WO3 Materials Research Articles

Study of WO3/Pt hydrogen sensitive film fabricated by Sol-Gel method

Pt-doped WO3 materials have good hydrogen-sensing properties, which are widely used in the field of hydrogen sensing. In this paper, Sol-Gel method is used to prepare WO3/Pt sensing material and sensing characteristic to hydrogen is characterized by transmission optical fiber hydrogen sensing system fabricated at home. By optimizing the fabrication parameters including sol-gel viscosity, aging time, Pt:W moral ratio and layers of the sensing film, the sensitivity and repeatability of the film were greatly improved. The repeatability of the film is further improved by irradiating the film with an UV lamp. Experimental results show that by increasing the number of film layers from one to five (the thickness of the film is about 222 nm, and the content of Pt element is 13.47% by SEM test), the sensitivity increased by 1.666 times. The repeatability of the film can be improved by 3% through the irradiation of the ultraviolet lamp. The optimized WO3/Pt film was tested continuously for 12 times at 5% hydrogen concentration, and the zero drift was only 0.723%.

Probing Local Ion Insertion through Strain-Current Correlation

Among different electrochemical energy storage devices, the ones that store a higher amount of energy (e.g., batteries) often undergo larger ion insertion-induced structural transformation and volume change, which results in lower rate performance. The ones that store a lower amount of energy (e.g., supercapacitors) usually show gradual structural change and smaller volume change. There is a strong correlation between electrochemistry and mechanical properties. Understanding the electro-chemo-mechanical coupling and controlling the ion insertion-induced strain is crucial for achieving high power and high energy storage devices. In-situ atomic force microscopy (AFM) is well suited to tackle this task as it allows tracking local volume changes and other mechanical responses sub-nanometer spatial resolution under the conditions close to the device operationIn this work, we monitored electrode volume change via in-situ AFM and demonstrated the electro-chemo-mechanical coupling behaviors during proton insertion into WO3 materials. The concept of mechanical cyclic voltammetry (mCV) curves was developed, and the relationship between electrochemical current and strain was investigated with simplified models. The results revealed multiple ion-intercalation processes with different mechanical responses are involved during electrode cycling. Local heterogeneity was investigated via mCV mapping, confirming that the charging mechanisms varied across the electrode. These local variations could be further correlated to local morphology, crystal orientations, or chemical compositions. We further demonstrate that the mCV approach is applicable to a variety of energy storage materials (e.g., birnessite and MXene) with the increasing complexity of current-deformation relationships.The work was supported by the Fluid Interface Reactions, Structures, and Transport (FIRST), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Measurements were performed at the Center for Nanophase Materials Sciences (CNMS), which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences.

Two-dimensional oxygen vacancy-doped tungsten oxide hydrate nanosheets for high-performance electrochromic device

Facile fabrication of advanced tungsten oxide (WO3) or WO3 hydrate materials with superior electrochemical and electrochromic properties is of great value in energy-related applications. Self-doping (oxygen vacancy doping) and nanostructure regulation are considered efficient strategies to enhance the performance of bulk WO3 materials. Herein, novel WO3-x hydrate nanosheets were prepared by a one-pot template/surfactant-free solvothermal method employing Na2WO4·2H2O as precursors and ethanol as solvent. The morphology, structure, and composition of the prepared WO3-x hydrate nanosheets were demonstrated by TEM, AFM, XRD, Raman spectrum, and XPS. Furthermore, WO3-x hydrate nanosheets films with mesostructured architecture were formed on FTO glass substrates by the dip-coating process, which exhibited excellent electrochemical and electrochromic performance. As a proof-of-concept example, an analog smart window device (ASWD) was assembled by using the WO3-x hydrate nanosheet film on FTO glass as the working electrode, an FTO glass as the counter electrode, and LiClO4 in propylene carbonate as the electrolyte. The fabricated ASWD presented fascinating electrochromic performance with a wide optical modulation range (82.1%) at the wavelength of 670 nm, moderate switching time (9.6/10.4 s for bleaching/coloration), high coloration efficiency (111.8 cm2/C) and good cyclic stability (maintains 71.6% of the maximum dynamic modulation range after 1000 cycles). Ascribed to the easy preparation process and outstanding electrochromic properties, this kind of WO3-x hydrate nanosheet and its corresponding electrochromic devices are believed to have great potential applications in energy-saving engineering.

Carbon tungsten oxide composite cathode materials for aluminum-ion batteries

Aluminum-ion batteries use more abundant materials and suffer from fewer safety risks than lithium-ion batteries. In this work, new cathode materials for Al-ion batteries were synthesized and tested. WO3, carbon materials, and WO3-carbon composite were prepared by sol-gel and chemical vapor deposition methods. These materials differ in microstructure and other physicochemical properties and the possibility of using them as cathode materials was tested. The correlation between the phase composition, structure, microstructure, electrical properties, and electrochemical performance was described based on X-ray diffraction, scanning electron microscopy, electrochemical impedance spectroscopy, and galvanostatic discharge results. WO3, Norit, and WO3/carbon core-shell composite materials exhibit the smallest average grain size in the range of tens of nanometers while materials based on potato starch carbons contain grains in the range of tens of micrometres. The highest values of the open cell voltage and capacitance of Al-ion cells were found for single-phase WO3 and Norit materials, whereas in the case of single-phase Carbon PS these parameters acquire much lower values.

Deep understanding in physical and electrochemical performance of WO3–TiO2 nanocomposite thin films deposited onto ITO and FTO coated glass substrates using a thermionic vacuum arc deposition system

In this work, WO3–TiO2 nanocomposite thin films were deposited via thermonic vacuum arc technique and the physical and electrochemical features of these nanocomposites were investigated. The average transmittance values were obtained 66.9% and 58.7%, particularly the mean absorbance values were 0.49 and 0.59 onto ITO and FTOcoated glass substrate. The optical band gap of the layers were calculated 2.59 and 2.62 eV upon ITO and FTO coated glass substrates, respectively. Measurement outputs show that both coated thin films are conductive and good storage capabilities for Li+ ions. The reversibility of the films is calculated at 7% and 15% on ITO coated glass and FTO coated glass substrates, respectively. Considering that WO3 and TiO2 materials separately show high quality electrochromic properties, it is aimed to produce these two materials as composites and to examine their electrochromic properties using different producing techniques.

Construction and excellent photoelectric synergistic anticorrosion performance of Z-scheme carbon nitride/tungsten oxide heterojunctions.

The use of heterojunctions for metal corrosion protection is a highly innovative and challenging task. Based on the composition and structure of tungsten oxide-based heterojunctions, Z-scheme heterojunctions were designed and synthesized by the electrostatic self-assembly method using energy band-matched g-C3N4 and WO3 materials. Applied in the field of anticorrosion, they overcame the problems of poor reduction ability and transmission inefficiency of traditional materials. The Z-scheme heterojunctions ensured unidirectional electron transfer, while the aggregation of the retained strongly reduced electrons on the surface of the iron substrates provided a strong driving force for retarding corrosion occurrence. Meanwhile, the inherent shielding properties of the two-dimensional material g-C3N4 and the confinement of chloride ions as an electroactive layer hindered the penetration of the corrosive solution. After being corroded for 72 h, the corrosion impedance of the g-C3N4/WO3 heterojunction system was improved by 640.11% compared with the epoxy resin coating. In addition, the g-C3N4/W18O49 heterojunction was synthesized by using mixed valence tungsten oxide, which overcame the problems of photogenerated electron yield and lifetime, and enhanced the anticorrosion performance compared with a single g-C3N4 phase. This research provided ideas for designing efficient and environmentally friendly heterojunction anticorrosion materials.

H2S sensing material Pt-WO3 nanorods with excellent comprehensive performance

The Pt-loaded WO3 materials have been synthesized via simple hydrothermal and chemical reduction methods. The microstructure of prepared Pt-WO3 exhibits as nanorods consisting of bundles of finer nanorods and the Pt nanoparticles with a size of ca. 5 nm loaded on the surface of WO3. The gas sensing measurements of Pt-WO3 material show excellent gas sensing selectivity to H2S compared with many other pollution gases (e.g. NO2, SO2, NH3, CO and CO2). In particular, 0.2 at% Pt-WO3 exhibits extremely high response (1638–10 ppm H2S), short response/recovery time (42 s/37 s) and low detection limit (1.27–5 ppb H2S) at 200 °C. The superior performance of 0.2 at% Pt-WO3 compared with pure WO3 mainly originate from its modulating action to conductive band electrons of WO3 and its catalysis to the chemisorption reaction on the surface.

Probing Local Ion Insertion via Electro-Chemo-Mechanical Coupling Responses

Electrochemical energy storage devices (e.g., Li-ion batteries and supercapacitors) store energy through electrolytic ion insertion in the electrode. During the ion insertion process, the electrode needs to open up or reorganize its crystallographic structure in order to host the ions, which results in macroscopic and microscopic deformation. The amount of energy barrier required for electrode structural change during the ion insertion process dictates the energy and power density and cycle life of the device. Therefore, understanding the electrode deformation and changes in mechanical responses during electrochemical events and their impact on devices’ performance is crucial for achieving high power and high energy storage devices. In-situ atomic force microscopy (AFM) is well suited to tackle this task as it allows tracking local volume changes and other mechanical responses sub-nanometer spatial resolution under the conditions close to the device operationIn this work, we demonstrate the electro-chemo-mechanical coupling behaviors of proton insertion into WO3 materials via in-situ AFM. The concept of mechanical cyclic voltammetry (mCV) curves was developed, and the relationship between electrochemical current and strain were investigated with simplified models. The results revealed multiple ion-intercalation process with different mechanical responses are involved during electrode cycling. Local heterogeneity was investigated via mCV mapping, confirming that the charging mechanisms varied across the electrode. These local variations could be further corelated to local morphology, crystal orientations or chemical compositions. Besides providing information of redox heterogeneity, the mechanical CV methodology allows us to circumvent the common issues that are often encountered in the global electrochemical characterizations (ex: cell resistance and unwanted parasitic reaction). We further demonstrate that the mCV approach is applicable to a variety of energy storage materials with increasing complexity of current-deformation relationships.The work was supported by the Fluid Interface Reactions, Structures and Transport (FIRST), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Measurements were performed at the Center for Nanophase Materials Sciences (CNMS), which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences.

Physical characterization of Ag:WO3 cermet films used as top electrode for stable and high contrast organic light-emitting diodes

A low reflectance green top-emitting OLED using a cermet Ag:WO3 thin film as a top cathode has been fabricated and fully characterized. The cermet film has been made by co-evaporating Ag and WO3 materials. Depending on the Ag concentration in the WO3 matrix, the optical and electrical properties vary a lot, as this will be investigated by optical simulations as well as by studying single film properties deposited on silicon and glass wafers. A plasmonic absorption of Ag occurs for metal concentrations around 60–70%, which confirms the “nano” nature of the cermet material, with Ag nanocrystals embedded in an amorphous WO3 oxide matrix (also confirmed by TEM). Using an optimal (optical, electrical) Ag:WO3 (70%) cermet composition as a top electrode in the OLED allows to strongly reduce the device mean reflectance in the visible while its contrast ratio becomes far better (maximum + 76% at 1000 lux) than a reference green device (with Ag as top electrode instead of Ag:WO3). The device with the cermet shows very good lifetimes when driven at constant current drive: an extrapolated lifetime of 90 000 h at 100 cd/m2 has been estimated, based on accelerating ageing tests done for 1000 cd/m2 to 20 kcd/m2 initial luminance values.

Synthesis Design of Electronegativity Dependent WO3 and WO3∙0.33H2O Materials for a Better Understanding of TiO2/WO3 Composites’ Photocatalytic Activity

The design of a semiconductor or a composite semiconductor system—with applications in materials science—is complex because its morphology and structure depend on several parameters. These parameters are the precursor type, solvent, pH of the solution, synthesis approach, or shaping agents. This study gives meaningful insight regarding the synthesis design of such WO3 materials. By systematically alternating the precursor (sodium tungstate dihydrate—NWH, or ammonium tungstate hydrate—AMT), subsequently shaping the agents (halide salts—NaX, KX, or hydrohalic acids—HX; X = F−, Cl−, Br−, I−), we have obtained WO3 semiconductors by hydrothermal treatment, which in composite systems can enhance the commercial TiO2 photocatalytic activity. We investigated three sample series: WO3-NWH-NaX/WO3-NWH-KX and, subsequently, WO3-AMT-HX. The presence of W+5 centers was evidenced by Raman and X-ray photoelectron spectroscopy. W+5 and W+6 species affected the band gap values of the NaX and KX series; a higher percentage of W+5 and, subsequently, W+6 caused a redshift, while, regarding the HX series, it led to a blue shift. Increased electronegativity of the halide anions has an unfavorable effect on the composites’ photoactivity. In contrast, in the case of hydrohalic acids, it had a positive impact.

Hierarchically Porous WO3/CdWO4 Fiber-in-Tube Nanostructures Featuring Readily Accessible Active Sites and Enhanced Photocatalytic Effectiveness for Antibiotic Degradation in Water

The intentional design and construction of photocatalysts containing heterojunctions with readily accessible active sites will improve their ability to degrade pollutants. Herein, hierarchically porous WO3/CdWO4 fiber-in-tube nanostructures with three accessible surfaces (surface of core fiber and inner and outer surfaces of the porous tube shell) were fabricated by an electrospinning method. This WO3/CdWO4 heterostructure, assembled by interconnected nanoparticles, displays good photocatalytic degradation of ciprofloxacin (CIP, 93.4%) and tetracycline (TC, 81.6%) after 90 min of simulated sunlight irradiation, much higher than the pristine WO3 (<75.3% for CIP and <53.6% for TC) or CdWO4 materials (<58.9% for CIP and <39.5% for TC). The WO3/CdWO4 fiber-in-tube promotes the separation of photoinduced electrons and holes and also provides readily accessible reaction sites for photocatalytic degradation. The dominant active species determined by trapping active species and electron paramagnetic resonance were hydroxyl radicals followed by photogenerated holes and superoxide anions. The WO3/CdWO4 materials formed a Z-scheme heterojunction that generated superoxide anion and hydroxyl radicals, leading to degradation of antibiotics (CIP and TC) via photocatalysis in aqueous solution.

Electronic properties, optical properties and diffusion behavior of WO3 with H+, Li+ and Na+ intercalated ions: A first-principles study

Tungsten trioxide (WO3) is a representative electrochromic material that can change their optical properties under voltage pulse and has attracted great interest in the applications of energy-efficient windows. Models of M0.125WO3 (M ​= ​H+, Li+ and Na+) were built to simulate the optical properties and diffusion behaviors of the colored state of WO3 materials by first-principles calculations. The results indicate that the Li+ intercalated WO3 shows the highest modulation efficiency of the visible light region, while the Na+ intercalated WO3 possesses the highest modulation efficiency of the infrared light (IR) region among all three systems. Moreover, the study of the diffusion behaviors illustrates that the diffusion energy barriers decrease along with the reduction of intercalated ion sizes. Thus, the diffusion energy barriers of H+, Li+ and Na+ in WO3 can be arranged in the order of Na+ ​> ​Li+ ​> ​H+, which demonstrates that H+, Li+ and Na+ intercalated ion may affect the response time in electrochromic WO3 windows.

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.

Nanostructure conversion and enhanced photoluminescence of vacancy engineered substoichiometric tungsten oxide nanomaterials

Properties of substoichiometric tungsten oxide (WO3-x) semiconducting nanomaterials in diverse applications are morphology-dependent. However, it remains challenging to control morphology and structure of WO3-x nanomaterials. Here, we report the solvothermal synthesis of WO3-x nanostructures with different morphologies in tungsten hexachloride-ethanol solution through adjusting the filling fraction of ethanol in autoclave. The structural and morphological conversion mechanisms are related to the changes in the viscosity and Brownian motion caused by the concentration of tungsten hexachloride in ethanol. The studies on the photoluminescence (PL) properties reveal that the WO3-x nanostructures emit ultraviolet, blue, green and red emissions. The PL emissions are attributed to the recombination between the electron occupying the resonant defect state in the conduction band and the hole in the valence band and the transitions between the conduction and valence bands as well as the transition between the oxygen vacancy states. The enhancement of PL intensity is related to the increase of oxygen vacancies and the phonon suppression during the PL emission as well as the nanocavity structure. Furthermore, the potential applications in the catalysis fields are discussed. These results provide a new technique to control the structure of WO3-x nanomaterials and contribute to the development of next-generation PL emission nanodevices based on vacancy- and structure-engineered WO3 materials and the rational design of catalytic materials.

DFT exploration of sensor performances of two-dimensional WO3 to ten small gases in terms of work function and band gap changes and I-V responses

A combination of density functional theory (DFT) and nonequilibrium Green function (NEGF) based simulation was employed to investigate the prospects of two-dimensional (2D) WO3 materials for gas sensing applications. The target gas molecules considered are O2, N2, NH3, NO, CO, CO2, CH4, C2H6, HCHO, and H2S. Our computed binding energies suggested that the interactions between the gas molecules and 2D WO3 nano-layers cleaved from (001) plane of WO3 bulk crystal are stronger than those with some other 2D materials like graphene and borophene. The electronic properties of adsorption systems such as band gaps, work functions and partial density of states were calculated and compared to the bare substrates. The results demonstrate high sensitivity and selectivity of the 2D WO3 nano-layers towards NH3, NO, HCHO, O2 and H2S. The computation of transport properties such as transmission functions and current-voltage (I-V) characteristics indicated that the presence and absence of gas molecules on the 2D WO3 nano-layers can well realize the electronic device characteristics (ON and OFF) of gas sensors. Theoretical recovery times were also calculated to estimate the reusability of the 2D WO3 nano-layers based gas sensors. Our results suggest that the 2D WO3 nano-layers are promising candidates for sensing applications to NH3, NO, HCHO, O2 and H2S, better than graphene and borophene.

Visible-light sensitization of anodic tungsten oxide layers with CuWO4

Anodic tungsten oxide is an attractive material for photoelectrochemical water splitting under solar irradiation, however due to several limitations, it absorbs only UV light and, therefore, one of the challenges is to transfer its photoresponse to the visible light region. In this paper, for the first time, it is proposed sensitization of anodic WO3 layers with copper tungstate by a wet impregnation method. The CuWO4–WO3 materials are obtained by immersion of anodic layers in a copper acetate solution and annealing at 500 °C in air atmosphere. As-received materials are characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), and Raman spectroscopy, Mott–Schottky measurements and photoelectrochemical (PEC) tests. Proposed visible-light sensitization with CuWO4 results in an enhanced photoelectrochemical response to visible light. Moreover, narrowing of the band gap (from 2.88 to 2.47 eV) with a prolonged impregnation time is also observed.

Structural evolution, optical properties, and photocatalytic performance of copper and tungsten heterostructure materials

Several studies reported that modifying CuO with CuWO4 can increase its photoactivity. In this study, copper and tungsten heterostructure materials were synthesized via a simple sol-gel method using ammonium paratungstate. The temperature’s influence (300, 500, 700, and 900 °C) was analyzed in the structural, morphological, microstructural, and optical properties of Cu and W materials using X-ray diffraction, infrared spectroscopy, field emission-scanning electron microcopy, transmission electron microscopy, diffuse reflectance spectroscopy, and dynamic light-scattering studies. The CuO diffraction patterns exhibited a tenorite phase formation, and the copper-tungsten materials diffractograms demonstrated the formation of CuO/CuWO4 at 300 and 500 °C and CuO/CuWO4/Cu2WO4/WO3 materials at 700 and 900 °C with crystallite sizes from 25 to 56 nm. Intense vibrational modes obtained at 300 °C for the CuWO4 phase decreased at 500 °C. Therefore, 500 °C is not a temperature that promotes CuO/CuWO4 heterostructure formation. Analyses conducted using microscopy techniques demonstrated the morphology of the CuO/CuWO4 heterostructure obtained at 300 °C, where CuWO4 nanoparticles covered the CuO polyhedral; microstructural analysis verified the heterostructure’s formation. The synthesized materials at 300 °C had an optical band gap of 2.66 eV (direct gap) and 1.35 eV and 2.11 eV (indirect gap), which were lower values than those of the CuO and CuWO4. The temperature at 300 °C proved to be optimal for the formation of the CuO/CuWO4 heterostructure. Only the material obtained at 300 °C exhibited a photocatalytic response in the rhodamine B degradation due to a possible interfacial charge transfer between the CuWO4 and CuO. The synthesis process used to obtain the CuO/CuWO4 heterostructure was novel, with a short processing time, low energy consumption and cost, and environmentally friendly properties.

Optical properties of doping electrochromic M0.125W0.875O3 (M=Mo, Nb, Ta, Ti, V): A first-principles study

Tungsten trioxide (WO3) is a representative electrochromic material that can change their optical properties under voltage pulse and has attracted great interest in the applications of energy efficient windows. Models of M0.125W0.875O3 and LixM0.125W0.875O3 (M=Mo, Nb, Ta, Ti, V) were built to simulate the optical properties of the bleached and colored state of WO3 materials by first-principles calculations. The results show that LixM0.125W0.875O3 (M= Nb, Ta, V) leads to an enhancement of the modulation efficiency in visible light and a decrease in the modulation efficiency in infrared (IR) region. Ti doping boosts an efficiency of the IR modulation while no modulation is observed in the visible light region. Mo doping promotes the coloration efficiency in both IR and visible regions. The predicted optical properties of these doped WO3 systems suggest the application in green house or thermal modulation smart window.

Z-scheme In2O3/WO3 heterogeneous photocatalysts with enhanced visible-light-driven photocatalytic activity toward degradation of organic dyes

To effectively decompose the organic dyes in wastewater, a novel all-solid state Z-scheme In2O3/WO3 heterostructured photocatalyst was successfully prepared by loading In2O3 nanoparticles onto WO3 nano-needles through a two-step hydrothermal–solvothermal method. The phase structures, morphologies, chemical compositions, and optical adsorption properties of these photocatalysts were characterized in detail. In the Z-scheme photocatalytic system, the built-in internal electric field can accelerate the recombination of useless photo-generated holes on the VB of In2O3 and electrons on the CB of WO3. The retaining photo-generated charge carriers on the CB of In2O3 and VB of WO3 possess strong redox ability. Therefore, the In2O3/WO3 heterogeneous photocatalysts exhibited remarkably improved photocatalytic activity toward degradation of organic dyes and tetracycline hydrochloride compared to pure WO3 and In2O3 semiconductor materials under visible-light irradiation. The recycling experiments showed that Z-scheme In2O3/WO3 heterogeneous photocatalyst could still degrade 86.6% of methylene blue and 86.4% of rhodamine B even after three cycles, confirming its high photo-stability. The trapping experiments demonstrated that photo-generated holes and ·O2− were the predominant active species for photocatalytic degradation of organic dyes. Based on the experimental results, a possible photocatalytic mechanism of Z-scheme In2O3/WO3 heterostructure was proposed. This investigation provided a novel approach for construction of efficient heterostructured photocatalysts for wastewater purification.

Effect of varying ethanol and water compositions on the acetone sensing properties of WO3 for application in diabetes mellitus monitoring

Tungsten oxide based gas sensors have attracted a lot of attention in breath acetone analysis due to their potential in clinical diagnosis of diabetes. The major problem with this material in sensor application has been remarkable response to all gases but low selectivity to specific gases. Herein, we report the gas sensing performance of WO3 materials which were synthesized by varying water and ethanol ratios using a facile solvothermal method for acetone detection. The gas sensing properties of as-prepared WO3 were tested on acetone C7H8, NO2, NH3, H2S and CH4 under relative humidity. X-ray diffraction patterns show that as-prepared WO3 samples are mainly composed of monoclinic WO3, a phase having relatively high selectivity to acetone. The as-prepared WO3 sensors produced using 51:49 ratio of water: ethanol show an increase in acetone response as the acetone concentration increases and a decrease in acetone response as the relative humidity increases. The sensor responded to a very low acetone concentration ranging from 0.5 to 4.5 ppm which is normally found in human breath. Furthermore, the sensor exhibited high sensitivity and selectivity to low ppm of acetone at 100 °C. On contrary, the sensor showed significantly lower response to other gases tested.