Gas-sensitive Properties Research Articles

Hydrothermal synthesis of NdFeO3 nanoparticles and their high gas-sensitive properties

N-butanol, a volatile organic compound prevalent in numerous industrial processes, poses significant risks to human health and the environment if not properly monitored. Consequently, the development of high-sensitivity n-butanol sensors is imperative. For this reason, NdFeO3 nanoparticles were successfully synthesized by hydrothermal method and used for the detection of n-butanol. They were fully analyzed using characterization techniques such as XRD, BET, EDX, SEM, TEM and XPS. The test results revealed that the prepared samples exhibited a granular structure with an average diameter of approximately 65 nm. The specific surface area measured 15.415 m2/g, and the pore size was determined to be 16.638 nm. The NdFeO3 sensor responds up to 441 for 100 ppm n-butanol at 260 °C, response and recovery times were 33 s and 7 s respectively. The response value of the NdFeO3 sensor is still 4.3 for 1 ppm n-butanol with a minimum detection limit of 0.024 ppm. Simultaneously, the NdFeO3 sensor has excellent selectivity, stability and moisture resistance. These good sensing properties indicate that this work provides a possible strategy for developing an economical and repeatable high performance gas sensor for the detection of n-butanol.

Novel β-CdSnO3-SnO2 nanorod-like heterostructure materials for enhancing n-butanol sensing

n-butanol detection is crucial to environmental protection and mankind’s health because of its toxicity and irritation to the respiratory system. Mono-metal oxide semiconductors (such as SnO2) often face disadvantages such as low sensitivity, insufficient selectivity, and a high detection limit. Constructing heterojunctions has been considered an efficient way to enhance the performance of MOS gas sensors. This work presents the synthesis of a series of β-CdSnO3-SnO2 nanorod-like heterostructures with good n-butanol sensitivity using a hydrothermal and post-calcination approach. The optimized CSO/SO-8 shows the highest response value about 90–100 ppm n-butanol at 190 °C, which is 15 times greater than that of SnO2, and 6.5 times more than that of β-CdSnO3. Meanwhile, the CSO/SO-8 also exhibits a short response and recovery time (1–2 s/63 s). More importantly, the detection limit is reduced to ppb level (50 ppb). The improved gas-sensitive properties can be explained by the formation of n-n heterojunctions between β-CdSnO3 and SnO2, which increases the content of chemisorbed oxygen, thus enhancing the performance of the gas-sensitive. Our work not only provides a material with n-n heterostructures but also the strategy for constructing heterojunctions to improve gas-sensitive properties.

Flower-like SnO2 nanorod aggregates modified with Co3O4 nanoparticles grown on reduced graphene oxide(rGO) sheets for xylene sensing

In this paper, the ternary composite of flower-like SnO2 nanorod aggregates modified with Co3O4 nanoparticles grown on rGO sheets were synthesized by a two-step process of water heating and water bath, and characterized by SEM, TEM, XRD, EDS, and XPS. The gas-sensitive performance test results revealed that the 15-rGO/SnO2/Co3O4 sensor exhibited a higher response value (I0/Ia=24.46) to 100 ppm xylene at the optimal working temperature of 175℃. In addition, the sensor could detect 10 ppb xylene, with a low detection limit. The gas-sensitive properties of 15-rGO/SnO2/Co3O4 were significantly improved due to the large specific surface area of rGO flakes and SnO2 slender nanorods, the catalytic action of p-type semiconductor Co3O4 and the existence of p-n-p double heterojunction. Due to the special nanostructure and synergistic effect of SnO2, rGO and Co3O4, the 15-rGO/SnO2/Co3O4 sensor enabled the efficient and selective detection of xylene.

The synergistic effect of Cd-doped and S-vacancies in CdxZn1-xIn2S4 2D nanosheets for high-performance triethylamine sensing

Ternary metal sulfides with suitable band gaps, high physicochemical stability, and unique two-dimensional (2D) nanostructures are expected to be the next-generation high-performance gas sensors following the MOS type. Doping engineering is utilized as an effective strategy to improve the semiconductor surface activity and enhance its gas-sensitive properties. In this paper, the energy band structure and surface chemical oxygen of ZnIn2S4 (ZIS) materials was tuned by selectively introducing substitutional Cd to replace the Zn sites in ZIS crystals. Meanwhile, the introduction of Cd-ions brings more abundant S vacancy defects, enhances the acid-base interactions at the interface, and pushes the extent of surface redox reactions. In addition, by combining the strong adsorption of ZIS to triethylamine, the CdxZn1-xIn2S4 nanosheets achieved highly improved sensing properties, including better response (63.38–100 ppm), enhanced selectivity (STEA/sother = 12.9), and accelerated response/recovery (4 s/32 s). The results confirm the feasibility of developing low-cost, high-performance 2D metal sulfide gas sensing materials through rational structural design and optimization.

A ppb-level NO2 gas sensor with ultra-high concentration shock resistance characteristics based on In2O3-In2(MoO4)3

Metal oxides are widely used because of their simple structure, low price, and excellent gas-sensitive properties. But now, the metal oxide sensor faces two challenges. One is that when the detection limit of the sensor is low, it will be affected by a high concentration of gas and fail in practical applications. Second, the metal oxide sensor is susceptible to temperature changes, resulting in inaccurate measurement results. To address the above problems, the performance of metal oxides is enhanced through doping. Indium oxide doped with various levels of indium molybdate was prepared using a two-step hydrothermal method resulting in a composite material with an n-n heterostructure. The interaction formed by the n-n heterostructure enhances the redox reaction between NO2 gas and the sensor, and the unique nano cluster structure provides more active sites for the sensor, significantly improving the gas performance of the sensor towards NO2. Sensors based on In2(MoO4)3 with a doping ratio of 4 % (the sample IM3) showed excellent gas sensitivity. The lower and upper detection limits of the sensor are 200 ppb (response is 1.46) and 150 ppm (response is 515.94), respectively. And the sensor has good resistance to ultra-high concentration (10000 ppm) nitrogen dioxide (NO2) impact. In the range of 130–170°C, the temperature has a small and linear effect on the sensor response, which is very beneficial for temperature correction of gas sensors. The sensor prepared by In2(MoO4)3 doped In2O3 composite material has a good potential for application in engineering practice.

Performance improvement of NiO/YSZ sensitive electrode for high temperature electrochemical NOx gas sensors

In the mixed-potential gas sensor, the electrode type, particle size, microstructural morphology, as well as the interface state between the oxide-sensitive electrode and the solid electrolyte, are the key factors for determining the magnitude of the mixed potential. NiO-based material with the addition of Y2O3-stabilized ZrO2 (YSZ) particles is considered as one of the promising sensitive electrode materials for preparing the mixed-potential NOx sensors due to its excellent gas sensitivity. In this paper, the preparation technology of NiO-sensitive electrodes is developed and optimized for improving NOx (NO and NO2) gas-sensitivity properties of the NOx sensors. The experimental results show that the addition of YSZ can effectively improve the agglomeration morphology of NiO particles in the NOx-YSZ-based electrode material during high temperature sintering (i.e. 1200 °C) and enhance the bonding strength with the solid electrolyte. The sensor which was prepared by using the developed NOx-YSZ-based electrode material with the YSZ addition of 20 wt% has the most sensitive response characteristic to NO gas, and its response potential value increases with NO gas concentration. Elevating electrode sintering temperature can increase the size of NiO particles and shorten the length of the three-phase boundary (TPB) in the sensitive electrode. The average length of TPB is the longest in the sensitive electrode sintered at 1000 °C which corresponds to the best sensitive response to NO gas. The sensitive electrode's thickness also affects the NO response sensitivity, and the sensor with an electrode thickness of 14 μm has the most NO response sensitivity. In addition, the NO/NO2 gas mixture test results indicate that the current developed sensor is more sensitive to NO2 gas than that of NO gas.

Theoretical insights into gas-sensitive properties of B, Ga and In doped WS2 monolayer towards oxygen-containing toxic gases

Oxygen-containing toxic gases such as CO and NOx (x = 1, 2) have presented significant challenges to both the atmospheric environment and human well-being, thus prompting the development of efficient gas sensors for their detection at room temperature. In this work, we investigated the feasibility of B, Ga, In-doped WS2 (B-WS2, Ga-WS2 and In-WS2) monolayers as potential gas-sensitive materials for monitoring CO and NOx based on first-principles calculations, with a specific focus on analyzing the adsorption energy, electronic properties and recovery time. The results show that the doping of B, Ga, In atoms enhances the conductivity of WS2 monolayer and significantly improves the adsorption properties of WS2 towards CO and NOx. With the exception of the CO@In-WS2 system, all the systems exhibit chemisorption with adsorption energies ranging from −0.56 eV to −3.18 eV. Interestingly, the presence of H2O, CO and N2 in the atmosphere does not affect the capturing ability of B-WS2, Ga-WS2 and In-WS2 towards the target gases. Moreover, with the exception of the CO@In-WS2 system, the critical desorption temperatures of CO and NOx all exceed 300 K, highlighting the potential of the B/Ga/In-WS2 as effective adsorbents for NO and NO2 at room temperature and standard atmospheric pressure. Finally, the sensitivity and recovery time of CO and NOx on doped WS2 are evaluated. The findings confirm that Ga-WS2 exhibits a well-balanced combination of sensitivity and response speed, making it suitable as a reusable gas sensor for the detection of CO and NO, while In-WS2 is suitable for detecting NO and NO2. This study offers valuable theoretical insights into the design of innovative gas nanosensors for the detection of oxygen-containing toxic gases.

Porous hollow sphere structure PrFeO3 as an efficient sensing material for n-butanol detection

N-butanol is a harmful volatile gas, so creating an appropriate n-butanol sensor is critical for preserving human health and the manufacturing environment. In contrast to single metal oxide semiconductors, multicomponent metal oxides, especially perovskite ternary metal oxides with the ABO3 structure, exhibit significant potential for development owing to their precise structures and diverse physicochemical properties. In this paper, three-dimensional porous hollow spheres PrFeO3 were synthesized by combining air annealing and hydrothermal techniques. The crystal structure, surface composition, chemical state, and morphology of PrFeO3 materials were evaluated using several kinds of characterization approaches. The gas sensitivity of PrFeO3 materials was also thoroughly explored. The results show that at the optimal working temperature of 280 ℃, the PrFeO3 material excels in n-butanol gas sensing, with a response of 85 for 100 ppm n-butanol. Additionally, the sensor demonstrates high selectivity for n-butanol gases, low concentration detection capability, outstanding repeatability, rapid reaction recovery time (18 s/13 s), long-term stability, and exceptional reproducibility. The unique morphology and high oxygen vacancy content of PrFeO3 provide numerous active sites on its surface, promoting the adsorption and desorption of n-butanol gas molecules and enhancing its gas-sensitive properties.

Theoretical Study of Dissolved Gas Molecules in Transformer Oil Adsorbed on Intrinsic and TM (Ta, V)-Doped MoTe2 Monolayer.

In this paper, CH4, C2H2, H2, and CO adsorbed on intrinsic MoTe2 monolayer and transition metal atom (Ta, V)-doped MoTe2 monolayer have been investigated with density functional theory based on first-principles study. The adsorption energy, geometries, band structures, and density of states of four gases (CH4, C2H2, H2, and CO) adsorbed on the MoTe2 and doped MoTe2 surfaces were analyzed. The results shown that the gas adsorption performance of transition metal atom (Ta, V)-doped MoTe2 monolayers is more superior than that of intrinsic MoTe2, and the adsorption energy and charge transfer of the adsorbed gases on the TM-MoTe2 monolayer are significantly increased in comparison with both sides. Among them, Ta-MoTe2 has the largest Eads value in the adsorbed CO system with a very small adsorption distance, as well as a more suitable recovery time of CO at room temperature, so Ta-MoTe2 can be a candidate material for CO detection. New atoms were introduced during the doping process, which increased the carrier density and carrier mobility of the material, thus improving the charge transfer at the surface of the material. which provides a direction for the gas-sensitive properties of metal Ta-modified MoTe2 materials.

Adsorption and gas sensing properties of Pdn(n=1–3) cluster-modified PtSe2 on transformer fault characterizing gases under biaxial strain and electric field

In this study, the adsorption behavior of three DGA gases (C2H2, C2H4, and CO) on monolayers of PtSe2 doped with metal clusters Pdn(n=1–3) was investigated using density-functional theory (DFT). The critical influence of the Pd clusters on the sensitivity of PtSe2 gas is revealed by in-depth analysis of the geometrical structure of the adsorption system, DCD, ELF, DOS and band gap. The results show that the detection performance of intrinsic PtSe2 monolayer is poor. However, the doping of Pdn(n=1–3) fundamentally changes the adsorption behavior of PtSe2 on C2H2 and C2H4 from an adsorptive to an exothermic reaction, and endows it with excellent adsorption, desorption, and gas sensitivity properties. In addition, the introduction of external electric field and biaxial strain can significantly change the charge transfer, band gap, and adsorption energy of each adsorption system, which suggests that the Pdn(n=1–3)-PtSe2 monolayer has excellent tunability and can be strain-modulated for gas detection.

One-step hydrothermal preparation of pine-dendritic La-doped CdS nanomaterials for n-butanol sensing

In this work, La-doped CdS composites with sparse pine-dendritic morphology were prepared using a convenient one-step hydrothermal method and tested for their gas-sensitive properties. Compared with the pure CdS-based sensor, the sensor L-3 (containing 3 mol% of La) demonstrated a noticeable increase in gas-sensitive performance to n-butanol, exhibiting the response value as high as 127 for 100 ppm n-butanol gas at 200 °C. Besides the fast recovery rate (only 2 s) for n-butanol, the device possessed good selectivity and repeatability, as well as excellent long-term stability. After a series of characterization via XRD, SEM, TEM, XPS and BET, it was established that the enhancement of the gas-sensitive performance might be related to the introduction of La ions, the electron sensitization effect, and the increase in the specific surface area.

Ammonia detection based on Pd/Rh-GaN and recognition of disease markers of nitrogen compounds assistant by deep learning

Bimetallic has received a lot of attention due to its excellent catalytic performance. Herein, bimetallic nanofilms were successfully modified on GaN epitaxial wafer by a co-reduction method in polyol solution, and different concentrations of Pd/Rh-GaN were obtained. Meanwhile, the morphology and structure of Pd/Rh-GaN were subjected to a series of measurements, and the gas sensors modified with bimetallic modification were also studied for gas sensitivity. The results of the gas-sensitive properties show that the Pd/Rh-GaN-0.25 sensor has outstanding gas-sensing performance with the highest sensitivity, the lowest limit of detection, and the fastest response/recovery time. In addition, we extended other bimetallic nanoparticles to Pd/Ru and Pt/Ru, and deep learning was combined with the sensor array to recognize three markers of nitrogen compounds (NH3, NO2, TMA) in Exhaled breath, achieving high precision recognition with up to 96 % accuracy. This work offers a new approach for the design and preparation of gas sensors for early warning of chronic kidney disease.

Defect Engineering for SnO2 Improves NO2 Gas Sensitivity by Plasma Spraying.

Large emissions of nitrogen dioxide (NO2) pose a significant threat to human health, Monitoring its content and implementing timely measures are crucial. Utilizing oxide semiconductors, such as tin dioxide (SnO2), has proven to be an effective way to detect and analyze NO2. The design and preparation of sensing materials with high sensitivity and excellent selectivity is the key to improve the detection efficiency. SnO2 nanopowders with small and uniform particle size, large specific surface area, adjustable defect content, and no impurities were prepared by a new plasma spraying method. The SnO2 nanopowders exhibit outstanding performance in detecting NO2 at a low temperature of 100 °C, the response to 5 ppm of NO2 reaches 48, and the material demonstrates rapid response and recovery times, coupled with excellent selectivity. The exceptional gas-sensitive properties can be attributed to the superior morphology and structure of SnO2. It provides more reaction sites for gas sensitive reactions, fast electron transport, a large number of charge carriers, and improved adsorption of the material to the target gas. This study provides valuable insights into nanomaterial preparation and the enhancement of gas-sensitive properties for SnO2.

Biologically templated Fe2O3–CuO heterojunction for ppb-level styrene gas detection

The widespread industrial use of styrene highlights the urgent need for detecting and monitoring its harmful gases. The innovation of this study lies in synthesizing uniform Fe2O3 nanoparticles using Ginkgo biloba and calcining them with CuOHF to prepare nanostructured materials, enhancing the performance of gas sensors. The effects of varying α-Fe2O3 additions and calcination temperatures on the structure and gas-sensitive properties of the composites were systematically investigated. The results revealed that the optimal operating temperatures of the CuO–10%Fe2O3-400 sensor were reduced by 80 and 50 °C, and its response to 100 ppm styrene at 200 °C was significantly enhanced by 3.2-fold and 4.2-fold, respectively, compared to the single Fe2O3 and CuOHF sensors. It is particularly noteworthy that the sensor exhibits excellent detection performance at a 50 ppb styrene concentration, with a response value of 1.2. The lamellar structure of CuOHF serves as a precursor for CuO, thereby increasing the surface area of the sensor in contact with the gas. During the calcination process, the released gases contribute to the formation of a porous structure, which together improves the adsorption capacity and stability of the sensor. Additionally, the heterojunction formed by the calcination of CuO (p-type) and Fe2O3 (n-type) enhances charge transfer and increases gas adsorption capacity, highlighting its potential as a gas sensor. This composite material exhibits good sensitivity and reliability in monitoring hazardous gases like styrene, underscoring the significant value of this study in environmental monitoring and safety control.

Adsorption and gas sensitivity properties of graphene and Rh-decorated graphene towards SF6 decomposed gases: A DFT study

In order to solve the serious threat of SF6 decomposed gases (H2S, SO2, SOF2, SO2F2) to the stable operation of electrical equipment. In this study, the geometric structure, adsorption energy, density of states (DOS), sensitivity based on band structure and recovery time of H2S, SO2, SOF2, SO2F2 on graphene and Rh-modified graphene (Rh-graphene) were investigated computationally by density functional theory (DFT). The geometric structure of Rh-graphene was optimized with an average Rh-C bond length of 1.891 Å. According to the analysis of DOS and band structure, the electrical conductivity has a little effect of the Rh-graphene compared with pristine graphene, but Rh modification can regulate the band gap of graphene. The adsorption energy (Ead) and the sensitivity (S) at work temperature indicate that graphene has ideal adsorption and sensing properties for SO2 and Rh-graphene reflects the excellent applicability as the SO2 and SO2F2 gases sensor with the sensitivity of approximately −99 % and −60 %, respectively. The Graphene/SO2 system owns the minimum recovery time of 2154.3 ps. The recovery time of Rh-graphene/H2S and SOF2 is several orders of magnitude smaller than Rh-graphene/SO2 and SO2F2. The analysis of DOS and band structure was used to explain the sensing mechanism. The study would lay a theoretical foundation for the development of SF6 decomposed gases sensor for electrical equipment insulation.

Gas sensitivity of PECVD β-Ga2O3 films with large active surface

The gas-sensitive properties of Ga2O3 films, first synthesized by plasma-enhanced chemical vapor deposition (PECVD), with respect to gaseous species of environmental and industrial interest were investigated in detail. The addition of some N2 during the PECVD process made it possible to reduce the inherent high resistance of Ga2O3 material and increase its gas sensitivity. The PECVD-Ga2O3 films demonstrated high responses to H2, O2 and NH3 with maximum response temperatures of 600 °C, 700 °C and 350 °C, correspondingly. The responses of Ga2O3 films to 1 vol % of H2, 40 vol % of O2 and 1 vol % of NH3 at these temperatures were 400.73 %, 480.22 % and 335.35 %, correspondingly. The short response and recovery times of 7.6 s and 31.0 s have been achieved under H2 exposure. A plausible mechanism of the sensory effect of the PECVD-Ga2O3 films was suggested. Thus, the PECVD synthesized Ga2O3 films demonstrate a large potential for the development of high-speed performance H2 and O2 sensors working at high temperatures.

Specificity of electrophysical and gas-sensitive properties of nanocomposite ZnO–TiO2 films formed by solid-phase pyrolysis

ZnO–TiO2 thin films containing 0.5 mol%, 1.0 mol%, and 5.0 mol% ZnO were synthesized by oxidative solid-phase pyrolysis. The materials contained anatase and rutile phases with particle size of 6–13 nm, as confirmed using X-ray phase analysis and scanning electron microscopy. When a certain number of ZnO crystallites appeared in the TiO2 film structure in the temperature range of room temperature to 220 °C, a two-level response of the film resistance was observed, differing by approximately 10%, as obtained by electrophysical measurements. The two-level response correlates with the formation of two donor energy levels of 0.28 and 0.33 eV in the band structure of the ZnO–TiO2 films. The donor level with a higher activation energy corresponded to the Ti vacancy (V−Ti), and that with a lower activation energy corresponded to the Zn vacancy (V−Zn). Two levels of gas-sensitive properties were noted for 0.5ZnO–TiO2, 1ZnO–TiO2, and 5ZnO–TiO2 under the influence of 50 ppm NO2 at 250 °C. Such two-level responses can be ascribed to the pinning of the Fermi level on ZnO and TiO2 nanocrystallites. The mechanism of the beak-shaped and two-level responses of sensors based on composite nanomaterials when exposed to various gases was elucidated.

SnO2 nanoparticles-decorated In2O3 and their enhanced acetone gas sensing properties

There are many articles on gas sensor research (Zhang et al., 2023; Sheng et al., 2022; Ma et al., 2023; Yuan et al., 2024) [1–4]，Me asuring the acetone content of exhaled breath can reflect changes in blood sugar in the body. Therefore, it is of great value to develop gas sensitive materials for detecting acetone gas effectively. In this paper, by adding SnO2 to In2O3. composite In2O3/SnO2 microspheres were prepared. Using XRD, SEM, TEM, XPS, PL and UV technology, the microstructure morphology and optical properties of In2O3/SnO2 were measured. The experimental results showed that the composite retained the advantages of In2O3 and SnO2 optimized the properties of the composite effectively, and reduced the photoluminescence intensity. The gas sensitive properties of In2O3/SnO2 composite samples were tested. The test results showed that compared with pure In2O3 samples, the optimal working temperature of In2O3/SnO2 was reduced by 30 °C–250 °C. The response value to acetone gas is increased to about 35. In addition, In2O3/SnO2 sensors also achieve good selectivity excellent moisture resistance. long-term stability. These results show that the heterojunction of SnO2 and In2O3 can be used as an excellent sensor for detecting acetone gas.

Quantum-level investigation of air decomposed pollutants gas sensor (Pd-modified g-C3N4) influenced by micro-water content.

In the electrical industry, there are many hazardous gases that pollute the environment and even jeopardize human health, so timely detection and effective control of these hazardous gases is of great significance. In this work, the gas-sensitive properties of Pd-modified g-C3N4 interface for each hazardous gas molecule were investigated from a microscopic viewpoint, taking the hazardous gases (CO, NOx) that may be generated in the power industry as the detection target. Then, the performance of Pd-modifiedg-C3N4 was evaluated for practical applications as a gas sensor material. Novelly, an unconventional means was designed to briefly predict the effect of humidity on the adsorption properties of this sensor material. The final results found that Pd-modified g-C3N4 is most suitable as a potential gas-sensitizing material for NO2 gas sensors, followed by CO. Interestingly, Pd-modified g-C3N4 is less suitable as a potential gas-sensitizing material for NO gas sensors, but has the potential to be used as a NO cleaner (adsorbent). Unconventional simulation explorations of humidity effects show that in practical applications Pd-modified g-C3N4 remains a promising material for gas sensing in specific humidity environments. This work reveals the origin of the excellent properties of Pd-modified g-C3N4 as a gas sensor material and provides new ideas for the detection and treatment of these three hazardous gases.

Doped rare earth elements enhance gas sensing properties of hollow spiral-like Mn(OH)F semiconductor sensors for acetate esters detection

This study successfully synthesized a series of Mn(OH)F hollow structures doped with rare earth elements (Sm, Nd, Ce, and Tb) using a hydrothermal method. A comprehensive analysis was conducted on the influence of these dopant elements on the morphology and gas-sensitive properties of Mn(OH)F. The gas-sensing performance of Mn(OH)F nanomaterials doped with Sm, Nd, Ce, and Tb was extensively investigated at 150℃ for methyl acetate, ethyl acetate, propyl acetate, and butyl acetate. The results demonstrated good gas-sensing capabilities, with responses reaching 2.0, 2.0, 2.0, and 2.5, respectively. Compared to undoped Mn(OH)F nanomaterials, the operating temperature of these sensors was reduced by about 100℃, and the response values were nearly tripled. Exceptional selectivity and stability were also observed. In addition, an in-depth exploration was conducted into the underlying mechanisms behind the enhanced gas response due to rare earth element doping. This study provides strong theoretical support for the development of efficient acetate ester gas sensors, demonstrating broad prospects for their widespread application in the industrial field.