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This article describes a simple though extremely effective sensor for acetone monitoring in the breath. The sensor is capable of monitoring the presence of acetone at parts per million (ppm) concentrations, thus being suitable for a diabetes diagnosis. It has a dimension of $3 {\,\,\mathrm {mm}} \times 6 {\,\,\mathrm {mm}}$ and a cost of less than one dollar. The small dimensions allow one to greatly limit the power required to increase its temperature, and its high selectivity with respect to other gases present in the breath reduces the risk of false-positive responses. The sensor is based on a thin alumina substrate on which platinum strips are deposited on both faces. A thin Nb2O5 layer with a nanometric thickness provides the required sensitivity and selectivity. Sensor prototypes have been characterized by field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) and proved an inherent linear response up to a few ppm of acetone. [ABSTRACT FROM AUTHOR]

Highlights • A new type NiO decorated SnO 2 vertical-standing nanotubes composite thin film was synthesized via a facile hydrothermal method. • Numerous SnO 2 vertical-standing nanotubes with the size of 200–300 nm in diameter and 1.5 μm in length formed a porous microstructure. • NiO nanoplates with the size of 20 nm in diameter decorated on the inside or outside surface of SnO 2 nanotubes formed a heterojunction structure. • The NiO/SnO 2 thin film gas sensor with an Ni2+/Sn4+ molar ratio of 5% exhibited excellent response characteristics to ethanol at 250 ℃. Abstract In this work, a new type NiO decorated SnO 2 vertical-standing nanotubes composite thin film was synthesized successfully via a facile hydrothermal method. The microstructure, physico-chemical surface state and morphology of the composite thin film were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The results showed that the NiO decorated SnO 2 vertical-standing nanotubes composite thin film with a coral-like microstructure was built of numerous 1D SnO 2 nanotubes with the size of 200–300 nm in diameter and 1.5 μm in length; while NiO nanoplates with the size of 20 nm in diameter decorated on the surface of SnO 2 nanotubes. Due to the enhanced adsorption of oxygen molecules, formation of p -NiO/ n -SnO 2 heterojunction and porous structure, the NiO/SnO 2 thin film gas sensor with an Ni2+/Sn4+ molar ratio of 5% exhibited high response value, good selectivity and quick response characteristics to ethanol at the optimum working temperature of 250 ℃. [ABSTRACT FROM AUTHOR]

Present work reports the preparation, properties of polyaniline (PANI) thin film and its application as NO gas sensor opertable at room temperature. PANI was successfully synthesized via chemical oxidative polymerization technique using aniline as a monomer and ammonium persulphate (APS) as oxidant. PANI thin film sensor was fabricated on corning glass substrate using spin coating technique. The film was characterized by XRD, TEM, SEM, FTIR and UV-Visible. The PANI film was found to give maximum sensing response of ~12.10 towards 100 ppm NO gas having with fast response and recovery times as ~11 s and 7 min. [ABSTRACT FROM AUTHOR]

Latent insulation defects introduced in manufacturing process of gas-insulated switchgears can lead to partial discharge during long-time operation, even to insulation fault if partial discharge develops further. Monitoring of decomposed components of SF6, insulating medium of gas-insulated switchgear, is a feasible method of early-warning to avoid the occurrence of sudden fault. Polyaniline thin-film with protonic acid deposited possesses wide application prospects in the gas-sensing field. Polyaniline thin-film sensors with only sulfosalicylic acid deposited and with both hydrochloric acid and sulfosalicylic acid deposited were prepared by chemical oxidative polymerization method. Gas-sensing experiment was carried out to test properties of new sensors when exposed to H2S and SO2, two decomposed products of SF6 under discharge. The gas-sensing properties of these two sensors were compared with that of a hydrochloric acid deposited sensor. Results show that the hydrochloric acid and sulfosalicylic acid deposited polyaniline thin-film sensor shows the most outstanding sensitivity and selectivity to H2S and SO2 when concentration of gases range from 10 to 100 μL/L, with sensitivity changing linearly with concentration of gases. The sensor also possesses excellent long-time and thermal stability. This research lays the foundation for preparing practical gas-sensing devices to detect H2S and SO2 in gas-insulated switchgears at room temperature. [ABSTRACT FROM AUTHOR]

Gas sensing response studies of the Ni 7+ ion irradiated (100 MeV) and non-irradiated SnO 2 thin film sensor prepared under same conditions have been performed towards SO 2 gas (500 ppm). The effect of irradiation on the structural, surface morphological, optical and gas sensing properties of SnO 2 thin film based sensor have been studied. A significant decrease in operating temperature (from 220 °C to 60 °C) and increased sensing response (from 1.3 to 5.0) is observed for the sample after irradiation. The enhanced sensing response obtained for the irradiated SnO 2 thin film based sensor is attributed to the desired modification in the surface morphology and material properties of SnO 2 thin film by Ni 7+ ions. [ABSTRACT FROM AUTHOR]

Large-scale production of reliable carbon nanotubes (CNTs) based gas sensors involves the development of scalable and reliable processes for the fabrication of films with controlled morphology. Here, we report for the first time on highly scalable, ultrathin CNT films, to be employed as conductometric sensors for NO 2 and NH 3 detection at room temperature. The sensing films are produced by dip coating using dissolved CNTs in chlorosulfonic acid as a working solution. This surfactant-free approach does not require any post-treatment for the removal of dispersants or any CNTs functionalization, thus promising high quality CNTs for better sensitivity and low production costs. The effect of CNT film thickness and defect density on the gas sensing properties has been investigated. Detection limits of 1 ppm for NO 2 and 7 ppm for NH 3 have been achieved at room temperature. The experimental results reveal that defect density and film thickness can be controlled to optimize the sensing response. Gas desorption has been accelerated by continuous in-situ UV irradiation. [ABSTRACT FROM AUTHOR]

The antimony-doped tin oxide thin films for gas sensors were prepared via a sol–gel route on alumina substrates. The influence of the antimony addition amount on the electrical resistance of thin films was concluded. The relationship between them was plotted in the coordinates of logarithmic resistance against doping amount. On the basis of the Schottky barrier model, a novel method was used to evaluate the width of depletion layer of semiconductive gas sensors by using the first-order derivative of logarithmic resistance with respect to doping amount. The values of the depletion layer width were calculated for the antimony-doped thin films. The H 2 S gas was used to examine the sensor properties, which positively correlated to the depletion layer width. The oxygen species of O 2− and O − were determined to be the adsorbates on SnO 2 grains with the same proportion at the operating temperature of 300 °C. The location of the Fermi level was found to be a crucial factor that dominated the calculation results. [ABSTRACT FROM AUTHOR]

Present paper reports the fabrication of zinc ferrite thin film sensor having two different types of surface morphologies (mixed shaped nanorods and vertically aligned nanorods) and their growth mechanism. The LPG sensing properties of the vertically aligned assembled nanorods are found improved significantly in comparison to mixed shaped nanorods. When we compare our sensor performance with other thin film sensors, it is found that the sensor performance obtained in this work is definitely better than that of others. Thus our investigation demonstrates the potential application of aligned nanorods in the fabrication of LPG sensor operable at room temperature. [ABSTRACT FROM AUTHOR]

Thin film gas sensors made of the MWCNTs•Fe2O3 (1:25) nanocomposite material with different structure of ohmic contacts were manufactured using the electron-beam spattering method. Investigations of the response of prepared sensors to such gases as methane, butane, hydrogen and ethanol vapors were carried out. It was established that sensors show significant response to hydrogen and ethanol vapors at relatively low temperatures of the working body. It was also established that the structure of ohmic contacts highly effects on sensors characteristics: sensors with different structure of ohmic contacts can be used as highly selective sensors for detection of small concentrations of ethanol vapors and hydrogen gas. [ABSTRACT FROM AUTHOR]

Thermal co-deposition of Sn and TeO2 in vacuum is used for preparing thin Sn-O-Te films, build-up of an oxide matrix and a finely dispersed phase of Te, Sn and/or SnTe. The method allows further doping with desired elements both in the microcrystallites and at their interfaces with the aim to obtain films with improved gas sensing properties. The as-deposited films are amorphous and show very good characteristics as humidity sensors, operating at room temperature. Upon thermal treatment the structure and composition change and depending on the doping elements and the working temperature the observed nanocrystalline films show sensitivity to some reduction gases (ethanol, etc.). No cross-sensitivity of the crystalline films to water vapor is observed. [ABSTRACT FROM AUTHOR]