve the sensor performance, Sensing mechanism, Types of adsorption depletion models.

A new on-chip Electrostatic Discharge (ESD) protection scheme is demonstrated for MicroElectroMechanical Systems (MEMS)based Embedded Sensor (ES) System-on-a-Chip (SoC). The ESD protection scheme includes ground-referenced protection cells implemented with novel multifinger thyristor-type devices for 1) the Input/Output (I/O) protection, 2) the power supply clamp, and 3) the protection at the internal sensors' electrodes. The I-V characteristics of the thyristor-type protection cells are adjusted for providing an optimum ESD protection per unit area. Transmission Line Pulsing (TLP) measurements and ESD testing show superb high conductance on-state I-V characteristics with no latch-up problem when thyristor-type devices are subjected to an ESD event, while very low leakage current is obtained at the SoC operating voltage.

Reducing the particle size of ceria nanostrutures could provide an efficient approach to improve gas sensing properties thereof. Here, we synthesized small CeO 2 nanoparticles (3-5 nm) in the support of [EMIM][Tf 2 N] ionic liquid. The obtained CeO 2 nanoparticles showed relatively large surface areas (68.29 m 3 /g) and especially high content of Ce 3+ ions (13.5 %), which increase the chemisorption of reagents and oxygen leading on enhancing gas sensing performance. Namely, at the optimal operating temperature of 400 o C, the gas response of synthesized CeO 2 sensor to 100 ppm of ethanol was 2.3, which was 1.83 times higher than that of commercial one (1.26). The superior gas sensing mechanism of synthesized CeO 2 was also discussed on the basis of the electrical resistance change. The present work could provide novel pathway to synthesize ceria and related materials, which would be possibly expected to be potential candidates for gas sensing, by the use of ionic liquid hereafter.

Semiconductor gas sensors are wildly applied in gas identification and temperature-modulated dynamic test method is frequently used to improve sensors' selectivity and stability. This paper introduces a new strategy combing wavelet decomposition and a distributed support vector machine network to identify gas mixtures. In a previous study concerning identifying gases of a few types, we had demonstrated that wavelet decomposition outperforms FFT in feature extraction from responses of thermally modulated semiconductor gas sensors. Here, we extend this method of recognizing gas mixtures of a large type and generalize the rules of selecting the character variables from decomposed wavelet coefficients as character variables. Besides, a distributed support vector machine network is introduced to discriminate the character variables into gas patterns instead of traditional BP neural network. Experiment results show that the strategy proposed here can perform accurate discrimination between hydrogen (H 2 ), carbon monoxide (CO), ethane (C 2 H 4 ) and their mixtures (total seven patterns) over a range of 50-1000 ppm, by using only one commercial metal oxide semiconductor gas sensor, and the discrimination result has advantages in restraining gas concentration variation, sensor's drift and environmental changes. Experimental result also suggests that a distributed support vector machine outperforms a single support vector machine and a BP neural network in performing gas mixture identification.

This method, which recognizes the species and concentration of gases by its Townsand discharge I–V curve, provides good stability and selectivity. Among the many factors affecting Townsand discharge, the most important one is the shape of the electrode. Four kinds of tip electrode are developed and discussed in this paper: metal, tungsten, carbon nanotube‐covered metal and carbon nanotube‐covered tungsten. The electric field of the tungsten tip is higher than that of the metal tip. If covered with carbon nanotube, the electric fields of both tips are threefold higher. Of the two tips, the carbon nanotube‐covered tungsten tip is the most promising. The large space between the two electrodes, which is 1.65 mm, helps the gas flow and the gas sensor recovery from electron affinity. Copyright © 2004 John Wiley & Sons, Ltd.

A new active layer for CO 2 sensing based on semiconducting CuO-Cu x Fe 3-x O 4 (with 0 ≤ x ≤ 1) nanocomposite was prepared by radiofrequency sputtering from a delafossite CuFeO 2 target using a specific in situ reduction method followed by post annealing treatment in air. The tenorite-spinel ferrite nanocomposite layer was deposited on a simplified test device and the response in a carbon dioxide atmosphere was measured by varying the concentration up to 5000 ppm, at different working temperatures (130-475 • C) and frequencies (0.5-250 kHz). The results showed a high response of 50% (R air /R CO 2 = 1.9) at 250 • C and 700 Hz for a CO 2 concentration of 5000 ppm.

Ga doped ZnO thin films have been deposited by Radio-Frequency (RF) magnetron sputtering on fused silica substrates. The structural analysis of the n-type sensitive material showed a preferential orientation in the [00l] direction. The microstructure of the thin film indicated an increasing grain size with the increase of the thicknesses. The micro sensor platforms have been fabricated with ZnO:Ga thin film deposited using a reliable stencil mask onto interdigitated electrodes containing micro-hotplates. The as fabricated micro sensor allowed to sense sub-ppm concentration (500 ppb) of nitrogen dioxide under cycled temperature mode. This system revealed promising sensing performance with a response R/R0 up to 18 at low temperature step (50 °C).

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

This paper deals with the design of an original microsystem devoted to the real time monitoring of air polluting gases in vehicle compartments. The selective detection is focused on two species, ozone and nitrogen dioxide, because of their specific toxicity. The gas sensing element is made of thin layers of an organic semiconductor provided with a specific chemical filter. A particular methodology of measurement is implemented, witch allows a selective sensing behaviour. On-board tests are presented.

In this article, we present new experimental data regarding the influence of ammonia (NH 3 ) and water (from wet atmospheres) in the conducting properties of lutetium bisphthalocyanine (LuPc 2 )-based films in two very different structural features, namely Langmuir-Blodgett (LB) and vacuum evaporated (VE) films, deposited onto interdigitated electrodes. We pay particular attention to the effect of the mass flow rate ratios of the active gases, which certainly influence the mechanism of conduction of the chemiresistors. The particular trends observed are discussed on the basis of two main contributions: the electronic effects and the competition between gases in the adsorption process.

Experimental data concerning the changes in the current-voltage (I-V) performances of a molecular material-based heterojunction consisting of hexadecafluorinated nickel phthalocyanine (Ni(F 16 Pc)) and nickel phthalocyanine (NiPc), (Au|Ni(F 16 Pc)|NiPc|Al) are introduced as an unprecedented principle of transduction for gas sensing performances. The respective n-and p-type doped-insulator behaviors of the respective materials are supported, owing to the observed changes in surface potential (using the Kelvin probe method) after submission to electron donor (ammonia) and electron acceptor gases (ozone). On the other hand, the bilayer device exhibits strong variations in the built-in potential of the junction and in its rectification ratio. Moreover, large increases occur in forward and reverse currents in presence of ammonia vapors. These make possible a multimodal principle of detection controlled by a combined effect between the heterojunction and the NiPc|Al contact. Indeed, this metal/organic junction plays a critical role regarding the steady asymmetry of the I-V profiles during the device's doping even using high ammonia concentrations. This approach offers a more sophisticated alternative to the classically studied, but at times rather operation-limited, resistive gas sensors.

We demonstrate that the 3.42 eV photoluminescence (PL) band in GaN is of the same intrinsic origin as the near-edge ∼3.47 eV band, but arises from regions of inversed polarity characterized by different strain and growth rate. Two absorption edges are thermally detected at 0.35 K in nanocolumn structures, exhibiting both bands. Micro-PL studies have shown similar temperature/power behavior of these bands, with a competition in intensity in closely spaced spots accompanied by alterations of exciton level ordering. Strain-induced one-dimensional carrier confinement in small inversion domains likely explains the discrete narrow lines observed between the bands.

Porphyrins and related macrocycles have been intensively exploited as sensing materials in chemical sensors, since in these devices they mimic most of their biological functions, such as reversible binding, catalytic activation, and optical changes. Such a magnificent bouquet of properties allows applying porphyrin derivatives to different transducers, ranging from nanogravimetric to optical devices, also enabling the realization of multifunctional chemical sensors, in which multiple transduction mechanisms are applied to the same sensing layer. Potential applications are further expanded through sensor arrays, where cross-selective sensing layers can be applied for the analysis of complex chemical matrices. The possibility of finely tuning the macrocycle properties by synthetic modification of the different components of the porphyrin ring, such as peripheral substituents, molecular skeleton, coordinated metal, allows creating a vast library of porphyrinoid-based sensing layers. From among these, one can select optimal arrays for a particular application. This feature is particularly suitable for sensor array applications, where cross-selective receptors are required. This Review briefly describes chemical sensor principles. The main part of the Review is divided into two sections, describing the porphyrin-based devices devoted to the detection of gaseous or liquid samples, according to the corresponding transduction mechanism. Although most devices are based on porphyrin derivatives, seminal examples of the application of corroles or other porphyrin analogues are evidenced in dedicated sections.

Novel flexible NO 2 gas sensors which, can function at room temperature, were formed by the layerby-layer (LBL) self-assembly of multi-walled nanotubes (MWCNTs) on plastic substrates. First, a negatively charged substrate was prepared by the formation of an organic monolayer (3-mercapto-1-propanesulfonic acid sodium salt; MPS) on a polyester (PET) substrate with a pair of comb-like Au electrodes. Then, two-cycle poly(4-styrenesulfonic acid-co-maleic acid)/poly(allylamine hydrochloride) (PSSMA/PAH) bilayers were deposited on an MPS-modified substrate. Finally, MWCNT multilayers were formed as alternating layers of cationic PAH and negatively charged MWCNTs on the modified substrate. Changes in charge density and the conformation of PSSMA at various pH conditions, caused the bilayer (PSSMA/PAH) that was prepared at pH 4 to be more flexible than that prepared at pH 8. The (MWCNTs/PAH) 10 multilayer thin film sensor was very flexible (there was only a 2% deviation in sensitivity when the sensor was bent at a downward angle of up to 60 • ), and high sensitivity, good linearity (R 2 = 0.9716), a rapid response and an undesirable cross-sensitivity effect. The detachment of adsorbed gas molecules by irradiation under UV was studied at room temperature.

A new hybrid SWCNTs/SnO 2 gas sensor is developed by adding single-walled carbon nanotubes (SWCNTs) into a SnO 2 substrate. The fabrication involved heat-treating the SWCNTs/SnO 2 layer, which was fabricated by spin coating using an organometallic solution of dispersed with SWCNTs. The hybrid sensor is utilized to detect NO 2 concentrations in flowing air or N 2 , by considering alterations in electrical properties. The tests are performed at room temperature. Two hybrid sensors with different concentrations of SWCNTs are examined to elucidate the effect of a concentration of SWCNTs on the sensing properties of the sensors. A SnO 2 sensor without SWCNTs, a blank sample, is also examined for comparison. Comparative gas sensing results reveal that the prepared hybrid SWCNTs/SnO 2 sensors exhibit much higher sensing sensitivity and recovery property in detecting NO 2 gas at room temperature than the blank SnO 2 sensor. This finding shows that doping with SWCNTs improves the sensitivity of hybrid sensors. Microstructural observations revealed that SWCNT bundles are embedded in the SnO 2 matrix. Therefore, a model is presented to relate potential barriers to electronic conduction in the hybrid material. This model suggests that the high sensitivity is associated with the stretching of the depletion layers at the grain boundaries of SnO 2 and the SWCNTs/SnO 2 interfaces when detected gases are adsorbed.

International audienceTungsten oxide WO3 thin films were prepared by dc reactive magnetron sputtering. The GLancing Angle Deposition (GLAD) technique was implemented to transform the typical dense microstructure into an inclined columnar and porous architecture. The incident angle α of the sputtered particles was 0 and 70° leading to a column tilt angle b of 0 and 40°, respectively. Conventional and inclined WO3 films were sputter deposited on a commercial hotplate system. Ozone gas was periodically injected from 0 to 220 ppb and the variation of resistance of the system was measured vs. time at 250°C. The conventional WO3 films exhibited a significant change of conductance as a function of the ozone injection. GLAD WO3 films with a columnar angle b = 40° were even more sensitive to the ozone pulses and the time of response or recovery was significantly enhanced. This ozone detection improvement was mainly attributed to the more porous structure of WO3 films produced by the GLAD method

PALABRAS CLAVES: familia, régimen de visitas, recluso, funciones de la pena, política criminal, nueva cultura penitenciaria, sistema penitenciario y carcelario. Este trabajo expone claramente la problemática penitenciaria que afecta a la sociedad colombiana debido a que no hay una política criminal conforme que garantice el respeto por los derechos humanos dentro de las prisiones y contrarreste los constantes brotes de violencia en la sociedad y en las prisiones.

BaTiO 3 -CuO films are obtained by RF magnetron sputtering on Si and alumina substrates and annealed at different temperatures in order to check their structural characteristics and also to test their electrical behaviour by means of impedance measurements under different CO 2 concentrations (0-2000 ppm). Pt and Ag are tested as electrode materials and the influence of Ag as surface and multilayer additive for sensor response enhancement is also studied.

In this work the sensing mechanism of p-type semiconducting NiO thin films under the exposure to formaldehyde is explained. The influence of the sensing layer thickness and annealing treatment on the structural, optical and electrical properties of the samples is studied. The height of the potential barrier is estimated from temperature-stimulated conductance measurements. The potential barrier height is linked to oxygen ionosorption on the semiconductor surface. Furthermore, Fourier transform-IR analysis was carried out in order to determine the chemical reactions that govern the process of gas detection and the temperature range at which they occur. As a result of the study, it is possible to explain how the thickness and annealing treatment affect the sensing mechanism of the samples.

Cubic structure was confirmed in all porous samples. The PS layer on the silicon wafer was growing and the grain size within this layer was increasing with etching time. Average roughness, root-mean-square roughness, photoluminescence peak intensity, and a minor shift to higher frequency (blue shift) were increased with decreasing average grain size.

The recycling of post-consumer soft-drink bottles poly (ethylene terephthalate) (PET) has been used as an additive in paint containing alkyd resin. Samples of paint containing PET (PPET) were applied in a film form on slides, and its thermal properties were evaluated for thermogravimetry (TG). The thermal behavior of PPET, it was possible to identify that the maximum of PET added to the paint without a change in the film properties was 1%. The kinetic parameters such as activation energy (E a ) and pre-exponential factor (A) were calculated using the isoconversional Flynn -Wall -Ozawa method for samples containing 0.5 to 1.0% of PET. The kinetic analysis indicates that there was a variation in E a values. The kinetic compensation effect (KCE), represented by the equation ln A = 0.105E -0.21 for the first stage of thermal decomposition. ..

This work aims the evaluation of the kinetic triplets corresponding to the two successive steps of thermal decomposition of Ti(IV)-ethylenediaminetetraacetate complex. Applying the isoconversional Wall-Flynn-Ozawa method on the DSC curves, average activation energy: E=172.4±9.7 and 205.3±12.8 kJ mol -1 , and pre-exponential factor: logA=16.38±0.84 and 18.96±1.21 min -1 at 95% confidence interval could be obtained, regarding the partial formation of anhydride and subsequent thermal decomposition of uncoordinated carboxylate groups, respectively. From E and logA values, Dollimore and Málek methods could be applied suggesting PT (Prout-Tompkins) and R3 (contracting volume) as the kinetic model to the partial formation of anhydride and thermal decomposition of the carboxylate groups, respectively.

Gas nano bio-sensors  exhibit  good sensing properties with the ability of nano-sensors to detect at low detection limits (ppm), effectively reacting with components  present in situ. In the structure of sanitary gas nano-sensors,  the surface properties of air molecules are the primary reactants.The development of nano-sensors for sanitary gases has been  a significant topic for their many applications in various food, chemical, sanitary, military and even space research industries  . Leakage of deadly gases is one of the daily dangers of industrial life. Unfortunately, existing alarms in the industry often fail to detect such leaking gases very late. Examples of these types of sensors are made of single-layer nanotubes with a thickness of about one nanometer and can absorb toxic gas molecules. They are also able to detect a small number of molecules of deadly gases in the environment. Such nano-sensors for sanitary gases are used to detect ammonia and nitrogen dioxide gases, which are among the toxic gases.

Hemorrhagic fever outbreaks are difficult to diagnose and control in part because of a lack of low-cost and easily accessible diagnostic structures in countries where etiologic agents are present. Furthermore, initial clinical symptoms are common and shared with other endemic diseases such as malaria or typhoid fever. Current molecular diagnostic methods such as polymerase chain reaction require trained personnel and laboratory infrastructure, hindering diagnostics at the point of need, particularly in outbreak settings. Therefore, rapid diagnostic tests such as lateral flow can be broadly deployed and are typically well-suited to rapidly diagnose hemorrhagic fever viruses, such as Ebola virus. Early detection and control of Ebola outbreaks require simple, easy-to-use assays that can detect very low amount of virus in blood. Here, we developed and characterized an immunoassay test based on immunochromatography coupled to silver amplification technology to detect the secreted glycoprotein of EBOV. The glycoprotein is among the first viral proteins to be detected in blood. This strategy aims at identifying infected patients early following onset of symptoms by detecting low amount of sGP protein in blood samples. The limit of detection achieved by this sGP-targeted kit is 2.2 x 10 4 genome copies/ml in plasma as assayed in a monkey analytical cohort. Clinical performance evaluation showed a specificity of 100% and a sensitivity of 85.7% when evaluated with plasma samples from healthy controls and patients infected with Zaire Ebola virus from Macenta, Guinea. This rapid and accurate diagnostic test could therefore be used in endemic countries for early detection of infected individuals in point of care settings. Moreover, it could also support efficient clinical triage in hospitals or clinical

We have developed a miniature polymer-based chemical gas sensor array on silicon using micromachining technology. The sensors use conductive polymer-carbon black composite films, which swell reversibly and induce a resistance change upon exposure to a wide variety of gases. Using a SU-8 photoresist, we have constructed high aspect ratio wells which can contain the polymer-carbon black-solvent liquid volume present during

Fig. 1. a) The structure of the mesoporous silicate film combined SPV gas sensor cell. b) A scheme of the energy band diagram: f s , V B , E F , E i , E c , and E v are the surface potential, bias voltage, Fermi level, intrinsic Fermi level, conduction band level, and valence band level, respectively.

This paper presents the design and experimental results for a 5 × 5 tin-oxide gas-sensor array system with particular focus on the employed multiplexed-analog-input 0.35 m CMOS interface circuit chip. This interface circuit reads the electrical signal of all the elements of the array in time sharing by means of a solid-state selector, actually exploiting a row-column query technique and provides digital output to a dedicated LabView TM Software. The proposed system shows very promising properties in terms of data redundancy in order to improve the signal-to-noiseratio in electronic nosing and for future studies about the influence of gas consumption rate over the metal oxide surface for a 2D array. Sensors fabrication details, electronic interface performance characterization and chemical measurements results are also reported for completeness.

In this work we present a novel multi-sensor unit to detect and discriminate unknown gases in uncontrolled environments. The unit includes three metal oxide (MOX) sensors with CMOS micro heaters, a plasmonic enhanced nondispersive infra-red (NDIR) sensor, a commercial temperature humidity sensor, and a flow sensor. The proposed sensing unit was evaluated with plumes of gases (propanol, ethanol and acetone) in both, a laboratory setup on a gas testing bench and on-board a mobile robot operating in an indoor workshop. It offers significantly improved performance compared to commercial systems, in terms of power consumption, response time and physical size. We verified the ability to discriminate gases in an unsupervised manner, with data collected on the robot and high accuracy was obtained in the classification of propanol versus acetone (96%), and ethanol versus acetone (90%).

Gas sensors are used in many different application areas. As many gas sensor components are battery heated, one major limit of the operation time is the power dissipated as heat. The aim of this work has been to simulate the heat transfer on a hydrogen gas sensor component. Modelling and simulations have been performed in FEMLAB. The partial differential equation with boundary conditions was solved and the solution was validated against experimental data. Convection increases with the increase of hydrogen concentration. A great effort was made to find a model for the convection. When the simulations were compared to experiments, it turned out that the theoretical convection model was insufficient to describe this small system involving hydrogen, which was an unexpected but interesting result.

This paper describes the formation of nanocrystalline tungsten oxide thin films by two-step thermal annealing of vacuum evaporated tungsten oxide films. The films were annealed at different temperatures to form semiconducting WO 3 films suitable for gas sensor and other electronic device applications. It was found that the film annealed at 300 8C have a uniform nanocrystalline structure compared with high temperature annealed films. When these nanocrystalline films were re-annealed in higher temperature region (>500 8C), no any variation of surface morphology and crystalline structure was observed. These experimental results indicated that stable nanocrystalline WO 3 films could be prepared by two-step annealing.

InO x thin films were grown by dc magnetron sputtering. Structural and morphological investigations carried out by XRD and AFM showed a strong correlation between crystallinity, surface topology and ozone sensitivity. The electrical conductivity exhibited a large change of six orders of magnitude during the processes of photoreduction/oxidation. It was concluded that it is mainly the grain size variation that determines the sensitivity of InO x films against ozone.

The CuO-functionalized SnO 2 nanowire (NW) sensors were fabricated by depositing a slurry containing SnO 2 NWs on a polydimethylsiloxane (PDMS)-guided substrate and subsequently dropping Cu nitrate aqueous solution. The CuO coating increased the gas responses to 20 ppm H 2 S up to ∼74-fold. The R a /R g value of the CuO-doped SnO 2 NWs to 20 ppm H 2 S was as high as 809 at 300 • C, while the cross-gas responses to 5 ppm NO 2 , 100 ppm CO, 200 ppm C 2 H 5 OH, and 100 ppm C 3 H 8 were negligibly low (1.5-4.0). Moreover, the 90% response times to H 2 S were as short as 1-2 s at 300-400 • C. The selective detection of H 2 S and enhancement of the gas response were attributed to the uniform distribution of the sensitizer (CuO) on the surface of the less agglomerated network of the SnO 2 NWs.

A monolithic gas sensor system is presented, which includes on a single chip an array of three metal-oxide covered microhotplates, each of which is individually addressable and can be operated at a defined temperature. The monolithically co-integrated circuitry consists of three independent temperature control loops for the microhotplates and an on-chip temperature sensor. An innovative design of a circular-shape microhotplate has been realized. Temperature homogeneity and thermal efficiency of the membrane were optimized for use with thick films of nanocrystalline metal oxides as sensitive layers. A SnO 2based sensing material with noble metal doping was operated at different temperatures as well as in temperature pulsing mode. Chemical sensor measurements have been conducted with, e.g., CO to show the system performance.