Gas Sensors Research Articles

A CuO/MoO3-based SO2 gas sensor with moisture resistance and ultra-fast response at 90°C

Sulfur dioxide (SO2) is a toxic and harmful decomposition product generated during arc discharge or partial discharge in sulfur hexafluoride (SF6) electrical equipment, which can corrode internal pipelines. Detecting SO2 is crucial for assessing the insulation condition of equipment and preventing faults. To overcome the challenges faced by traditional SO2 gas sensors, including high operating temperatures, slow response times, and poor moisture resistance, this paper proposes a novel SO2 gas sensor based on CuO/MoO3. The morphology, composition, and chemical states of the materials were analyzed using different characterization techniques. At 90°C, the S2 sensor (CuO: MoO3=1: 1) exhibited a fast response time (10 s) to 10 ppm SO2 and demonstrated good moisture resistance (a 1 % change in relative humidity (RH) has the same effect on the sensor as 25.9 ppb SO2). The response of the S2 sensor to 100 ppm SO2 was 26.5. Additionally, the voltage sensitivity of the S2 sensor at low (1–10 ppm) and high (10–100 ppm) concentrations are 658.74 mV/ppm and 33.43 mV/ppm, respectively. Therefore, the S2 sensor is more suitable for low concentration conditions. These good sensing characteristics of the S2 sensor are owing to the high content of oxygen vacancies (39.2 %) and the heterojunction effect in the composite material. Additionally, this sensor exhibits excellent anti-interference capabilities, including moisture resistance and high selectivity. Therefore, the CuO/MoO3-based SO2 gas sensor can be effectively applied to detect the decomposition of SF6.

Ir doping improved oxygen activation of WO3 for boosting acetone sensing performance at low working temperature

Thermally excited oxygen activation is the key to realize gas sensing by semiconductor. However, the relevant strategies and mechanisms are rarely studied. Herewith, the model material of highly oxygen catalytic active Ir doped WO3 (Ir-WO3) is prepared to elucidate the impact of enhanced oxygen activation on sensing performance. Interestingly, the 0.5 wt% Ir doped WO3 successfully reduced the working temperature of WO3 from 370 to 260 ℃ and significantly enhanced the response from 25.1 to 127.9 (at 50 ppm) for acetone. Meanwhile, the sensor also has fast response/recovery times (∼8.3/3.8 s), long-term stability, low detection limit (19 ppb) and high selectivity. Gas sensitive performance tests, in situ-DRIFTS and DFT calculations reveal that the Ir doping facilitates the oxygen adsorption and activation, which can significantly weaken the activation energy of acetone at low temperatures and contribute to enhance sensing performance. Our work paves a new pathway to improving metal oxide-based gas sensors at lower operating temperatures.

Susceptible Detection of Organic Molecules Based on C3B/Graphene and C3N/Graphene van der Waals Heterojunction Gas Sensors.

Constructing van der Waals (vdW) heterostructures is a prospective approach that is essential for developing a new generation of functional two-dimensional (2D) materials and designing new conceptual nanodevices. Using density-functional theory combined with a nonequilibrium Green's function approach allows for the theoretical and systematic exploration of the electronic structure, transport properties, and sensitivity of organic small molecules adsorbed on 2D C3B/graphene (Gra) and C3N/Gra vdW heterojunctions. Calculations show the metallic properties of C3B/Gra and C3N/Gra after the formation of heterojunctions. Interestingly, the heterojunctions C3B/Gra (C3N/Gra) for the adsorption of small organic molecules (C2H2, C2H4, CH3OH, CH4, and HCHO) at the C3B (C3N) side are sensitive to the chemisorption of C2H2 and C2H4. Similarly, the Gra/C3B is chemisorbed for both C2H2 and C2H4 when adsorbed on Gra side, while it is only chemisorbed for C2H2 in Gra/C3N. Interestingly, all heterojunctions on different sides are physisorbed for CH3OH, CH4, and HCHO. Furthermore, the calculated I-V curves demonstrate that the devices based on the adsorption of C2H2 and C2H4 at each side of the heterojunction have remarkable anisotropy, in with the current being considerably greater in the zigzag direction than in the armchair direction. More specifically, with C2H2 adsorbed on the Gra side, the sensitivity along the armchair direction is up to 85.0% for Gra/C3B and close to 100% for Gra/C3N. This study reveals that C3B/Gra (C3N/Gra) heterojunctions with high selectivity, high anisotropy, and excellent sensitivity are highly prospective 2D materials for applications, which further contributes new insights into the development of future electronic nanodevices.

Gas leakage detection system for domestic and industrial applications

Liquefied Petroleum Gas (LPG) is a highly inflammable gas used as sources of energy in automobiles, industries and for domestic cooking. Disaster occurs when LPG leaks and is in contact with the source of fire which may claim lives and destroy properties. Hence, its early detection is essential for preventing disaster. This paper presented smart detection of LPG leakage in domestic homes and industries. The system consisted of MQ-2 gas sensor which sensed the presence of the gas in the air and sent signal to the Arduino micro controller. The micro-controller informed the embedded Global System for Mobile Communication (GSM) module to send message in form of Short Message Service (SMS) to the users to swing into action in a bid to prevent outbreak of fire. Performance tests carried out to evaluate the system showed the capability of the system to concurrently send SMS to different subscribers and produce audible alarm. It was also observed that SMS was sent to users in a timely and efficient manner. The system could be useful in residential homes and industrial premises for preventing fire hazards.

An unprecedented sensitive material for detecting trimethylamine derived from polyoxometalates @ bimetallic metal organic frameworks

Polyoxometalates (POMs) and metal organic frameworks (MOFs) have attracted increasing attention in the gas sensor field for the detection of volatile organic compounds. Herein, we present novel sensitive materials (PW12-NiO-ZnO hollow polyhedron) derived from POMs@bimetallic MOFs by using a one-step solvothermal approach. The micro-nano structure, compositions, and other chemical and physical properties of the samples were clarified through characterization such as XRD, SEM, TEM and XPS. Significantly, sensor based on PW12-NiO-ZnO hollow polyhedron presents a notable response value as high as 62.6 toward 100 ppm trimethylamine at 350℃, which is nearly 4.3 times that of pure ZnO. Moreover, we conducted other performance tests on the sensor to verify the high selectivity, good response/recovery properties and perfect long-term stability toward trimethylamine. Importantly, possible products on the surface of sensitive materials were analyzed by in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS). In addition, these improved sensing performances is most benefiting from the incorporation of polyoxometalates and the p-n heterojunction between NiO and ZnO. As a pioneering study, this work provides an effective approach for designing diverse sensitive materials in the sensor applications.

Effect of Spin Speed on the Physical Characteristics of CuO Films Synthesized by Sol–Gel Spin Coating for H2S Gas Sensing

Effect of Spin Speed on the Physical Characteristics of CuO Films Synthesized by Sol–Gel Spin Coating for H2S Gas Sensing

Emergent Technologies in Human Detection for Disaster Response: A Critical Review

In the face of natural disasters, the rapid detection of trapped victims is crucial for effective search and rescue (SAR) operations. This review critically examines the emergent technologies in human detection that are pivotal in disaster response. Current methodologies for human detection encompass a variety of techniques: Radar, Artificial intelligence (AI), Drones, Robotics, Gas sensors, Acoustic, Infrared, and Optical detection. These methods are specifically designed to detect human presence in disaster scenarios by leveraging principles from electromagnetic, acoustic, AI-based algorithms, gas sensors, and optical detection. However, these technologies face challenges and limitations. They often depend on environmental conditions, encounter obstacles that affect their penetration capabilities, and have limited spatial resolution due to complex backgrounds. This paper aims to provide a comprehensive overview of the state-of-the-art in human-detection technologies, assess their impact on SAR missions, and offer insights into future advancements that could further enhance the survivability of disaster-stricken individuals.

Single ZnO Nanowire for Electrical and Optical NO2 Gas Sensing: Origin of Reversible and Irreversible Gas Effects Investigated by Photoluminescence Spectroscopy.

In this work, the gas sensing properties of a single ZnO nanowire (NW) are investigated, simultaneously in terms of photoluminescence (PL) and photocurrent (PC) response to NO2 gas, with the purpose of giving new insights on the gas sensing mechanism of a single 1D ZnO nanostructure. A single ZnO NW sensing device was fabricated, characterized, and compared with a sample made of bundles of ZnO NWs. UV near-band-edge PL emission spectroscopy was carried out at room temperature and by lowering the temperature down to 77 K, which allows detection of resolved PL peaks related to different excitonic transition regions. Surface effects were observed in PL maps, considering different nano and microstructures. Electrical and optical measurements were acquired at the same time during the NO2 gas exposure, allowing for the comparison of PL and PC response times and signal recovery. During NO2 gas desorption, irreversible behavior in the surface-related and donor-acceptor pair (DAP) regions is interpreted as the effect of an initial transient when electronic transfer from the gas molecules to the bulk occurs through the ZnO NW surface which acts as a channel. To the best of our knowledge, this is the first work which investigates the simultaneous PL optical and PC electrical response signals of a single ZnO NW to gas exposure.

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.

Convective assembly of silica colloidal particles inside photonic integrated chip-based microfluidic systems for gas sensing applications.

Optofluidics is a new field of modern science that stands at the interface of microfluidics and photonics and has good prospects for application in gas sensors. Microfluidics offers a promising platform for tuning and assembling monolayer structures that are used as sensitive layers for gas detection. Herein, we evaluate the concept of monolayer formation on a silicon nitride substrate enabling a surface coverage up to 59% through a microfluidic convective assembly and couple it with a photonic integrated chip to probe gas sensing performance.

H2S gas sensing based on CuNi MOFs derivative with TiO2 quantum dot decoration applied for meat freshness detection

As food safety issues have been widely revealed and exposed, the pursuit of food for people has shifted from food and clothing to fresh and healthy. Currently, there are many detection systems for detecting meat freshness on the market. However, most of the problems still exist are that they cannot be monitored in real time, cannot guarantee traceless monitoring, and the cost is high. To solve these problems, this work has built a portable meat freshness detection system based on copper oxide (CuO)/nickel oxide (NiO) doped titanium oxide (TiO2) quantum dot composites and added real-time monitoring and remote monitoring and finally packaged it into an intelligent food box. Real-time monitoring of the freshness of meat can be carried out in a specific range regardless of the space. Hydrogen sulfide (H2S) has always been an essential indicator of meat decay. Therefore, in this paper, an H2S gas sensor based on CuO/NiO doped TiO2 quantum dot composites material is designed and fabricated, which can effectively and quickly identify H2S. The gas sensor exhibits excellent gas sensing characteristics for H2S with a detection limit of 100 parts per billion (ppb) and has excellent selectivity and repeatability, which because of the presence of p-p type heterojunctions in CuO/NiO. In addition, the feasibility of the system and material for analyzing the meat deterioration process is demonstrated through the test of different meat samples. It is firmly believed that this new type of sensor mentioned in this paper can make contribution to food quality monitoring.

Imaging of Volatile Organic Compounds Using a Single Nanowire-Based Electronic Nose for Future Biomedical Applications.

This study introduces an array of semiconductor oxide single nanowires fabricated using advanced semiconductor processing techniques, including electron beam lithography and thin-film deposition, which is well-suited for large-scale nanowire integration. A four-channel nanowire array consisting of tin oxide (SnO2), indium oxide (In2O3), ferric oxide (Fe3O4), and titanium oxide (TiO2) was developed. As a proof of concept, we converted the response curves of the sensor array to heat maps, enabling comprehensive feature representation. The fabricated electronic nose (E-nose) was utilized to detect three types of volatile organic compounds (VOCs), with the results visualized in a heat map format. Additionally, the performance of each individual sensor was quantitatively studied, highlighting the array's potential for enhanced gas detection and analysis. To further illustrate the interaction between gas molecules and the nanowires, we visualized the gas response results by mapping the sensor's signal changes. These visualizations provide a clear representation of how different gas molecules interact with specific nanowires. For example, the heat maps reveal distinct response patterns for each type of VOC, allowing for the identification and differentiation of gases based on their unique signatures. This visualization technique not only enhances the understanding of gas-nanowire interactions but also demonstrates the effectiveness of the E-nose in distinguishing between various VOCs. The SnO2 nanowire gas sensor showed enhanced gas response compared to other materials. The SnO2 and TiO2 gas sensors showed enhanced response (62 and 56 s) and recovery times (100 and 37 s).

Persistently boosted TEA sensing performance of In2O3 hollow spheres by sequentially modified with Bi2O3 and Pt nanoparticles

Exploring rational and feasible strategies to boost the gas sensing performance of metal oxide semiconductor (MOS) has attracted a growing concern because it is an inevitable path for advanced gas sensor. Herein, a Bi2O3 and Pt co-modification approach was proposed to upgrade the triethylamine (TEA) sensing performance of In2O3. To expound it, a series of hollow spheres (HSs) with different compositions including In2O3, Bi2O3-modified In2O3 (Bi2O3/In2O3), and Bi2O3 and Pt co-modified In2O3 (Pt/Bi2O3/In2O3) were prepared through a solvothermal-calcination route combined with subsequent chemical reduction. After the evolution from In2O3 to binary Bi2O3/In2O3 and ternary Pt/Bi2O3/In2O3 composites, the sensor exhibited a persistently boosted sensing performance to TEA, particularly of higher sensitivity (increased from 0.0219 to 0.0369 and 1.0319/ppm within 1–30 ppm), better selectivity (STEA/Methane increased from 17.6 to 23.7 and 257.2), and faster response speed (response time decreased from 7 to 3 and 1 s for 100 ppm TEA). Additionally, the best Pt/Bi2O3/In2O3 sensor also presented good repeatability and stability. The sensitization effects of Pt and Bi2O3-In2O3 p-n heterojunction were discussed in detail.

UV-activated high-performance formaldehyde gas sensor based on P25/ZnO microspheres

UV-activated high-performance formaldehyde gas sensor based on P25/ZnO microspheres

Recent progress of cataluminescence sensing based on gas-solid interfaces.

Cataluminescence (CTL) has emerged as a sensing transduction principle of gas-solid interface for constructing gas sensors that present fast response, high sensitivity, and online monitoring. It has thus been widely associated with the field of chemical analysis and catalytic science. Herein, the latest developments in CTL sensors are reviewed, and the status quo of CTL-based gas sensing systems is discussed. In particular, the basic principles and sensing systems of CTL are outlined, including performance enhancement strategies for specific targets and recognition methods for multiple targets. Moreover, the important applications of CTL sensors are listed and classified, including environmental pollutant monitoring, product quality control, clinical diagnosis, and evaluation of catalyst performance. Finally, based on abundant case reports, the current conundrums of CTL sensors are summarized and their future development trends are also put forward.

Highly efficient SnO2-Carbon nanosphere heterojunctions decorated with Ag for detecting isopropanol at low operating temperatures

The design of a sensing material for detecting isopropanol gas with low operating temperature is extremely important for miniaturization and wearability of gas sensors. Herein, a novel gas sensor based on SnO2-Carbon nanosphere heterojunctions decorated with Ag nanoparticles (SCA) was fabricated and its gas sensing performance was evaluated and compared systematically. The measurement results indicated that the sensing performance was influenced by the ratio of Sn/C and the length of Ag plating, and the SCA sensor provided the best response. For 100 ppm isopropanol at 100 °C, the SCA sensor exhibited a response value of 50.51, a response time of 7 s and a recovery time of 60 s. The enhanced sensing performance and reduced operating temperature of the SCA could be attributed to the synergistic effect of the SnO2-Carbon nanosphere heterojunctions and the significant catalytic performance of the decorated Ag nanoparticles. In addition, the density functional theory calculation method based on the first-principles theory was used to study the adsorption performance and electronic behavior, as well asthe influence of Ag decoration on SnO2 for isopropanol detection. The calculated results were consistent with the experimental results.

Hybrid System of Polystyrene and Semiconductor for Organic Electronic Applications

While organic semiconductors hold significant promise for the development of flexible, lightweight electronic devices such as organic thin-film transistors (OTFTs), photodetectors, and gas sensors, their widespread application is often limited by intrinsic challenges. In this article, we first review these challenges in organic electronics, including low charge carrier mobility, susceptibility to environmental degradation, difficulties in achieving uniform film morphology and crystallinity, as well as issues related to poor interface quality, scalability, and reproducibility that further hinder their commercial viability. Next, we focus on reviewing the hybrid system comprising an organic semiconductor and polystyrene (PS) to address these challenges. By examining the interactions of PS as a polymer additive with several benchmark semiconductors such as pentacene, rubrene, 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene), 2,8-difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene (diF-TES-ADT), and 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT), we showcase the versatility of PS in enhancing the crystallization, thin film morphology, phase segregation, and electrical performance of organic semiconductor devices. This review aims to highlight the potential of an organic semiconductor/PS hybrid system to overcome key challenges in organic electronics, thereby paving the way for the broader adoption of organic semiconductors in next-generation electronic devices.

Low Temperature Plasma-Assisted Double Anodic Dissolution: A New Approach for the Synthesis of GdFeO3 Perovskite Nanoparticles.

Orthorhombic perovskite GdFeO3 nanostructures are promising materials with multiferroic properties. In this study, a new low-temperature plasma-assisted approach is developed via dual anodic dissolution of solid metallic precursors for the preparation of perovskite GdFeO3 nanoparticles (NPs) that can be collected both as colloids as well as deposited as a thin film on a substrate. Two solid metallic foils of Gd and Fe are used as precursors, adding to the simplicity and sustainability of the method. The formation of the orthorhombic perovskite GdFeO3 phase is supported by high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman measurements, while a uniform elemental distribution of Gd, Fe, and O is confirmed by energy dispersive X-ray spectroscopy, proving the successful preparation of ternary compound NPs. The magnetic properties of the NPs show zero remnant magnetization typical of antiferromagnetic materials, and saturation at high fields that can be caused by spin interaction between Gd and Fe magnetic sublattices. The formation mechanism of ternary compound NPs in this novel plasma-assisted method is also discussed. This method is also modified to demonstrate the direct one-step deposition of thin films, opening up opportunities for their future applications in the fabrication of magnetic memory devices and gas sensors.

Ultrasensitive xylene sensor based on RuO2-modified BiVO4 nanosheets

Two-dimensional (2D) BiVO4 nanosheets (NSs), featuring distinctive chemical properties and dangling-bond-rich surfaces, are promising for developing high-performance gas sensors. However, the previously reported 2D BiVO4 NSs-based devices suffer from a low responsivity and poor selectivity. In this work, we introduce RuO2 nanoparticles to boost the gas sensing properties of 2D BiVO4 NSs-based sensor. Intriguingly, the RuO2-decoration changes the selectivity of the corresponding gas sensor from acetone to xylene. Compared to the pristine BiVO4 sensor, the RuO2-BiVO4 sensor displays a reduced optimal operating temperature of 260℃ and exhibits a response of 19.0–5 ppm xylene, reaching a five-fold enhancement. Simultaneously, the RuO2-BiVO4 sensor also exhibits a rapid response and recovery time of 10 and 25 s respectively, as well as robust long-term stability with less than 5 % variation in response after a storage of 60 days. The improvement in sensing performance can be attributed to the RuO2-decoration from three aspects: heterojunction construction, surface state modulation and gas oxidation catalysis on the surface. This work not only provides a high-performance xylene sensing material but also provides insightful comprehension regarding the modification effects of RuO2.

Flexible hybrid nanostructured chemiresistive sensing platform for low-temperature trace hydrogen detection

The prevalence of hydrogen (H2) utilization across commercial and industrial sectors has spurred the innovation of various H2 gas sensors. However, their practical implementation has been hindered by issues such as cost inefficiency, low sensitivity, inadequate selectivity, and limitations in low-temperature sensing capabilities. Consequently, the development of a sensor capable of surmounting these challenges is paramount for widespread adoption. In this study, a cost-effective approach has been used to fabricate a flexible hybrid nanostructured platform on polyethylene terephthalate (PET) substrate incorporating a combination of zinc oxide (ZnO), titanium oxide (TiO2), and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). This platform has undergone meticulous morphological characterization and comprehensive evaluation for H2 gas sensing applications at both room temperature and 50˚C. The results reveal that the developed PEDOT:PSS/TiO2/ZnO NWs sensor exhibits superior H2 gas sensing characteristics with 141 % and 163 % higher response by proportions at 100 ppb and 100 ppm, respectively outperforming other prepared devices in the same environment. Thus demonstrating exceptional sensitivity of 0.448 %/ppm with three cycle repeatability, H2 selectivity and nine months of stability at low temperatures. Moreover, the sensor has an ultralow limit of detection (LOD) of ∼9 ppt, along with a rapid response time of 65 s and a recovery time of 42 s at an H2 concentration of 100 ppb. This research drives the advancement of efficient, rapid-responsive, and discerning trace detection of H2 gas at low temperatures.