金属氧化物半导体基三乙胺传感器研究进展

三乙胺是一种应用广泛但对人体有毒副作用的挥发性有机物,需要长期有效的监测,开发一种性能稳定、安全可靠的三乙胺气敏传感器,实现对环境中三乙胺气体浓度实时检测,对于三乙胺的安全储存、运输和使用等环节是至关重要的。金属氧化物半导体基气敏传感器具有制备简单、价格低廉、响应值高等优点,在三乙胺气体的检测中具有不可替代的作用。重点介绍了基于金属氧化物半导体的三乙胺传感器最新研究进展。综述了近年来包括掺杂、异质结、有机金属骨架和氧化还原石墨烯在内的关于金属氧化物半导体基三乙胺气敏材料的制备和性能等方面的研究成果。论述了金属氧化物半导体基复合材料对三乙胺气敏性能的机理。展望了金属氧化物基三乙胺气敏材料的未来研究方向。     

ZnSnO3气敏材料研究进展

作为一种重要的半导体气敏材料,ZnSnO_3气敏传感器被用于检测甲醛、丙酮、乙醇、三乙胺等气体。本文综述了近年来,不同方法制备的ZnSnO_3气敏材料以及金属和金属氧化物掺杂的ZnSnO_3气敏材料的研究进展,指出ZnSnO_3气敏材料的不足及未来的研究发展方向。     

氧化锌基硫化氢气敏材料的研究进展

阐述了氧化锌基气敏材料的类型及现状,总结了单一氧化锌,金属掺杂氧化锌以及金属氧化物复合氧化锌气体传感器对硫化氢气体气敏性能的研究进展,简要分析了金属氧化物气体传感器的气敏机理,同时对氧化锌气体传感器的实际检测应用进行了分析和展望.     

沸石及其复合物气体传感器的研究与应用

半导体金属氧化物是一种常见的气敏材料,以该类型材料作为敏感材料可以设计出具有不同传感原理的气体传感器,但选择性和灵敏度不佳却一直是该类气体传感器的不足。为了解决该问题,常将气敏材料与沸石进行复合,制备金属氧化物/沸石气体传感器,利用沸石独特的物理、化学特性来改善金属氧化物的气敏特性。近年来,许多研究者对金属氧化物/沸石气体传感器进行了研究,使该类传感器对目标气体的选择性与灵敏度均有了提升。为了更好地总结已有的研究内容,以气体传感器的检测原理为主线,对金属氧化物/沸石气体传感器进行了总结,结合沸石对气敏特性的改善进行归纳梳理,从传感器的制备方法、气敏特性和敏感机理等多方面进行了详细的整理和分析,为后续此类工作的开展提供基础。     

硼掺杂Co3O4海胆状微球的制备及其乙醇气敏强化机制

四氧化三钴（Co₃O₄）是一种p型半导体,可作为气体传感材料。非金属硼（B）具有吸电子特性,将其与p型半导体气敏材料进行掺杂,可增加材料的空穴载流子浓度,从而提高材料的气敏性能。本文以六水合硝酸钴[Co(NO₃)₂·6H₂O]、硼酸（H₃BO₃）和尿素[CO(NH₂)₂]为原料,采用低温一步水热法成功制备了B掺杂Co₃O₄海胆状微球。通过X射线衍射仪（XRD）、扫描电镜（SEM）、透射电镜（TEM）、X射线光电子能谱仪（XPS）和拉曼光谱仪（Raman）对掺杂B前后的Co₃O₄进行结构表征,探究B掺杂对其气敏性能的影响。结果表明：B掺杂对Co₃O₄材料的气敏性能有明显的强化作用。当掺杂摩尔比为Co∶B=8∶1时,B-Co₃O₄对1×10⁵μg/L乙醇的最佳工作温度为180℃,灵敏度响应达到26.8,是相同条件下纯Co₃O₄的4.4倍。B-Co₃O₄在较低的工作温度下,具有良好的灵敏度、选择性和稳定性,是一种性能优良的气敏材料。     

基于第一性原理的金属掺杂WS2增强气体传感器性能研究

对于驾驶舱空气安全质量问题越来越受到人们的关注,而空气质量检测与传感器相关。本文通过第一性原理方法系统的研究金属(Au、Pt、Ag)掺杂二维材料WS₂提升气体CO、NO、SO₂的检测性能和性质,包括吸附行为、吸附能和电荷转移。结果表明,Ag、Au掺杂WS₂单层后的电子性质具有金属属性,吸附能相应的增加;另外气体距离基底的距离变小;除Pt掺杂吸附NO气体,基底作为电子的受体,其余基底均作为电子的供体。通过分析得到了Ag、Au掺杂的WS₂单层对于检测三种有害气体非常有效,气敏性能为NO₂大于SO₂大于CO。本研究从理论角度研究了二维材料WS₂掺杂Au、Pt、Ag检测气体CO、NO、SO₂的灵敏性,为气体传感器的开发提供新的思路和途径。     

SnO2纳米材料气敏性能的研究进展

近年来,金属氧化物半导体气敏传感器已经广泛地应用于人们的日常生活中,并成为传感器领域的重要分支。其中,SnO_2是最早被研究的一类气敏材料,属于典型的n型半导体金属氧化物,具有制备简单、成本低廉、性质稳定等优点。主要介绍了SnO_2纳米材料气敏性能的研究进展,详细描述了该材料的气敏机理、改性手段,并对其实用化的前景进行了展望。     

导电聚合物气敏传感器研究进展

气敏传感器是利用材料的气敏特性实现目标气体浓度检测的电子元器件,在生产安全、环境监测、临床医学等领域均有广泛应用。气敏材料主要分为金属氧化物半导体材料、导电聚合物(CP)材料、金属有机框架材料。导电聚合物因其成本低、易于合成,在室温下对氨气等有害气体表现出良好的响应的特点而受到广泛关注。近年来导电聚合物复合物的研究也极大地提高了导电聚合物的气敏性能。分析了导电聚合物电阻调控机理,重点介绍了近年来对氨气、二氧化氮、硫化氢等气体的导电聚合物及其复合物的气敏传感器的研究进展,简要介绍了导电高分子在甲醇、三乙胺、一氧化碳等气体检测中的研究情况,最后展望了导电聚合物在气体传感领域的应用前景。     

SnO2气敏材料的研究进展

SnO2气敏传感器具有元件制作简单、使用寿命长、稳定性好、对气体的响应时间短等优点,已成为一个重要的研究课题.气敏反应是气体与材料表面接触后发生的化学反应,因此材料的表面组成、掺杂改性、缺陷分布、比表面积等都会影响材料的气敏性能.本文综述了近年来SnO2气敏材料的不同制备方法,以及金属氧化物和贵金属掺杂的SnO2气敏材...     

氧化锌的合成、结构表征与气敏性能研究

以锌粉为原料,采用燃烧法合成六方晶系氧化锌。采用X射线衍射仪对ZnO样品进行了结构表征。对样品的气敏元件进行了在甲醇、乙醇、丙酮气体中的气敏性能测试,该类元件属于金属氧化物半导体气敏元件。对浓度范围为5～200 mg/kg的甲醇、乙醇、丙酮气体测试表明,所有气敏元件在相同工作电压下对乙醇的灵敏度大于其他气体。该气敏元件对甲醇、乙醇、丙酮气体具有较好的气敏性能,并且具有很短的响应时间。     

Solid state ceramic gas sensors based on interfacing ionic conductors with semiconducting oxides

Solid-state ceramic NO_x sensors based on interfacing an ionic conductor (NASICON) with semiconducting oxides (rare earth perovskite-type oxides) were investigated. NASICON powders were pressed into thimbles 12 mm long with 3 mm inner diameter and 4 mm outer diameter, then sintered at 1270°C in air. A Pt wire was attached to the outer surface of the tubes using a platinum paste. A uniform Au/Pd (60 wt.%) coating, permeable to oxygen but not to NO_x, was sputtered for 40 min on the sensor external surface to allow the exposure of both electrodes to the gas atmosphere without using reference air. Windowless energy-dispersive spectroscopy (EDS) was used to evaluate the chemical composition of the Au–Pd layer before and after the performance of sensing tests. Sodalite powder as an auxiliary phase was tightly packed into the NASICON thimbles with a Pt lead for the electrical contact. To get an in-situ NO conversion to NO₂, a Pt-loaded alumina powder was used as a catalyst and incorporated with the sensor on the top of the auxiliary phase. Nano-sized and chemically-pure rare earth perovskite-type oxide (LaFeO₃, SmFeO₃, NdFeO₃ and LaCoO₃) powders, prepared by the thermal decomposition of the corresponding hexacyanocomplexes, were also used in the electrochemical cells. Each of the tested oxides was packed into the thimbles replacing the sodalite and the Pt-loaded alumina catalyst. Tests were performed also using only the perovskitic oxides. The microstructure of the materials tested was evaluated using scanning electron microscopy (SEM). The NO₂ sensing properties of the prototype sensors were investigated at controlled temperature (in the range 300–600°C) by measuring the electromotive force (EMF) at different NO₂ concentrations (in the range 2–2000 ppm in air). Some measurements were performed at various NO concentrations diluted with Ar. The results obtained showed a promising NO₂ sensing performance when ferrites were used. SmFeO₃ has a lower catalytic effect on NO oxidation than the Pt-loaded alumina catalyst, and has a similar effect to sodalite when used as auxiliary phase. The perovskite-type oxides are more preferable as auxiliary phase than sodalite because they improve the stability of the electrochemical sensor performances.     

The prior rules of designing Ti3C2Tx MXene-based gas sensors

Working temperature, sensitivity, and selectivity are some of the characteristics of the applied gas sensors. How to design and fabricate an ideal gas sensor working at room temperature is still challenging and attracting lots of interest. Two-dimensional (2D) materials with ultra-thin structure have been demonstrated as a family of ideal candidates to achieve this goal. Among them, Ti₃C₂T_x MXene, a kind of layered sheet synthesized by selectively etching MAX phases materials, shows remarkable potential to be the sensitive materials solely or in a composite. However, their designing rules are still lacking critical thinking from the viewpoint of the intrinsic property of Ti₃C₂T_x MXene based materials. In this article, two critical features, i.e., the thickness of the sensitive materials, and the scope of the analytes, are elaborated towards Ti₃C₂T_x MXene based gas sensors after characterizing the performance of sensing reducing gases (NH₃ and CO) and oxidizing gas (NO₂). First, the thinner the Ti₃C₂T_x MXene sensitive layer, the better the sensitivity. Second, the Ti₃C₂T_x MXene based gas sensor is not suitable for strong and moderate oxidation gas due to its ease of oxidation. These two rules are demonstrated, and could be considered with priority both in the future researches and practical applications.     

Effect of sintering temperature on the electrical and gas sensing properties of tin oxide powders

Tin oxide is an n-type semiconducting material having superior properties that can be utilized in several applications. The warning and detection of several dangerous gases in the environment are possible by utilizing gas sensors. The comprehensive functionality of these sensors could help to reduce the risk of severe health hazards and unexpected explosion risks. Tin oxide-based gas sensors exhibit reliable gas sensing performances along with respectful sensitivity and selectivity. Tin oxides in micro-and nano-particle forms provide an extremely high surface-to-volume ratio, which is favorable for gas sensors. Processing and synthesis of tin oxide particles accompany high-temperature processes, and this paper focuses on studying the effect of sintering temperatures on the structural and grain size of the commercially available tin oxide particles. The surface morphology of the tin oxide samples sintered at three different temperatures of 1100, 1200, 1300 ^°C shows a clear difference in the grain size and further affecting the dielectric properties of the materials. The gas sensing performances of three tin oxide samples are investigated by fabricating a pellet-type gas sensor. The sensor with the sintering temperature of 1200 ^°C exhibits the best gas-sensing performance with high response and low limit of detection (LOD). Our results suggest that the sintering temperature plays a vital role in deciding the dielectric properties and grain sizes, which are important parameters that affect the gas sensing behavior of tin oxide micro-and nano-particles.     

Light-activated room-temperature gas sensors based on metal oxide nanostructures: A review on recent advances

Many recent efforts are directed toward developing high-performance gas sensors based on metal oxide nanostructures operating at room temperature, as it lowers the power consumption, simplifies the device fabrication as well as improves the safety and stability of the sensors. The light-activated gas sensing technology was intensively studied because of its high effectiveness in improving the gas sensing performance of metal oxide nanostrctures at room temperature. This review is covers comprehensive advances in the emerging and feasible approaches for improving nanostructured metal oxide-based gas sensors by light activation, especially the progresses made in the last five years. We first summarize the effects of light-activation on gas sensing behavior of metal oxide nanostructures with some new insights into the related mechanisms. For enhancing the light-activated gas-sensing performance some possible strategies are then introduced, which include the modification of the size, dimension, nanoarchitecture, porous or hierarchical structure and doping or defect engineering, as well as the construction of nanocomposite sensing materials. Finally, some recent developments in light source and device structure design towards low power gas sensor systems are discussed. We hope that this review would provide some useful information to the design of light-activated metal oxide gas sensors operating at room temperature.     

Development of Agile Titania Sensors Via High-Temperature Reductive Etching Process (HiTREP©): I. Structural Reorganization

High selectivity, enhanced sensitivity, short response times and long shelf-life are much sought-after features in solid-state chemical sensors for the detection and metering of gas(es) of interest. Because the sensing mechanism of semiconducting oxides is invariably surface dominated, benign microscopic features are desirable to realize a useful sensing material. In principle, such morphological features could be incorporated in a number of semiconducting oxides by employing a technique based on thermodynamic consideration of the metal/metal oxide coexistence. By dynamically modulating the equilibrium oxygen partial pressure across the metal/metal oxide proximity line, renewed formulation and growth of an oxide surface on an atomic/submolecular level with exotic morphological features under conditions of oxygen "deprivation" or "enrichment" has been achieved practically in a number of potential ceramic sensor systems. In the case of oxides that are not amenable to such classical oxygen partial pressure modulation, a novel high-temperature reductive etching process (HiTREP^©) could be exploited to recreate the smart nanofeatures to impart the desired accentuation effect. This surface modification method was applied to a new commercially available aqueous plasma electro-deposited (PED) titania thick film, and the microscopic results of this strategy are presented.     

Rapid evaluation of oxidation catalysis by gas sensor system: total oxidation, oxidative dehydrogenation, and selective oxidation over metal oxide catalysts

The rapid evaluation of catalysis is an indispensable technology for the success of combinatorial chemistry. A small-sized, less expensive, easily operating screening is desirable for parallel settings which dramatically shortens the evaluation time. Recent advances in gas sensors have enabled us to use them for the rapid evaluation of oxidation catalysis. Three typical catalytic oxidations over metal oxide catalysts were evaluated by gas sensor systems optimized for each catalytic system. The first one is the total oxidation of carbon monoxide in air. Five catalytic combustion-type gas sensors were used in a parallel reactor system to shorten the evaluation time. The second one is the oxidative dehydrogenation (ODH) of ethane over the mixed oxide of nickel and iron. The evaluation of the ODH catalysis was performed by a selective olefin sensor which determines the concentration of C₂H₄ in C₂H₆. The third one is the selective oxidation catalysis of propane over alkali modified Fe/SiO₂. The effluents including CO, CO₂, aldehydes and ketones in propane were analyzed by the CO, CO₂ and semiconductor-type gas sensors selective toward aldehydes and ketones. These evaluation results indicated that gas sensors have a good potential for the rapid evaluation of oxidation catalysts.     

Electronic noses,a different approach to the sensitivity and selectivity issues

Many approaches have been made during the past years to the gas sensing task. It may be addressed using one sensor or a set of arranged sensors. Solid state chemical sensing has been systematically used for the development of gas sensor devices, based on semi conducting metal oxides. There are three major issues related to chemical sensing: sensitivity, selectivity and stability. Selectivity may be improved by the use of sensor arrays (also referred as electronic noses), while the use of additives may improve sensitivity (pure doped materials or porosity control). In this paper we describe our current work about the sensitivity and selectivity issues. A tentative explanation of the observed resistance and impedance changes by porosity control is given.     

A novel ethanol sensor with high response based on one-dimensional YFeO3 nanorods

As the cognition of metal oxide semiconductor becomes deeper and deeper, their excellent sensing ability has also been demonstrated. The gas sensors with metal oxide semiconductor as basis materials have become a hot topic at present. Enhancing the sensitivity and reducing the test limit of the sensor are exceedingly important topic. It is crucial to regulate the morphology of metal oxide semiconductor materials to improve the gas sensing performance. Low-dimensional materials such as quantum dots, one-dimensional nanowires and nanorods usually show the excellent gas-sensitive properties. In this work, one-dimensional YFeO₃ nanorods were synthesized by electrospinning technology. The one-dimensional rod-like structure enables more active sites to be exposed on the surface of materials, which can effectively promote the adsorption process of the YFeO₃ nanorods to the test gases, so as to improve the gas sensing performance. Found by testing the gas sensitivity, YFeO₃ nanorods responds far better to ethanol than other tested gases. The response and recovery time of YFeO₃ nanorods to 100 ppm ethanol at 350 °C was approximately 19 s and 9 s, respectively. It indicates that the response and recovery ability of YFeO₃ nanorods to ethanol were excellent. The study can provide technical reference for subsequent preparation of remarkable performance ethanol sensor and enrich the materials category of gas sensor fields.