High-performance Gas Sensors Research Articles

First-principles study of WS2 monolayer decorated with noble metals (Pt, Rh, Ir) as the promising candidates to detect nitrogenous poisonous gases

Rapid identification of nitrogenous toxic gases (NPGs, including NO, NO2, NH3, and HCN) emitted from industrial processes is essential for environmental preservation. In this research, the first-principles calculations have been employed to systematically investigate the adsorption behavior and sensing characteristics of Pt, Rh, Ir-modified WS₂ monolayers (Pt-WS2, Rh-WS2, and Ir-WS2) towards these NPGs, with the aim of assessing the potential of WS2-based gas sensors for NPG detection. The results show that Pt, Rh, and Ir atoms can be stably anchored on the WS2 surface, enhancing its chemical stability and the quantity of active sites. Additionally, the strong orbital hybridization between these noble metal atoms and gas molecules enhances the adsorption capacity of WS₂, markedly boosting the adsorption potency of these modified substances towards NPGs (Eads≥−0.69 eV) while maintaining high selectivity toward NPGs in the presence of interfering gases (H2O, N2, CO2). Analysis of the density of states, charge density distribution, and electron localization function indicates weak chemical adsorption of HCN on Pt-WS2, Rh-WS2, and Ir-WS2, while strong chemical adsorption is observed for NO, NO2, and NH3. Furthermore, the adsorption of NO and NO₂ leads to significant band gap changes (∆Eg > 30%) of Pt-WS2, Rh-WS2, and Ir-WS2, and the response of work function to NH₃ and HCN adsorption is similarly pronounced (∆Φ > 15%). Finally, analysis of recovery time indicates that Pt-WS2 and Rh-WS2 can serve as work function gas sensors for HCN and as adsorbents for NO, NO2, and NH3 at room temperature, whereas Ir-WS2 can function as a reusable gas sensor for the effective detection of HCN at high temperature. This investigation establishes a robust theoretical framework for the development and manufacture of high-performance WS₂-based gas sensors.

CsPbBr3 Quantum Dot Modified In2O3 Nanofibers for Effective Detection of ppb-Level HCHO at Room Temperature under UV Illumination.

The design of high-performance and low-power formaldehyde (HCHO) gas sensors is of great interest to researchers for environmental monitoring and human health. Herein, In2O3/CsPbBr3 composites were successfully synthesized through an electrospinning and self-assembly approach, and their ultraviolet-activated (UV-activated) HCHO gas-sensing properties were investigated. The measurement data indicated that the In2O3/CsPbBr3 sensor possesses an excellent selectivity toward HCHO. The response of the In2O3/CsPbBr3 sensor to 2 ppm of HCHO was 31.4, which was almost 11 times larger than that of In2O3 alone. Besides, the In2O3/CsPbBr3 sensor also displayed extraordinary linearity (R2 = 0.9696), stable reversibility, and ideal humidity resistance. Interestingly, the gas-sensing properties of the In2O3/CsPbBr3 sensor were further improved (Ra/Rg = 54.8) under UV light irradiation. Meanwhile, the response/recovery time was shortened to 7/9 s. The improvement of HCHO-sensing properties might be ascribed to the distinctive structure of In2O3 nanofibers, the adsorption capacity of cesium lead bromide quantum dots (CsPbBr3 QDs) for UV light, and the synergistic effect of heterostructures between the components. Density functional theory (DFT) was implemented to discuss the adsorption ability and electronic characteristics of HCHO at the surface of In2O3/CsPbBr3 composites. Especially, this research points out new constructive thoughts for the exploitation of UV light improved gas-sensing materials.

A novel peony shaped ZnO and its excellent ethanol gas-sensing performance

In order to improve the gas-sensing performance of ZnO, a novel peony shaped ZnO stacked with nanosheets were prepared using hydrothermal method, and the obtained ZnO was characterized and tested for gas sensitivity. The results showed that the particle distribution of the peony shaped ZnO was uniform, with a particle size of about 0.8μm. The gas-sensing response test results show that the peony shaped ZnO has excellent selectivity to ethanol gas. When the concentration of ethanol gas is 100ppm, the gas-sensing response of the peony shaped ZnO to ethanol gas reaches 17.4, and the response time and recovery time are 8 seconds and 12 seconds, respectively. Even at an ethanol gas concentration of 2ppm, the gas-sensing response of the peony shaped ZnO to ethanol gas can reach 2.1. Compared to existing literature reports, the peony shaped ZnO prepared in this paper has better gas-sensing performance. This study will provide data support and theoretical reference for the development of high-performance gas sensors.

Synthesis and Characterization of TiO2 Nanotubes for High-Performance Gas Sensor Applications

In this study, we investigated the fabrication, properties, and sensing applications of TiO2 nanotubes. A pure titanium metal sheet was used to demonstrate how titanium dioxide nanotubes can be used for gas-sensing applications through the electrochemical anodization method. Subsequently, X-ray diffraction indicated the crystallization of the titanium dioxide layer. Scanning electron microscopy and transmission electron microscopy then revealed the average diameter of the TiO2 nanotubes to be approximately 100 nm, with tube lengths ranging between 3 and 9 µm and the thickness of the nanotube walls being about 25 nm. This type of TiO2 nanotube was found to be suitable for NO2 gas sensor applications. With an oxidation time of 15 min, its detection of NO2 gas showed a good result at 250 °C, especially when exposed to a NO2 gas flow of 100 ppm, where a maximum NO2 gas response of 96% was obtained. The NO2 sensors based on the TiO2 nanotube arrays all exhibited a high level of stability, good reproducibility, and high sensitivity.

Development of High-Performance Ethanol Gas Sensors Based on La2O3 Nanoparticles-Embedded Porous SnO2 Nanofibers.

Porous pure SnO2 nanofibers (NFs) and La2O3 nanoparticles (NPs)-embedded porous SnO2 NFs were successfully synthesized via electrospinning followed by calcination. These materials were systematically evaluated as gas-sensing elements in metal-oxide-semiconductor (MOS) sensors. The La2O3 NPs embedded in porous SnO2 NFs demonstrated superior gas-sensing performance compared to pure SnO2 NFs. Specifically, the incorporation of La2O3 resulted in a 12-fold enhancement in gas-sensing response towards ethanol, significantly improving both sensitivity and selectivity by tuning the carrier concentration and modifying oxygen deficiencies and chemisorbed oxygen levels. Thus, La2O3 NPs embedded in SnO2 NFs present a promising strategy for the development of high-performance ethanol gas sensors.

Miniaturized Electrochemical Gas Sensor with a Functional Nanocomposite and Thin Ionic Liquid Interface for Highly Sensitive and Rapid Detection of Hydrogen.

Hydrogen has been widely used in industrial and commercial applications as a carbon-free, efficient energy source. Due to the high flammability and explosion risk of hydrogen-air mixtures, it is vital to develop sensors featuring fast-responding and high sensitivity for hydrogen leakage detection. This paper presents a miniaturized electrochemical gas sensor by elaborately establishing a nanocomposite and thin ionic liquid interface for highly sensitive and rapid electrochemical detection of hydrogen, in which a remarkable response time and recovery time of approximately 6 s was achieved at room temperature. A screen-printed carbon electrode was modified with a reduced graphene oxide-carbon nanotube (rGO-CNT) hybrid and platinum-palladium (Pt-Pd) bimetallic nanoparticles to realize high sensitivity. To achieve miniaturization and high stability of the sensor, a thin-film room-temperature ionic liquid (RTIL) was employed as the electrolyte with a significantly decreased response time. The fast-responding hydrogen sensor demonstrates excellent performance with high sensitivity, linearity, and repeatability at concentrations below the lower explosive limit of 4 vol %. The engineered high-performance interface and gas sensor provide a promising and effective strategy for gas sensor design and rapid hazardous gas monitoring.

Hierarchical Heterojunctions of Metal Sulfide WS2 Nanosheets/Metal Oxide In2O3 Nanofibers for an Efficient Detection of Formaldehyde.

The construction of transition metal dichalcogenides (TMDs) heterojunctions for high-performance gas sensors has garnered significant attention due to their capacity to operate at low temperatures. Herein, we realize two-dimensional (2D) WS2 nanosheets in situ grown on one-dimensional (1D) In2O3 nanofibers to form heterostructures for formaldehyde (HCHO) gas sensors. Capitalizing on the p-n heterojunctions formed between WS2 and In2O3, coupled with the high surface-to-volume ratio characteristic of 1D nanostructures, the WS2/In2O3 NFs sensor demonstrated an elevated gas response of 12.6 toward 100 ppm HCHO at 140 °C, surpassing the performance of the pristine In2O3 sensor by a factor of two. Meanwhile, the sensor presents remarkable repeatability, rapid response/recovery speed, and good long-term stability. The superior sensing capabilities of WS2/In2O3 NFs heterojunction are attributed to the combined impact of the increased charge transfer and the presence of more sites for gas adsorption. The research endows a potent approach for fabricating TMD heterojunctions to significantly enhance the gas sensing properties of gas sensors at relatively low temperatures.

Highly responsive gas sensors based on grain boundary–rich polycrystalline few-layer MoS2 films for NO2 detection

Abstract This study addresses the issues of insufficient sensitivity and poor reversibility for NO2 detection by successfully fabricating a sensor based on uniform and high-quality few-layer MoS2 polycrystalline material using chemical vapor deposition. This approach aims to improve the response of the sensor by exploiting the abundance of grain boundary (GB) defects in polycrystalline MoS2 membranes. Comprehensive surface morphology analysis of the few-layer MoS2 polycrystalline films was conducted using microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy to characterize their chemical composition and properties. Subsequently, evaluation of 1–100-ppm NO2 was conducted at room temperature (25°C). The results show excellent performance of the sensor, with a response range of 11–82.24. Notably, under ultraviolet excitation at room temperature, this sensor exhibits a response time of only 41 s to 50 ppm of NO2 with complete recovery and improved sensitivity, maintaining reliable stability over eight weeks. Furthermore, the findings reveal that the sensor demonstrates high selectivity toward NO2 gas with limit of detection and limit of qualification values of 10 and 34 ppb, respectively. Owing to the abundant adsorption sites provided by GB defects in polycrystalline thin films, the response performance of the sensor is effectively enhanced. This study provides valuable insights into the future design and development of high-performance NO2 gas sensors.

Ammonia Sensing Performance at Room Temperature of Ca-Doped CNFs/Al2O3 Gas Sensor.

When NH3 in the environment exceeds a certain concentration, it may have adverse effects on human health. Ammonia gas sensors currently on the market usually work under high temperatures and are not only expensive but also have poor performance in terms of selectivity. Therefore, the preparation of an ammonia gas sensor that works at room temperature, is low cost, and has high sensitivity and selectivity is particularly important. This paper introduces a room temperature ammonia gas sensor based on a Ca-doped CNFs/Al2O3 nanocomposite material, prepared using electrospinning, pre-oxidation, and carbonization processes. The surface morphology, microstructure, and chemical composition of the materials have been characterized by scanning electron microscopy, Raman, and X-ray photoelectron spectroscopy. The Ca-doped CNFs/Al2O3 gas sensor has excellent selectivity for ammonia at room temperature and low sensitivity to other volatile gases such as ethanol, dimethylformamide, HCl, and methanol. At 100 ppm of NH3, the response value of the Ca-doped CNFs/Al2O3 gas sensor can reach 22.73, demonstrating excellent repeatability and long-term stability. Its performance is not affected by environmental temperature and humidity, providing great convenience for practical applications. In addition, we also discuss the sensing mechanism of the Ca-doped CNFs/Al2O3 gas sensor. This paper not only provides effective materials and methods for the development of high-performance room temperature ammonia gas sensors but is also expected to play a role in the field of environmental monitoring.

Long-term reliable wireless H2 gas sensor via repeatable thermal refreshing of palladium nanowire

The increasing significance of hydrogen (H2) gas as a clean energy source has prompted the development of high-performance H2 gas sensors. Palladium (Pd)-based sensors, with their advantages of selectivity, scalability, and cost-effectiveness, have shown promise in this regard. However, the long-term stability and reliability of Pd-based sensors remain a challenge. This study not only identifies the exact cause for performance degradation in palladium (Pd) nanowire H2 sensors, but also implements and optimizes a cost-effective recovery method. The results from density functional theory (DFT) calculations and material analysis confirm the presence of C = O bonds, indicating performance degradation due to carbon dioxide (CO2) accumulation on the Pd surface. Based on the molecular behavior calculation in high temperatures, we optimized the thermal treatment method of 200 °C for 10 minutes to remove the C = O contaminants, resulting in nearly 100% recovery of the sensor’s initial performance even after 2 months of contamination.

Room-temperature self-calibrating sensor based on CsPbBr3/SnO2 for detecting low-concentration sulfur dioxide

Sulfur dioxide (SO2) is a colorless toxic gas, and accurate monitoring of its concentration is important for safety. However, accuracy is often interfered by humidity. To address the issues, in this work, a self-calibrating SO2 sensor based on CsPbBr3/SnO2 was prepared, the sensor exhibited an excellent response to parts per billion (ppb) levels of SO2 at room temperature, which is rarely achieved by other SO2 sensors. The response sensitivity of the sensor to 600 ppb SO2 reached up to 0.53 with response/recovery times of 17/285 s. In addition, the CsPbBr3/SnO2-based SO2 gas sensor showed a low detection limit, good reproducibility, and high selectivity. Moreover, theoretical calculations show that the gas recognition mechanism is attributed to the significant changes in the band structure and density of states of the heterojunction materials CsPbBr3/SnO2 after gas adsorption, thereby altering the charge carrier transport behavior and electrical properties. A self-calibrating algorithm MobileNetV2 was employed to eliminate humidity interference and effectively identify low-concentration SO2 in humid environments, and the recognition accuracy rate is 0.85. This work demonstrates the production of a high-performance SO2 gas sensor, and provides an effective method to eliminate the interference of humidity, making it significant in environmental monitoring and air quality control.

N-n type In2O3@-WO3 heterojunction nanowires: enhanced NO2 gas sensing characteristics for environmental monitoring.

Solvothermal synthesis of 1D n-In2O3@n-WO3 heterojunction nanowires (HNWs) and their NO2 gas sensing characteristics arereported. The n-In2O3@n-WO3 HNWs have been well-characterised using XRD, Raman spectroscopy, XPS, SEM and HRTEManalyses. The NO2 sensing performance of n-In2O3@n-WO3 HNWs showed superior performance compared withpristine WO3 NWs. Due to the distinctive configuration of WO3-In2O3 heterojunctions, the n-In2O3@n-WO3 HNWs demonstrated remarkable sensitivity reaching 182% in response towards 500ppb of NO2 gas at operating temperature of 200°Cwhich is nearly 3.5 times greater than the response observed with pristine WO3 (50%). Moreover, the n-In2O3@n-WO3 HNWs also exhibited fast response (8-13s)/recovery (54-62s) time characteristics. A plausible sensing mechanism has been discussed. The enhancement in sensor characteristics shows that n-In2O3@n-WO3 HNWs could serve as a promising material for high-performance NO2 gas sensors for real-time environmentalmonitoringapplications. This work could provide new understandings of the sensing mechanism of n-In2O3@n-WO3-based heterojunction nanowires, which can be applied to the design of novel n-n type MOS heterojunction materials for the application of low-temperature real-time high-performance NO2 sensors.

Self-doped Na-carbon materials derived from a lyocell fiber for a high-performance trimethylamine gas sensor at room temperature

In this study, biomass-derived carbon material obtained from Lyocell fibers was first utilized as a gas sensor. The impacts of varying pyrolytic carbonization temperatures and pregrinding treatments on the structure, surface morphology, elemental composition, and gas sensitivity of the samples were thoroughly examined. The CL-500 sensor can realize rapid detection of trimethylamine with a high response (12.79k%, 500 ppm) and high selectivity at room temperature; the response/recovery times are 10 s and 2 s, respectively, and the theoretical detection limit is 3.96 ppm. Moreover, after four months, the response of the CL-500 sensor to trimethylamine fluctuated by less than 9.7 % compared with that of the fresh sensor, indicating good stability. It also shows good recovery after seven consecutive response-recovery cycles. Additionally, the CL-500 sensor has promising applications in real-life fish freshness monitoring. Theoretical calculations indicate that the introduction of trace amounts of Na enhances the sensing performance of this sensor for target gases. This study serves as a guide for developing cost-effective, high-performance gas sensors, promoting the efficient and high-value utilization of biomass waste.

High-performance trimethylamine gas sensor based on Sn-W co-doped MOF-derived hollow flower-like nickel oxide

In this study, a simple hydrothermal method was used to synthesize metal-organic framework-derived Sn/W co-doped NiO hollow flower-like spherical structure. The prepared NiO composites were utilized to prepare gas sensors to explore the response characteristics to different gases. The results showed that the response of the bimetal-doped NiO hollow microspheres to trimethylamine was 95 at 100 ppm, which was 63 times that of the pristine NiO nanoflowers. In addition, the sensor has a ppb-level detection limit for trimethylamine (0.1 ppm, 1.5). These good sensing performance of the Sn/W co-doped NiO sensor are not only affected by the initial resistance(Ra), but are also closely related to the rich oxygen vacancies, special hollow flower-like spherical structure and high Ni3+/Ni2+ ratio in the composite nanomaterials. This study provides an elegant co-doping method to improve the gas sensing performance of P-type MOS.

ZnSnO3 micro-polyhedrons with oxygen defects derived from rubidium incorporation for enhanced ethanol detection

Detecting ethanol in ambient air is of great significance in protection of ecological environment, human health and social economy. Herein, a strategy is adopted to substantially improve the gas sensing performance of the ZnSnO3 micro-polyhedrons through rubidium (Rb) doping. In this study, a series of ZnSnO3 micro-polyhedrons with different amounts of Rb doping were successfully synthesized through a typical hydrothermal procedure and air sintering. The sensor based on 2 mol% Rb-doped ZnSnO3 exhibits high response value (108) and rapid response/recover speed (20/8 s) to 100 ppm ethanol at 260 °C, as well as outstanding repeatability and stability. Combining theoretical calculations and various characterization techniques, the improved sensing property of the 2 mol% Rb-doped ZnSnO3 to ethanol gas can be ascribed to the large specific surface area and the abundant surface defects induced by Rb incorporation. We believe that this study opens up a new perspective for developing efficient and high-performance ethanol gas sensor.

Recent Advances in Engineering of 2D Layered Metal Chalcogenides for Resistive-Type Gas Sensor.

2D nanomaterials have triggered widespread attention in sensing applications. Especially for 2D layered metal chalcogenides (LMCs), the unique semiconducting properties and high surface area endow them with great potential for gas sensors. The assembly of 2D LMCs with guest species is an effective functionalization method to produce the synergistic effects of hybridization for greatly enhancing the gas-sensing properties. This review starts with the synthetic techniques, sensing properties, and principles, and then comprehensively compiles the advanced achievements of the pristine 2D LMCs gas sensors. Key advances in the development of the functionalization of 2D LMCs for enhancing gas-sensing properties are categorized according to the spatial architectures. It is systematically discussed in three aspects: surface, lattice, and interlayer, to comprehend the benefits of the functionalized 2D LMCs from surface chemical effect, electronic properties, and structure features. The challenges and outlooks for developing high-performance 2D LMCs-based gas sensors are also proposed.

Wearable Inorganic Oxide Chemiresistor Based on Flexible Al2O3-Stabilized ZrO2 Ceramic Sponge Substrate for NO2 Sensing.

Wearable gas sensors, possessing the advantages of high sensitivity, excellent flexibility, high permeability, low weight, and workability at ambient conditions, hold great promise for real-time health monitoring and early warnings of poisonous gases. However, obtaining high-performance wearable gas sensors utilizing the current well-developed inorganic semiconductor oxide sensing materials is still very limited due to their fragile and rigid nature. Herein, a newly designed wearable gas sensor based on an all-inorganic ASZ (Al2O3-stabilized ZrO2)/ZnO/SnO2 nanofibers is introduced for the first time. The flexible ASZ ceramic sponge substrate (with a Young's modulus of 4.15 MPa) and ultrathin ZnO/SnO2 sensing layer endow the wearable gas sensor with promising properties such as super flexibility (with a bending radius of 5 mm), high gas permeability, and low weight. Furthermore, driven by UV light irradiation, this all-inorganic wearable sensor also demonstrates a stable NO2 sensing response under different bending states at room temperature, which enables the gas sensor to be more compatible with wearable sensing applications. This work offers a general method to achieve a high-performance wearable gas sensor based on inorganic materials and provides new insights into their potential in wearable gas-sensing applications.

Construction of a novel Mott-Schottky heterostructure gas sensor g-C3N4/SnO2 with layered nanorods array for high-sensitivity acetone detection

Developing exhaled acetone sensors with high performance can be effectively applied to the medical diagnosis and the health monitoring. Herein, a two-dimensional (2D) layered graphitic carbon nitride (g-C3N4) with tunable electronic structure, abundant edge sites, and high stability is proposed, and it is further coupled with stannic oxide (SnO2) by one-step hydrothermal approach to construct a Mott-Schottky heterostructure with layered nanorods array. The exceptional response of the as-fabricated g-C3N4/SnO2 gas sensor to 50 ppm acetone at 100 °C is four times higher than that of the pristine SnO2 sensor. Additionally, the g-C3N4/SnO2 sensor’s remarkable selectivity, long-term stability against acetone gas, and detection limit of 250 ppb are exhibited. The unique hierarchical design and the Mott-Schottky heterostructure creation which validated by electrochemical study, may be in charge of the enhanced acetone sensing capabilities of g-C3N4/SnO2 gas sensor. This work will provide a concise and effective avenue to construct hierarchical composite with Mott-Schottky heterostructure for high-performance acetone gas sensor.

Facile synthesis of ultrafine WO3 nanoparticles for highly sensitive acetoin biomarker gas detection

Facile synthesis of metal oxide semiconductors (MOSs) nanoparticles with ultrafine size is quite promising to improve gas sensing performance due to the large effect of the particle size on the electron depletion layer (EDL), however, which is currently difficult to realize. In this work, we synthesized ultrafine WO3 nanoparticles of 20 ∼ 30 nm via room-temperature hydrolysis with following annealing and investigated the gas sensing performance of the WO3 nanoparticles towards acetoin biomarker released by Listeria monocytogenes (LMs). The WO3 gas sensor displays high response (Ra/Rg = 32.0@5 ppm), excellent selectivity and low detection limit at 140 °C. The ultrafine size of WO3 comparable to its Debye length can lead to a larger variation of EDL thus a higher sensor response. Our work has provided a facile, low cost and large-scale synthetic route to constructing high-performance acetoin biomarker gas sensors and might contribute to the development for LMs detection.

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

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