Gas Sensor For Detection Research Articles

Gas sensing performance of Ti3C2Tx MXene heterojunction structures in greenhouse environments: a mini review

With the continuous advancement of smart greenhouse technologies, digital and information-based environmental monitoring has emerged as a focal point of research. The development of high-performance gas sensors is central to achieving this objective. In recent years, MXene materials have been widely applied in the field of gas sensors due to their excellent ion mobility, favorable hydrophilicity, outstanding electronic conductivity, and unique physicochemical properties. Various MXene heterojunction structures have been synthesized for gas detection. This review aims to summarize the current state of research on Ti3C2Tx-based gas sensors, explore methods for synthesizing different morphologies of Ti3C2Tx heterojunction structures, and evaluate the sensing behaviors of these configurations to fully harness their potential for gas monitoring in greenhouse environments. Additionally, an in-depth analysis of the sensing mechanisms associated with Ti3C2Tx heterojunction structures will be provided, offering theoretical support for future investigations. The findings indicate that Ti3C2Tx-based nanomaterials demonstrate considerable promise as high-performance sensors for gas detection in greenhouse settings. This innovative research not only provides new insights into the development of gas sensor technologies but also serves as an important foundation for the digitization of environmental monitoring.

Hydrogen Gas Sensing Performance of Iron Oxide‐Decorated Carbon Nanotubes: The Influence of Iron Oxide Species and Concentration

In this study, a solvothermal method was used to synthesize a composite of iron oxide nanostructures on carbon nanotubes (CNTs), which was applied as a resistive sensor for hydrogen gas (H2) detection. The nanocomposite was produced with three different iron oxide concentrations (Fe1@CNT, Fe2@CNT, and Fe3@CNT) to investigate the effect of iron species on CNTs and their interaction with hydrogen. Electron microscopy revealed that increasing iron oxide content led to the deterioration of the CNT walls. Raman and FTIR spectra confirmed the predominant presence of α‐Fe2O3 (hematite) on the CNTs, while XPS analysis verified the presence of multiple iron oxides species. High‐resolution XPS of the Fe 2p region indicated the existence of Fe3O4 (magnetite), Fe2O3 (hematite), and FeO (iron(II) oxide) associated with the CNTs. The sample with the lowest iron oxide concentration (Fe1@CNT) showed a 45% sensor response to hydrogen in a dry air atmosphere and the longest recovery time, suggesting a stronger interaction between hydrogen and the nanocomposite. Molecular dynamics simulations and density functional theory calculations further revealed that the presence of iron oxide on the CNT surface significantly altered its electronic properties, particularly by introducing more electronic states near the Fermi level, which enhanced electronic exchange between H2 and the carbon nanotube containing iron oxide.

Low Power Gas Sensors: From Structure to Application.

Gas sensors are pivotal across industries, encompassing environmental monitoring, industrial safety, and healthcare. Recently, a surge in demand for low power gas sensors has emerged, driven by the huge need for applications in portable devices, wireless sensor networks, and the Internet of things (IoT). The practical realization of a densely interconnected sensor network demands gas sensors to have low power consumption for energy-efficient operation. This Perspective offers a comprehensive overview of the progress of low-power sensors for gas and volatile organic compound detection, with a keen focus on the interplay between sensing materials (including metal oxide semiconductors, metal-organic frameworks, and two-dimensional materials), sensor structures, and power consumption. The main gas sensing mechanisms are discussed, and we delve into the mechanisms for achieving low power consumption including material properties and sensor design. Furthermore, typical applications of low power gas sensors are also presented, including wearable technology, food safety, and environmental monitoring. The review will end by discussing some open questions and ongoing needs.

Exceptional Electrical Detection of Trace NO2 via Mixed Metal MOF-on-MOF Film-Based Sensors.

The tunability of metal-organic frameworks (MOFs) makes them exceptional materials for the development of highly selective, low-power sensors for toxic gas detection. Herein, we demonstrate enhanced detection of NO2 gas by a MOF-based electrical impedance sensor made using a unique mixed metal MOF-on-MOF synthesis. A combined experimental and computational study was performed using the exemplar NixMg1-x-MOF-74 to understand the fundamental structure-property relationships behind metal mixing and MOF film synthesis methods on sensor performance. Density functional theory results indicated that the presence of Ni in Mg-MOF-74 increased framework stability and increased the electron density of states at lower energies near the HOMO, as well as enhanced the NO2-Mg adsorption interaction. Impedance data of the NixMg1-x-MOF-74 films with larger Ni contents showed greater impedance change after exposure to 1 ppm of NO2 gas. Furthermore, when synthesized through either a drop-cast or direct solvothermal film growth approach, the monometallic Ni-based sensors had the best performance. However, the mixed metal NixMg1-x-MOF-74 sensors synthesized through a MOF-on-MOF approach resulted in the highest impedance change, outperforming all monometallic Ni-based sensors. In particular, the mixed metal Ni-on-Mg-MOF-74 film was the best-performing sensor with an impedance change of 309 upon trace NO2 exposure. Change in impedance response after NO2 exposure was improved by 52% compared to the best monometallic Ni-on-Ni-MOF-74 sensor. Structural analysis of the Ni-on-Mg film showed that the first Mg-MOF-74 layer acts as a structural template controlling the structural features of the final film after metal exchange with Ni. This led to improved film quality, evidenced by the greater crystallinity and larger MOF grain sizes, and resulted in enhanced sensor performance which was not achievable through other metal mixing methods. Altogether, this study identifies structure-property relationships and synthetic templating methods that inform MOF-based sensor design, allowing for improved detection of toxic compounds.

Biocompatible sensors for ammonia gas detection

In this work, three different dyes have been tested for the determination of gaseous ammonia. This gas is one of the products of microbial degradation and therefore its presence is an indicator of deterioration and could be used as a food freshness indicator.Three different sensors have been prepared and tested, two of them using the natural pigments curcumin and anthocyanin and the other one using bromothymol blue. All of them are biocompatible and therefore allowed to use in contact with food.Different compositions, materials for deposition, stability and reversibility for ammonia gas detection have been studied under high humidity conditions simulating real packaged food conditions. Colorimetry is the technique used to obtain the analytical parameter, the H coordinate of the HSV colour space, simply using a camera, avoiding the use of complex instrumentation.Sensibility, toxicity grade and stability found show that the sensor could be implemented in packaged food and form the basis of a freshness indicator for the food industry.

Gas Detection and Classification Using Multimodal Data Based on Federated Learning.

The identification of gas leakages is a significant factor to be taken into consideration in various industries such as coal mines, chemical industries, etc., as well as in residential applications. In order to reduce damage to the environment as well as human lives, early detection and gas type identification are necessary. The main focus of this paper is multimodal gas data that were obtained simultaneously by using multiple sensors for gas detection and a thermal imaging camera. As the reliability and sensitivity of low-cost sensors are less, they are not suitable for gas detection over long distances. In order to overcome the drawbacks of relying just on sensors to identify gases, a thermal camera capable of detecting temperature changes is also used in the collection of the current multimodal dataset The multimodal dataset comprises 6400 samples, including smoke, perfume, a combination of both, and neutral environments. In this paper, convolutional neural networks (CNNs) are trained on thermal image data, utilizing variants such as bidirectional long-short-term memory (Bi-LSTM), dense LSTM, and a fusion of both datasets to effectively classify comma separated value (CSV) data from gas sensors. The dataset can be used as a valuable source for research scholars and system developers to improvise their artificial intelligence (AI) models used for gas leakage detection. Furthermore, in order to ensure the privacy of the client's data, this paper explores the implementation of federated learning for privacy-protected gas leakage classification, demonstrating comparable accuracy to traditional deep learning approaches.

UV-enhanced Mg:MOF-ZnO sensor for n-butanol gas detection at a lower operating temperature

In this study, a novel UV-enhanced Mg-doped MOF-ZnO sensor was investigated for its efficient detection of n-butanol gas at lower temperatures. The composite samples were prepared by the co-precipitation method with the appropriate component ratio. The structure, morphology, and optical properties of the as-prepared samples were systematically analyzed through XRD, SEM, TEM, BET, XPS, and UV–vis characterizations. The gas-sensitive performances based on the pristine MOF-ZnO and Mg-doped MOF-ZnO sensor series with the doping levels of 1 %, 3 %, 5 %, and 7 % (wt%) were comprehensively evaluated by adopting the gas-sensitive system. Among them, the 3 % Mg:MOF-ZnO sensor has given prominence to the largest specific surface area and highest oxygen vacancy concentration demonstrating the most excellent gas-sensing performance. Furthermore, with the aid of UV excitation, the 3 % Mg:MOF-ZnO sensor had achieved the enhanced response value of 2049 that was 4.44 times higher than that of pristine MOF-ZnO to 100 of ppm n-butanol at a low temperature of 246 °C, additionally presented out the superior reproducibility with speedy response/recovery time (12/22 s), the theoretical detection limit as low as 200 ppb, as well as the excellent long-term stability and selectivity for n-butanol. This study offers a promising strategy for the well-development of high-performance n-butanol sensors.

High-sensitive and fast-responsive In2O3 thin film sensors for dual detection of NO2 and H2S gases at room temperature

In this work, the room-temperature dual gas sensing characteristics of indium oxide (In2O3) thin films towards NO2 and H2S have been studied. In2O3 thin films were synthesized by the thermal oxidation of indium metal films of various thicknesses in the range of 50–250 nm deposited by thermal evaporation method. Grazing incidence X-ray diffraction (GI-XRD) revealed the change in preferred orientation of In2O3 thin films corresponding to varying thickness, while field-emission electron microscopy studies showcased evolving surface morphologies from individual grains to granular network with respect to the increase in film thickness. Investigations were made on the ability of In2O3 thin films to detect various low concentrations of nitrogen dioxide (NO2) and hydrogen sulfide (H2S) gases at ambient temperature. In2O3 thin films synthesized using 100 nm thick In films exhibited good sensing response of around 58 and 68 % towards NO2 and H2S gases of 5 ppm respectively, at room temperature (27 °C) with the response time of 36 and 18 s. Remarkably, the lower experimental detection limit of these toxic gases could be extended up to 100 ppb. Using X-ray photoelectron spectroscopy, a large presence of surface oxygen is observed on the In2O3 thin film. The sensor has demonstrated remarkable sensing abilities, including strong selectivity, quick sensing response, and good repeatability.

High Selectivity MEMS C2H2 Sensor for Transformer Fault Characteristic Gas Detection**

AbstractAcetylene (C2H2), as an important characteristic gas in transformer fault diagnosis, should be accurately detected and effectively distinguished from other dissolved gases (H2, CH4, C2H6, C2H4, CO, CO2), which is crucial to determine whether the fault occurs and the fault type, but also faces challenges now. The rational design and employment of rare earth and noble metals are expected to address this issue. In this work, SnO2‐3 at% Sm2O3‐1 at% PdO based MEMS gas sensor was prepared to achieve high performance detection of C2H2 which has a response value of 56 to 50 ppm C2H2, response/recovery time of 2 s/136 s, lower detection limit of 1 ppm, power consumption of 15.5 mW, and weak cross sensitivity to other transformer fault characteristic gases. Lewis acids and bases theory was used to explain the reason why rare earth Sm is a benefit element to improve selectivity to C2H2. The formation of oxygen vacancies and hetero junctions was used to explain the increased sensitivity of the material. This study proved the feasibility of rare earth and noble metals as potential additives to enable advanced gas‐sensitive materials for highly selective transformer fault characteristic gas C2H2 detection.

Utilizing acid-etched Fe-waste for sustainable synthesis of conductive perovskite-type materials from automotive industrial residue

A common method for reducing waste and environmental problems brought on by landfills is to reuse waste, especially heavy metals such as iron. Automotive industrial waste containing Fe-rich metal is successfully transformed into a highly pure structure of Fe2O3 using an etching method with HNO3 acid. This resulting structure serves as a precursor for synthesizing LaNi1-xFexO3±δ perovskite conducting materials. The desired perovskite conductive phase can be produced by substituting Fe2O3-treated waste at the B-site (Ni position) before calcination at 1200 °C. However, LaNiO3±δ and LaNi0.6Fe0.4O3±δ could not be synthesized under ideal conditions, as indicated by XRD analysis using TOPAS software, which revealed the presence of undesirable phases. Both compounds, LaNiO3±δ and LaNi0.6Fe0.4O3±δ demonstrated electrical conductivity with values of 362 S/cm and 42 S/cm at 550 °C, respectively. Nonetheless, electrical conductivity of both compounds decreased due to unintended phase contamination during the synthesis process. The Fe2O3-substituted compounds at the Ni position, in an exact amount of 1 mol, exhibited minimal electrical conductivity. Although the synthesis conditions to produce a single phase of LaFeO3±δ were identified, LaFeO3±δ, despite its low electrical conductivity, is frequently used in electrical devices as a gas detection sensor. The thermal expansion coefficient of all synthesized waste samples is represented in the range of 12–13 × 10−6 °C−1, which is comparable to IT-SOFC electrolyte materials. Furthermore, microstructural investigation revealed that the introduction of Fe into LaNiO3±δ reduced particle size and porosity, ultimately resulting in higher densities. These findings were confirmed through synchrotron radiation x-ray tomographic microscopy (SR-XTM) analysis. The research suggests that converting Fe-waste into a pure phase of Fe2O3 using a strong acid etching technique can serve as a viable precursor for synthesizing conductive materials. This approach enhances the value of industrial waste while also reducing its volume.

Natural Hydrogen in the Northern Perth Basin, WA Australia: Geospatial Analysis and Detection in Soil Gas for Early Exploration

The scope of this work is to empirically check and prove the practical applicability of the Primordially Hydridic Earth (PHE) concept for early exploration of the resources of naturally occurring hydrogen. With the PHE concept postulates interpreted within the local geological, tectonic, petrological and geophysical context, the reconnaissance plan, as well as the field exploration and data acquisition programs, were put together and implemented in the field. The results obtained from the surface (<1m deep) soil gas survey performed in Western Australia (WA) resulted in values of hundreds of ppm H<sub>2</sub>, including three samples with a concentration of hydrogen exceeding the gas sensor detection limit of 2,000 parts per million (ppm) (the all-Australia record). Similarly, several of the shallow soil samples used for obtaining headspace gas extracts yielded dozens % H<sub>2</sub>, which was established utilizing Gas Chromatography (GC) technology. The latter tests established the all-Australia record of 58.3% (norm.) H<sub>2</sub> concentration from 15 m depth, being the highest reading from the area of research. At one location, a concentration of He exceeding 8,000ppm was detected in a 1m surface soil gas sample analyzed by the independent lab. The most important outcome was finding natural hydrogen where it was expected and predicted. On the other hand, H<sub>2</sub> concentrations exceeding the natural background of 1-3ppm were not detected in the soil gas readings outside of the areas identified using the PHE concept as a theoretical foundation. It may be stated that overall, the practical application of the PHE concept along with the thoroughly planned utilization of carefully selected exploration techniques brings satisfactory results.

SnO2 Nanowire/MoS2 Nanosheet Composite Gas Sensor in Self-Heating Mode for Selective and ppb-Level Detection of NO2 Gas

The development of low-cost and low-power gas sensors for reliable NO2 gas detection is important due to the highly toxic nature of NO2 gas. Herein, initially, SnO2 nanowires (NWs) were synthesized through a simple vapor–liquid–solid growth mechanism. Subsequently, different amounts of SnO2 NWs were composited with MoS2 nanosheets (NSs) to fabricate SnO2 NWs/MoS2 NS nanocomposite gas sensors for NO2 gas sensing. The operation of the sensors in self-heating mode at 1–3.5 V showed that the sensor with 20 wt.% SnO2 (SM-20 nanocomposite) had the highest response of 13 to 1000 ppb NO2 under 3.2 V applied voltage. Furthermore, the SM-20 nanocomposite gas sensor exhibited high selectivity and excellent long-term stability. The enhanced NO2 gas response was ascribed to the formation of n-n heterojunctions between SnO2 NWs and MoS2, high surface area, and the presence of some voids in the SM-20 composite gas sensor due to having different morphologies of SnO2 NWs and MoS2 NSs. It is believed that the present strategy combining MoS2 and SnO2 with different morphologies and different sensing properties is a good approach to realize high-performance NO2 gas sensors with merits such as simple synthesis and fabrication procedures, low cost, and low power consumption, which are currently in demand in the gas sensor market.

Functional F-doped SnSx modified ZnOHF heterojunctions for efficient NO2 gas sensing

Constructing heterojunctions in semiconductor-based sensors is a vital method of modulating electronic structures and designing high-performance sensors for toxic gas detection. In this study, F-doped SnSx (F-SnSx) decorated ZnOHF composites were acquired via a two-step solvothermal method. The experimental results confirmed the establishment of heterojunctions between ZnOHF and F-SnSx. The optimized F-SnSx decorated ZnOHF snowflake-like nanoflowers-based NO2 sensors exhibited incomparable selectivity along with supreme sensitivity (S = 137–10 ppm NO2 at 200 ℃), rapid responding/recovering speed (34 s/6 s) and low detection limit (50 ppb). NO2 sensing mechanism and the influence of humidity interference on NO2 sensing performances were fully discussed. This work not only evidences the great potential of F-SnSx/ZnOHF snowflake-like nanoflowers for NO2 recognitions but also paves a feasible routine for advancing NO2 sensing performances by electronic structure regulations.

Fast and green synthesis of iron oxide using low-power laser sintering on reduced graphene oxide sensor for ammonia gas detection

Oxide materials are important for gas sensing applications. Unfortunately, most of the synthesis methods use many toxic chemicals and need long calcination at high temperatures. Thus, developing simple and green synthesis processes, which can be performed fast and at low temperatures, is imperative for both industrial manufacturers and our environment. Here, our fast and green synthesis method based on low-power laser sintering for producing FeOx (with Fe2O3 as the main composition) is presented. Besides, FeOx particles were decorated on reduced graphene oxide (RGO) to form a resistive sensor. Notably, our FeOx material can reduce the response of RGO toward acidic gas (NO2) but it enhances the RGO response toward the basic NH3 gas. Particularly, our hybrid FeOx/RGO sensor can detect NH3 gas at above 2 ppm under dry and humidified conditions (<85 % RH). That effect of FeOx is found due to the formation of alpha-phase Fe2O3 which acts as a p-type semiconductor, which is explored and explained in the discussion section. Finally, our findings not only reveal the potential of our hybrid sensing materials for practical NH3 sensing applications but also confirm the usefulness of laser-sintering to produce catalytic oxide materials environmentally friendly and at low cost.

Front cover Image

The cover image of the publication eom2.12453 showed how lignin, a bio‐polymer material, significantly enhances the sensitivity of MXene composite as a 2D materials chemiresistive sensor for molecular gas detection. This study also demonstrated a hybridized MXene composite flexible chemiresistive sensor, which paves the way for new solid‐state sensing platforms for curvature structures.image

A Novel Molybdenum Disulfide-Based High-Precision Microwave Sensor for Methanol Gas Detection at Room Temperature

A Novel Molybdenum Disulfide-Based High-Precision Microwave Sensor for Methanol Gas Detection at Room Temperature

RGO/CuCl-Based Flexible Gas Sensor for High-Concentration Carbon Monoxide Gas Detection at Room Temperature.

Carbon monoxide (CO) gas sensors are widely used, especially for environmental monitoring in confined spaces such as the landscape of mining cave ruins in mining parks, which is essential for ensuring the health and safety of tourists and staff. In this paper, a flexible CO gas sensor based on polyimide, interdigital electrodes, and reduced graphene oxide (RGO)/cuprous chloride (CuCl) composite film is designed and manufactured for reliable room temperature detection of high-concentration CO gas. The structure size of RGO/CuCl gas-sensitive film is 5 × 5 mm. The RGO with a 62.65% C-C bond is prepared by the thermal reduction method. The test results show that the sensor has a high response in the range of 400-2000 ppm CO gas concentration, and the maximum response is 1.56. The linear correlation coefficient of the sensor is 0.981, which indicates that the sensor has good output response characteristics. The response time of the sensor for 400 ppm CO gas is 332 s, which indicates that the sensor has a fast response rate. Furthermore, compared with other gases, the sensor shows higher gas selectivity for CO gas. This sensor has the characteristics of small size and easy attachment; therefore, it can be installed on the shoulder or helmet of tourists' safety suits, providing personalized real-time warning prompts for tourists' physical health status.

H2S sensitivity of transition metal-doped Y2CF2 with F-vacancies: A DFT study

In this study, Density Functional Theory (DFT) was used to investigate the potential of Y2CF2, a two-dimensional (2D) material, as a promising sensor for H2S gas detection. The effects of F-defects and transition metal (TM = Ti, V, Cr, Zr, Nb, Mo) doping on the geometric, electrical, and sensitive properties of Y2CF2 were examined. With pristine Y2CF2, physical adsorption toward H2S was observed, while with F-vacancies, chemical adsorption occurred. The adsorption capacities of the TM-doped systems for H2S were influenced by the specific doping atoms. For Ti-, V-, and Nb-doped adsorption systems, adsorption energies and charge transfer were higher, and the desorption time was faster. For V-doped Y2CF2, there was an obvious change in the band gap after H2S gas molecules were adsorbed, and this can be used as a signal for H2S gas detection. Therefore, because of the high sensitivity, obvious change of band gap, and appropriate desorption time, V–Y2CF2 has excellent potential for application as sensor for H2S gas detection. The findings of this study highlight the material's promising potential in sensor research.

Heterostructure engineering of In2O3/ErVO4 hairy curd for high-performance TEA gas sensors

Triethylamine (TEA) is a mephitic volatile organic compound, which has huge damage to human body. Therefore, the development of gas sensitive materials for the effective detection of TEA has important application value. In this paper, In2O3, ErVO4 and In2O3/ErVO4 composite samples were successfully synthesized by hydrothermal method. The In2O3/ErVO4 composite of In2O3 and ErVO4 has a spherical structure with a rough surface, and forms a variety of porous structures, which effectively increases the specific surface area of the composite (58.9551m2/g), thereby improving the gas sensitivity to TEA. In2O3/ErVO4 composites can achieve a higher response to 100 ppm TEA (S = 54.73), have a lower optimal operating temperature (250 °C) compared with In2O3 pure samples, and have a faster recovery time (52 s) compared with ErVO4 pure samples. In addition, In2O3/ErVO4 sensors also achieve good selectivity, excellent moisture resistance, long-term stability. The microstructure of the sample was significantly changed by ErVO4 recombination. These alterations include an increase in specific surface area, a decrease in particle size, an increase in the utilization of the sensitive body, an increase in the proportion of vacancy oxygen, a decrease in the optical band gap, and an increase in electron transport efficiency. These results show that the combination of ErVO4 and In2O3 to construct heterojunction can achieve excellent sensor for TEA gas detection.

WSN-Based Data Acquisition System for Collecting Environmental Pollution Factors for Green City

Implementation with a portable, intelligent weather station is to upgrade the system for environmental management and monitoring. This gadget measures and assesses meteorological and air quality data by real-time implementation through the Internet of Things technology to provide important environmental condition insights. The monitoring station's hardware parts include the ESP32 board, MQ2, MQ3, and MQ135 sensors for gas detection. Such an intelligent weather monitoring station can easily be deployed in different environments due to its portability and versatility. This small station size and its wireless link will enable effective data collection and transfer and integration into other systems of the present day. The existing environmental monitoring system takes the temperature and humidity and measures ammonia, benzene, alcohol, smoke, and carbon monoxide. Therefore, data is brought to the monitoring station, where it communicates in real time for the users to review and analyse on the online platform Blynk. It enables users to easily make data presentations and create notifications and dashboards using a mobile app of Blynk and the web platform, enabling them to create interfaces that meet their satisfaction easily. Users may also upload the uploaded data to a web server for remote access and analysis, which eases scalability and flexibility. Portable intelligent weather monitoring station has significant areas of influence on applications like public health, urban planning, and environmental monitoring, among others. It thus provides decision-makers with information on pollution management and climate resilience. This provides a sustainable and resilient future; it is approachable since the interface used in the system is accessible, befitting the two settings: urban and rural. The Intelligent Portable Weather Monitoring Station provides great usefulness in the disclosure, development, innovation of technology, and practice in the quest for meeting challenges of the environment with the promotion of sustainability. This not only allows smarter and more sustainable city development with effective environmental monitoring and management that includes IoT technologies but can also allow flexible data transmission facilities.