Search Results (327)

Zinc oxide (ZnO) nanomaterials have emerged as promising candidates for gas sensing applications due to their high sensitivity, fast response–recovery cycles, thermal and chemical stability, and low fabrication cost. However, the performance of pristine ZnO remains limited by high operating temperatures, poor selectivity, and suboptimal detection at low gas concentrations. To address these limitations, significant research efforts have focused on dopant incorporation and polymer hybridization. This review summarizes recent advances in dopant engineering using elements such as Al, Ga, Mg, In, Sn, and transition metals (Co, Ni, Cu), which modulate ZnO’s crystal structure, defect density, carrier concentration, and surface activity—resulting in enhanced gas adsorption and electron transport. Furthermore, ZnO–polymer nanocomposites (e.g., with polyaniline, polypyrrole, PEG, and chitosan) exhibit improved flexibility, surface functionality, and room-temperature responsiveness due to the presence of active functional groups and tunable porosity. The synergistic combination of dopants and polymers facilitates enhanced charge transfer, increased surface area, and stronger gas–molecule interactions. Where applicable, sol–gel-based studies are explicitly highlighted and contrasted with non-sol–gel routes to show how synthesis controls defect chemistry, morphology, and sensing metrics. This review provides a comprehensive understanding of the structure–function relationships in doped ZnO and ZnO–polymer hybrids and offers guidelines for the rational design of next-generation, low-power, and selective gas sensors for environmental and industrial applications. Full article

In this study, two types of gas sensors—silicone-based interdigital electrode and silicon micropillar sensors based on rGO and rGO/SnO₂—were fabricated. Their gas-sensing performance was investigated at room temperature. First, interdigital electrodes of different channel widths were fabricated to investigate the impact of the channel width parameter. Subsequently, the rGO/SnO₂ doping ratio in the composite material was varied to identify the optimal composition for gas sensitivity. Additionally, triangular and square-arrayed silicon micropillar substrates were fabricated via photolithography and inductively coupled plasma etching. The rGO/SnO₂-based gas sensor on a silicon micropillar substrate exhibited an ultra-high specific surface area. The triangular micropillar arrangement of rGO/SnO₂-160 demonstrates the best performance, showing approximately 14% higher response and a 106 s reduction in response time compared with interdigital electrode sensors spray-coated with the same concentration of rGO/SnO₂ when tested at room temperature under 250 ppm NO₂. The optimized sensor achieves a detection limit as low as 5 ppm and maintains high responsiveness, even in conditions of 60% relative humidity (RH). Additionally, the repeatability, selectivity, and stability of the sensor were evaluated. Finally, structural and morphological characterization was conducted using XRD, SEM, TEM, and Raman spectroscopy, which confirmed the successful modification of rGO with SnO₂. Full article

In this article, we present density functional theory (DFT) calculations for $Z{n}_{(1-x)}{M}_{x}O$, where M represents one of the following substitutional metallic impurities: Ga, Cd, Cu, Pd, Ag, In, or Sn. Our study is based on the wurtzite structure of pristine ZnO. We employ the Quantum Espresso package, using a fully unconstrained implementation of the generalized gradient approximation (GGA) with an additional U correction for exchange and correlation effects. We analyze the density of states, energy gaps, and absorption spectra for these doped systems, considering the limitations of a finite-size cell approximation. Rather than focusing on precise numerical values, we highlight the following two key aspects: the location of impurity-induced electronic states and the overall trends in optical properties across the eight systems, including pristine ZnO. Our results indicate that certain dopants introduce electronic levels within the band gap, which enhance optical absorption in the visible, near-infrared, and near-ultraviolet regions. For instance, Sn-doped ZnO shows a pronounced absorption peak at ∼2.5 eV, which is in the middle of the visible spectrum. In the case of Ag and Pd impurities, they lead to increased electromagnetic radiation absorption at the near ultra-violet spectrum. This represents a promising performance for efficient solar radiation absorption, both at the Earth’s surface and in outer space. Furthermore, Ga- and In-doped ZnO present bandgaps of ∼0.9 eV, promising an interesting performance in the near infrared region. These findings suggest potential applications in solar energy harvesting and selective sensors. Full article

Hierarchical NiO-SnO₂ nanoflowers were prepared via a one-step hydrothermal method. The morphology, structure and components of the hierarchical NiO-SnO₂ nanoflowers were examined via scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The ethanol gas-sensing performance was systematically analyzed between pure hierarchical SnO₂ nanoflowers and the hierarchical NiO-SnO₂ nanoflowers. The results indicated that the hierarchical NiO-SnO₂ nanoflowers showed better gas-sensing properties than the pure hierarchical SnO₂ nanoflowers at 164 °C. The enhanced gas-sensing performance was ascribed to the formation of p-n heterojunctions between p-type NiO and n-type SnO₂. Additionally, NiO has a catalytic role. Therefore, hierarchical NiO-SnO₂ nanoflowers could be a potential gas-sensing material for the fabrication of high-quality ethanol gas sensors. Full article

In this study, multivariate data processing during thermal modulation of the SnO₂–PdO gas sensor was performed using the multivariate calibration (MC) method. We propose to supplement this method with a procedure that allows the solving of problems of both quantitative and qualitative analysis. The advantage of the extended method (Multivariate Calibration for Selective Analysis, MCSA) compared to other methods is its modest requirements for computing resources, which allows it to be easily implemented on standard microcontrollers. The MCSA method opens up the prospect of creating compact gas analyzers of a new generation, capable of selective gas analysis in hard-to-reach places in an autonomous mode. The implementation of the MCSA method was demonstrated using the example of selective determination of hydrogen sulfide and carbon monoxide by a sensor whose temperature periodically changed from 100 to 450 °C. The training sample data were transformed by the MCSA method, which allowed for successful qualitative and quantitative analysis of the test sample data. Full article

The development of gas sensors with high sensitivity and low operating temperatures is essential for practical applications in environmental monitoring and industrial safety. SnO₂-based gas sensors, despite their widespread use, often suffer from high working temperatures and limited sensitivity to H₂ gas, which presents significant challenges for their performance and application. This study addresses these issues by introducing a novel SnO₂-based sensor featuring a three-dimensional (3D) nanostructure, designed to enhance sensitivity and allow for room-temperature operation. This work lies in the use of a 3D anodic aluminum oxide (AAO) template to deposit SnO₂ nanoparticles through ultrasonic spray pyrolysis, followed by modification with platinum (Pt) nanoparticles to further enhance the sensor’s response. The as-prepared sensors were extensively characterized, and their H₂ sensing performance was evaluated. The results show that the 3D nanostructure provides a uniform and dense distribution of SnO₂ nanoparticles, which significantly improves the sensor’s sensitivity and repeatability, especially in H₂ detection at room temperature. This work demonstrates the potential of utilizing 3D nanostructures to overcome the traditional limitations of SnO₂-based sensors. Full article

As lithium-ion batteries (LIBs) gain widespread use, detecting electrolyte–vapor emissions during early thermal runaway (TR) remains critical to ensuring battery safety; yet, it remains understudied. Gas sensors integrating oxide nanostructures offer a promising solution as they possess high sensitivity and fast response, enabling rapid detection of various gas-phase indicators of battery failure. Utilizing this approach, 3D ordered tin oxide (SnO₂) nanostructures were synthesized using polystyrene sphere (PS) templates of varied diameters (200–1500 nm) and precursor concentrations (0.2–0.6 mol/L) to detect key electrolyte–vapors, especially ethyl methyl carbonate (EMC), released in the early stages of TR. The 3D ordered SnO₂ nanostructures with ring- and nanonet-like morphologies, formed after PS template removal, were characterized, and the effects of template size and precursor concentration on their structure and sensing performance were investigated. Among various nanostructures of SnO₂, nanonets achieved by a 1000 nm PS template and 0.4 mol/L precursor showed higher mesoporosity (~28 nm) and optimal EMC detection. At 210 °C, it detected 10 ppm EMC with a response of ~7.95 and response/recovery times of 14/17 s, achieving a 500 ppb detection limit alongside excellent reproducibility/stability. This study demonstrates that precise structural control of SnO₂ nanostructures using templates enables sensitive EMC detection, providing an effective sensor-based strategy to enhance LIB safety. Full article

The organic volatile compound gases (VOCs) emitted by the rubber running tracks in the park pose a threat to human health. Currently, the challenge lies in how to detect the VOC gas concentration to ensure it is below the level that is harmful to human health. This study developed a low-power acetone gas sensor based on SnO₂/Nb₂C MXene composites, designed for monitoring acetone gas in pocket park rubber tracks at room temperature. Nb₂C MXene was combined with SnO₂ nanoparticles through a hydrothermal method, and the results showed that the SnO₂/Nb₂C MXene composite sensor (SnM-2) exhibited a response value of 146.5% in detecting 1 ppm acetone gas, with a response time of 155 s and a recovery time of 295 s. This performance was significantly better than that of the pure SnO₂ sensor, with a 6-fold increase in response value. Additionally, the sensor exhibits excellent selectivity against VOCs, such as ethanol, formaldehyde, and isopropanol, with good stability (~20 days) and reversibility (~50). It can accurately recognize acetone gas concentrations and has been successfully used to simulate rubber track environments and provide accurate acetone concentration data. This study provides a feasible solution for monitoring VOCs in rubber tracks and the foundation for the development of low-power, high-performance, and 2D MXene gas sensors. Full article

The influence of Cd doping on the performance of ZnSn(OH)₆ (ZHS) as a gas sensor was systematically investigated through experimental and theoretical approaches. ZHS and Cd-doped ZHS samples were synthesized using the hydrothermal method. The microstructures of pure and Cd-doped ZHS were characterized using various techniques. The results revealed that the pure ZHS sample exhibits good crystallinity and an octahedral morphology with particle sizes ranging from 800 to 1900 nm. After Cd doping, the particle size range was decreased to 700–1500 nm. A systematic investigation of the gas-sensing properties revealed that Cd-doped ZHS exhibits superior sensing performance toward ethanol gas compared to pure ZHS. Under operating conditions of 240 °C, 100 ppm concentration, and 30% relative humidity, the response of ZHS to ethanol gas exhibited a significantly higher value compared to other tested gases. After Cd doping, the response approximately doubled. Density functional theory calculations of electronic structures revealed that the enhanced ethanol sensing mechanism of Cd-doped ZHS is attributed to the narrowed band gap caused by Cd doping, which increases electron concentration and enhances ${\mathsf{O}}^{-}$ ion adsorption on the surface. Full article

Triethylamine (TEA), a volatile organic compound (VOC), has important applications in industrial production. However, TEA has an irritating odor and potential toxicity, making it necessary to develop sensitive TEA gas sensors with high efficiency. This study focused on preparing LaFeO₃ nanoparticles modified by SnS₂ nanosheets (SnS₂/LaFeO₃ composite) using a hydrothermal method together with sol–gel technique. According to the comparison results of the gas-sensing performance between pure LaFeO₃ and SnS₂/LaFeO₃ composite with varying composition ratios, 5% SnS₂/LaFeO₃ sensor had a sensitivity for TEA that was 3.2 times higher than pure LaFeO₃ sensor. The optimized sensor operates at 140 °C and demonstrates strong stability, selectivity, and long-term durability. Detailed analyses revealed that the SnS₂ nanosheets enhanced oxygen vacancy (O_V) content and carrier mobility through heterojunction formation with LaFeO₃. This study provides insights into improving gas-sensing performance via p-n heterostructure design and proposes a novel LaFeO₃-based material for TEA detection. Full article

Chemical nanosensors based on tin dioxide (SnO₂) and zinc oxide (ZnO) nanoparticles (NPs) were developed and characterized for the detection of low concentrations of atmospheric pollutants, such as nitrogen dioxide (NO₂) and carbon monoxide (CO). The sensing layers were prepared using three fabrication methods: drop-casting, electrospray, and spark ablation coupled with an inertial impaction printer, to compare their performance. Multiple surface characterization techniques were carried out to investigate the surface morphology and elemental composition of the deposited layers such as SEM (scanning electron microscopy) and XPS (X-ray photoelectron spectroscopy) analyses. UV light photoactivation enabled the sensors to detect ultra-low concentrations of the target gases at room temperature (100 ppb NO₂ and 1 ppm CO). The measurements were conducted at 50% relative humidity to simulate real environmental conditions. All sensors were capable of detecting the target gases. Drop-casting is the simplest and most cost-effective technique, but it is also the least reproducible. In contrast, sensors based on the spark ablation technique achieved more homogeneous sensing layers, with practically no nanoparticle agglomeration, resulting in devices with lower noise and drift in their electrical response. Full article

Thin TiO₂–SnO₂ nanocomposite films with high gas sensitivity to NO₂ were synthesized by oxidative pyrolysis and comprehensively studied. The composite structure and quantitative composition of the obtained film nanomaterials have been confirmed by X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy, which causes the presence of n-n heterojunctions and provides improved gas-sensitive properties. The sensor based on the 3TiO₂–97SnO₂ film has the maximum responses, which is explained by the existence of a strong surface electric field formed by large surface potentials in the region of TiO₂–SnO₂ heterojunctions detected by the Kelvin probe force microscopy method. Exposure to low-intensity radiation (no higher than 0.2 mW/cm², radiation wavelength—400 nm) leads to a 30% increase in the sensor response relative to 7.7 ppm NO₂ at an operating temperature of 200 °C and a humidity of 60% RH. At room temperature (20 °C), under humidity conditions, the response is 1.8 when exposed to 0.2 ppm NO₂ and 85 when exposed to 7.7 ppm. The lower sensitivity limit is 0.2 ppm NO₂. The temporal stability of the proposed sensors has been experimentally confirmed. Full article

Sarin is an extremely toxic and fast-acting chemical warfare nerve agent that poses a serious threat to human health, necessitating the development of appropriate sensing technologies. Dimethyl methylphosphonate (DMMP), which has a chemical structure similar to that of sarin but is non-toxic, is often used as a simulation agent in related research. Among promising gas-sensing materials, CuFe₂O₄ exhibits suitable thermal stability. It is easily produced and has low toxicity. Its performance can be enhanced using heterogeneous ion doping to increase the number of surface defects and content of adsorbed oxygen. Therefore, a solvothermal method was adopted in this study to prepare CuFe₂O₄ hollow microspheres that were subsequently doped with different ratios of Sn⁴⁺ or Sn²⁺. Detailed characterizations of the obtained materials were conducted, and the corresponding CuFe₂O₄-based gas sensors were fabricated. Their gas-sensing performance against DMMP was studied to analyze and discuss the gas-sensing and sensitization mechanisms associated with Sn⁴⁺ and Sn²⁺ doping. The CuFe₂O₄-based sensor doped with 2 mol% Sn²⁺ exhibited excellent gas-sensing performance in response to a 1 ppm concentration of DMMP, with response and recovery times of 12 and 63 s, respectively. Notably, its response to 1 ppm DMMP (16.27) was 3.3-fold higher than that to 1 ppm 2-CEES (4.98). The doped CuFe₂O₄ sensor exhibited superior response–recovery characteristics and enhanced moisture resistance compared to the undoped sensor. Full article

The gas-sensitive performance and selectivity of gas sensors via different Sn-doped indium oxide (In₂O₃) films have been investigated. The response characteristics were significantly enhanced to methanol (CH₄O), ethanol (C₂H₆O), and acetone (C₃H₆O) with the increase in Sn content, while the response time and the recovery time became shorter. The sensor exhibited the strongest response to ethanol, followed by acetone and then methanol with all the ratios of In₂O₃ (90%, 85%, and 80%) and SnO₂ (10%, 15%, and 20%). The mechanism of Sn doping on the gas sensing selectivity was calculated using the density functional theory (DFT) method, which perfectly explained the experimental results. The sensors demonstrated high selectivity towards ethanol, even in the presence of interfering gases. In addition, the sensors showed effective detection of the target gas with 10 ppb and demonstrated good repeatability. This work systematically analyzed the priority selectivity of In₂O₃-based gas sensors, providing a new path for gas detection in multi-interference and complex environments. Full article

A Pt@CeLaCoNiOx/Co@SnO₂ laminated MOS sensor was prepared using Co@SnO₂ as the gas-sensitive film material and Pt@CeLaCoNiOx as the catalytic film material. The sensor was verified to exhibit good sensing performances for dimethyl methylphosphonate, a simulant of Sarin, under a temperature modulation, and characteristic peaks appeared in the resistance response curves only for dimethyl methylphosphonate. The Article Swarm Optimization-Backpropagation Neural Network had a good ability to identify the resistance response data of dimethyl methylphosphonate. The identification accuracy increased as the concentration of dimethyl methylphosphonate increased. This scheme can effectively identify whether the test gas contained dimethyl methylphosphonate or not, which provided a reference for achieving the high selectivity of the MOS sensor for Sarin. Full article