Free‐Standing Functionalized Graphene Oxide Solid Electrolytes in Electrochemical Gas Sensors

A free‐standing sulfonic acid functionalized graphene oxide (fSGO)‐based electrolyte film is prepared and used in an electrochemical gas sensor, an alcohol fuel cell sensor (AFCS), for the detection of alcohol. The fSGO electrolyte film‐based AFCS detects ethanol vapor with excellent response, linearity, and sensitivity, since it possesses a high proton conductivity (58 mS cm^?1 at 55 °C). An ethanol detection limit level as low as 25 ppm is achieved and high selectivity for ethanol over acetone is demonstrated. These results do not only show the promising potential of fSGO films in an electrochemical gas sensors, specifically a portable breathalyzer, but also open an alternative pathway to investigate the application of graphene derivatives in the field of gas sensors.     

气体声表面波传感器的研究进展

主要从声表面波(SAW)结构和敏感膜的角度综述了SAW气体传感器的研究现状。重点分析了国外出现的换能器新型结构,对其优点进行了初步分析,并和传统的SAW气体传感器结构做了比较,指出这些新结构尽管存在一些缺点,目前还不能取代传统的通用式结构,但是在某些特殊场合具有传统结构所不具备的优点。在敏感膜方面,主要从新材料方面入手,分析了目前主要使用的敏感膜材料,并结合SAW气体传感器的发展趋势,总结出敏感膜的发展方向。同时,对SAW气体传感器的其他组成部分如衬底材料和信号处理电路也作了简单的回顾,最后结合国内外研究成果对SAW气体传感器的发展做了展望。     

Current-Mirror-Based Potentiostats for Three-Electrode Amperometric Electrochemical Sensors

We present a new circuit topology for potentiostats that interface with three-electrode amperometric electrochemical sensors. In this new topology, a current-copying circuit, e.g., a current mirror, is placed in the sensor current path to generate a mirrored image of the sensor current. The mirrored image is then measured and processed instead of the sensor current itself. The new potentiostat topology consumes very low power, occupies a very small die area, and has potentially very low noise. These characteristics make the new topology very suitable for portable or bioimplantable applications. In order to demonstrate the feasibility of the new topology, we present the results of a potentiostat circuit implemented in a 0.18- $mu{hbox {m}}$ CMOS process. The circuit converts the sensor current to a frequency-modulated pulse waveform, for which the time difference between two consecutive pulses is inversely proportional to the sensor current. The potentiostat measures the sensor current from 1 nA to 1 $mu{hbox {A}}$ with better than 0.1% of accuracy. It consumes only 70 $muhbox{W}$ of power from a 1.8-V supply voltage and occupies an area of 0.02 ${hbox {mm}}^{2}$.      

声表面波气体传感器研究进展

从机理模型构建、物理功能结构优化两方面出发对覆盖聚合物敏感膜的高性能声表面波(SAW)气体传感器技术进行了研究和探讨.实验研制了一种以具有高频率稳定性的声表面波延迟线型振荡器为传感元,结合六氟异丙醇基聚硅氧烷敏感膜的SAW传感器,开展了针对DMMP的检测实验,检测下限与检测灵敏度分别达到了0.04 mg/m3和485 Hz/mg/m3.     

BN-C Hybrid Nanoribbons as Gas Sensors

The effects of carbon monoxide (CO) and ammonia (NH₃) molecules adsorption on the various composites of boron nitride and graphene BN-C hybrid nanoribbons are investigated using the non-equilibrium Green’s function (NEGF) technique based on density functional theory (DFT). The effects of adsorption with possible random configurations on the average of the density of states (DOS), transmission coefficient, and the current–voltage (I–V) characteristics are calculated. The results indicate that, by embedding armchair graphene nanoribbon (AGNR) with boron nitride nanoribbon (BNNR), the various electronic properties can be observed after gas molecule adsorption. The electronic structure and gap of hybrids system is modified due to gas adsorption, and the systems act like the n-type semiconductor by NH₃ molecule adsorption. The hybrid structures due to their tunable band gap are better candidates for gas detecting compared to the pristine BNNRs and AGNRs.     

用光学传感器提高石油和天然气的开采量

随着市场对石油需求量的增加,世界各相关石油公司都在致力于寻找开采现存石油的新方法.     

H2S气体传感器的进展

综述了Ｈ２Ｓ半导体气体传感器的制备及敏感机理，添加剂ＣｕＯ化合物可以明显提高对Ｈ２Ｓ气体的灵敏度与选择性，最后，介绍了一种似乎合理的敏感机制。     

全固态气体传感器的研究进展

本文介绍全固态气体传感器的研究进展,包括半导体氧化物传感器,固体电解质传感器、催化燃烧式传感器以及基于其他原理的气体传感器.     

Gas Sensors: Ultrasensitive and Highly Selective Gas Sensors Based on Electrospun SnO2 Nanofibers Modified by Pd Loading (Adv. Funct. Mater. 24/2010)

This work presents a new route to suppress grain growth and tune the sensitivity and selectivity of nanocrystalline SnO₂ fibers. Unloaded and Pd‐loaded SnO₂ nanofiber mats are synthesized by electrospinning followed by hot‐pressing at 80 °C and calcination at 450 or 600 °C. The chemical composition and microstructure evolution as a function of Pd‐loading and calcination temperature are examined using EDS, XPS, XRD, SEM, and HRTEM. Highly porous fibrillar morphology with nanocrystalline fibers comprising SnO₂ crystallites decorated with tiny PdO crystallites is observed. The grain size of the SnO₂ crystallites in the layers that are calcined at 600 °C decreases with increasing Pd concentration from about 15 nm in the unloaded specimen to about 7 nm in the 40 mol% Pd‐loaded specimen, indicating that Pd‐loading could effectively suppress the SnO₂ grain growth during the calcination step. The Pd‐loaded SnO₂ sensors have 4 orders of magnitude higher resistivity and exhibit significantly enhanced sensitivity to H₂ and lower sensitivity to NO₂ compared to their unloaded counterparts. These observations are attributed to enhanced electron depletion at the surface of the PdO‐decorated SnO₂ crystallites and catalytic effect of PdO in promoting the oxidation of H₂ into H₂O. These phenomena appear to have a much larger effect on the sensitivity of the Pd‐loaded sensors than the reduction in grain size.     

A Thin-Film Platform for Chemical Gas Sensors

In the study, a technique for formation of planar microheaters that make it possible to heat an active zone to a temperature higher than 500°С is proposed and successfully implemented. The developed heating elements are distinguished by low power consumption, short response time, and extremely high resistance to impact loads. The synthetic approaches used in the work (anodic oxidation, photolithography, and magnetron sputtering) feature manufacturability and scaling simplicity. This makes planar heating elements a promising platform based on which semiconductor and thermocatalytic sensors of toxic and explosive gases may be created.     

环境中金属镉的电化学传感器测定方法研究

由于金属镉的毒性给环境造成严重影响，所以迫切需要建立一种便宜、快速，用于测定低含量镉离子的检测方法。对于环境中金属镉的测定前人已研究出许多方法，其中电化学方法以其简易快捷、廉价、测量装置能小型化、灵敏度高、适合现场采样测量等优点为人们所推崇。综述了近十年以来一系列用于环境中金属镉测定的电化学传感器测定方法，并且讨论了各种电化学传感器对于环境中金属镉测定应用的优缺点，集中比较了各种方法相对应的检测限。     

Humidity-Initiated Gas Sensors for Volatile Organic Compounds Sensing

A new volatile organic compounds (VOCs) sensing concept called humidity-initiated gas (HIG) sensors is described and demonstrated. HIG sensors employ the impedance of water assembled at sensor interfaces when exposed to humidity to sense VOCs at low concentrations. Here, two HIG sensor variants are studied—Type I and Type II. Type I sensors benefit from simplicity, but are less attractive in terms of key performance metrics, including response time and detection limits. Type II sensors are more complex, but are more attractive in terms of key performance metrics. Notably, it is observed that the best-in-class Type II HIG sensors achieve <2 min response times and <10 ppb detection limit for geranyl acetone, a VOC linked to the asymptomatic form of Huanglongbing (HLB) citrus disease. Both Type I and Type II sensors are assembled from off-the-shelf materials and demonstrate remarkable stability at high humidity. HIG sensors are proposed as an attractive alternative to existing VOCs sensors for remote field detection tasks, including VOCs detection to diagnose HLB citrus disease.     

Encapsulation of Semiconductor Gas Sensors with Gas Barrier Films for USN Application

Sensor nodes in ubiquitous sensor networks require autonomous replacement of deteriorated gas sensors with reserved sensors, which has led us to develop an encapsulation technique to avoid poisoning the reserved sensors and an autonomous activation technique to replace a deteriorated sensor with a reserved sensor. Encapsulations of In₂O₃ nanoparticles with poly(ethylene‐co‐vinyl alcohol) (EVOH) or polyvinylidene difluoride (PVDF) as gas barrier layers are reported. The EVOH or PVDF films are used for an encapsulation of In2O3 as a sensing material and are effective in blocking In2O3 from contacting formaldehyde (HCHO) gas. The activation process of In2O3 by removing the EVOH through heating is effective. However, the thermal decomposition of the PVDF affects the property of the In₂O₃ in terms of the gas reactivity. The response of the sensor to HCHO gas after removing the EVOH is 26%, which is not significantly different with the response of 28% in a reference sample that was not treated at all. We believe that the selection of gas barrier materials for the encapsulation and activation of In2O3 should be considered because of the ill effect the byproduct of thermal decomposition has on the sensing materials and other thermal properties of the barrier materials.     

Energy-Efficient Gas Sensors Based on Nanocrystalline Indium Oxide

Semiconductors - The effect of the nanocrystal size on the sensitivity of nanocrystalline indium oxide In2O3 with an extremely small size of nanocrystals (from 7 to 40 nm) synthesized by the...     

推陈出新,创办高水平的《学报》品牌——庆贺《军医进修学院学报》创刊30周年

电子束光刻(EBL)具有高的分辨率,能制备具有亚微米尺寸的声表面波(SAW)器件.一种采用EBL技术制备用于气体传感器的具有亚微米尺寸的SAW延迟线的方法:首先利用EBL在压电衬底上获得叉指换能器(IDT)的电子抗蚀剂图形;然后用剥离工艺制作出IDT电极.通过邻近效应校正和提高场拼接精度,制作的叉指电极具有一致性,电极形貌好.相对于干法刻蚀工艺,剥离工艺避免了对压电衬底表面的物理损伤.该技术为实现特征尺寸达到百纳米级的更高工作频率SAW器件的制造提供了很好的途径.     

掺杂WO_3基丙酮气敏元件的研制

在WO3粉体材料中加入一定质量分数(w)的掺杂剂(Pt、Pd、PtO2、PdCl2、SnO2、SiO2、Al2O3),于恒温600℃烧结1h制作成旁热式丙酮气体敏感元件。采用静态电压测量法,研究和分析了不同的加热电压与不同掺杂配方元件灵敏度(β)的关系,进一步分析了掺杂剂对元件的响应与恢复时间的影响。实验结果表明,掺入质量分数为0.5%的Pt粉,在加热功率为600mW时,丙酮气敏元件的灵敏度提高约8倍,元件的响应时间和恢复时间分别缩短了约60%和88%。     

用于气体频谱分析传感器的245 GHz次谐波接收机

提出了一种用于气体频谱分析传感器的混频器优先的245 GHz次谐波接收机。该接收机具有高线性度、高带宽、低噪声系数、低功耗和高集成度的特点。该接收机由2次无源反接并联二极管对(APDP)次谐波混频器、120 GHz推推型压控振荡器-分频器链路和120 GHz功率放大器构成。采用特征频率/最大振荡频率为300 GHz/500 GHz的SiGe BiCMOS工艺进行实现。结果表明,该接收机芯片的转换增益为-16 dB,带宽为14 GHz,单边带噪声系数为19 dB,输入1 dB压缩点为0 dBm,功耗为213 mW。     

碳纳米管场效应型DMMP气敏传感器研究

基于单壁碳纳米管(SWCNT)的场效应气体传感器由于具有传感性能好、体积小、室温操作和加偏压自我解吸附等优良性能,有着广泛的应用前景。利用单壁碳纳米管自组装技术在SiO2/Si基底上制备均匀分布的SWCNT薄膜,将其作为沟道制作了具有灵敏开关特性的场效应晶体管(FET),该FET器件的开关比达到105。将此FET器件作为气体传感芯片用于甲基膦酸二甲酯(DMMP)气体分子的检测。结果显示,当通入DMMP气体时,器件的阈值电压向负栅电压方向移动。当DMMP体积分数为5×10-6,栅压为-10 V时,器件的灵敏度达到32%,响应时间为300 s。在15 V的栅压下器件能够很快地实现气体解吸附。     

Semiconducting ZnO Nanofibers as Gas Sensors and Gas Response Improvement by SnO2 Coating

ZnO nanofibers were electro‐spun from a solution containing poly 4‐vinyl phenol and Zn acetate dihydrate. The calcination process of the ZnO/PVP composite nanofibers brought forth a random network of polycrystalline würtzite ZnO nanofibers of 30 nm to 70 nm in diameter. The electrical properties of the ZnO nanofibers were governed by the grain boundaries. To investigate possible applications of the ZnO nanofibers, their CO and NO₂ gas sensing responses are demonstrated. In particular, the SnO2‐deposited ZnO nanofibers exhibit a remarkable gas sensing response to NO2 gas as low as 400 ppb. Oxide nanofibers emerge as a new proposition for oxide‐based gas sensors.     

lntra-Cavity Absorption Sensors for Gas Detection Using Wavelength Sweep Technique

Wavelength sweep technique （WST） is introduced into intra-cavity fiber laser （ICFL） for low concentration gas detection. The limitation induced by noise can be eliminated using this method, and the performance of the system is improved. The sensitivity of the system is reduced to less than 300 ppm. With WST, sweeping characteristic of the ICFL can be described according to known gas absorption spectra.