Resistive-type Gas Sensors Research Articles

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.

Impact of Ag2O on the gas sensing properties of the star-shaped BaTiO3/ZnO heterostructures

In this work, star-shaped heterostructures of Ag2O/BaTiO3/ZnO were proposed as resistive-type gas sensors. Through combined analyzes of XRD, SEM, and EDS, the structure, surface morphology, and the elemental composition of the synthesized materials were confirmed. The star-shaped morphology of BaTiO3/ZnO was found to be intact even after loading with different quantities of Ag2O, as revealed by the SEM analysis. The impact of loading different amounts of Ag2O (ranging from 1 % to 3 %) on the sensors' ability to detect volatile organic compounds (VOCs) and carbon dioxide (CO2) was concretely gauged by their response, response/recovery times, selectivity, and long-term stability. For the detection of ethanol/acetone, CO2, and methanol, a 1:2 M ratio of BaTiO3/ZnO with 1 % and 2 % Ag2O, and a 1:3 M ratio of BaTiO3/ZnO with 1 % Ag2O were determined as the optimum content, respectively. From the gas sensing analysis, Ag2O/BaTiO3/ZnO sensors with different amounts of Ag2O additive gave different optimal temperatures for different target gases. Lower operating temperatures, i.e. 180 °C, and 260 °C for CO2 and VOCs, respectively, rapid responsivity with a response time of <1 s for VOCs, and fast recovery times (as low as 10, 13, and 6 s for ethanol, acetone, and methanol vapors, respectively) were observed. More importantly, the sensor exhibited good selectivity for several possible interferences. The underlying reasons for the acceleration of the gas molecules adsorption, hence the fast sensor response, are the high specific surface area established by the star-shaped morphology, and compatible energy band alignment at the p/n interface coupled with the catalytic effect induced by Ag2O.

Defective Diamane: A Superior Sensor for Toxic Gases Capture and Detection with Excellent Selectivity, Sensitivity, and Reversibility at Room Temperature.

The toxic gases emitted from industrial production have caused significant damage to the environment and human health, necessitating efficient gas sensors for their detection and removal. In this work, first-principles calculations are employed to investigate the potential application of diamanes for high-performance toxic gas sensors. The results show that nine gas molecules (CO, CO2, NO, NO2, NH3, SO2, N2, O2, and H2O) are physisorbed on pristine diamane by weak van der Waals interactions. After introducing H/F defects, diamane can effectively capture specific toxic gases (CO, NO, NO2, and SO2) in the presence of interfering gases (N2, O2, and H2O), suggesting excellent selectivity and anti-interference ability. Orbital hybridization and significant charge redistribution between gas molecules and defective diamane dominate the enhanced adsorbate-substrate interactions. More importantly, the high sensitivity and good reversibility of defective diamane for detecting CO, NO, and SO2 molecules enable its reuse as a superior resistance-type gas sensor. Our calculations provide valuable insights into the potential of defective diamane for detecting toxic gases and shed light on the practical application of novel carbon-based materials in the gas-sensing field.

Fully Inkjet-Printed Gas-Sensing Antenna Based on Carbon Nanotubes for Wireless Communication Applications

This study presents a fully inkjet-printed antenna based on carbon nanotubes (CNTs) for ammonia-gas-sensing. The antenna-embedded CNT film must satisfy strict requirements in terms of resistance, uniformity, and stability. Various resistive-type gas sensors based on CNTs, which are controlled by droplet spacing (DS) and multiple passes, are realized by inkjet-printing technology to investigate their sensing characteristics. The gas response decreases with increasing CNT density; however, the distribution of repeatability is tighter because the connection junctions among CNTs increase and the conductive paths saturate. The relationship between CNT density and gas-sensing response is presented for the first time. According to the response of the resistive-type gas sensors, low resistance and stable sensing response of a DS = 20 μm and 20-pass CNT film is suitable for embedding into an antenna for gas-sensing. The sensitivities of insertion and return losses under exposure to NH3 of the gas-sensing antenna demonstrate a linear relationship and reproducibility. The gas-sensing antenna based on CNT films exhibits two-dimensional value responses, real-time gas detection, reproducibility, and reversibility, which provide a viable option for wireless sensing systems.

Exploration of Pt-doped Janus WSSe monolayer as a typical gas sensor for condition assessment in XLPE cables

To evaluate the operation status of the XLPE cables in the power system, we purpose Pt-doped WSSe (Pt-WSSe) monolayer as a novel gas sensor for detections of the XPLE typical gases under the insulation defects. The adsorption and sensing mechanisms of the Pt-WSSe monolayer upon five typical gases, namely CO, C2H6, C2H4O, C4H6O and C8H8O are uncovered in this work, using the first-principles theory. We find that the for Pt-doping on Se-surface of the Janus WSSe monolayer is more energy-favorable and chemical stable, with the formation energy of −0.29 eV, and the bandgap of the identified Pt-WSSe monolayer is obtained as 1.34 eV. Besides, the Pt-WSSe monolayer performs chemisorption upon CO, C2H4O, C4H6O and C8H8O molecules, while performs physisorption upon C2H6 molecule, and the adsorption energies are calculated as −1.88, −0.97, −0.77, −1.55 and −1.62 eV, respectively. These gas interactions deform the electronic property of the Pt-WSSe monolayer, causing the remarkably change in its bandgap, and the caused sensing responses indicate the strong potential to be a potential resistance-type gas sensor upon CO, C2H4O and C4H6O detections, with the sensing response of −93.4 %, −97.5 % and −99.7 %, respectively. Moreover, the limited change in the work function (WF) of Pt-WSSe monolayer suggests its unsuitability to be a WF-type gas sensor for detection of XLPE typical gas species. All these findings not only illustrate the Pt-doping behavior on the physicochemical properties of Janus WSSe monolayer, but also uncover the gas sensing mechanism of metal-doped Janus TMDs for explorations of novel sensing materials.

Optimization of the Technology of Creating Sensitive Gas Sensors Based on Zinc Oxide

The main achievements in the development of resistive type gas sensors are analyzed, in particular, the creation of nanostructures based on metal oxides, which make it possible to significantly improve the performance characteristics of the sensors. Experimental samples of the gas sensor based on ZnO were obtained by magnetron sputtering on direct current. The effectiveness of the gas sensor system for recognition and analysis of gases and their mixtures has been established. A study of the sensitivity of experimental samples to the influence of the target gas CO was carried out. The target gas concentration varied from 50 to 150 ppm. It was established that the ZnO-based gas sensor exhibits the highest sensitivity at a target gas concentration of 100 ppm. The sensitivity of the gas sensor increases with increasing exposure time to the target gas.

UV light activated g-C3N4 nanoribbons coated surface acoustic wave sensor for high performance sub-ppb level NO2 detection at room temperature

The demand for efficient gas sensors in detecting low ppb-level NO2 gas is increasing rapidly for the human life and environmental protection. In this regard, surface acoustic wave (SAW) based gas sensor with selectively coated one dimensional (1D) graphitic carbon nitride (g-C3N4/GCN) nanostructure interface layer is a viable strategy for the sub-ppb level NO2 gas detection at room temperature (RT∼30 °C). Here, we explore SAW gas sensor employed with 1D GCN nanoribbons (NRs) for NO2 detection under UV-irradiation at RT. Intriguingly, the GCN NRs SAW sensor achieves an ultrahigh frequency response (Δf∼28.13 kHz), short response/recovery times (131 s/116 s), excellent selectivity to NO2 (10 ppm) gas and also records a lowest detection limit (∼42 ppb) under UV activation at RT. The enhanced sensing performances were attributed to the high mass loading effect induced by the enhanced charge transfer between the 1D GCN NRs surface and NO2 gas molecules, boosted by the photoexcited charge carriers, numerous surface sites, and improved specific surface area of 1D GCN NRs. The proposed GCN NRs SAW sensor demonstrates exceptional repeatability, good long-term stability with a minimal loss in its Δf, and exhibited robust sensitivity towards NO2 (10 ppm) under diverse relative humidity conditions (0–80%) at RT. The peculiar sensing results of GCN NRs SAW sensor was elucidates using energy band theory sensing mechanism assisted with resistive type gas sensor. Overall, this study offers significant insights into the development of cost-effective real-time RT based NO2 sensor, paving the way for practical air quality monitoring.

Polymer sorted and released semiconductive single-walled carbon nanotubes for highly sensitive NH3 vapor detection

Carbon nanotubes (CNTs) are considered to be ideal channel materials for building highly sensitive gas sensors. However, achieving high purity of semiconductor single-walled carbon nanotubes (sc-SWCNTs) is still a challenging. In this research, fluorene, thiophene (side-chain imine-contained) and different molar ratio (0%, 15%, 33%, 50%, 67%) of pyrimidine contained donor-accepter type conjugated polymers were synthesized in order to separate the sc-SWCNTs from commercially available plasma SWCNTs, and the released sc-SWCNTs were applied to fabricate devices to detect the low concentrations of ammonia vapor. Based on UV characterization, the polymer with a ratio of 50% pyrimidine ring showed excellent selectivity to sc-SWCNTs, and purity of the released sc-SWCNTs reached to 99%. A comparative study of the sensing performance of resistive-type gas sensors based on four SWCNTs for ammonia vapor showed that the released sc-SWCNT-based sensor responds rapidly to ammonia vapor at ambient temperature and exhibits high response and selectivity. At the similar level of 5 ppm ammonia vapor concentration, the sensing response of the released sc-SWCNTs-based sensor (16.7%) was 1.1, 1.7, and 7.9 times higher than those of the polymer@sc-SWCNTs compound, sc-SWCNTs-excess polymer mixture and raw SWCNTs-based devices respectively. The theoretical detection limit of the released sc-SWCNTs-based device reached to 14.9 ppb.

Pristine and Ni-doped WTe2 monolayer for adsorption and sensing of C2H2 and C2H4 in oil-immersed transformers: A DFT study

Upon the adsorption and sensing of C2H2 and C2H4, we purpose pristine WTe2 monolayer as a promising candidate and uncover the enhanced mechanism of Ni-doping towards such two gas species in this work, using the density functional theory (DFT) method. Results show that pristine WTe2 monolayer performs physisorption upon C2H2 and C2H4 molecules with adsorption energies of −0.57 and −0.63 eV, and the small changes in its bandgap indicate the unsuitability for gas sensing use. The Ni-doping is energy-favorable with formation energy of −0.15 eV by substituting a Te atom on the WTe2 surface, and C2H2 and C2H4 adsorptions are both determined as chemisorption with adsorption energies of −1.40 and −1.22 eV. The electron redistributions are dramatically promoted in the Ni-WTe2/gas systems, and the obvious decrease of bandgap in Ni-WTe2 monolayer after C2H2 and C2H4 adsorptions, about 25.6% and 12.6%, suggests the strong potential for its exploration as a resistance-type gas sensor with sensing response of −97.8% and −85.4%. The analysis of recovery property reveals the reusability of Ni-WTe2 monolayer after several seconds exposure under UV light at 398 K. These findings give a deep insight into the WTe2-based gas sensor upon the typical gases in the transformer oil.

Conductometric sensor of hierarchical Bi2MoXW1−XO6 microcages in sensing three gases NH3, isopropanol and ethanol

Selective detection of multiple reducing gases on one resistive-type gas sensor is desired for highly integrated devices. In this work, we successfully synthesized porous Mo-doped Bi2WO6 microcages via one-step hydrothermal method with triple selectivity in sensing ammonia, isopropanol and ethanol. 1 at% Mo-doped Bi2WO6 microcages increase in resistance once exposed to reducing gases including isopropanol, acetone, CH4, CO and ethanol at room temperature (RT), revealing its p-type sensing nature. On the contrary, an opposite trend of resistance variation is observed in ammonia detection due to the unique sensing mechanism, leading to simultaneous ammonia and isopropanol selective sensing at RT. Ulteriorly, excellent selectivity to ethanol is achieved by modulating the operating temperature to 350 ℃. Interestingly, 1 at% Mo-doped Bi2WO6 microcages exhibit n-type sensing behavior at high temperatures. The corresponding p-to-n conductivity transition resulted from raising the operating temperature is clarified in detail.

Adsorption and sensing of dissolved gas molecules in transformer oil on Rh-doped MoTe2 monolayer: A first-principles study

Oil-immersed transformer plays a significant role in power systems, whose insulation failure will threaten the stable operation of the system, thus the requirements for its operational stability are higher. In this paper, the Rh-doped MoTe2 (Rh-MoTe2) monolayer is proposed for the detection of several typically dissolved gas molecules (CO, H2 and CH4) based on the first-principles density functional theory (DFT). It is found that the Rh dopant preferred to be adsorbed through the TMo site with maximum binding energy (Eb) of −3.43 eV. Then, the adsorption of Rh-MoTe2 on CO, H2 and CH4 molecules is investigated with adsorption energy (Ead). Furthermore, the band gaps of CO and H2 systems have significantly reduced, showing their excellent potential as resistance-type gas sensors; while CH4 is not suitable for detection due to the weak interaction. This study illustrates the physicochemical properties of Rh-MoTe2 monolayer and reveals its promising applications in dissolved gas analysis (DGA).

Ga-Doped ZnO Microbelts Based Resistive-type Sensor for Detection of Acetylene Gas

Structural materials with shorter gas diffusion pathways, lower electrical resistance, and crystal size play a vital role in resistive-type gas sensors. In the present work, ZnO was doped with Ga to lower its electrical resistance and inhibit crystal growth for acetylene sensing. Ga-doped ZnO microbelts were synthesized by electrospinning a solution containing metal precursors and quillaja saponin as a template for the evolution of the belt structure, followed by calcination to achieve microbelts with a BET surface area of 68.5 m2 g–1, an average pore size of 4.6 nm, and ZnO crystals as small as 16.5 nm. The Ga-doped ZnO microbelts exhibited a response (Ra/Rg) of up to 21.0, and a fast response (7.6 s) to 20 ppm acetylene at 400 °C in dry conditions. The materials also showed outstanding repeatability of response of 10.04 ± 0.04 against 10 cycles of 5-ppm acetylene, a response of 2.0 to acetylene as low as 0.2 ppm, and excellent selectivity against 5 ppm of hydrogen, pentane, toluene, carbon monoxide, and methane. The results suggested that Ga doping could effectively improve the electrical conductivity and acetylene sensing performance of ZnO-based sensors.

Sensing property of Pt-doped Janus SnSSe monolayer upon thermal runaway gases in the lithium-ion battery with effects of biaxial strains and electric fields

The sensitive detection of the thermal runaway gases has been proposed as a workable technique to conduct the thermal runaway analysis in a Li-ion battery. In this work, we propose the Pt-doped Janus SnSSe (Pt-SnSSe) monolayer as a promising sensing material for detections of three typical fault gases, namely CO, CO2 and C2H4, to realize the above purpose. Results show that the Pt dopant prefers to be anchored on the Se-surface of the pristine SnSSe monolayer, with the binding force (Eb) of − 1.36 eV; chemisorption is determined for CO and C2H4 systems with adsorption energy (Ead) of − 1.17 and − 0.92 eV while physisorption is determined for the CO2 system with Ead of − 0.13 eV. The analyses of band structure (BS) and density of state (DOS) reveals the deformed electronic property of Pt-SnSSe monolayer upon gas adsorptions, and the changes of bandgap in the gas adsorbed system manifest its potential as a resistance-type gas sensor with desirable sensitivity of − 99.5 % and − 97.1 % for CO and C2H4 detections. Moreover, the applied biaxial strains and electric fields in the CO and C2H4 systems demonstrate the tunable charge-transfer and bandgap of Pt-SnSSe monolayer upon their detections with admirable sensing response. The findings in this work uncover the desirable gas sensing potential of SnSSe-based material and the especial property of the Janus structure, which we hope can stimulate more edge-cutting studies in the gas sensing field.

Single Rh atom decorated pristine and S-defected PdS2 monolayer for sensing thermal runaway gases in a lithium-ion battery: A first-principles study

This work using the first-principles theory studies the physicochemical properties Rh-decorated pristine and S-defected PdS2 monolayer, named Rh@PdS2 and Rh-PdS2 monolayer, and their sensing performance towards the thermal runaway gases in the lithium-ion battery. Results indicate that the binding energies for such two systems are as -4.43 and -4.02 eV, respectively; two surfaces both behave chemisorption upon CO and C2H2 molecules while behave physisorption upon H2, CO2 and CH4 molecules. The analyses of band structure and density of states for gas adsorptions on Rh@PdS2 and Rh-PdS2 monolayer reveal the deformed electronic properties in two surfaces and the bonding nature, and their potentials as resistance-type gas sensors with better sensing and recovery performances in the Rh@PdS2/gas systems. The analysis of work function (WF) suggest the good potential of two surfaces as WF-based gas sensors with comparable performances. This work compares the electronic and sensing properties of two metal-doping manner on the PdS2 monolayer, uncovering the sensing potential of PdS2-based material upon gas species. We believe that the findings in this work would be beneficial to stimulate more researches to investigate the PdS2-based materials with different metal-doping methods for application in some other fields.

Adsorptions of C5F10O decomposed compounds on the Cu-decorated NiS2 monolayer: a first-principles theory

This study using the first-principles theory investigates the geometric and electronic properties of Cu-decorated NiS2 (Cu–NiS2) monolayer, and the adsorption and sensing performance of Cu–NiS2 monolayer upon five C5F10O decomposed species, in order to explore its potential to evaluate the operation status of C5F10O-based insulation devices. It is found that the Cu atom prefers to be trapped on the H1 site of the NiS2 monolayer with the formation energy of −3.09 eV without the cluster issue. The chemisorption is determined in the Cu–NiS2/C2F6O3 with an adsorption energy of −1.05 eV, while physisorption is identified in the C3F6, CF2O, C2F6 and CF4 systems. The analyses of electronic property and recovery property reveal the strong potential of Cu–NiS2 monolayer to be a reusable C3F6 or CF2O sensor at room temperature, to be a high-sensitive and one-shot C2F6O3 sensor instead and is not suitable for C2F6 and CF4 sensing due to the low sensitivity. This work is meaningful in terms of proposing novel sensing material for application in the power system to ensure the good operation of C5F10O-based insulation devices. Research Highlights Cu-decorating behaviours on a pristine NiS2 monolayer are studied. The sensing mechanisms of Cu–NiS2 monolayer upon five C5F10O decomposed species are expounded. The sensing potential of Cu–NiS2 monolayer as a resistance-type gas sensor is explored.

Research on synthesis of Cu&lt;sub&gt;3&lt;/sub&gt;Mo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt;/MoO&lt;sub&gt;3&lt;/sub&gt; nanocomposite and trimethylamine gas sensing properties

Aquatic products contain an incredibly high nutritional value for the human body and gradually become indispensable ingredients on the Chinese table. Trimethylamine (TMA) from the deterioration of aquatic products can serve as an indicator to measure fish freshness. It is a challenge to develop an instant, fast, convenient, and efficient gas sensor for fish freshness. In this study, a novel Cu&lt;sub&gt;3&lt;/sub&gt;Mo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt;/MoO&lt;sub&gt;3&lt;/sub&gt; composite gas sensing material is prepared by introducing Cu&lt;sub&gt;3&lt;/sub&gt;Mo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt; nanoparticles on the surface of MoO&lt;sub&gt;3&lt;/sub&gt; nanobelts. The results of SEM and TEM images show that the Cu&lt;sub&gt;3&lt;/sub&gt;Mo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt; nanoparticles are uniformly dispersed. Then, the TMA sensing performance of a resistance-type gas sensor based the prepared Cu&lt;sub&gt;3&lt;/sub&gt;Mo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt;/MoO&lt;sub&gt;3&lt;/sub&gt; composite is tested at optimal operating temperature (240 °C). the results show that the sensor possesses good response (13.9) at low concentration (5×10&lt;sup&gt;–6&lt;/sup&gt;), with excellent low detection limit (2×10&lt;sup&gt;–7&lt;/sup&gt;). The response time is also significantly shortened. The high sensing performance of Cu&lt;sub&gt;3&lt;/sub&gt;Mo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt;/MoO&lt;sub&gt;3&lt;/sub&gt; composite is attributed to the heterojunction interface, which promotes the separation of electrons from holes through its strong oxygen adsorption and catalytic effect. This significantly improves the electron transport properties and gas sensing characteristics of the composite material. Electrons flow from MoO&lt;sub&gt;3&lt;/sub&gt; nanoribbons to Cu&lt;sub&gt;3&lt;/sub&gt;Mo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt;, and the Fermi level reaches equilibrium. This process results in the formation of an electron loss layer underneath MoO&lt;sub&gt;3&lt;/sub&gt;, and the charge transfer channel narrows, which is consistent with previous result. When trimethylamine dissociates on the nanoribbons to release electrons, the balance of the fermi lever is disrupted, and electrons flow from MoO&lt;sub&gt;3&lt;/sub&gt; to Cu&lt;sub&gt;3&lt;/sub&gt;Mo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt;. As a result, the charge transfer channel becomes thinner, resulting in resistance modulation and increased sensitivity. In addition, the enhancement of trimethylamine sensing performance of Cu&lt;sub&gt;3&lt;/sub&gt;Mo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt;/MoO&lt;sub&gt;3&lt;/sub&gt; nanocomposite can be explained by the enhancement of gas adsorption and diffusion: MoO&lt;sub&gt;3&lt;/sub&gt; nanoribbons as a skeleton can effectively disperse Cu&lt;sub&gt;3&lt;/sub&gt;Mo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt; particles and increase the adsorption capacity of gas molecules. And the enhanced response of Cu&lt;sub&gt;3&lt;/sub&gt;Mo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt;/MoO&lt;sub&gt;3&lt;/sub&gt; may be due to the good catalytic effect of Cu&lt;sub&gt;3&lt;/sub&gt;Mo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt;, which is conducive to oxygen adsorption. This work provides a new strategy for preparing high-performance MoO&lt;sub&gt;3&lt;/sub&gt;-based gas sensing materials.

Favorable sensing property of Pt-doped Janus HfSSe monolayer upon H2S and SO2: a first-principles theory

In this paper, we investigate the adsorption performances of the pristine and Pt-doped HfSSe (Pt-HfSSe) monolayer upon H2S and SO2 molecules based on the first-principles theory. Results indicate that the Pt dopant preferred to be doped on the Se-surface of the HfSSe monolayer with the formation energy (Ef) of −1.06 eV. The Pt-HfSSe monolayer has remarkably improved adsorption energy (Ead) upon H2S and SO2, calculated as −0.614 and −0.918 eV respectively which are about 2.6 and 2.9 times than those in the counterpart systems. The BS and DOS analysis reveal the sensing mechanism of Pt-HfSSe monolayer for detection of H2S and SO2 and manifest its strong potential as a resistance-type gas sensor with sensing response of 26.3% and −70.1%, respectively, and the desirable recovery property in the Pt-HfSSe/gas systems offers it good reusability at 298 K. Our theoretical findings suggest that the Pt-HfSSe monolayer is a promising room-temperature gas sensor for detection of such two toxic gases with admirable sensitivity. This work is beneficial to propose novel 2D sensing materials for toxic gas detection, and paves the way for further experimental researches to realize their application in some typical fields.

(Invited) Ceramic Nano-Heterostructures By Materials Design: Platforms for Sensing Applications – Opportunities and Challengess

This talk summarizes R&D efforts in the author’s laboratory on the fabrication of oxide nano-heterostructures, exploiting intrinsic material properties, that are highly scalable and do not require use of lithography. One such process creates crystallographically oriented nanofiber arrays of single crystal TiO2 in H2/N2 environment. H2/N2 heat treatment was also used to grow nanofibers on polycrystalline SnO2, showing directional growth on grains with crystal facets. We have also developed a process to create nanofibers of TiO2 on Ti metal/alloys via oxidation under a limited supply of oxygen. In another process, SnO2 nanowires grown from commercial FTO slides using the vapor-liquid-solid (VLS) method were placed in a microwave-assisted hydrothermal chamber where TiO2 nanorods nucleated radially from the SnO2 nanowire cores. We developed yet another interesting nano-structure (nanoislands and/or nanobars) during thermal annealing of an oxide (GDC) on top of another oxide (YSZ) substrate that self-assembles along the softest elastic direction of the substrate. What is common about these structures is that they are fabricated without the use of lithographic techniques and involves simple processes such as gas-phase reactions and stress-driven processes. These nano-heterostructures can be used as platforms for chemical sensing, catalysis, photocatalysis, photovoltaics and biomedical applications. Sensing application presents opportunities and challenges that are presented including an Open access Database Of Resistive type gas Sensors (ODORS) that has been developed and can be used to select suitable sensing materials.

First-principles investigation of Pt-doped MoTe2 for detecting characteristic air decomposition components in air insulation switchgear

Air-insulated switchgear plays a significant role in electrical engineering; the running stability of this equipment is required higher. In this work, the Pt-doped MoTe2 (Pt-MoTe2) monolayer is proposed as a novel sensing material for the detection of air decomposition components: NO2 and O3, to evaluate the operation status of air insulation switchgear. The Pt dopant is stably anchored on the MoTe2 surface with the binding force (Eb) of −3.02 eV, and the band gap decreases after Pt-doping on the pure MoTe2 monolayer. Besides, the Pt-MoTe2 monolayer behaves as chemisorption upon NO2 and O3 molecules adsorption with adsorption energy (Ead) of −1.750 eV, −2.045 eV, respectively. Furthermore, the NO2 and O3 molecules behave as electron-acceptor withdrawing charges from the Pt-MoTe2 monolayer, based on the Hirshfeld analysis. Comparing two gas systems, it is found that band gap decreases in both gas systems, and the degree of decrease varies significantly, which makes it possible to develop resistance-type gas sensor to detect NO2 and O3 molecules. Our calculations give an insight into the physicochemical property of Pt-MoTe2 monolayer, and elucidate their promising potential as novel gas sensors for air insulating switchgear.

Nb-doped PtS2 monolayer for detection of C2H2 and C2H4 in on-load tap-changer of the oil-immersed transformers: A first-principles study

First-principles calculations are conducted to investigate the Nb-doped PtS2 (Nb-PtS2) monolayer for sensing C2H2 and C2H4 in the on-load tap-changer of the oil-immersed transformers. The adsorptions of two gases on the Nb-PtS2 monolayer are verified as chemisorption with adsorption energies of −2.47 and −1.0.91 eV, as confirmed by Hirshfeld analysis, charge density difference and orbital density of state. The band structure indicates the good sensing response of 1206.7% and −4717.4%, for C2H2 and C2H4 detections, suggesting its strong potential as a resistance-type gas sensor for their detections. This work paves the ways to explore novel PtS2-based gas sensor effectively.