Gas Sensors Research Articles

Highly Sensitive Diethylamine Detection at Room Temperature Using g-C3N4 Nanosheets Decorated with CuO Hollow Polyhedral Structures.

Chemiresistive-based metal oxide semiconductor (MOS) gas sensors are widely used in gas sensing due to their advantageous properties. Graphitic carbon nitride (g-C3N4) and metal oxide heterostructure materials can improve charge transport properties, selectivity, and sensitivity in MOS gas sensor materials. Herein, for the first time, CuO hollow polyhedral structures (HPSs) were synthesized via a hydrothermal technique and annealed at different temperatures, with the 400 °C annealed (CuO-400 HPSs) demonstrating remarkable sensing capabilities for diethylamine (DEA) gas at room temperature (RT). The x-g-C3N4 nanosheets were decorated with CuO HPSs in varying amounts (x = 0.8, 1.8, 2.1, and 3.1 wt %) and then annealed at 400 °C for x-g-C3N4-CuO-400 hollow polyhedral heterostructures (HPHSs). Indeed, among the synthesized samples, the 1.8%-g-C3N4-CuO-400 HPHSs have a higher sensitivity to DEA (resistance change in gas (Rg) and air (Ra); Rg/Ra= 65 @ 20 ppm), a low detection limit (Rg/Ra= 6 @ 500 ppb), wide dynamic response (Rg/Ra= 190 @ 80 ppm), strong stability (30 days), and 21.6 times higher sensitivity than pure CuO at RT toward 20 ppm of DEA. The exceptional gas-sensing behavior can be attributed to various factors, including controlled annealing conditions that result in the formation of well-defined structures and greater porosity, efficient charge transfer properties resulting from an optimized ratio of g-C3N4 to CuO in HPHSs, an abundance of defects, unsaturated Cu sites, and synergistic effects. The study presents a universal strategy for generating sensitive and selective g-C3N4-based composite materials for low-temperature gas sensors.

Printable MXene Ink Hybridized with ZSM-5 for Gas Sensing and CO2 Capturing

MXene has garnered significant attention as a two-dimensional material with exceptional physicochemical properties for gas sensing development. This study utilized ZSM-5 nanoparticles loaded with MXene to prepare printable inks, aiming to explore novel applications of MXene in the gas sensing field. The morphology of MXene/ZSM-5 was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), demonstrating the typical layered structure of MXene and particle morphology of composite ZSM-5. X-ray photoelectron spectroscopy (XPS) confirmed no production of TiO2 by providing valence information on elements. Thermogravimetric analysis (TG) revealed excellent thermal stability. To verify functional gas sensing feasibility, various hydrocarbons and common gases underwent adsorption and desorption tests (BET). Results showed that MXene loaded with ZSM-5 exhibited good adsorbability for C4H10, C7H8, SF6, H2O and O2 while having a certain trapping effect on CO2. Through testing and analyzing printing results, it was found that the MXene/ZSM-5 ink overcame dispersion issues present in pure MXene ink.

High selectivity and sensitivity through nanoparticle sensors for cleanroom CO2 detection

Clean room facilities are becoming more popular in both academic and industry settings, including low-and middle-income countries. This has led to an increased demand for cost-effective gas sensors to monitor air quality. Here we have developed a gas sensor using CoNiO2 nanoparticles through combustion method. The sensitivity and selectivity of the sensor towards CO2 were influenced by the structure of the nanoparticles, which were affected by the reducing agent (biofuels) used during synthesis. Among all reducing agents, urea found to yield highly crystalline and uniformly distributed CoNiO2 nanoparticles, which when developed into sensors showed high sensitivity and selectivity for the detection of CO2 gas in the presence of common interfering volatile organic compounds observed in cleanroom facilities including ammonia, formaldehyde, acetone, toluene, ethanol, isopropanol and methanol. In addition, the urea-mediated nanoparticle-based sensors exhibited room temperature operation, high stability, prompt response and recovery rates, and excellent reproducibility. Consequently, the synthesis approach to nanoparticle-based, energy efficient and affordable sensors represent a benchmark for CO2 sensing in cleanroom settings.

Highly sensitive acetone gas sensor based on gold nanoparticles modified W18O49 porous polymeric spheres

Highly sensitive acetone gas sensor based on gold nanoparticles modified W18O49 porous polymeric spheres

Micropatternable Ink Composed of MAX Phase ZIF-8 for Gas Sensing Applications

This work provides a detailed introduction to the preparation methods, structural characteristics, and various performance tests of the Ti3C2/ZIF-8 composite material. Initially, the composite material is obtained through the synthesis, mixing, and subsequent processing of MXene solution and ZIF-8 nanoparticles. The coating structure and properties were comprehensively characterized using SEM, TEM, and XRD. These analyses revealed the material's layered structure, high crystallinity, and surface activity. BET analysis of Ti3C2/ZIF-8 also shows excellent gas adsorption-desorption performance, having an especially high-efficiency adsorption capacity for VOCs. TGA further demonstrates the thermal stability and chemical stability of Ti3C2/ZIF-8 and its printability was tested indicating widespread application potential in coating preparation through ultrasonic spray technology. Finally, we show methods to regulate and control coating thickness and roughness for precision manufacturing. These analyses together emphasize the application value of Ti3C2/ZIF-8 in fields such as gas-storage, gas-separation, and environmental monitoring.

Strain and Electric Field Engineering of G-ZnO/SnXY (X, Y = S, Se) S-Scheme Heterostructures for Photocatalyst and Electronic Device Applications: A Hybrid DFT Calculation.

Using hybrid density functional theory calculations, we systematically study the biaxial strain and electric field modulated electronic properties of g-ZnO/SnS2, g-ZnO/SnSe2, and g-ZnO/SnSSe S-scheme van der Waals heterostructures (vdWHs). g-ZnO/SnS2 and g-ZnO/SnSSe are found to be promising photocatalysts for water splitting with high solar-to-hydrogen efficiencies, even under acidic, alkaline, and high-stress conditions. The strain effect on the bandgaps of g-ZnO/SnXY is explained in detail according to the correlation between geometry structure and orbital hybridization of SnXY, which could help understand the strain-induced band structure evolutions in other SnXY (X, Y = S, Se)-based vdWHs. It is surprising that under an external electric field, g-ZnO/SnS2, g-ZnO/SnSe2, and g-ZnO/SnSSe can offer the occupied nearly free-electron (NFE) states. In many materials, NFE states are usually unoccupied and is not conducive to the charge transport. The NFE state in g-ZnO/SnSe2 is the most sensitive to the electric field and might be promising electron transport channel in nanoelectronic devices. g-ZnO/SnSe2 might also have application potential in gas sensors and high-temperature superconductors.

Achieving Room-Temperature ppb-Level H2S Detection in a Au-SnO2 Sensor with Low Voltage Enhancement Effect.

Although semiconductor metal oxide-based sensors are promising for gas sensing, low-power and room temperature operation (24 ± 1 °C) remains desirable for practical applications particularly considering the request of energy saving or net zero emission. In this study, we demonstrate a Au/SnO2-based ultrasensitive H2S gas sensor with a limit of detection (LOD) of 2 ppb, operating at very low voltages (0.05 to 0.5 V) at room temperature. The Au/SnO2-based sensor showed approximately 7 times higher response (the ratio of change in the current to initial current) of ∼270% and 4 times faster recovery (126 s) compared to the pure SnO2-based sensor when exposed to 500 ppb H2S gas concentration at 0.5 V operating voltage at relative humidity (RH) 17.5 ± 2.5%. The enhancement can be attributed to the catalytic characteristics of AuNPs, increasing the number of adsorbed oxygen species on sensing material surfaces. Additionally, AuNPs aid in forming flower-petal-like Au/SnO2 nanostructures, offering a larger surface area and more active sites for H2S sensing. Moreover, at low voltage (<1 V), the localized dipoles at the Au/SnO2 interface may further enhance the absorption of polar oxygen molecules and hence promote the reaction between H2S and oxygen species. This low-power, ultrasensitive H2S sensor outperforms high-powered alternatives, making it ideal for environmental, food safety, and healthcare applications.

Conductivity and response formation of semiconductor gas sensors based on tin dioxide nanomaterials

Conductivity and response formation of semiconductor gas sensors based on tin dioxide nanomaterials

Correlation between CO2 Sensitivity and Channel-Layer Thickness in In2O3 Thin-Film Transistor Gas Sensors

Correlation between CO2 Sensitivity and Channel-Layer Thickness in In2O3 Thin-Film Transistor Gas Sensors

Enhancing Structural Integrity, Optical Properties, and Room Temperature Formaldehyde Sensing Through Optimized Spray Deposition Rates

This study explores the impact of deposition rate on the properties of TiO2 thin films produced via spray pyrolysis, focusing on their application in gas sensors. The analysis covers structural, morphological, optical, and gas sensing characteristics of TiO2 films deposited at rates between 1 and 2.5 ml min−1. Studies show optimizing TiO2 film deposition rates at 2 ml min−1 significantly enhances formaldehyde detection, improving selectivity and achieving a rapid response of 7.52 at 20 ppm concentration. This study underscores the pivotal role of deposition rate optimization in augmenting the gas-sensing efficacy of TiO2 films, particularly for formaldehyde detection at ambient conditions. Optimal deposition rates are instrumental in enhancing sensor performance. The synergistic application of XRD and Raman spectroscopy unequivocally confirmed the presence of the TiO2 anatase phase, which is of paramount significance in gas sensing applications. FESEM furnished high-resolution insights into the surface morphology, revealing a spherical architecture. Furthermore, UV–vis spectroscopy was employed to assess the optical band gap of the films, which exhibited a decrement correlating with the rate of deposition. Notably, a deposition rate of 2 ml min−1 markedly improved the TiO2 films’ sensing performance. These insights are critical for developing cost-effective, high-performance gas sensors for cutting-edge applications.

Lab-on-Device Synthesis of Hierarchical Macro/Mesoporous WO3 Semiconducting Films for High-Performance H2S Sensing.

The performance consistency of the gas sensor is strongly dependent on the interface binding between the sensitive materials and the electrodes. Traditional powder coating methods can inevitably lead to differences in terms of substrate-film interface interaction and device performance, affecting the stability and lifetime. Thus, efficient growth of sensitive materials on device substrates is crucial and essential to enhance the sensing performance, especially for stability. Herein, hierarchically ordered macro/mesoporous WO3 films are in situ synthesized on the electrode via a facile soft/hard dual-template strategy. Orderly arrayed uniform polystyrene (PS) microspheres with tailored size (ca. 1.2µm) are used as a hard template, and surfactant Pluronic F127 as a soft template can co-assemble with tungsten precursor into ordered mesostructure in the interstitials of PS colloidal crystal induced by solvent evaporation. Benefiting from its rich porosity and high stability, the macro/mesoporous WO3-based sensor shows high sensitivity (Rair/Rgas = 307), fast response/recovery speed (5/9 s), and excellent selectivity (SH2S/Smax > 7) toward 50ppm H2S gas (a biomarker for halitosis). Significantly, the sensors exhibit an extended service life with a negligible change in sensing performance within 60 days. This lab-on-device synthesis provides a platform method for constructing stable nanodevices with good consistency and high stability, which are highly desired for developing high-performance sensors.

Theoretical insights into the adsorption and gas sensing performance of Fe/Cu-adsorbed graphene.

The binding mechanism of gas molecules on material surfaces is essential for understanding adsorption and sensing performance. In the present study, we examine the interaction of some volatile organic compounds (VOCs), including HCHO, C2H5OH, and CH3COCH3, on pristine graphene and its Fe/Cu-adsorbed surfaces using first-principles calculations. The results indicate that the adsorption of these molecules on graphene is regarded as physisorption, while chemisorption is observed for Fe/Cu attached surfaces. The binding of sites on molecules and surfaces primarily involves hydrogen bonds for the pure form of graphene. In contrast, stable interactions occur at functional groups such as >CO, -OH with Fe/Cu atoms, as well as CC bonds of π-rings on modified structures of graphene. It is noticeable that stronger adsorption is observed in the case of Fe addition (Gr-Fe) compared to Cu (Gr-Cu), enhancing the gas adsorption and sensing performance on graphene. Remarkably, the graphene surfaces supported by Fe and Cu improved selectivity in detecting VOC molecules, particularly C2H5OH and CH3COCH3 for Gr-Fe, and HCHO for Gr-Cu. Quantum chemical analyses reveal that the Fe/Cu⋯O/C contacts are covalent interactions, contributing significantly to the stability of configurations and sensing properties of Fe/Cu-adsorbed graphene. In summary, the observed improvements in selectivity, enhanced adsorption strength, and the identification of crucial interactions at the surface offer valuable insights into designing highly efficient gas sensors and developing advanced sensing materials.

Preparation and Application of Rubber Fruit Shell Carbon as Decoration Material on ZnO for H2S Gas Sensors

Preparation and Application of Rubber Fruit Shell Carbon as Decoration Material on ZnO for H2S Gas Sensors

A Highly Selective MEMS-Based Gas Sensor With Gelatin-Carbon Black Composite Film Fabricated by the Thin-Film-Needle-Coating Method

A Highly Selective MEMS-Based Gas Sensor With Gelatin-Carbon Black Composite Film Fabricated by the Thin-Film-Needle-Coating Method

MgxNi1−xO-based Gas Sensors with Various Mg/Ni Ratios

MgxNi1−xO-based Gas Sensors with Various Mg/Ni Ratios

A sensitive methane gas sensor based on sagnac interferometer with a cryptophane-A film-coated birefringent photonic crystal fiber : design and FEM simulation

Abstract As being sensitive to methane gas, cryptophane-A is widely used in fiber optic methane gas sensors. In order to further improve the sensitivity, a Sagnac interference (SI) was constructed with a cryptophane-A film coated birefringent photonic crystal fiber (PCF) to realize the methane gas sensing. Cryptophane-A film absorbs the methane gas and as a result its refractive index decreases linearly with the increasing of methane gas concentration. Simulation results utilizing the finite element method demonstrate that sensitivity reaches 124.4 nm/% when the methane concentration ranges from 0% to 3.5%. The high sensitivity performance ensures a candidate of the designed sensor in early warning of methane gas leakage.&amp;#xD;

Microheaters for Thermal Analysis and Gas Sensing Applications

Microheaters for Thermal Analysis and Gas Sensing Applications

Resistive gas sensors for the detection of NH3 gas based on 2D WS2, WSe2, MoS2, and MoSe2: A review.

Transition metal dichalcogenides (TMDs) with a two-dimensional (2D) structure and semiconducting features are highly favorable for the production of NH3 gas sensors. Among the TMD family, WS2, WSe2, MoS2, and MoSe2 exhibit high conductivity and a high surface area, along with high availability, reasons for which they are favored in gas-sensing studies. In this review, we have discussed the structure, synthesis, and NH3 sensing characteristics of pristine, decorated, doped, and composite-based WS2, WSe2, MoS2, and MoSe2 gas sensors. Both experimental and theoretical studies are considered. Furthermore, both room temperature and higher temperature gas sensors are discussed. We also emphasized the gas-sensing mechanism. Thus, this review provides a reference for researchers working in the field of 2D TMD gas sensors.

Enhanced Gas Sensing Characteristics of a Polythiophene Gas Sensor Blended with UiO‐66 via Ligand Functionalization

Enhanced Gas Sensing Characteristics of a Polythiophene Gas Sensor Blended with UiO‐66 via Ligand Functionalization

Rod-Like MnMoO4 with Excellent Electrochemical Performance as Sensing Material to Detect Triethylamine

Rod-Like MnMoO4 with Excellent Electrochemical Performance as Sensing Material to Detect Triethylamine