Gas-sensing Characteristics Research Articles

The Fabrication of Au@C Core/Shell Nanoparticles by Laser Ablation in Solutions and Their Enhancements to a Gas Sensor.

A convenient and flexible route is presented to fabricate gold noble metal nanoparticles wrapped with a controllable ultrathin carbon layer (Au@C) in one step based on laser ablation of the noble metal targets in toluene-ethanol mixed solutions. The obtained metal nanoparticles were <20 nm in size after ablation, and the thickness of the wrapped ultrathin carbon layer was 2 nm in a typical reaction. The size of the inner noble metal nanoparticles could be controlled by adjusting the power of laser ablation, and the thickness of the ultrathin carbon layer can be controlled from 0.6 to 2 nm by laser ablation in different components of organic solution. Then the resultant Au@C core/shell nanoparticles were modified on the surface of In2O3 films through a sol-gel technique, and the hydrogen sulfide (H2S) gas-sensing characteristics of the products were examined. Compared to pure and Au-modified In2O3, the Au@C-modified In2O3 materials exhibited a revertible and reproducible performance with good sensitivity and very low response times (few seconds) for H2S gas with a concentrations of 1 to 5 ppm at room temperature. Evidence proved that the ultrathin carbon layer played an important role in the improved H2S sensor performance. Other noble metals wrapped by the homogeneous carbon shell, such as Ag@C, could also be prepared with this method.

Humidity-Independent Oxide Semiconductor Chemiresistors Using Terbium-Doped SnO2 Yolk-Shell Spheres for Real-Time Breath Analysis.

The chemiresistive sensing characteristics of metal oxide gas sensors depend closely on ambient humidity. Herein, we report that gas sensors using Tb-doped SnO2 yolk-shell spheres can be used for reliable acetone detection, regardless of the variations in humidity. Pure SnO2 and Tb-doped SnO2 yolk-shell spheres were prepared via ultrasonic spray pyrolysis and their chemiresistive sensing characteristics were studied. The sensor resistance and gas response of the pure SnO2 yolk-shell spheres significantly changed and deteriorated upon exposure to moisture. In stark contrast, the Tb-doped SnO2 yolk-shell spheres exhibited similar gas responses and sensor resistances in both dry and humid [relative humidity (RH) 80%] atmospheres. In addition, the Tb-doped SnO2 yolk-shell sensors showed a high gas response (resistance ratio) of 1.21 to the sub-ppm-levels (50 ppb) of acetone with low responses to the other interference gases. The effects of Tb oxide and the chemical interactions among the Tb oxide, SnO2, and water vapor on this humidity-independent gas sensing behavior of the Tb-doped SnO2 yolk-shell sensors were investigated. This strategy can provide a new road to achieve highly sensitive, selective, and humidity-independent sensing of acetone, which will facilitate miniaturized and real-time exhaled breath analysis for diagnosing diabetes.

Effect of the Functionalization of Porous Silicon/WO₃ Nanorods with Pd Nanoparticles and Their Enhanced NO₂-Sensing Performance at Room Temperature.

The decoration of noble metal nanoparticles (NPs) on the surface of metal oxide semiconductors to enhance material characteristics and gas-sensing performance has recently attracted increasing attention from researchers worldwide. Here, we have synthesized porous silicon (PS)/WO3 nanorods (NRs) functionalized with Pd NPs to enhance NO2 gas-sensing performance. PS was first prepared using electrochemical methods and worked as a substrate. WO3 NRs were synthesized by thermally oxidizing W film on the PS substrate. Pd NPs were decorated on the surface of WO3 NRs via in-situ reduction of the Pd complex solution by using Pluronic P123 as the reducing agent. The gas-sensing characteristics were tested at different gas concentrations and different temperatures ranging from room temperature to 200 °C. Results revealed that, compared with bare PS/WO3 NRs and Si/WO3 NRs functionalized with Pd NPs, the Pd-decorated PS/WO3 NRs exhibited higher and quicker responses to NO2, with a detection concentration as low as 0.25 ppm and a maximum response at room temperature. The gas-sensing mechanism was also investigated and is discussed in detail. The high surface area to volume ratio of PS and the reaction-absorption mechanism can be explained the enhanced sensing performance.

Investigation of Sm1−xCaxFe0.7Co0.3O3 films (x = 0.0–0.3) prepared by modified sol–gel spin-coating method for carbon monoxide and propane gas sensing

Sm1−xCaxFe0.7Co0.3O3 thin film gas sensors with different calcium concentrations (x = 0.0–0.3) were prepared using a modified sol–gel spin-coating method and then annealed at 650 °C for 2 h in air. The thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and electrical resistance measurements at concentrations from 1 to 200 ppm for carbon monoxide (CO) and from 1 to 500 ppm for propane (C3H8) in the temperature range of 25–300 °C for both gases. The resulting XRD data reveal that a pure phase with perovskite structure was obtained for each substitution in x and corresponds to the orthorhombic system with a Pbnm space group. Topography and roughness of the coating were obtained by AFM; roughness results of the sample do not significantly affect the response of the sensor, but the Ca2+ content does. Morphology of the nanoparticles and the thickness of each doping in calcium were observed by SEM, and the thickness was around 300 nm. The gas-sensing characteristics of the Sm–Ca–Fe–Co–O system were investigated in CO and C3H8 gases. It was found that the electrical resistance and gas-sensing characteristics were influenced by the substitution of Sm2+ by Ca2+ ions. When x was greater than or equal to 0.2 and CO concentration was 200 ppm and operating temperature was 300 °C, there was a higher response of the sensor, reaching up to 100%. For operating temperatures below 100 °C, the response of the Sm1−xCaxFe0.7Co0.3O3-based sensors to CO or C3H8 was < 5% regardless of the degree of substitution of Ca. On the other hand, at temperatures above 100 °C, the response depended on the gas to be sensed. In addition, the partial substitution of Ca in the structure increased the response of the sensor in relation to CO and C3H8 concentrations. It is suggested that this is due to the process of electric valence compensation.

Gas Sensing Characteristics of ZnO Thin Films Exposed to Ethanol

There are hundreds of nature and man-made volatile organic compounds (VOC) in atmosphere. Many of them have adverse effects on environments and human health. Ethanol (EtOH) is a frequently encountered VOC in our living environments, and an important interfering gas in breath analyses. Effective monitoring of EtOH is, therefore, beneficial to air pollution control and disease diagnosis. ZnO is an n-type semiconductor, and has been widely studied as a chemoresistive sensor for EtOH detection. In this work, we studied the sensing property of ZnO toward EtOH, and characteristic response features were examined for selectivity improvement. The ZnO sensor was prepared by sputter-depositing a 50 nm-thick ZnO thin film on the Al electrodes, which were thermal evaporated on a thermal oxide substrate and patterned by a stainless steel (SS) hard mask. During the gas sensing test, the ZnO sensor was exposed to a dry air gas mixture of EtOH of various concentrations at different temperatures. The ZnO sensor responses weakly to the EtOH gas mixture below 150oC. However, the sensor has a quick conductance rise upon the exposure to EtOH at 150oC and above, manifesting the nature of n-type oxides according to the oxygen ionosorption model. Figure 1a shows the electrical response of the sensor exposed to 0.15 ppm EtOH at different temperatures. Note that a conductance drops right after the early conductance rise and the characteristic response feature is more apparent at higher temperatures and lower EtOH concentrations. In our previous work, we found that PdO, when exposed to EtOH between 100-250oC, exhibits a similar response feature but in a reverse manner, i.e. a quick conductance drop followed by a rise (see Fig.1b). Since PdO is a p-type oxide, the opposite response behavior suggests that the n-type ZnO sensor has a sensing mechanism likely analogous to the PdO sensor when exposed to EtOH. On the basis of the previous study on the PdO sensor, we ascribe the formation of the characteristic response feature to the combined effects of the reduction of preadsorbed oxygen anions and the ZnO substrate by EtOH and the subsequent adsorption of hydrogen and oxygen adatoms on reduced ZnO nanodomains. Chemical and material characterizations, such as XPS, TDS and DRIFTS have been carried out to examine surface and gaseous species produced in the EtOH sensing reaction In summary, we studied the gas sensing behavior of the sputter-deposited ZnO thin film toward ethanol. A characteristic electrical response feature is observed and its shape greatly depends on the sensing temperature and the EtOH concentration. The response feature is a result of various surface processes, including reduction of oxygen anions and the ZnO substrate, which induces the conductance rise, and adsorption of hydrogen and oxygen adatoms on reduced ZnO nanodomains, which reduces the conductance. The distinct response feature is useful for characteristic feature extraction in pattern recognition algorithms to improve the selectivity of the sensor. Figure 1

Synthesis of TiO2:Ce nanoparticles for development of ammonia gas sensors

A less time consuming and cost ineffective sol–gel method was used to synthesis TiO2 nanoparticles and TiO2:Ce nanoparticles. All the samples were characterized by XRD, UV–Vis, FTIR, PL, SEM, TEM and Raman analysis. The thermal properties were studied by TG/DTA analysis. XRD analysis confirms the formation of anatase TiO2 phase with a preferred orientation along (101) direction and that the lattice constants increased with increasing the Ce doping level. The UV–Vis reflectance spectra showed that cerium doping shift in the reflectance spectra to the visible region and increase the bandgap. The TEM images indicate the particle sizes in the range between 10 and 15 nm for anatase phase TiO2 at 400 °C. Raman spectroscopy was used to identify and quantity the amorphous and crystalline TiO2 phases. All the Ce-doped TiO2 samples showed higher PL intensity than undoped TiO2. The visible emission peaks of pure and Ce-doped TiO2 nanoparticles are mainly associated with oxygen vacancies. The impedance spectrum also exhibited a decreased semicircle radius with the exposure ammonia gas increase from 50 to 250 ppm thereafter slightly increased. Impedance spectroscopy analysis showed that the resistance variation due to grain boundaries significantly contributed to the gas sensor characteristics.

CuBi2O4 Prepared by the Polymerized Complex Method for Gas-Sensing Applications.

Multicomponent oxides can be extensively explored as alternative gas-sensing materials to binary oxides with their structural and compositional versatilities. In this work, the gas-sensing properties of CuBi2O4 have been investigated toward various reducing gases (C2H5OH, NH3, H2, CO, and H2S) and oxidizing gas (NO2) for the first time. For this, the powder synthesis has been developed using the polymerized complex method (Pechini method) to obtain a single-phase polycrystalline CuBi2O4. The defect, optical, and electronic properties in the prepared CuBi2O4 powder were modulated by varying the calcination temperature from 500 to 700 °C. Noticeably, a high concentration of Cu+-oxygen vacancy ([Formula: see text]) defect complexes and isolated Cu2+ ion clusters was found in the 500 °C-calcined CuBi2O4, where they were removed through air calcination at higher temperatures (up to 700 °C) while making the compound more stoichiometric. The change in the intrinsic defect concentration with the calcination temperature led to the variation of the electronic band gap energy and hole concentration in CuBi2O4 with the polaronic hopping conduction (activation energy = 0.43 eV). The CuBi2O4 sensor with 500 °C-calcined powder showed the highest gas responses (specifically, 10.4 toward 1000 ppm C2H5OH at the operating temperature of 400 °C) with the highest defect concentration. As a result, the gas-sensing characteristics of CuBi2O4 are found to be dominantly affected by the intrinsic defect concentration, which is controlled by the calcination temperature. Toward reducing H2S and oxidizing NO2 gases, the multiple reactions arising simultaneously on the surface of the CuBi2O4 sensor govern its response behavior, depending on the gas concentration and the operating temperature. We believe that this work can be a cornerstone for understanding the effect of chemical defect on the gas-sensing characteristics in multicomponent oxides.

A Comparative Study of Chemically and Biologically Synthesized MgO Nanomaterial for Liquefied Petroleum Gas Detection

The exceptional chemical and physical properties of nanostructured materials are extremely suitable for designing new and enhanced sensing devices, particularly gas sensors and biosensors. The present work describes the synthesis of magnesium oxide (MgO) nanoparticles through two methods: a green synthesis using aloe vera plant extract and a chemical method using a glycine-based solution combustion route. In a single step, the extracted organic molecules from aloe vera plants were used to reduce metal ions by the green method. MgO nanoparticles were coated onto the interdigital electrode using the drop-drying method. The dynamic gas-sensing characteristics were measured for liquefied petroleum gas (LPG) at different concentrations and various temperatures. The MgO nanoparticles were characterized by using x-ray diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy to determine the size and structure of the particles. The product’s functional properties were analyzed by Fourier transform-infrared spectroscopy and UV–visible spectroscopy. We found that the LPG sensing behavior of biologically synthesized MgO registers excellent sensitivity at various operating temperatures.

Effect of Gold Nanoparticles Incorporation on Electrical Conductivity and Methane Gas Sensing Characteristics of Lead Sulfide Colloidal Nanocrystals

PbS nanocrystals (NCs) have recently shown the capability of room temperature sensing of some gasses like methane (CH4). Incorporation of silver nanoparticles (NPs) has been previously shown to improve methane sensing characteristics of PbS NCs. Gold (Au) is another noble metal, which is commonly used as additive to modify gas sensing properties of semiconductors. Here, in this paper, it is shown how the incorporation of an appropriate amount of Au NPs improves methane sensing characteristics of PbS NCs. Electrical conductivity, sensor response, and sensor speed are studied as a function of Au concentration (0%, 0.5%, 1%, 1.5%, and 2%). The best modifications were achieved by the addition of 1% Au into PbS NCs matrix.

One-pot electrospinning and gas-sensing properties of LaMnO3 perovskite/SnO2 heterojunction nanofibers

Using nanostructured composite materials is an effective way to obtain high-performance gas sensors. This work used p-type LaMnO3 perovskite-structured semiconductor as a novel promoter for SnO2 nanofibers and studied the gas-sensing characteristics. Nanofibers of 0–2.5-mol% LaMnO3/SnO2 were synthesized via one-pot electrospinning. Compared with pristine SnO2, LaMnO3/SnO2 composite nanofibers exhibited smaller particle size (10–30 nm) and higher BET surface area. XPS revealed that oxygen surface absorption decreased with increasing LaMnO3 content. 0.3-mol% LaMnO3/SnO2 exhibited significantly enhanced ethanol sensitivity relative to pristine SnO2. A response of 20 was obtained at the optimum temperature of 260 °C for 100-ppm ethanol. Higher LaMnO3 loading led to decrease of the ethanol response. The impact of LaMnO3 loading on the sensing behavior of SnO2 nanofibers was discussed in terms of p-n heterojunction formation and changes in the microstructure and catalytic properties.

Surface Properties of Nanostructured, Porous ZnO Thin Films Prepared by Direct Current Reactive Magnetron Sputtering.

In this paper, the results of detailed X-ray photoelectron spectroscopy (XPS) studies combined with atomic force microscopy (AFM) investigation concerning the local surface chemistry and morphology of nanostructured ZnO thin films are presented. They have been deposited by direct current (DC) reactive magnetron sputtering under variable absolute Ar/O2 flows (in sccm): 3:0.3; 8:0.8; 10:1; 15:1.5; 20:2, and 30:3, respectively. The XPS studies allowed us to obtain the information on: (1) the relative concentrations of main elements related to their surface nonstoichiometry; (2) the existence of undesired C surface contaminations; and (3) the various forms of surface bondings. It was found that only for the nanostructured ZnO thin films, deposited under extremely different conditions, i.e., for Ar/O2 flow ratio equal to 3:0.3 and 30:3 (in sccm), respectively, an evident and the most pronounced difference had been observed. The same was for the case of AFM experiments. What is crucial, our experiments allowed us to find the correlation mainly between the lowest level of C contaminations and the local surface morphology of nanostructured ZnO thin films obtained at the highest Ar/O2 ratio (30:3), for which the densely packaged (agglomerated) nanograins were observed, yielding a smaller surface area for undesired C adsorption. The obtained information can help in understanding the reason of still rather poor gas sensor characteristics of ZnO based nanostructures including the undesired ageing effect, being of a serious barrier for their potential application in the development of novel gas sensor devices.

Room temperature NO2 sensing properties of Au-decorated vanadium oxide nanowires sensor

We investigated the gas-sensing properties of gold nanoparticles decorated VO2 nanowires sensor to NO2 at room temperature. The vanadium dioxide nanowires were synthesized by a chemical vapor deposition method and Au nanoparticles were decorated on VO2 nanowires via an ion sputtering method at different sputtering time (10s, 20s, 30s). Field emission scanning electron microscope and X-ray diffraction were used to characterize the morphology and crystal structure of the compositions. The results show that VO2 nanowires are monoclinic crystal structures and the size and amount of Au nanoparticles are affected by sputtering time. The gas-sensing characteristics were tested via a home-made static gas-sensing system. It is found that the 10s-Au decorated VO2 nanowires sensor exhibits the highest sensitivity to NO2 at 0.5–5ppm and the optimal operating temperature is room temperature (25℃). The enhancement in response was attributed to the “spillover effect” and the change of depletion layer caused by Au nanoparticles. The 10s-Au decorated VO2 nanowires has the best response due to the small size and the high amount of Au nanoparticles accelerate the dissociation and adsorption of oxygen on the surface of VO2 nanowires. This study may provide guidelines for the development of new metal decorated gas sensors.

Gas-sensing performances of Cd-doped ZnO nanoparticles synthesized by a surfactant-mediated method for n-butanol gas

Zinc oxide nanoparticles with the different Cd doping contents were prepared by with a surfactant-mediated method in this paper. The effects of Cd doping on the gas sensing properties of the ZnO nanoparticles were studied. The morphology and microstructure of as-prepared samples were characterized by X-ray diffraction (XRD); scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM), respectively. The results reveal that all the products are the high crystalline hexagonal wurtzite ZnO crystal structure. The gas-sensing characteristics of the Cd doped ZnO nanoparticles for volatile organic compounds (VOCs) were investigated. At its optimal operation temperature of 300 °C, the sensing properties of the Cd doped ZnO nanoparticles for n-butanol gas exhibit a high-performance gas sensing performances including high gas response, good selectivity, response/recovery time, and repeatability as well as stability. Especially, its response reaches 130 for 100 ppm n-butanol of ZnO nanoparticles with 2.5% Cd doping. Those values demonstrate the potential of using as-prepared Cd doped ZnO nanoparticles for n-butanol gas detection, making them to be promising candidates for practical detectors to n-butanol gas. Apart from these, the mechanism related to the advanced properties was also investigated and presented.

TeO2–decorated W18O49 nanorods with highly enhanced gas-sensing performance towards nitrogen dioxide

Surface functionalization is an effective approach for improving the gas-sensing capabilities of one-dimensional (1D) metal oxides. In this work, tellurium dioxide nanoparticles–decorated tungsten oxide nanorods (TeO2 NPs@W18O49 nanorods) were prepared via a facile two-step process, i.e. solvothermal synthesis of W18O49 nanorods followed by hydrolysis deposition of TeO2 NPs, for gas-sensing applications. In the TeO2 decoration process, sodium dodecyl benzene sulfonic acid was introduced as surfactant to assure formation and attachment of highly discrete, tiny TeO2 NPs on whole surface of nanorods. The microstructures of the decorated nanorods were characterized, and the effect of TeO2 decoration on the gas-sensing characteristics of W18O49 nanorods was investigated. It is found that TeO2 decoration reduces the optimal operating temperature of W18O49 nanorods-based sensor from 200 to 150 °C. The W18O49 nanorods decorated with discrete TeO2 NPs display about four-fold enhancement in gas response to 0.1–1 ppm NO2 at 150 °C compared to pure W18O49 nanorods. The underlying mechanism for the enhanced response of the decorated sensor was demonstrated based on an electronic sensitization-related conductance effect model.

Inhomogeneous Oxygen Vacancy Distribution in Semiconductor Gas Sensors: Formation, Migration and Determination on Gas Sensing Characteristics

The density of oxygen vacancies in semiconductor gas sensors was often assumed to be identical throughout the grain in the numerical discussion of the gas-sensing mechanism of the devices. In contrast, the actual devices had grains with inhomogeneous distribution of oxygen vacancy under non-ideal conditions. This conflict between reality and discussion drove us to study the formation and migration of the oxygen defects in semiconductor grains. A model of the gradient-distributed oxygen vacancy was proposed based on the effects of cooling rate and re-annealing on semiconductive thin films. The model established the diffusion equations of oxygen vacancy according to the defect kinetics of diffusion and exclusion. We described that the steady-state and transient-state oxygen vacancy distributions, which were used to calculate the gas-sensing characteristics of the sensor resistance and response to reducing gases under two different conditions. The gradient-distributed oxygen vacancy model had the applications in simulating the sensor performances, such as the power law, the grain size effect and the effect of depletion layer width.

TiO2 nanoparticles functionalized by Pd nanoparticles for gas-sensing application with enhanced butane response performances

Pd functionalized TiO2 nanoparticles were synthesized by a facile hydrothermal method. The structure, morphology, surface chemical states and surface area were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N2 adsorption-desorption isotherms, respectively. The as-synthesized pure and Pd functionalized TiO2 nanoparticles were used to fabricate indirect-heating gas sensor, and the gas-sensing characteristics towards butane were investigated. At the optimum temperature, the sensors possess good response, selectivity, response/recovery, repeatability as well as long-term stability. Especially for the high response, the response of 7.5 mol% Pd functionalized TiO2 nanoparticles based sensor reaches 33.93 towards 3000 ppm butane, which is about 9 times higher than that of pure TiO2 nanoparticles. The response and recovery time are 13 and 8 s, respectively. Those values demonstrate the potential of using as-synthesized Pd functionalized TiO2 nanoparticles as butane gas detection, particularly in the dynamic monitoring. Apart from these, a possible mechanism related to the enhanced sensing performance is also investigated.

Mesoporous SnO2 Nanotubes via Electrospinning-Etching Route: Highly Sensitive and Selective Detection of H2S Molecule.

We report the facile synthesis of thin-walled SnO2 nanotubes (NTs) with numerous clustered pores (pore radius 6.56 nm) and high surface area (125.63 m2/g) via selective etching of core (SiO2) region in SiO2-SnO2 composite nanofibers (NFs), in which SnO2 phase preferentially occupies the shell while SiO2 is concentrated in the center of the composite NFs. The SiO2-etched SnO2 NTs are composed of ultrasmall crystallites (∼6 nm in size) originating from crystal growth inhibition by small SiO2 domains, which are partially segregated in the polycrystalline SnO2 shell during calcination. These features account for efficacious diffusion and innumerable active sites, which maximize interaction between background gas (air) and analyte gas (H2S). Evaluation of gas-sensing performance of the porous SnO2 NTs before and after decorating the exterior and interior walls with Pt nanoparticles (NPs) reveals exceptional selectivity and superior response (Ra/Rg) of 154.8 and 89.3 to 5 and 1 ppm of H2S, respectively. Excellent gas-sensing characteristics are attributed to the porous topography, nanosized crystallites, high surface area, and the catalytic activity of Pt/PtOx NPs.

Ultra-high sensitive and selective H2 gas sensor manifested by interface of n–n heterostructure of CeO2-SnO2 nanoparticles

Detection of toxic and explosive gases in a selective manner and with higher sensitivity in industries and homes remains very challenging. Therefore, herein, we report on the ultra-high sensitive and selective hydrogen gas sensing using CeO2-SnO2 mixed oxide heterostructure synthesized by a simple hydrothermal method. The BET, photoluminescence, X-ray photoelectron spectroscopy and electron paramagnetic resonance analyses demonstrated that the CeO2-SnO2 heterostructure comprehends a high surface area and a large number of defects related to oxygen vacancies. The formation of heterojunction in CeO2-SnO2 nanostructures was confirmed by the non-linear behaviour I–V curve. The gas-sensing characteristics of the CeO2-SnO2 heterostructure showed shorter response and recovery times of approximately 17 and 24s, respectively, together with high sensitivity (19.23ppm−1) to 40.00ppm H2 gas at 300°C. The improved H2 gas sensing response of 1323 at 60ppm H2 gas is correlated with the higher surface area, pore diameter, surface defects and CeO2-SnO2 heterojunction emerging at the interfaces between the CeO2 and SnO2 serves as additional reaction sites and as well as exposed facets creating the surface to be extremely reactive for the adsorption of oxygen species. The high H2 gas selectivity observed for the CeO2-SnO2 makes them possible candidates for monitoring H2 gas at low concentrations (ppm levels).

A low temperature butane gas sensor used Pt nanoparticles-modified AZO macro/mesoporous nanosheets as sensing material

This paper reported the synthesis and gas-sensing properties of Pt nanoparticles modified Al-doped ZnO (AZO) macro-/mesoporous nanosheets, which were prepared via a solution combustion approach with a subsequent heat treatment at 400°C for 50min. The high performance in detecting butane were achieved for the well-adhered products with unique porous surface appearance on the sensors fabricated using indirect heating method, which demonstrated the superiority of solution combustion synthesis (SCS) in synthesizing complex oxides. The possible explanations of the high butane gas-sensing characteristics of these sensors were based on the results of BET and XPS. The large surface area could provide sufficient interface between the materials and butane gas, and the adsorbed oxygen species having strong oxidation activity could break the butane molecules into CO2 and H2O. The gas-sensing properties of Pt-modified AZO were investigated by testing the gas responses towards butane. The maximum response of the 5% Pt-AZO based gas sensor reached 56.52–3000ppm butane at 200°C. What’s more, the sensor also exhibited good short- and long-term stability, repeatability and selectivity, which made it a potential candidate in the application of monitoring butane. In the end, the possible mechanisms of gas-sensing properties were discussed.

Gas Sensing Characteristics of MoO3 Thin Films Prepared by Glancing Angle Magnetron Sputtering

Gas Sensing Characteristics of MoO₃ Thin Films Prepared by Glancing Angle Magnetron Sputtering