Potential Applications In Gas Sensors Research Articles

Theoretical designing of Ni-doped PtSTe monolayer as a promising gas sensor upon thermal runaway gases in the Li-ion battery

This study proposes Ni-doped Janus PtSTe (Ni-PtSTe) as a novel sensing material for detecting three critical gases (CO, CO2, and C2H4), with potential applications in gas sensors and Li-ion battery monitoring. The Ni-doping favors the Te surface of the PtSTe monolayer, with a formation energy of -1.19 eV. The adsorption capacity follows the order: CO > C2H4 > CO2, with chemisorption in CO and C2H4 systems and physisorption in CO2 system. The analysis of electronic properties in gas adsorbed Ni-PtSTe systems indicate a reduced bandgap in CO and C2H4 systems, resulting in the sensing response of 99.25% and 97.71%, respectively. The work function increases significantly in the presence of CO and C2H4, suggesting its suitability as a work function-based sensor. These results highlight the promising sensing capabilities of Ni-PtSTe monolayer, expanding the horizon for PtSTe-based materials and inspiring cutting-edge research.

Cerium-Doped Oxide-Based Materials for Energy and Environmental Applications

Cerium is a rare-earth metal commonly used as a dopant in various metal oxides to enhance their performances or provide optoelectronic properties. Cerium oxide (ceria) is particularly valuable owing to its unique properties and applications in various fields, such as biomedical research, photovoltaics, and industrial catalytic processes. This review focuses on the use of cerium and ceria doping in the synthesis of SiO2 and ZnO. Studies have shown that Ce-doped SiO2 thin films exhibit luminescence properties and proton shielding capabilities, and that Ce-doped ZnO has potential applications in gas sensors. In this review, we highlight the potential for controlling the luminescence and optical characteristics of these materials via cerium doping, opening up possibilities for various technological advancements and potential applications of cosmic ray shielding in space photovoltaics.

Gas Sensitive Materials Based on Polyacrylonitrile Fibers and Nickel Oxide Nanoparticles

The results of the synthesis of PAN/NiO composite fibers by the electrospinning method are presented. The electrospinning installation included a rotating drum collector for collecting fibers. Nickel oxide nanoparticles were synthesized by solution combustion synthesis from nickel nitrate and urea. It was shown that monophase NiO nanoparticles with average particle sizes of 154 nm could be synthesized by this method. NiO nanoparticles were investigated by X-ray diffraction analysis and scanning electron microscopy. Based on NiO nanoparticles, composite PAN/NiO fibers were obtained by electrospinning. The obtained composite fibers were modified with heat treatment (stabilization and carbonization) processes. Obtained C/NiO fibers were investigated by SEM, and EDAX. It was shown that obtained composite fibers could be used for the detection of acetone and acetylene in air. These results show that C/NiO based electrospun fibers have potential applications in gas sensors.

Edge‐Enriched Mo2TiC2Tx/MoS2 Heterostructure with Coupling Interface for Selective NO2 Monitoring

AbstractEndowed with rich terminal groups, good electrical conductivity, and controllable structure, transition metal carbides/nitrides (MXenes) have attracted extensive attention for potential application in gas sensor, but long‐standing challenges of the MXenes (titanium carbide as the representative) are their limited selectivity and sensitivity. Herein, a high‐active double transition‐metal titanium molybdenum carbide (Mo2TiC2Tx) with superstrong surface adsorption (−3.12 eV) for NO2 gas molecule is proposed, and it is further coupled with molybdenum disulfide (MoS2) by interface modulation to construct an edge‐enriched heterostructure. Due to the synergistic effect of strong adsorption, rich adsorption sites, and coupling interface of Mo2TiC2Tx/MoS2 composite, the as‐fabricated Mo2TiC2Tx/MoS2 gas sensor exhibits an outstanding response toward NO2 with high selectivity against various interference gases, which is well supported by density functional theory calculations. Meanwhile, the sensor exhibits a sensitivity of 7.36% ppm−1, detection limit of 2.5 ppb, and reversibility at room temperature. A portable, wireless NO2 monitoring system is demonstrated for gas leakage searching and dangerous warning based on Mo2TiC2Tx/MoS2 gas sensor. This work facilitates the gas sensing application of MXenes, and provides an avenue for the development of wireless sensing system in environmental monitoring and safety assurance.

Annealing Effect on Nanocrystalline SnO2 Thin Films Prepared by Spray Pyrolysis Technique

In recent years, a transparent conducting oxide (TCO) SnO2 semiconductor have gained considerable attention due to their potential application in gas sensors. More number of studies on TCO oxide have focused on the semiconducting metal oxides in which an intensive argument is that the transparent semiconductors. The SnO2 thin films were deposited at 400 °C and then annealed at 500 °C and 600 °C and its structural, optical and electrical properties were characterized. The doping stoichiometric ratio was maintained as 4% and the resulting solution was sprayed on glass substrate which was kept at nozzle distance of 25 cm and the spray rate was 10 mL/min. The prepared pure SnO2 thin films have been characterized by different methods such as XRD, FESEM, UV-Vis NIR and EDAX analyses. It was found that the nanocrystalline SnO2 grains possesses structural features of the tetragonal rutile structure. Hence the prepared thin films are justified to be nanocrystalline and also the mean crystalline size decreased with respect to annealing temperature.

Adsorption Of CO On Cu-doped MoS2 Sheet: A First Principles Study

Owing to the large surface area, 2D materials are used for sensing gas molecules, which are important for environmental protection and human health. Using the first principles calculations based on density functional theory (DFT), the adsorption of CO gas molecule on the Cu substituted MoS2 is studied in terms of adsorption energy, charge transfer and density of states (DOS). The strong interaction between Cu metal and the MoS2 sheet suggests the stability of the Cu doped MoS2 system at ambient conditions. It is further found that on doping Cu into MoS2 sheet facilitated the adsorption strength of CO molecule as compared to pristine MoS2 sheet. The results show that MoS2 with doped Cu atom can essentially trap the hazardous molecules and may have potential application in gas sensors.

Design of hollow dodecahedral Cu2O nanocages for ethanol gas sensing

P-type metal oxide semiconductors with special morphology have received high expectation for their potential application in gas sensors. We have synthesized hollow dodecahedral Cu2O nanocages with exposed (1 1 1) planes by a simple solution growth approach at room temperature. Characterization results indicate that the diameters of Cu2O nanocages are about 200 nm. Gas sensing performance of the Cu2O nanocages is investigated towards ethanol gas. Remarkably, the response of Cu2O reaches 4.6 at a low working temperature of 250 °C when the concentration is 100 ppm. The unique structure of Cu2O benefits the sensing performance owing to its active (1 1 1) planes.

CuO-ZnO hetero-junctions decorated graphitic carbon nitride hybrid nanocomposite: Hydrothermal synthesis and ethanol gas sensing application

ZnO and CuO have attracted considerable attention for their potential application in gas sensors. However, they also have some disadvantages, such as high operating temperature and poor sensitivity. Graphitic carbon nitride (g-C3N4) has been widely used as metal-free catalyst and catalyst support in gas sensing field due to its unique chemical stability and excellent substrate characteristics. In this study, a one-step hydrothermal method was developed for the preparation of a CuO-ZnO/g-C3N4 ternary composite. The as-prepared samples were characterized by using the XRD, SEM, TEM, FTIR, UV–vis and XPS techniques. The analysis results indicated that the ternary composite was synthesized successfully. The morphological analyses demonstrated that the flake-like CuO and ZnO nanoparticles were wrapped and connected by g-C3N4 nanosheet. The as-prepared CuO-ZnO/g-C3N4 exhibited obviously enhanced sensing properties to ethanol, which were 1.34 times and 2.17 times higher than that of CuO-ZnO and CuO, respectively. The improving gas sensing properties were related to the valid p-n junctions of CuO-ZnO and excellent substrate effect of g-C3N4 nanosheet.

Two-dimensional Au-1,3,5 triethynylbenzene organometallic lattice: Structure, half-metallicity, and gas sensing.

On the basis of first-principles calculations, we investigated the structural and electronic properties of the two-dimensional (2D) Au-1,3,5 triethynylbenzene (Au-TEB) framework, which has been recently synthesized by homocoupling reactions in experiments. Featured by the C-Au-C linkage, the 2D Au-TEB network has a kagome lattice by Au atoms and a hexagonal lattice by organic molecules within the same metal-organic framework (MOF), which exhibits intrinsic half-metallicity with one spin channel metallic and the other spin channel fully insulating with a large energy gap of 2.8 eV. Two branches of kagome bands are located near the Fermi level, with each branch including one flat band and two Dirac bands, which originates from the out-of-plane dxz and dyz orbitals of Au and may lead to many exotic topological quantum phases. We further studied the adsorption of F atoms, Cl atoms, and small gas molecules including O2, CO, NO2, and NH3 on the Au-TEB network, aiming to exploit its potential applications in gas sensors. Detailed analyses on adsorption geometry, energy, molecular orbital interaction, and electronic structure modification suggest the great potential of Au-TEP as a promising alternative for gas sensing. We expect these results to expand the universe of low-dimensional half-metallic MOF structures and shed new light on their practical applications in nanoelectronics/spintronics.

Soft-templated synthesis of mesoporous nickel oxide using poly(styrene-block-acrylic acid-block-ethylene glycol) block copolymers

In this work, we report the soft-templated preparation of mesoporous nickel oxide using an asymmetric poly(styrene-block-acrylic acid-block-ethylene glycol) (PS-b-PAA-b-PEG) triblock copolymer. This block copolymer forms a micelle consisting of a PS core, a PAA shell and a PEG corona in aqueous solutions, which can serve as a soft template. Specifically, the PS block forms the core of the micelles on the basis of its lower solubility in water. The anionic PAA block interacts with the cationic Ni2+ ions present in the solution to generate the shell. The PEG block forms the corona of the micelles and stabilizes the micelles by preventing secondary aggregation through steric repulsion between the PEG chains. In terms of textural characteristics, the as-synthesized mesoporous NiO exhibits a large average pore size of 35 nm with large specific surface area and pore volume of 97.0 m2 g−1 and 0.411 cm3 g−1, respectively. It is expected that the proposed soft-templated strategy can be expanded to other metal oxides/sulfides in the future for potential applications in gas sensors, catalysis, energy storage and conversion, optoelectronics, and biomedical applications.

Sensing of CO and NO on Cu-Doped MoS2Monolayer-Based Single Electron Transistor: A First Principles Study

Owing to the large surface area, 2-D materials are being used for sensing gas molecules, which are important for environmental protection and human health. Using first principle calculations, adsorption of CO and NO gas molecules on Cu-substituted monolayer MoS2 is studied in terms of energy, charge transfer, and density of states. Further, the behavior of CO and NO on Cu-substituted monolayer MoS2-based single electron transistor (SET) is explored. Strong interaction between Cu metal and MoS2 sheet suggests the stability of the Cu-doped MoS2 system at ambient conditions. It is further found that on doping Cu into MoS2 sheet, the adsorption strength of CO and NO molecules got enhanced as compared with the pristine MoS2 sheet and, hence, possesses better sensing capability. The sensing response of the Cu-doped MoS2 sheet in the SET environment toward these molecules is studied from the calculated charge stability diagram that serves as a unique fingerprint of each adsorbed molecule. The charging energy is reduced when Cu impurity is added to MoS2 for CO/NO adsorption, which makes such system more suitable in low-powered SET devices. The results show that SET based on Cu-doped MoS2 can essentially detect hazardous molecules and is proved to have potential application in gas sensors.

Influence of pH in La-doped SnO2 nanoparticles towards sensor applications

The present investigation has been carried out to optimize the pH level of lanthanum (La)-doped tin dioxide (SnO2) nanoparticles towards the potential application in gas sensor. The La-doped SnO2 nanoparticles were synthesized by sol-gel method in different pH values varying from acidic to base nature. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), ultraviolet (UV), photoluminescence (PL), and scanning electron microscopy (SEM) techniques. The XRD, UV, and PL analyses show the pH influences on the crystallite size of La-doped SnO2 nanoparticles. The SEM images show the formation of porous structure at pH 11. Also, the electrical conductivity of 1 mol% La-doped SnO2 at pH 3 and pH 11 were measured by impedance analyzer. In addition, we have fabricated and demonstrated device performance of synthesized La-doped SnO2 nanoparticles for gas-sensing application. Real-time current response and long-time response to the gas sensing were also studied for the fabricated device.

Aligned Array of Porous Silicon Nanowires for Gas-Sensing Application

Porous silicon nanowires (SiNWs) array was prepared by a one-step metal-assisted chemical etching (MACE) method in HF/AgNO3 solution, and the potential application in gas sensor was explored. The nanowire length is found to be corrective to the etching time while the diameter and porous feature remain stable. The porous SiNWs array shows high active surface area and vertically aligned configuration favorable for gas adsorption and rapid gas diffusion. The NO2 sensing properties of the as-prepared porous SiNWs were measured at room temperature upon exposure to NO2 gas with varied concentrations. It is found that the gas sensor based on the porous SiNWs array exhibits a clear response with low noise at room temperature to extremely dilute NO2 gas as low as 50 ppb. Rapid response and recovery are achieved simultaneously owing to the highly ordered microstructure. The response time and recovery time are 5 s and 31 s for 50 ppb NO2 gas exposure, respectively. Therefore, the sensor based on the porous SiNWs array is capable of the rapid detection of NO2 gas with ppb level at room temperature.

Catalyst-Free Synthesis of ZnO Nanowires on Oxidized Silicon Substrate for Gas Sensing Applications.

In the present work, we report the synthesis of nanostructured ZnO by oxidation of zinc film without using a seed or catalyst layer. The zinc films were deposited on oxidized Si substrates by RF magnetron sputtering process. These were oxidized in dry and wet air/oxygen ambient. The optimized process yielded long nanowires of ZnO having diameter of around 60-70 nm and spread uniformly over the surface. The effect of oxidation temperature, time, Zn film thickness and the ambient has strong influence on the morphology of resulting nanostruxctured ZnO film. The films were characterized by scanning electron microscopy for morphological studies and X-ray diffraction (XRD) analysis to study the phase of the nanostructured ZnO. Room temperature photoluminescence (PL) measurements of the nanowires show UV and green emission. A sensor was designed and fabricated using nanostructured ZnO film, incorporating inter-digital-electrode (IDE) for the measurement of resistance of the sensing layer. The gas sensing properties were investigated from the measurement of change in resistance when exposed to vapours of different volatile organic compound (VOC) such as acetone, ethanol, methanol and 2-propanol. The results suggest that ZnO nanowires fabricated by this method have potential application in gas sensors.

Effect of fluorine, chlorine and bromine doping on the properties of gadolinium doped barium cerate electrolytes

The high temperature proton conductors have attracted considerable interest for their potential application in gas sensors, hydrogen separators and fuel cells. Among various kinds of proton conducting materilas, rare earth doped barium cerate based ceramics display the highest conductivity, but their practical applications are limited because their well-recognized poor chemical stability against CO2 and/or H2O steam. In this work, F, Cl and Br doped BaCe0.90Gd0.1O3-δ (BCG) materials were prepared via a solid–state reaction method with CuO as sintering aid to improve the materials chemical stability. The experimental results display that the added F, Cl or Br enters into the lattice of BCG without causing structure and morphology change. Halogen (F, Cl and Br) doping effectively enhances chemical stability of BCG in CO2 and H2O steam due to decreasing the materials basicity. Br doped BCG exhibits the best chemical stability as well as relatively high electrical conductivity. CuO addition reduces sintering temperature by 150 °C.

Highly sensitive formaldehyde chemical sensor based on in situ precipitation synthesis of ZnSnO3 microspheres

Highly sensitive formaldehyde chemical sensor was fabricated using uniform and mono-disperse ZnSnO3 microspheres, which were successfully prepared by a template-free, economical in situ precipitation method combined with subsequent calcination. The orientation and morphology of the precursor, ZnSn(OH)6 microspheres, were carefully controlled by adjusting the added amount of NaOH. This facile process may provide an approach to synthesis of functional nanomaterials with unique structures and excellent physicochemical properties. Moreover, the as-fabricated sensors based on the ZnSnO3 microspheres showed high response and short response-recovery time toward formaldehyde. To 50 ppm formaldehyde, the sensor response (S) was 17 at a working temperature of 260 °C, and the response and recovery time were 6 and 18 s, respectively. The gas response of sensors based on the ZnSnO3 microspheres was linear with the concentration of formaldehyde in the range of 5–100 ppm with a correlation coefficient of 0.997. These results showed that the as-prepared ZnSnO3 microspheres have a potential application in gas sensor.

Size dependent strain and nanomagnetism in CoFe2O4 nanoparticles

The objective of this work is to investigate strain and magnetism at the nano scale in CoFe2O4 nanoparticles. CoFe2O4 nanoparticles of controlled size were synthesized using a chemical co-precipitation method at different reaction temperatures and molar concentrations of reagents without using any surfactant. Size dependent strain, structural, optical, morphological and magnetic properties of CoFe2O4 nanoparticles were investigated. Particle size was calculated by size distribution curve using FESEM images. It was observed that structural orientation and characteristic features of the strain are dependent on CoFe2O4 particle size. The formation of CoFe2O4 nanoparticles was confirmed by XRD, FESEM, Raman and FTIR spectroscopy. The good correlation between XRD analysis and Raman study was observed with the help of Raman shift (cm−1) as a function of uniform and non-uniform strain curves for all sizes of CoFe2O4 nanoparticles. The size-dependent superparamagnetic properties of CoFe2O4 nanoparticles were studied systematically. The blocking temperature, coercivity and saturation magnetization increase on increasing the size of the CoFe2O4 nanoparticles was observed. Blocking temperature is a maximum temperature, above which the exchange bias does not occur. The size of the CoFe2O4 nanoparticles estimated from blocking temperature measurements correlated well with FESEM and XRD measurements. These CoFe2O4 nanoparticles have potential applications in gas sensors operating in hazardous environments.

Direct growth of ZnO nanodisk networks with an exposed (0 0 0 1) facet on Au comb-shaped interdigitating electrodes and the enhanced gas-sensing property of polar {0 0 0 1} surfaces

ZnO nanodisk networks were grown directly on Au comb-shaped interdigitating electrodes on SiO2/Si substrate by thermal evaporation of a mixture of ZnCl2 and InCl3·4H2O at 450°C in air. The nanodisk has hexagonal shape with a side length of ∼1.8μm, a diagonal of ∼3.8μm and thickness 64-125nm. It grows mainly along 0 1 1¯ 0 directions, and is enclosed by ±(0001) top and bottom surfaces. The as-prepared ZnO nanodisks having mostly {0001} facets exhibit better gas-sensing performance for NH3, N(C2H5)3 and C2H5OH comparing to ZnO nanorods with 0 1 1¯ 0 facets. The sensor response measured at 300°C are 1.68, 11.84 and 10.19 for NH3, N(C2H5)3 and C2H5OH with concentration 5, 10 and 10ppm, respectively. The enhancement in the gas-sensing properties is mainly attributed to the exposed {0001} facets which provide more active sites for oxygen adsorption and subsequent reaction with the vapor than 1 0 1¯ 0 facets, and therefore improved response. The observation motivates us to further explore new synthetic methods to prepare other metal oxides with a high percentage of reactive facets with potential applications in gas sensors, photocatalysts, solar cells, and optoelectronic devices.

ChemInform Abstract: Gas Sensors Based on One Dimensional Nanostructured Metal‐Oxides: A Review

AbstractReview: 106 refs.

Synthesis of self-assembled 3D hollow microspheres of SnO2 with an enhanced gas sensing performance

In this paper, three-dimensional (3D) SnO2 hollow microspheres composed of numerous subunits of nanorods are prepared through a facile one-pot hydrothermal method. These SnO2 microspheres are structurally characterized by X-ray diffraction, field-emission scanning electron microscope, and high resolution transmission electron microscope, respectively. It is shown that the hierarchical SnO2 microspheres ranged from 600 to 900nm in diameter are constructed from self-assembled one-dimensional tetragonal prism SnO2 nanorods. Most importantly, the gas sensor based on these hierarchical SnO2 microspheres exhibits excellent selectivity and fast response–recovery capability to ethanol. The response and recovery times are 2.6s and 11s, respectively, if the sensor is exposed to 50ppm ethanol at the optimal operating temperature of 280°C. The present study could offer potential applications in gas sensors.