WO3 Gas Research Articles

Facile synthesis of ultrafine WO3 nanoparticles for highly sensitive acetoin biomarker gas detection

Facile synthesis of metal oxide semiconductors (MOSs) nanoparticles with ultrafine size is quite promising to improve gas sensing performance due to the large effect of the particle size on the electron depletion layer (EDL), however, which is currently difficult to realize. In this work, we synthesized ultrafine WO3 nanoparticles of 20 ∼ 30 nm via room-temperature hydrolysis with following annealing and investigated the gas sensing performance of the WO3 nanoparticles towards acetoin biomarker released by Listeria monocytogenes (LMs). The WO3 gas sensor displays high response (Ra/Rg = 32.0@5 ppm), excellent selectivity and low detection limit at 140 °C. The ultrafine size of WO3 comparable to its Debye length can lead to a larger variation of EDL thus a higher sensor response. Our work has provided a facile, low cost and large-scale synthetic route to constructing high-performance acetoin biomarker gas sensors and might contribute to the development for LMs detection.

Research on the application of WO3 gas sensor based on noble metals modification in cable fire detection

In the monitoring of cable fire, it is of great significance to be able to conduct early fire warning, which requires that sensors have high sensitivity to the cable vapors at low temperatures. In this study, WO3 thick films modified with Au, Pd, and Pt single or bimetallic nanoparticles were fabricated via magnetron sputtering. Gas sensors utilizing these materials exhibited significant response to the low-temperature vapor emitted by YJV22 and YJY23 cables. Among them, Pd/WO3-20 demonstrated a response value of 20 to the vapor of 81[Formula: see text]C YJV22 cables, marking a remarkable 6.3-fold increase compared to pure WO3, and the response time was 13 s. Similarly, Pt/WO3-10 exhibited a response value of 11.11 to the vapor of 104[Formula: see text]C YJY23 cables, representing a 6.9-fold enhancement over pure WO3 with a response time of 12 s. The heating temperature of cables remains below their critical threshold, indicating that it is in the early stages of cable fires, the findings hold significant implications for early warning systems designed to detect cable fires promptly.

Black Phosphorus-Tungsten Oxide Sandwich-like Nanostructures for Highly Selective NO2 Detection.

Modern chemical production processes often emit complex mixtures of gases, including hazardous pollutants such as NO2. Although widely used, gas sensors based on metal oxide semiconductors such as WO3 respond to a wide range of interfering gases other than NO2. Consequently, developing WO3 gas sensors with high NO2 selectivity is challenging. In this study, a simple one-step hydrothermal method was used to prepare WO3 nanorods modified with black phosphorus (BP) flakes as sensitive materials for NO2 sensing, and BP-WO3-based micro-electromechanical system gas sensors were fabricated. The characterization of the as-prepared BP-WO3 composite through X-ray diffraction scanning electron microscopy and X-ray photoelectron spectroscopy confirmed the successful formation of the sandwich-like nanostructures. The result of gas-sensing tests with 2-14 ppm NO2 indicated that the sensor response was 1.25-2.21 with response-recovery times of 36 and 36 s, respectively, at 190 °C. In contrast to pure WO3, which exhibited a response of 1.07-2.2 to 0.3-5 ppm H2S at 160 °C, BP-WO3 showed almost no response to H2S. Thus, compared with pure WO3, BP-WO3 exhibited significantly improved NO2 selectivity. Overall, the BP-WO3 composite with sandwich-like nanostructures is a promising material for developing highly selective NO2 sensors for practical applications.

Preparation of Pt/WO3@ZnO hollow spheres for low-temperature and high-efficiency detection of triethylamine.

In this work, hollow spherical Pt-loaded WO3/ZnO heterostructured composites were prepared by a chemical liquid phase synthesis method. The morphology, crystal structure and components of the composites were characterized by SEM, TEM, XRD, XPS, etc. The sensing performance for various gases was also tested. Compared with the pristine WO3 (S = 44@225 °C, 50 ppm) gas sensor, the gas sensor that is functionalized with 1 wt% Pt and 0.5 mmol ZnO (1Pt/WZ-2) has a high response of 842-50 ppm at a relatively low temperature of 100 °C for TEA, with a quick response/recovery time of 34/120 s, a lower detection limit of 50 ppb, and good selectivity and moisture resistance. This study provides a highly efficient synthesis method of composite materials for TEA gas detection and the sensitivity mechanism is also discussed in detail.

Low-temperature and high-efficient detection of triethylamine based on Pt/PtO2 loaded WO3 gas sensors

Triethylamine (TEA) is a kind of flammable and pungent gas, which widely exists in our daily life. It is very important to monitor TEA gas rapidly and selectively at low temperatures. In this work, hierarchical structured WO3 nanomaterials assembled from two-dimensional rectangular nanoflakes were prepared by a simple solvothermal method. On this basis, TEA gas sensors were fabricated successfully by applying different amounts of noble metal Pt on WO3. The results showed that the sensing behavior of WO3 loaded with 1 at% Pt/PtO2 was remarkably improved (3323.5–50 ppm TEA, 137.5 °C) about 90 times than pure WO3 (37–50 ppm TEA, 225 °C), and the response time was shortened to 16 s (pure WO3 was 40 s). In addition, the selectivity of the sensor to TEA was excellent, as well as good repeatability and long-term stability. The improvement of gas sensing performance can be attributed to the catalytic spillover effect of Pt/PtO2, and the existence of heterojunction between PtO2 and WO3, etc. Moreover, density functional theory calculations were used to explain the excellent selectivity of WO3 for TEA. This work provides a new idea for real-time and accurate detection of TEA at low temperatures.

Rapid detection of ppb level electrolyte leakage of lithium ion battery（LIB）by WO3 hollow microsphere gas sensor

As known, the leakage of lithium battery (LIB) electrolyte is an important cause for runaway failure of LIB, so it has great significance to develop an approach for electrolyte leakage detection with low detection limit and fast response. In this work, we developed a Pd-doped WO3 gas sensor, taking the main component of electrolyte Ethyl Methyl Carbonate (EMC) as the target gas. The sensor has a hollow microsphere structure assembled by nano-particles, and the sensor with Pd doping ratio of 1.5% has the best gas sensing performance. At 275 ℃, the response to 10 ppm EMC is 17.8, and still 45% to EMC as low as 100 ppb. Furthermore, the response time is fast as 19 s to 10 ppm EMC. In addition, the sensor also shows novel stability and gas selectivity, the fluctuations of baseline resistance and response just were 0.77% and 4.6%, respectively. The results show that the sensor can detect extremely low concentration of EMC gas with fast response, and has great application potential in the field of lithium battery safety.

One-step hydrothermal synthesis of urchin-like WO3 with excellent ammonia gas sensing property

In this work, the urchin-like WO3 has been successfully synthesized via one-step hydrothermal method. The crystal structure, chemical composition, morphology, specific surface area and gas sensing property of WO3 are tested by various instruments. The WO3 gas sensor exhibits high gas response, unique selectivity and good repeatability and stability to 30 ppm ammonia, confirming that the urchin-like WO3 would be a candidate material to monitor ammonia.

Ru, Pd doped WO3 nanomaterials: A synergistic effect of noble metals to enhance the acetone response properties

Noble metals (NMs) have an enormous impact on the intrinsic properties of the metal oxides. We report the synergistic effect of Ruthenium (Ru) and Palladium (Pd) noble metals on the enhancement of gas sensing properties of pure tungsten oxide (WO3). The gas sensing material is synthesized by simple and straight forward precipitation route, and its physico-chemical analyses are determined using XRD, FESEM, TEM/HRTEM, FFT, UV–Vis, XPS, EDAX, and BET measurements. Use of the developed material as a gas sensor is evaluated using several target gases (oxidizing as well as reducing), with acetone showing the best selectivity. The noble metal doping and hence catalytic action improved the gas response qualities. The synergistic effect of Ru and Pd on WO3 gas response properties are identified, where the effect is 99.80% sensitivity, and lower response/recovery time (10 s and 2 min) at 300 °C operating temperature. Nonetheless, the sensors displayed better gas sensing properties even at lower operating temperatures ranging from 200 to 275 °C. In addition, the synergistic effect has displayed the dramatic enhancement in the sensitivity to 76.44% at barely 10 ppm acetone concentration. This particular result will undoubtedly be helpful for diagnostic purpose of diabetic patients, and a strong candidate for prospective gas sensing applications, particularly acetone.

A new combined transient extraction method coupled with WO3 gas sensors for polluting gases classification

PurposeThe purpose of this paper is to deal with the classification improvement of pollutant using WO3 gases sensors. To evaluate the discrimination capacity, some experiments were achieved using three gases: ozone, ethanol, acetone and a mixture of ozone and ethanol via four WO3 sensors.Design/methodology/approachTo improve the classification accuracy and enhance selectivity, some combined features that were configured through the principal component analysis were used. First, evaluate the discrimination capacity; some experiments were performed using three gases: ozone, ethanol, acetone and a mixture of ozone and ethanol, via four WO3 sensors. To this end, three features that are derivate, integral and the time corresponding to the peak derivate have been extracted from each transient sensor response according to four WO3 gas sensors used. Then these extracted parameters were used in a combined array.FindingsThe results show that the proposed feature extraction method could extract robust information. The Extreme Learning Machine (ELM) was used to identify the studied gases. In addition, ELM was compared with the Support Vector Machine (SVM). The experimental results prove the superiority of the combined features method in our E-nose application, as this method achieves the highest classification rate of 90% using the ELM and 93.03% using the SVM based on Radial Basis Kernel Function SVM-RBF.Originality/valueCombined features have been configured from transient response to improve the classification accuracy. The achieved results show that the proposed feature extraction method could extract robust information. The ELM and SVM were used to identify the studied gases.

Nanostructured WO3 based gas sensors: a short review

Purpose This paper aims to focus on the basic principle of WO3 gas sensors to achieve high gas-sensing performance with good stability and repeatability. Metal oxide-based gas sensors are widely used for monitoring toxic gas leakages in the environment, industries and households. For better livelihood and a healthy environment, it is extremely helpful to have sensors with higher accuracy and improved sensing features. Design/methodology/approach In the present review, the authors focus on recent synthesis methods of WO3-based gas sensors to enhance sensing features towards toxic gases. Findings This work has proved that the synthesis method led to provide different morphologies of nanostructured WO3-based material in turn to improve gas sensing performance along with its sensing mechanism. Originality/value In this work, the authors reviewed challenges and possibilities associated with the nanostructured WO3-based gas sensors to trace toxic gases such as ammonia, H2S and NO2 for future research.

New Chemoresistive Gas Sensor Arrays for Outdoor Air Quality Monitoring: A Combined R&D and Outreach Activities

New Chemoresistive Gas Sensor Arrays for Outdoor Air Quality Monitoring: A Combined R&D and Outreach Activities

Improved acetone gas sensing performance based on optimization of a transition metal doped WO3 system at room temperature

This paper proposes an effective strategy of material system optimization to improve acetone gas sensing performance based on hydrothermally processed transition metal (Fe, Co or Ni)-doped WO3 materials. A detailed comparison of the capability of pure WO3 and X:WO3 (X = Fe, Co, Ni) to sense acetone gas at room temperature was performed. It was found that the sensitivity of Ni:WO3 nanoflowers to acetone was much higher than that of pure WO3, Fe:WO3 and Co:WO3 under white light irradiation. To obtain a highly sensitive acetone gas sensor, the molar doping ratio of Ni to WO3 was further optimized. It was found that 3%Ni:WO3 had the highest response–recovery speed and the best target gas selectivity. Acetone with a concentration as low as 2 ppm can be detected at room temperature (20 °C). The sensitivity enhancement mechanism of the Ni:WO3 gas sensor is also discussed. It is expected that under white light irradiation the proposed Ni-doped WO3 can be used as a highly sensitive and selective acetone gas sensor at room temperature.

New Chemoresistive Gas Sensor Arrays for Outdoor Air Quality Monitoring: A Combined R&D and Outreach Activities

New Chemoresistive Gas Sensor Arrays for Outdoor Air Quality Monitoring: A Combined R&D and Outreach Activities

2-D to 3-D conversion of WO3 nanostructures using structure directing agent for enhanced NO2 gas sensing performance

An exotic 3-D tungsten oxide (WO3) microflower was synthesized via low-cost and environmental-friendly hydrothermal strategy. The effect of structure-directing agent on the formation of 3-D microflowers from a 2-D nanosheets of WO3 and its gas sensing behavior are investigated. The as-synthesized WO3 powder was used in morphological, structural and phase studies by X-ray diffraction (XRD), scanning electron microscopy (SEM), FT-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The WO3 samples were found to be polycrystalline with monoclinic crystal structure. The SEM micrographs revealed the formation of 3-D microflowers made up of two-dimensional (2-D) multi-directional dendritic nanoplates. The potassium hydroxide (KOH) acts as a structure-directing agent in the formation of 3-D microflowers of WO3 sample. To further understand the formation of 3-D microflowers of WO3 sample, concentration-dependent experiments were carried out by varying KOH concentration and the formation mechanism was investigated. The synthesized WO3 microstructures were subjected to detailed gas sensing tests for different gases at an optimized temperature. A selective, sensitive gas response was obtained for WO3 gas sensor. The lower detection limit is about 1 ppm at 150 °C working temperature for an optimized WO3 gas sensor. The gas sensing results indicate that the 3-D microflower-like WO3 nanostructures are highly promising for applications as gas sensors.

Fabrication of single crystalline WO3 nano-belts based photoelectric gas sensor for detection of high concentration ethanol gas at room temperature

WO3 gas sensing material was synthesized by hydrothermal process, exhibiting a belt-like surface morphology. By comparing and analysing the UV–vis absorption spectra, it is shown that the band gap of WO3 nano-belts (NBs) is 0.56 eV larger than that of WO3 nano-particles (NPs). Surface photo-voltage (SPV) spectra and SPV phase spectra indicate that the direction of the surface built-in electric field is from the surface to the bulk of WO3 NBs and the surface band bending is upwards. WO3 NBs based photoelectric gas sensor was assembled for detecting high concentration of C2H5OH at room temperature. The results demonstrate that the WO3 NBs based photoelectric sensor exhibits higher sensitivity and resolution to high concentration (1000 ppm–20000 ppm) of ethanol at room temperature than WO3 NPs based photoelectric sensor. WO3 NBs are promising candidates of gas sensing material used to fabricate photoelectric gas sensor for high concentration C2H5OH detection operating at room temperature.

Highly Sensitive and Selective CO/NO/H2/NO2 Gas Sensors Using Noble Metal (Pt, Pd) Decorated MOx (M = Sn, W) Combined With SiO2 Membrane

0.5 mol% Pt decorated SnO 2 (Pt-SnO 2 ), 0.5 mol% Pd decorated SnO 2 (Pd-SnO 2 ), 0.5 mol% Pt decorated WO 3 (Pt-WO 3 ), and 0.5 mol% Pd decorated WO 3 (Pd-WO 3 ) gas sensing films were fabricated by screen printing. Subsequently, SiO2 membrane was deposited in situ by CVD. The response of the sensing films to CO, NO, H 2 , and NO 2 were investigated. Pt-SnO 2 , Pd-SnO 2 , and Pt-WO 3 with SiO2 membrane deposited for 20 min (Pt-WO 3 -SiO 2 ) and Pd-WO 3 showed highly sensitive and selective to CO, NO, H 2 , and NO 2 at each optimal operating temperature respectively. Different enhancements of response to target gases might be associated to the combined effects of electronic, chemical sensitizations, and “support effect”. The highly sensitive and selective gas sensors in this paper can be integrated into a gas sensor array to fabricate an electronic nose for H 2 , CO, NO, and NO 2 detection.

One-step growth of wafer-scale monolayer tungsten disulfide via hydrogen sulfide assisted chemical vapor deposition

Wafer-scale monolayer WS2 has been widely investigated. Here, we report a repeatable and low-cost one-step chemical vapor deposition method for the direct growth of a 4-in. monolayer WS2 film on a thermal oxide silicon wafer by using WO3 and H2S gas as precursors. H2S gas exhibits a high vulcanization ability and can effectively reduce the growth temperature of WS2 to 825 °C. The growth process follows a self-limiting growth to form a monolayer polycrystalline film, which is merged via many stable small-angle grain boundaries. The wafer-scale monolayer WS2 film shows uniform and high-quality electrical properties. This method helps promote the future production and application of wafer-scale monolayer sulfide.

Superior triethylamine detection at room temperature by {-112} faceted WO3 gas sensor

Effective detection of triethylamine (TEA) is important for the human health and environment, while challenging. In this study, a novel hierarchical flower-like WO3 nanomaterial was synthesized using a microwave-assisted gas-liquid interface method. The morphology and exposed facets of WO3 nanomaterials can be manipulated through the control of the volume ratio between the water and ethylene glycol (EG) during the synthesis. Our results demonstrate that the samples prepared with water/EG ratio of 8:32 are mainly exposed {-112} facets, which have the best gas sensing response of 180.7 to 100 ppm TEA at room temperature (RT). Its superior gas sensing performance and stability are also evidenced by the short recovery speed of 72 s to 100 ppm TEA at RT. More importantly, our experiments revealed an excellent selectivity in terms to other volatile organic compounds and further confirmed by the first-principles theoretical results. The outcomes of this study suggest that the surface engineering technique is a promising approach to improve the gas sensing performance of metal oxides gas sensor and show great potential for TEA practical detection and monitoring.

The effect of different surface morphologies on WO3 and WO3-Au gas-sensors performance

The high porous surface of tungsten oxide (WO3) gas sensor was deposited by physical vapor deposition (PVD) technique on interdigital FTO-glass substrate deposited by DC sputtering method through the change of substrate position. In order to investigation the effect of Au nanoparticles as dopant on gas sensor performance, these nanoparticles were decorated by PVD method on the surface of high porous WO3 gas sensor. The crystal structure and morphology properties of WO3 gas sensor were evaluated by XRD and FESEM. Furthermore, the NO2 gas sensing properties for three samples including common, high porous and Au decorated high porous surfaces were detected. The Au decorated high porous gas sensor exhibited much higher response, shorter response and recovery time and excellent selectivity to NO2 gas at an operating temperature of 130 °C in compared to other samples.

Gasochromic WO3 Nanostructures for the Detection of Hydrogen Gas: An Overview

Hydrogen is one of the most important gases that can potentially replace fossil fuels in the future. Nevertheless, it is highly explosive, and its leakage should be detected by reliable gas sensors for safe operation during storage and usage. Most hydrogen gas sensors operate at high temperatures, which introduces the risk of hydrogen explosion. Gasochromic WO3 sensors work based on changes in their optical properties and color variation when exposed to hydrogen gas. They can work at low or room temperatures and, therefore, are good candidates for the detection of hydrogen leakage with low risk of explosion. Once their morphology and chemical composition are carefully designed, they can be used for the realization of sensitive, selective, low-cost, and flexible hydrogen sensors. In this review, for the first time, we discuss different aspects of gasochromic WO3 gas sensor-based hydrogen detection. Pristine, heterojunction, and noble metal-decorated WO3 nanostructures are discussed for the detection of hydrogen gas in terms of changes in their optical properties or visible color. This review is expected to provide a good background for research work in the field of gas sensors.