Ethanol-sensing Characteristics Research Articles

Enhanced ethanol-sensing characteristics of Au decorated In-doped SnO2 porous nanotubes at low working temperature

In this work, Au decorated In-doped SnO2 (Au@In2O3-SnO2) porous nanotubes (PNTs) were fabricated via electrospinning and a subsequent calcination treatment. The In-doped SnO2 PNTs with various Au/Sn molar ratios possessed good ethanol sensing properties. As a result, the 3 % mol Au decorated In-doped SnO2 PNTs had high response to ethanol (Ra/Rg = 316.8–100 ppm) and can detect ethanol down to 50 ppb at a low working temperature of 150 °C. In addition, the gas sensor also had high selectivity, good reversibility and long-term stability. The enhanced sensing performance was mainly ascribed to the increase of oxygen vacancies, catalytic activity of Au nanocatalysts, and porous structures. The sensing results demonstrated that Au@In2O3-SnO2 PNTs had the great potential for ethanol detecting, and provide a facile method for rationally designing other types of gas sensors.

Effects of catalytic combustion behavior and adsorption/desorption properties on ethanol-sensing characteristics of adsorption/combustion-type gas sensors

ABSTRACT Adsorption/combustion-type gas sensors, subspecies of catalytic combustion-type gas sensors, show large dynamic responses to volatile organic compounds (VOCs) under the operation with a mode of pulsed temperature heating, because of the flash catalytic combustion of target VOCs adsorbed on the gas-sensing films. Catalytic combustion behavior of ethanol over γ-Al2O3 powders loaded with and without 1 wt% Pt and/or 10 wt% metal oxide (MO: CeO2 or Bi2O3) and their adsorption/desorption properties of ethanol (adsorption temperature: 150°C) were investigated, and then the ethanol-sensing characteristics of the sensors utilizing the gas-sensing materials (low and high temperatures under dynamic operation: 150°C and 450°C, respectively) have been discussed on the basis of the findings on both their catalytic combustion behavior and adsorption/desorption properties. Especially, the co-loading of Pt with CeO2 onto γ-Al2O3 was the most effective in enhancing the dynamic response, because the relatively small amounts of various compounds that were adsorbed on the surface at 150°C efficiently oxidized at the initial stage of the pulse-driven heating to form CO2. The effects of low and high temperatures under the pulse-heating operation on the ethanol-sensing properties of the sensor utilizing γ-Al2O3 co-loaded with Pt and CeO2 were also clarified on the basis of the above findings.

Facile synthesis of LaNi1-xTixO3 nanoparticles and enhanced ethanol-sensing characteristics

Nanoparticles of LaNi1-xTixO3 (0 ≤ x ≤ 0.2) with perovskite structure were successfully synthesized by the sol-gel method. The thermal decomposition characteristics, crystal structure, chemical composition and morphology of the nanoparticles were investigated. The prepared LaNiO3 nanoparticles have a particle size distribution of 30–50 nm and a phase formation temperature of about 500 °C. The B-site Ti4+ doping can substitute Ni3+ in the crystal without changing the rhombohedral structure of LaNiO3, but causing lattice expansion. The gas sensors based on the LaNi1-xTixO3 nanoparticles heat-treated at 700 °C exhibit excellent responses to ethanol, showing nearly linear relationships for the ethanol concentration range of 100–500 ppm. The Ti doping at B-site can increase the number of electrons in the redox reaction and suppress grain growth, thus increasing the specific surface area of the material and contributing to the gas response. For an operation temperature of 300 °C, the LaNi0.8Ti0.2O3 nanoparticles display excellent ethanol-sensing performance, including good repeatability and prominent selectivity to ethanol vapor. The results suggest that LaNi1-xTixO3 nanoparticles are potential candidates for ethanol detection.

Multifunctional Screen-Printed TiO2 Nanoparticles Tuned by Laser Irradiation for a Flexible and Scalable UV Detector and Room-Temperature Ethanol Sensor.

Recently, multifunctional devices printed on flexible substrates, with multisensing capability, have found new demand in practical fields of application, such as wearable electronics, soft robotics, interactive interfaces, and electronic skin design, revealing the vital importance of precise control of the fundamental properties of metal oxide nanomaterials. In this paper, a novel low-cost and scalable processing strategy is proposed to fabricate all-printed multisensing devices with UV- and gas-sensing capabilities. This undertaken approach is based on the hierarchical combination of the screen-printing process and laser irradiation post-treatment. The screen-printing is used for the patterning of silver interdigitated electrodes and the active layer based on anatase TiO2 nanoparticles, whereas the laser processing is utilized to fine-tune the UV and ethanol-sensing properties of the active layer. Different characterization techniques demonstrate that the laser fluence can be adjusted to optimize the morphology of the TiO2 film by increasing the contribution from volume porosity, to improve its electrical properties and enhance its UV photoresponse and ethanol-sensing characteristics at room temperature. Furthermore, results of the UV and ethanol-sensing investigation show that the optimized UV and ethanol sensors have good repeatability, relatively fast response/recovery times, and excellent mechanical flexibility.

Monomer: Design of ZnO Nanostructures (Nanobush and Nanowire) and Their Room-Temperature Ethanol Vapor Sensing Signatures.

Ethanol serves as a biomarker as well as a chemical reagent for several applications and has been predominantly used as an alternative fuel (E10 and E85). Development of sensors for the detection and monitoring of ethanol vapor at lower operating temperatures has gathered momentum in the recent past. In this work, we reported the synthesis of self-assembled ZnO nanowires using electrospun technique without using any external surfactants or capping agents and their room temperature ethanol sensing properties. An inherent template namely monomer of the polymer poly(vinyl alcohol) (PVA) with two different molecular weights (14 000 and 140 000 g mol-1) was used along with the precursor zinc acetate dihydrate. The ZnO-PVA nanofibers have been tranformed to ZnO nanospheres and nanowires after calcination. The ratio of zinc precursor concentration to PVA polymer led to the enhanced carrier concentration of the resultant ZnO nanowire that enhanced, in turn, the sensing response toward ethanol vapor. The developed sensing elements have been systematically characterized to correlate their structural, morphological, and electrical properties with the respective room-temperature ethanol-sensing characteristics. The role of grain features and low activation energy of ZnO nanowires in coordination with the low dipole moment of ethanol resulted in the excellent response of 78 toward 100 ppm at room temperature with ultra-sensitive response and recovery times (9 and 12 s, respectively).

Microstructural, Optical and Ethanol Sensing Characteristics of CBD-synthesised AgO Thin Film: Influence of Bath Temperature

Microstructural, Optical and Ethanol Sensing Characteristics of CBD-synthesised AgO Thin Film: Influence of Bath Temperature

Nanostructured perovskite oxides – LaMO3 (M=Al, Co, Fe) prepared by co-precipitation method and their ethanol-sensing characteristics

Nanostructured La-based perovskite oxides − LaMO3 (M=Al, Co, Fe) were synthesized by a new co-precipitation procedure using metal nitrate and carbonate salts as starting materials. X-ray diffraction and energy dispersive X-ray spectroscopic results confirmed the formation of single-phase nanocrystalline perovskite oxides with high purity. Characterizations by scanning/transmission electron microscopy and nitrogen adsorption revealed that LaAlO3 was produced in the form of rectangular porous nanorods exhibiting much larger surface area and porosity compared with densely aggregated LaCoO3 particles and loosely clustered LaFeO3 nanoparticles with cracked-egg morphologies. The materials were characterized for gas sensing towards ethanol at 200–350°C. From gas-sensing results, the LaAlO3 sensor displayed n-type gas-sensing behaviors with considerably higher ethanol response than p-type LaFeO3 and LaCoO3 sensors, respectively. In particular, the LaAlO3 sensor exhibited a high response of 16.45–1000ppm ethanol and excellent ethanol selectivity against NO2, SO2, CO and H2 at 350°C. The superior gas-sensing performances could be attributed to the effective receptor function, transducer function and utility factor of LaAlO3 nanorod structures prepared by the co-precipitation method.

Doping effect of In2O3 on structural and ethanol-sensing characteristics of ZnO nanotubes fabricated by electrospinning

Indium-doped ZnO (IZO) nanotubes with various indium contents (0.01–0.20) were synthesized via a facile electrospinning method. Results of X-ray diffraction and transmission electron microscopy demonstrate that all samples are consisted of hexagonal wurtzite-typed ZnO, showing a well-crystallized indium-zinc-oxide solid solution when only a small amount of zinc ions substituted by indium ions (0.01). Once the amount of indium dopants ≥0.05, there will form some amorphous In2O3, leading to a pronounced decrease in grain sizes. Gas-sensing performances revealed that the IZO nanotube-based sensors have enhanced ethanol-sensing characteristics, especially, sensor based on IZO-0.01 nanotubes shows the highest response (Ra/Rg=81.7), which is twice that of the undoped ZnO nanotubes (40.0) toward 100ppm ethanol at an operating temperature of 275°C. And IZO-0.20 nanotube-based sensor presents a relatively high response at high ethanol concentrations. Our research suggested that these remarkable enhanced ethanol-sensing properties can be closely related to the formation of indium-zinc-oxide solid solutions and/or heterostructures between ZnO and amorphous In2O3.

A highly sensitive ethanol sensor based on Ag@TiO2 nanoparticles at room temperature

In this study, the ethanol-sensing characteristics of Ag@TiO2 nanoparticles were investigated. The morphology, structure, and formation mechanism of the Ag@TiO2 core–shell nanoparticles were carefully studied using X-ray diffraction, transmission electron microscopy, ultraviolet–visible spectroscopy, ZetaSizer Nano ZS and energy-dispersive X-ray spectroscopy. A gas sensing study showed that Ag@TiO2 is a promising sensor for detecting ethanol gas at low concentrations (below 5ppm) at room working temperature. Ag@TiO2 exhibited a sensor response of 1.04–4.35 at the ethanol concentration from 0.15ppm to 5ppm. In addition, the sensor presented an excellent selectivity and stability for ethanol gas. This systematic study of the promising ethanol-sensing characteristics of Ag@TiO2 nanoparticles can facilitate the development of sensors that detect ethanol gas.

Ethanol Sensing Characteristics of Sn-Doped ZnO Tetrapods Sensor

Sn-doped ZnO tetrapods (T-SnZnO) were successfully synthesized using a simple thermal oxidation reaction method. Zn powder with 20 mol% of Sn powder was used as raw material and synthesized at temperature of 1,000°C under normal atmosphere. FE-SEM images revealed that the T-SnZnO exhibited a four symmetry legs with the length of 1.94±0.42 μm and the width of 260±40 nm. EDS analysis confirmed that the tetrapods contain small amount of Sn. XRD analysis indicated that the tetrapods exhibited a wurtzite hexagonal ZnO structure corresponded to Raman results. The lattice parameters a and c were 3.2494 Å and 5.2057 Å, respectively. The T-SnZnO were fabricated as ethanol sensor and tested with ethanol concentration of 50, 200, and 1,000 ppm at operating temperature between 280°C-340°C by observing I-V curve of the sensors. The sensor response increased as the increasing of the operating temperature and the ethanol concentration. Moreover, the enhancement of ethanol sensor response was observed, and the highest sensor response of 30.4 was detected at 340°C. The sensor response was higher than those of ZnO tetrapods, TiO2-ZnO tetrapods, ZnO nanowires, and TiO2-ZnO nanowires sensors.

The properties of ethanol gas sensor based on Ti doped ZnO nanotetrapods

An ethanol gas sensor was fabricated based on Ti doped ZnO nanotetrapods which were prepared by chemical vapor deposition (CVD) of ZnO nanotetrapods followed by co-annealing with TiO 2 powder. X-ray diffraction (XRD), Raman spectra and scanning electron microscopy (SEM) were used to characterize the morphology and structure of the as-obtained sample and the ethanol-sensing characteristics of the device were investigated. ZnO:Ti sensors show higher gas response than ZnO counterparts towards 100 ppm ethanol gas at a temperature of 260 °C. The recovery times of the devices are 3.1 min for ZnO:Ti and 10.1 min for ZnO, respectively. The enhancement of sensing properties of ZnO:Ti tetrapods indicates the potential application for fabricating low power and highly sensitive gas sensors.

Synthesis and enhanced ethanol sensing characteristics ofα-Fe2O3/SnO2 core–shell nanorods

α-Fe2O3/SnO2 core–shell nanorods are synthesized via a three-step process. X-ray diffraction (XRD),scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysesreveal that their diameters and lengths are respectively in the ranges 35–120 nm and0.35–1.2 µm, and the thickness of the shell composed of 3.5 nmSnO2 nanoparticles is about 10 nm. The core–shell nanostructures exhibit adramatic improvement in ethanol sensing characteristics compared to pureα-Fe2O3 nanorods. The sensor response is up to 19.6 under 10 ppm ethanol exposure at220 °C. Both the response time and the recovery time of the core–shell structures are less than 30 s. Basedon the space–charge layer model and semiconductor heterojunction theory, the small thickness of theSnO2 shell and the formation of heterojunctions contribute to the enhanced ethanolsensing characteristics. Our results demonstrate that one-dimensional metal oxidecore–shell nanostructures whose shell thickness is smaller than the Debye length arevery promising materials for fabricating gas sensors with good performances.

Ethanol Sensing Characteristics of ZnO Nanostructures Impregnated by Gold Colloid

ZnO nanostructures were synthesized by thermal oxidation reaction from zinc powder and then impregnated by gold colloid. The gold colloid was prepared by chemical reduction technique and had red color. The heating temperature and sintering time of thermal oxidation were 700 °C and 24 hours, respectively under oxygen atmosphere. The morphology of ZnO nanostructures and ZnO impregnated gold colloid were studied by field emission scanning electron microscope (FE-SEM). The diameter and length of pure ZnO and ZnO impregnated gold colloid were about the same value and were in the range of 100-500 nm and 2.0-7.0 µm, respectively. The ethanol sensing properties of ZnO impregnated by gold colloid were tested in ethanol atmosphere at ethanol concentrations of 1000 ppm and at an operating temperature of 260-360 °C. It was found that the sensitivity and response time were improved for gold impregnated sensor with an optimum operating temperature of 300°C due to the enhanced reaction between the ethanol and the adsorbed oxygen at an optimum temperature.

Low-temperature growth and ethanol-sensing characteristics of quasi-one-dimensional ZnO nanostructures

ZnO nanorods, nanobelts, nanowires, and tetrapod nanowires were synthesized via thermal evaporation of Zn powder at temperatures in the range 550–600 °C under flow of Ar or Ar/O 2 as carrier gas. Uniform ZnO nanowires with diameter 15–25 nm and tetrapod nanowires with diameter 30–50 nm were obtained by strictly controlling the evaporation process. Our experimental results revealed that the concentration of O 2 in the carrier gas was a key factor to control the morphology of ZnO nanostructures. The gas sensors fabricated from quasi-one-dimensional (Q1D) ZnO nanostructures exhibited a good performance. The sensor response to 500 ppm ethanol was up to about 5.3 at the operating temperature 300 °C. Both response and recovery times were less than 20 s. The gas-sensing mechanism of the ZnO nanostructures is also discussed and their potential application is indicated accordingly.

Ethanol-sensing characteristics of CdFe 2O 4 sensor prepared by sol–gel method

CdFe 2O 4 powder with the structure of spinel-type was fabricated by sol–gel method in the citric acid system. The structure and the crystal phase of the powder were characterized on an X-ray diffractometer (XRD). The shape and the size were analyzed by transmission electron microscope (TEM). Several items were investigated, including effects of calcining temperature on gas-sensing properties, gas response vs. working temperature, selectivity and long-term stability. The results demonstrated that the CdFe 2O 4 sensor prepared with the powder calcined at 700 °C has a high response, an excellent selectivity, a quick response behavior, and a good stability to ethanol comparing with the CdFe 2O 4 sensors which dealt with at other temperatures. Its response to 100 ppm ethanol is 55 working at 250 °C.

Influence of Thickness on Ethanol Sensing Characteristics of Doctor-bladed Thick Film from Flame-made ZnO Nanoparticles

ZnO nanoparticles were produced by flame spray pyrolysis (FSP) using zincnaphthenate as a precursor dissolved in toluene/acetonitrile (80/20 vol%). The particleproperties were analyzed by XRD, BET, and HR-TEM. The sensing films were produced bymixing the particles into an organic paste composed of terpineol and ethyl cellulose as avehicle binder and were fabricated by doctor-blade technique with various thicknesses (5,10, 15 μm). The morphology of the sensing films was analyzed by SEM and EDS analyses.The gas sensing characteristics to ethanol (25-250 ppm) were evaluated as a function of filmthickness at 400°C in dry air. The relationship between thickness and ethanol sensingcharacteristics of ZnO thick film on Al2O3 substrate interdigitated with Au electrodes wereinvestigated. The effects of film thickness, as well as the cracking phenomenon, though,many cracks were observed for thicker sensing films. Crack widths increased withincreasing film thickness. The film thickness, cracking and ethanol concentration havesignificant effect on the sensing characteristics. The sensing characteristics with variousthicknesses were compared, showing the tendency of the sensitivity to ethanol decreasedwith increasing film thickness and response time. The relationship between gas sensingproperties and film thickness was discussed on the basis of diffusively and reactivity of thegases inside the oxide films. The thinnest sensing film (5 μm) showed the highest sensitivityand the fastest response time (within seconds).

Electrical properties and ethanol-sensing characteristics of perovskite La 1 − xPb xFeO 3

The nanocrystalline La 1 − x Pb x FeO 3 ( x = 0.0–0.50) powders with orthorhombic perovskite phase were prepared by a sol–gel method. The Pb-doping restrained the growth of the crystallite size. The electrical properties and ethanol-sensing characteristics of the La 1 − x Pb x FeO 3 system were investigated. The results demonstrated that the resistance and conduction type (p- or n-type) of the perovskite oxides changed with the increasing composition x. Among the oxides with compositions of x = 0.30–0.50, La 0.68Pb 0.32FeO 3 ( x = 0.32) showed the best ethanol gas-sensing characteristics.

Microheater-integrated single gas sensor array chip fabricated on flexible polyimide substrate

A microheater-integrated sensor substrate for the single 16-channel sensor array chip was prepared from a polyimide film by modifying the fabrication processes used in the flexible printed circuit technology. Conductive copper layers were patterned to form interdigitated detection electrodes and a resistive heating line at front and backsides, respectively. The microheater was found to have the power consumption of 1.35 mW mm −2 at an operation temperature of 40 °C and was possible to act as a thermometer, simultaneously, possessing the temperature coefficient of resistance of 37 × 10 −4 °C −1. Vapor-sensing materials were deposited on the detection electrodes by casting of carbon black–polymer composite solutions. Their ethanol-sensing characteristics have been investigated carefully as a function of the analyte concentration and the operation temperature. The response magnitude linearly intensified with increasing the ethanol concentration in the wide range of 60–8000 ppm in air and generally decreased as the operation temperature goes from 22 to 60 °C. This temperature dependence could be explained with the variation in analyte solubility induced by the thermodynamic enthalpy change during the sensing process. By using the sensor array chip and the principal component analysis, classification was successfully made among the three different volatile organic compounds of ethanol, toluene and benzene.

Fabrication and ethanol sensing characteristics of ZnO nanowire gas sensors

Based on the achievement of synthesis of ZnO nanowires in mass production, ZnO nanowires gas sensors were fabricated with microelectromechanical system technology and ethanol-sensing characteristics were investigated. The sensor exhibited high sensitivity and fast response to ethanol gas at a work temperature of 300 °C. Our results demonstrate the potential application of ZnO nanowires for fabricating highly sensitive gas sensors.

Ethanol-sensing characteristics of barium stannate prepared by chemical precipitation

Perovskite-type oxide BaSnO 3 has been prepared at reduced temperature. The cubic BaSnO 3 phase forms at 400°C when a precipitation method is applied. Thermal analysis indicates that the decomposition temperature of BaSn(OH) 6 is below 600°C. The trace amounts of BaCO 3 in the precipitate are due to the reaction of barium ions with the atmospheric CO 2 in a strong basic solution. Conductance measurement between 200 and 550°C indirectly demonstrates the gas-sensing mechanism of BaSnO 3 might be a surface-controlled process. The gas-sensing properties of BaSnO 3 to ethanol are first reported. The sensor made of the BaSnO 3 prepared by a precipitation method exhibits low responses to LPG, petrol, H 2 and CO but high response and good selectivity to ethanol. The as-prepared BaSnO 3 is a promising ethanol-sensing material.