Gas Sensor Applications Research Articles

DFT Study on the Janus ZrSSe Monolayer for Its Potential Application in NO Gas Sensing.

The growth of industry has resulted in increased global air pollution, necessitating the urgent development of highly sensitive gas detectors. In this work, the adsorption of the Janus ZrSSe monolayer for CO, CO2, NH3, NO, NO2, and O2 was studied by first-principles calculations. First, the stability of the ZrSSe monolayer is confirmed through calculations of cohesive energy and AIMD simulations. Furthermore, the calculations indicate that the Se layer exhibits higher selectivity and sensitivity toward gas molecules compared to the S layer. Specifically, among the gases adsorbed on the Se layer, NO has the shortest adsorption distance (1.804 Å), the lowest adsorption energy (-0.424 eV), and the greatest electron transfer (0.098 e). Additionally, density of states analysis reveals that adsorption of NO, NO2, and O2 on the Janus ZrSSe monolayer can induce a transition from a nonmagnetic to a magnetic state. The adsorption of NO not only alters the magnetic state but also induces a transition from a semiconductor to metal, which is highly advantageous for gas sensing applications. There results suggest that the Janus ZrSSe monolayer has the potential to serve as a highly sensitive detector for NO gas.

Investigating the adsorption performance of agricultural greenhouses hazardous gases on Rh doped HfX2 (X=S, Se) monolayers through DFT for potential gas sensor applications

This study uses density functional theory to study the adsorption performance of agricultural greenhouses hazardous gases on Rh doped HfX2 (X=S, Se) monolayers. After multiple geometric optimizations, the most stable adsorption configuration was found. The results indicate that the adsorption energy of Rh doped HfX2 monolayers is very stable for adsorbing small molecule gases. The change in the total density of states of the adsorption system reveals the transfer and recombination of electrons during the adsorption process, and the partial density of states helps to understand the interactions between bonding atoms. Molecular orbital analysis shows that LUMO is mainly concentrated near Hf atoms, while HOMO is mainly concentrated near X atoms, Rh atom, and gases. By calculating the work function, the interaction strength and electron transfer mechanism between the adsorbent and the metal surface are revealed. In addition, the recovery time indicates that HfX2 and Rh-HfSe2 are excellent adsorbents for these four gases at room temperature, but when HfS2 operates at 473 K, it will be an efficient and excellent gas sensor for the four gases. Thus, Rh-HfS2 can be a feasible resistance sensing material for Cl2 and SO2. This DFT results provide a theoretical basis for potential gas sensor applications of Rh doped HfX2 (X=S, Se) monolayers, leading to the design and development of more efficient greenhouse gas identification sensor devices.

Synthesis, characterization, and gas-sensing application of Cd0.5Zn0.5NdxFe2–xO4 nanoparticles

Fabrication of Cd0.5Zn0.5NdxFe2–xO4 nanoparticles, with x = 0.00, 0.01, 0.02, 0.04, 0.06, and 0.08, has been carried out using a wet chemical co-precipitation method. The effect of the rare earth Nd3+ doping on the prepared ferrites was structurally investigated using x-ray diffraction (XRD) along with Rietveld refinement. The results indicate great crystallinity in the FCC Fd3m spinel structure of Cd0.5Zn0.5NdxFe2–xO4 nanoparticles. The lattice parameter increases with the increase of doping concentration from 8.5378 until 8.5432 Å and the crystallite size obtained using Debye-Sherrer, Williamson–Hall, Size-strain plot (SSP), and Halder-Wagner (H-W) methods, decreases until the solubility limit of the materials is at x = 0.04. By using transmission electron microscopy (TEM), the morphological analysis reveals the spherical shape of the samples with minor agglomeration with the aid of using a Polyvinylpyrrolidone (PVP) capping agent. The grain size ranges from 14.37 to 15.24 nm. Raman spectroscopy verifies the incorporation of Nd3+ in the octahedral sites and the decrease in particle size. The elemental composition was verified using x-ray photoelectron spectroscopy (XPS). The magnetic properties were studied using a vibrating sample magnetometer (VSM) and it shows superparamagnetic behavior with a decrease in the saturation magnetization from 2.207 to 1.918 emu g−1 and an increase in coercivity from 7.194 to 14.397 G. The prepared materials were tested as liquefied petroleum gas (LPG) sensors by studying their sensitivity, selectivity, optimum working temperature, response, and recovery times. Nd3+ doping shows a great increase in LPG sensing sensitivity 4 to 20 times than the pure samples. The doping concentration also decreases the response and recovery times.

Architectures of MoS2/SnO2 nanoflowers for NO2 gas detection

In this research, a two-step hydrothermal technique is used to fabricate a NO2 gas sensor based on MoS2 nanoflowers with SnO2 nanoparticles. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), were used to determine the morphologies, nanostructures, and compositions of the materials. The nanocomposites consisting of MoS2/SnO2 demonstrated a remarkable sensing response (38.6) towards 100 ppm of NO2. Moreover, the nanocomposites showed a rapid response and recovery time (42/147 S) when exposed to 100 ppm at temperature (250 °C). The MoS2/SnO2 nanocomposites demonstrated exceptional selectivity to NO2 against CO, NH3, and H2S, as well as demonstrated good repeatability. The significant gas detection characteristics could potentially be controlled by the distinctive structures of thin layers assembled into flower-like formations of two-dimensional MoS2. The multi-joint nanostructures promote the process of transferring the electrical charge of the carrier and the response to MoS2/SnO2 and NO2. The fabricated sensors are considered as potential candidates for the commercial in the nitrogen dioxide gas-sensing applications.

Self-Assembled Ti3C2TX MXene Thin Films for High-Performance Ammonia Sensors

MXenes have emerged as a fascinating material for RT gas-sensing applications due to their outstanding properties. This work reports the design and fabrication of a high-performance ammonia sensor based on MXenes material. To improve its sensing performance, a MXenes nanosheets thin film with a thickness of ≈ 10 nm was prepared using a scalable self-assembled method. Specifically, we employed the controlled and enhanced interfacial self-assembled method to fabricate a continuous and conductive MXene ultra-thin film. The morphology and the structure of the produced MXene materials and their films were characterized by combining multi-characterization tools. Altoghether, these highlight the uniform and continuous deposition of the MXene nanosheets film on the glass substrate. The electrical characterization indicates a sheet resistance value of 4.82 × 105 Ω/sq. The fabricated devices present good RT sensing performances for NH3 detection, ranging from 1 to 20 ppm. This demonstrates the outstanding sensitivity of MXene with a value of 1.92 % for the lowest concentration (1 ppm), a fast response (179 s) and a recovery time of (612 s), which is related to the high quality of the ultra-thin MXene sensiting layer. Moreover, the sensors demonstrate high degree of stability and excellent reproducibility, make them suitable candidate for practical applications like environmental monitoring.

Electrohydrodynamic-Jet-Printed SnO2-TiO2-Composite-Based Microelectromechanical Systems Sensor with Enhanced Ethanol Detection.

Ethanol sensors have found extensive applications across various industries, including the chemical, environmental, transportation, and healthcare sectors. With increasing demands for enhanced performance and reduced energy consumption, there is a growing need for developing new ethanol sensors. Micro-electromechanical system (MEMS) devices offer promising prospects in gas sensor applications due to their compact size, low power requirements, and seamless integration capabilities. In this study, SnO2-TiO2 nanocomposites with varying molar ratios of SnO2 and TiO2 were synthesized via ball milling and then printed on MEMS chips for ethanol sensing using electrohydrodynamic (EHD) printing. The study indicates that the two metal oxides dispersed evenly, resulting in a well-formed gas-sensitive film. The SnO2-TiO2 composite exhibits the best performance at a molar ratio of 1:1, with a response value of 25.6 to 50 ppm ethanol at 288 °C. This value is 7.2 times and 1.8 times higher than that of single SnO2 and TiO2 gas sensors, respectively. The enhanced gas sensitivity can be attributed to the increased surface reactive oxygen species and optimized material resistance resulting from the chemical and electronic effects of the composite.

2H-SnS2 assembled with petaloid 1T@2H-MoS2 nanosheet heterostructures for room temperature NO2 gas sensing.

In this study, we explored the gas-sensing capabilities of MoS2 petaloid nanosheets in the metallic 1T phase with the commonly investigated semiconducting 2H phase. By synthesizing SnS2 nanoparticles and MoS2 petaloid nanosheets through a hydrothermal method, we achieve notable sensing performance for NO2 gas at room temperature (27 °C). This investigation represents a novel study, and to the best of our knowledge no, prior similar investigations have been reported in the literature for 1T@2HMoS2/SnS2 heterostructures for room temperature NO2 gas sensing. The formed heterostructure between SnS2 nanoparticles and petaloid MoS2 nanosheets exhibits synergistic effects, offering highly active sites for NO2 gas adsorption, consequently enhancing sensor response. Our sensor demonstrated a remarkable sensing response (R a/R g = 7.49) towards 1 ppm of NO2, rapid response time of 54 s, baseline recovery in 345 s, good selectivity and long-term stability, underscoring its potential for practical gas-sensing applications.

Understanding the NaxMnO2 System: A Thermodynamics and XPS Approach.

The NaxMnO2 system is an important class of materials with potential applications in rechargeable batteries, supercapacitors, catalysts, and gas sensors. This work reports the synthesis of NaxMnO2 (x = 0.39, 0.44, 0.48, 0.66, and 0.70) compounds and their characterization by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and impedance spectroscopy (IS) techniques. The compounds in this series exhibit a significant variation in their structures with the extent of Na-content. The change in the nature of bonding with increasing Na content was investigated, and its effect on material stability as well as electrotransport properties was investigated. A detailed thermodynamic evaluation of these materials was carried out employing calorimetric techniques, and the data were correlated with changes in the chemical environment around the Na ion. This analysis is crucial for predicting the thermodynamic stability of NaxMnO2 compounds under different environments for their applications in Na-ion batteries.

Synthesis, characterization and sensing applications of TiO2 doped MOF composites for selective detection of ammonia at room temperature

Herein, we have developed a highly sensitive chemiresistive TiO2 doped metal–organic framework(MOF) composite-based sensor for ammonia detection at room temperature. Two novel Ti-MOFs@TiO2 composites are developed employing terephthalic acid and 2-amino terephthalic acid as organic linkers with Titanium tetra isopropoxide (TTIP) as a metal source by solvothermal technique. The morphology and crystallinity of synthesized compounds were characterized by using Field-emission scanning electron microscopy (FE-SEM) with EDX analysis, X-ray diffraction (PXRD), XPS and Brunauer–Emmett–Teller (BET) analysis techniques. MIL-125@TiO2 sensors exhibited a more specific surface area (374.74 m2 g−1) than the other three compounds. For gas-sensing applications, all composite materials were exposed to different gas vapours like ammonia, formaldehyde, acetic acid, ethyl alcohol, acetone, xylene, toluene and benzene at room temperature. The sensing results indicate that the sensors exhibit excellent response at low concentrations of ammonia, formaldehyde and acetic acid gases (1 ppm level). The enhanced sensor response was attributed to MIL-125@TiO2 (85 response at 50 ppm) and NH2-MIL-125@TiO2 (71 response at 50 ppm) towards ammonia gas and shows a better selectivity, sensitivity and repeatability to ammonia gas. All the materials exhibited less response times (between 8 and 45 sec) and more recovery times (between 13 and 125 sec).

Nebulized spray pyrolysis deposited CdO thin films for liquefied petroleum gas and ethanol gas sensor

High quality cadmium oxide (CdO) thin films were prepared through an inexpensive and simple nebulized Spray Pyrolysis (neb-SP) technique. The transparent conducting CdO thin films deposited at different substrate temperatures (TS) for the ethanol and liquefied petroleum gas (LPG) sensor application. XRD, SEM, UV–vis Spectroscopy and Hall Effect were done to study the structural, morphological, optical and electrical properties respectively. Polycrystalline nature thin films shows (1 1 1) cubic structure as the prominent peak. Surface morphology studies reveal that the grain size and roughness of the films are increased with increase in the substrate temperature. The average transmittance of the yellowish transparent CdO thin films is about 57%, thus the films are transparent in the visible region. The optical band gap (Eg) value of the CdO films increased from 2.16 to 2.28 eV with increase in the TS from 225 °C to 300 °C. The minimum value of electrical resistivity of the films is 1.40 × 10−3 Ωcm obtained at 275 °C. The neb-SP deposited CdO thin film (275 °C) shows maximum response to the ethanol and LPG gas sensitivity of 31.87% and 16.4% respectively at operating temperature of 573 K. Thus the results authenticate that the CdO thin films deposited low substrate temperature with high quality can be achieved via neb-SP technique compared to other wet chemical or physical method.

Synthesis, Characterisation, and Applications of TiO and Other Black Titania Nanostructures Species (Review)

Black titania, a conductive ceramic material class, has garnered significant interest due to its unique optical and electrochemical properties. However, synthesising and properly characterising these structures pose a considerable challenge. This diverse material family comprises various titanium oxide phases, many of them non-stoichiometric. The term “black TiO2” was first introduced in 2011 by Xiaobo Chen, but Arne Magneli’s groundbreaking discovery and in-depth investigation of black titania in 1957 laid the foundation for our understanding of this material. The non-stoichiometric black titanium oxides were then called the Magneli phases. Since then, the science of black titania has advanced, leading to numerous applications in photocatalysis, electrocatalysis, supercapacitor electrodes, batteries, gas sensors, fuel cells, and microwave absorption. Yet, the literature is rife with conflicting reports, primarily due to the inadequate analysis of black titania materials. This review aims to provide an overview of black titania nanostructures synthesis and the proper characterisation of the most common and applicable black titania phases.

Optical and ammonia sensing properties of Mn doped ZnO nanostructured films for gas sensors application

Optical and ammonia sensing properties of Mn doped ZnO nanostructured films for gas sensors application

Synthesis and Characterization of Mg-doped ZnO Nanoparticles for Gas-sensing Applications

Synthesis and Characterization of Mg-doped ZnO Nanoparticles for Gas-sensing Applications

Synthesis and Characterization of Nanostructured Cerium-Doped Zinc Oxide Thin Films for Selective Nitrogen Dioxide Gas Sensing Applications

Zinc oxide thin films doped with cerium were synthesized through facile spray pyrolysis technique and subsequently characterized via an array of analytical methods, including X-ray diffraction, ultraviolet-visible diffused reflectance absorption spectroscopy, photoluminescence, scanning electron microscopy and energy-dispersive X-ray spectroscopy techniques. The operative mechanism of the semiconductor metal oxide gas sensors is predicated on the modulation of electrical conductivity in response to varying gaseous atmospheres, under the influence of disparate thermal conditions. The nitrogen dioxide gas-sensing performance of the films demonstrated a noteworthy gas response of 18% at an elevated temperature of 400°C for a concentration of 100 ppm, accompanied by rapid response and recovery times of 23 and 60 s, respectively.

Exploring the ammonia gas sensing properties of Gd doped CeO2 thin films deposited by spray pyrolysis method

The present study investigates the synthesis and characterization of Gd-doped CeO2 thin films using a simple nebulizer spray pyrolysis method for ammonia sensing application. The films were prepared with varying Gd concentrations from 1 to 5 wt%. The structural, morphological, and optical properties of the samples were analyzed to examine the effect of Gd doping on physical parameters, and the results show that the 4 wt% Gd doped sample exhibits the highest crystallite size, uniform particle size distribution, and a smaller optical band gap. Additionally, the presence of defects and oxygen vacancies in the host lattice is enhanced in this sample. The gas sensing properties of the 4 wt% Gd doped CeO2 exhibits a gas responsivity of 731 %, rise time of 10.4 s, and fall time of 9.2 s indicating that the fabricated thin film sensor was found to be ideal for room temperature gas sensing application. Overall, the study demonstrates that the 4 wt% Gd doped CeO2 thin film is a promising candidate for commercial gas sensor applications.

Fabrication of crystalline silicon nanowires coated with graphene from graphene oxide on amorphous silicon substrate using excimer laser

In this work, we report a single-step graphene-coated crystalline silicon nanowires (SiNWs) manufacturing technique. We report a one-step fabrication technique of SiNWscoated reduced graphene oxide using a krypton fluoride (KrF) excimer laser. The SiNWs have been manufactured by redistributing the silicon mass within the sample without etching any of the deposited amorphous silicon (a-Si) and then adding a synthesized graphene oxide suspension using the modified Hummers' method. The process is optimized to ensure that the graphene is completely reduced and that the crystalline nanowires are formed. In order to allow full control of the dimension of the generated nanowires, the properties of the excimer laser have been investigated. Additionally, graphene-coated Si nanowires have also been synthesized to be used for gas-sensing applications in the future. In this work, we are eviting the repetition of the previously published work by the same research group for the sake of brevity. But the reader can refer to the previously published work on the study of the effect of different parameters on the SiNWs growth like the study of the effect of changing the normalized frequency on the size of the grown SiNWs in terms of length and diameter as well as other parameters mentioned in the previously published work in the references.

Synthesis and Characterization of Co2O3 Thin Films by Pulsed Laser Deposition Method and Investigation Zscan and Gas Sensing Applications

Synthesis and Characterization of Co2O3 Thin Films by Pulsed Laser Deposition Method and Investigation Zscan and Gas Sensing Applications

Enhanced Ethanol Gas Sensor Performance through Adsorption Energy Analysis of Gd-Doped LaFeO3 with rGO Coating: A Density Functional Theory Study

LaFeO3 (LFO) is commonly used as a material for gas sensor applications. However, the LFO material in ethanol gas sensor applications can still improve sensitivity and selectivity parameters. Gadolinium (Gd) doping is widely used in gas sensor applications to increase the sensitivity of gas sensors. In addition, reduced graphene oxide (rGO) materials are commonly used in gas sensor applications to increase gas sensors' selectivity, sensitivity, and working temperature. This study analyzed the effect of Gd doping (LGFO) and the addition of an rGO single layer on LFO material (LGFO@rGO) on sensitivity and selectivity based on the adsorption energy of the system with ethanol gas molecules. Density Functional Theory studies were conducted to yield insight into the LGFO or LGFO@rGO – ethanol gas interactions and the sensitivity and selectivity improvement by changing adsorption energy. Based on the analysis, the presence of Gd doping and single-layer rGO could increase the adsorption energy. The addition of the rGO layer showed an escalation of the adsorption energy of about 9.45%, 2.49 eV in the LGFO to -2.75 eV LGFO@rGO. This improved adsorption capacity translates to a higher sensitivity for detecting lower concentrations of ethanol gas. This result shows the potential of LGFO and LGFO@rGO as ethanol gas sensor materials.

ZnO/TiO2 hetero-structured nanosheets for effectively detecting formaldehyde at room temperature

In this study, ZnO/TiO2 nanosheets were synthesized using a hydrothermal method followed by annealing. The resulting hierarchical ZnO–TiO2 heterostructures exhibited improved gas-sensing performance compared with pure ZnO. We demonstrated that tuning the ratio of Zn to Ti components in the heterostructure allowed us to adjust the sensor stability, with the best- performing sample having a Zn:Ti ratio of 2:1. A notable reduction was observed in both the sensor response and recovery times, down to 22 and 17 s, respectively, by utilizing nanosheet- structured ZnO/TiO2 heterojunctions. To gain insight into the interaction between the sensing materials and formaldehyde (HCHO) molecules, we performed first-principles calculations to examine the density of states, charge transfer, and energy of adsorption. Our approach to constructing heterogeneous structures contributes to overcoming the low desorption efficiency and slow response-recovery time of pure ZnO for gas-sensing applications.

Optical properties of NiO films: Effect of nitrogen-doping, substrate temperature and band gap estimation using machine learning

In this study, nickel oxide (NiO) thin films were synthesized on glass substrates using RF magnetron sputtering with varying nitrogen (N) doping ratio and substrate temperatures to explore modifications in their structural, morphological, and optical properties. The films were prepared using a high-purity NiO target under controlled sputtering conditions. Structural analysis by X-ray diffraction revealed an improvement in crystallinity in the (200) direction with increasing N ratio. In contrast, higher N ratio led to the suppression of (111) and (220) peaks, indicating a significant influence of N on the crystal structure and orientation. The films’ thickness and morphology, examined using scanning electron microscopy and energy-dispersive X-ray spectroscopy, showed uniform and homogeneous growth with smooth surface topologies. Optical properties, assessed by UV–Vis-NIR spectrophotometry, demonstrated a decrease in transmittance and a redshift in the absorption edge with increased N doping, corresponding to a narrowing of the energy bandgap from 3.7 eV to 3.45 eV. This bandgap reduction is attributed to N incorporation substituting oxygen sites, introducing defect states within the band structure. Additionally, the impact of substrate temperature on film growth enhanced crystallinity and orientation along the (111) plane at higher temperatures, with a simultaneous reduction in film thickness due to increased adatom mobility and potential thermal decomposition. The evaluation of Kernel Ridge Regression (KRR) and Ridge Regression (RR) models revealed their effectiveness in predicting band gap values for thin films at varying substrate temperatures and thicknesses. While RR excelled in predicting a band gap of 3.6 eV for a film with a substrate temperature of 24 °C and a thickness of 112.7 nm, KRR outperformed in predicting a band gap of 3.65 eV for a film with a substrate temperature of 24 °C and a thickness of 107 nm. These findings elucidate the dual influence of N doping and substrate temperature on enhancing the functional properties of NiO thin films, promising for applications in optoelectronic devices and gas sensors.