SnO2-Ag-SnO2结构元件室温下对H2S的敏感特性研究

以SnCl4和O2为源物质,采用等离子增强化学气相沉积(PECVD)和浸渍法掺Ag技术制备了SnO2-Ag-SnO2结构薄膜,在20℃下该结构薄膜对H2S具有良好的气敏特性,即高灵敏度、良好的选择特性和开关式响应特性.     

Gas sensing properties at room temperature of a quartz crystal microbalance coated with ZnO nanorods

Gas sensors based on a quartz crystal microbalance (QCM) coated with ZnO nanorods were developed for detection of NH₃ at room temperature. Vertically well-aligned ZnO nanorods were synthesized by a novel wet chemical route at a low temperature of 90 °C, which was used to grow the ZnO nanorods directly on the QCM for the gas sensor application. The morphology of the ZnO nanorods was examined by field-emission scanning electron microscopy (FE-SEM). The diameter and length of the nanorods were 100 nm and 3 μm, respectively. The QCM coated with the ZnO nanorods gas sensor showed excellent performance to NH₃ gas. The frequency shift (Δf) to 50 ppm NH₃ at room temperature was about 9.1 Hz. It was found that the response and recovery times were varied with the ammonia concentration. The fabricated gas sensors showed good reproducibility and high stability. Moreover, the sensor showed a high selectivity to ammoniac gas over liquefied petroleum gas (LPG), nitrous oxide (N₂O), carbon monoxide (CO), nitrogen dioxide (NO₂), and carbon dioxide (CO₂).     

Love wave hydrogen sensors based on ZnO nanorod film/36°YX-LiTaO3 substrate structures operated at room temperature

Love wave hydrogen sensors based on ZnO nanorod layers deposited on 36°YX-LiTaO₃ substrates have been studied. The ZnO nanorod layers are prepared by two steps: first, the seed layers, as well the guiding layers of the Love wave devices, are deposited by RF magnetron sputtering; second, the nanostructural layers, as well the sensing layers of the sensors, are grown by hydrothermal synthesis. Two kinds of ZnO layers have been analyzed by XRD, SEM and XPS. The XRD shows that both ZnO layers have (0 0 2) oriented wurtzite structures. The SEM results reveal that the morphologies of the deposited ZnO seed layers are continuous and compact, while the hydrothermal treated layers are with nanorods almost perpendicular to the substrate surfaces. Finally, the hydrogen sensing responses of the Love wave sensors activated by Pt catalysts are measured for various concentrations of hydrogen in synthetic air at room temperature. The results show that the sensors have high sensitivity and repeatability as the nanorod layers are optimized, such as the frequency shift 8 kHz toward 0.04% of H₂ in synthetic air is obtained while the height of the nanorod layer is about 2.1 μm and the central frequency of the sensor is about 125.5 MHz. The XPS analyses of the sensitive layers show that there are oxygen vacancies in the layers, so the oxygen vacancy model is used to explain the hydrogen sensing mechanism of the Love wave sensors.     

Sensing mechanism of room temperature CO2 sensors based on primary amino groups

This work reports measurements to elucidate the reaction mechanisms of sensitive materials containing primary amino groups with CO₂. The sensing mechanism is based on their ability to perform reversible acid-base reactions. The effect discussed for most of the previously used sensing layers concerns the formation of bicarbonate species, which requires H₂O as well as an increased temperature. By using work function readout technology an operation at room temperature of the sensing layers is enabled providing satisfying sensor responses in terms of SNR (signal noise ratio) and response time. In contrast to the previously investigated higher operation temperature, the response resulting from a room temperature measurement appears to be dominated by the reversible formation of carbamate, which does not require the presence of water. The presence of carbamate is considered to be the reason of the improved sensing performance of this sensing material at room temperature with work function readout.To confirm this hypothesis, DRIFT-MIR, Raman, XPS and NMR spectroscopy were employed to investigate the formation of species after manufacturing of the sensitive layers. Besides the formation of bicarbonate, the results show a strong indication for carbamate formation.     

Synthesis of ZnO nanorods and its application in NO2 sensors

One-dimensional (1D) ZnO nanorods with pencil-like shape and high aspect ratio were successfully synthesized using a cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal process at 90 °C. The surface morphology and structure of nanocrystals were characterized by FE-SEM, XRD and XPS analysis. Experimental results show that the surfactant and base concentration play important roles in the formation and growth orientation of ZnO nanorods. The ZnO nanorods synthesized exhibits high response and selectivity to NO₂, the highest response to 40 ppm NO₂ reached 206 and the selectivity with respect to CO and CH₄ at same concentration reached 10.3 and 30 times, respectively. The effects of synthesis method, surfactant and calcination condition on sensing properties were systematically investigated. The results indicate that the CTAB-assisted low temperature hydrothermal process is a potentially facile method for synthesis of 1D ZnO nanorods and excellent potential candidates as gas sensing materials.     

Development of high sensitivity tin oxide based sensors for gas/odour detection at room temperature

An effort has been made to develop thick film tin oxide gas sensors which could detect various gases/odours at room temperature. To achieve this, the fabricated sensors were annealed in oxygen plasma for various durations. It was then found that, the room temperature sensitivity of such sensors was increased to about ten times as compared to the sensitivity of the non-annealed sensors. Further, plasma annealed sensors are found to be practically independent of temperature and the room temperature sensitivity of these sensors are found to be about 1.5 times the sensitivity of the conventional sensors at its operating temperature of 300°C. Studies on the variation of d.c. resistance, sensitivity, temporal response, current–temperature characteristics and impedance spectroscopy with the annealing time have also been made. These studies reveal that, with the increase in annealing time, there is a permanent gradual reduction in the d.c. resistance of annealed sensors. Further, it is also observed that with the increase in annealing time, the response time improves, barrier height reduces, barrier capacitance increases and the dependence of the sensitivity with temperature reduces while the sensitivity itself improves many-fold.     

基于微通道的ZnO纳米棒生物荧光检测研究

利用种子法和水热合成技术,分别在常规条件下和阵列式微通道中制备氧化锌(ZnO)纳米棒.采用扫描电子显微镜(SEM)、X射线衍射(XRD)等分析方法表征ZnO纳米棒的表面形貌特点和晶体结构.结果表明:微通道中制备的ZnO纳米棒的比表面积、结晶度和c轴取向性均有较大程度的提高.同时,建立了基于阵列式微通道的ZnO纳米棒生物荧光检测方法,利用ZnO纳米棒可显著增强荧光信号,对异硫氰酸荧光素标记的羊抗牛IgG抗体的检测限为1×10-4 μg/mL.     

石墨烯/氧化钨复合材料室温响应NO2传感器

采用溶剂热法制备了石墨烯/氧化钨复合材料,通过XRD,SEM,Raman表征方法对复合材料形貌、晶体结构进行表征,结果表明:制备的氧化钨为六方相结构的WO3,呈现一维管状形貌,石墨烯均匀分散在复合材料中.石墨烯/氧化钨复合材料涂覆在叉指电极制作成传感器进行气敏性能测试,结果表明:传感器可室温条件下实现对NO2检测,检测...     

常温下氧化钨基NO2传感器气敏特性的光照强度依赖研究

为了研究WO3的常温气敏性能,以热氧化钨丝的方法制备WQ3纳米材料并制作厚膜气敏元件,通过XRD对材料的晶体结构进行表征,对敏感元件进行了气敏性能测试,测得该元件在常温、0.4W/cm2紫外光(波长:300～450nm)辐照条件下对50ppm的NO2的灵敏度S=15.4,响应时间τres=2.5s,恢复时间τrec=18.1s;在加热功率为0.81W条件下,元件对50ppm NO2的灵敏度为S=22.5,响应时间τres=1.5s,恢复时间τrec=10.7s,研究了灵敏度对光功率密度和加热功率的依赖关系,实验结果表明WO3纳米材料在常温、紫外光照条件下对NO2具有较好的气敏性能.     

SnO_2纳米棒的乙醇气体敏感特性研究

在NaC l+KC l熔盐介质中,在660℃下对利用微乳技术制备的前驱物进行焙烧,成功合成了SnO2纳米棒。利用TEM,XRD对SnO2纳米棒形貌、成分进行了表征和分析,SnO2纳米棒直径为10~20 nm,长度从几百个纳米到几个微米。研究表明:以SnO2纳米棒为原料制备的厚膜气敏元件,对乙醇具有较高的灵敏度、好的选择性和响应-恢复特性。     

Fabrication at wafer level of miniaturized gas sensors based on SnO2 nanorods deposited by PECVD and gas sensing characteristics

SnO₂ nanorods were successfully deposited on 3″ Si/SiO₂ wafers by inductively coupled plasma-enhanced chemical vapour deposition (PECVD) and a wafer-level patterning of nanorods layer for miniaturized solid state gas sensor fabrication were performed. Uniform needle-shaped SnO₂ nanorods in situ grown were obtained under catalyst- and high temperature treatment-free growth condition. These nanorods have an average diameter between 5 and 15 nm and a length of 160-300 nm. The SnO₂-nanorods based gas sensors were tested towards NH₃ and CH₃OH and gas sensing tests show remarkable response, showing promising and repeatable results compared with the SnO₂ thin films gas sensors.     

Hydrogen gas sensor based on nanofibers TiO2-PVP thin film at room temperature prepared by electrospinning

Microsystem Technologies - TiO2/PVP nanofibers (NFs) have been deposited onto glass substrate by electrospinning method. X-ray diffraction analysis confirms the formation of anatse phase with high...     

High-sensitivity NO2 gas sensors based on flower-like and tube-like ZnO nanomaterials

Hierarchical flower-like and 1D tube-like ZnO architectures were synthesized by a microemulsion-based solvothermal method. Technologies of XRD, SEM and TEM were used to characterize the morphological and structural properties of the products. The influence of the flower-like and tube-like morphologies on their NO₂ sensing properties was investigated. The experimental results showed that high-sensitivity NO₂ gas sensors were fabricated. The sensitivity of the tube-like ZnO gas sensor was much higher than that of the flower-like ZnO gas sensor and the tube-like ZnO gas sensor exhibited shorter response time. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique was employed to investigate the NO₂ sensing mechanisms. Free nitrate ions, nitrate and nitrite were the main adsorbed species during the adsorption, and NO also existed in the initial period of surface reoxidation. Furthermore, N₂O was formed via NO⁻ and N₂O₂⁻ stemmed from NO and increased upon rising temperature. Moreover, the PL spectra and the XPS spectra further proved that the intensity of donors (oxygen vacancy (V_O) and zinc interstitial (Zn_i)) and surface oxygen species (O₂⁻ and O₂) involved in the gas sensing mechanism leaded to the different sensitivities.     

ZnO hierarchical nanostructures grown at room temperature and their C2H5OH sensor applications

Highly crystalline ZnO hierarchical nanostructures were prepared at room temperature through the alkaline hydrolysis of zinc salt by the forced mixing of two immiscible solutions: Zn-nitrate aqueous solution and oleic-acid-dissolved n-hexane solution. The oleic acid acted as a surfactant in the room-temperature formation of well-defined ZnO hierarchical nanostructures, which subsequently demonstrated a sensitive and selective detection of C₂H₅OH. The responses of these hierarchical nanostructures to 10-100 ppm C₂H₅OH ranged from 15.7 to 177.7, which were 7-9 times higher than those of the agglomerated nanoparticles.     

室温固相合成纳米SnO_2及气敏性能研究

用室温固相法合成了SnO2 纳米粉体,在粉体材料中添加无机造孔剂调整材料的微结构。考察不同烧结温度和造孔剂添加量对气敏性能的影响。结果表明:适宜的无机造孔剂和烧结温度能改善气敏材料的微结构,从而提高气敏性能。材料对乙醇有较好的敏感性和选择性。在4. 5V加热电压下,对体积分数为5×10-4的乙醇、汽油和丙酮的灵敏度分别为85. 91, 8. 34和8. 37。     

体积连接性指数预测离子液体的室温粘度

离子液体(ILs)被视为潜在的"绿色溶剂",在溶剂的应用过程中粘度是最重要的热力学数据之一,但目前ILs的粘度数据仍然较为缺乏,除实验测定外,基团贡献、连接性指数等思想也为设计和筛选ILs提供了重要的性质预测方法。在已有的基于分子体积的粘度预测方法基础上,结合分子连接性指数来区分ILs不同基团的连接方式,建立了一个新的体积连接性指数模型用于预测ILs的室温粘度。由于该模型的基本参数来源于确定的基团物理体积值,因此为预测未知的ILs粘度等性质提供了可能性。通过对90种ILs室温粘度的预测,结果表明平均相对偏差为5.95%,方差检验所得的R~2和rmsd分别为0.9905和21cP,证明建立的模型可用于预测ILs的室温粘度。     

基于光谱微型检测室互补温度控制器设计

为满足光谱微型检测室对温度快速稳定和精确控制的要求,设计了一种基于加热棒快速加热和帕尔贴(Peltier)稳定恒温的样品检测室气浴温度控制系统。系统以微控器为核心,集成模糊比例—积分—微分(PID)控制算法,实现了快速加热和精确恒温的互补功能。与现有的单一温度控制系统(水浴帕尔贴恒温控制)进行了对比实验测试,结果表明:检测室内样品反应体系的温度能够在5 min内精确稳定在(40±0. 3)℃内,缩短了温度控制时间,且温度控制的重复性好、准确度高,满足光谱类微型检测室对温度控制的要求。     

单总线多点分布式温度监控系统的设计

本文设计了一个单总线多点分布式温度测控系统,该系统可以进行远程单线多点数据采集与控制,并具有数据存储、温度曲线显示、打印等数据库功能。并为数据处理与融合,以及专家数据库建立了一个智能化应用平台。利用这一平台,可以方便地开发具有多温度点测量与控制的应用系统。采用了数字化测量技术,具有测量误差小、抗干扰能力强、成本低等特点。     

基于Sensirion SHT系列传感器的分布式温湿度监测系统

设计了一种基于SensirionSHT温湿度传感器的温湿度监控系统.采用多级分布式结构和多单片机设计思想,系统由SensirionSHT温湿度传感器,单片机,嵌入式电力线载波调制解调器(PLC),和顶端服务器组成.主要完成了系统的软硬件设计,实现了一种面向物流仓储的温湿度监控系统.     

基于STC12C5A16S2的温度采集系统的设计

以半导体器件的物理特性和电学特性为依据,设计了一种低温自启动恒温加热器,保证系统内部温度处于芯片正常工作范围内,并以尽可能少的元件构成完整的闭环控制系统。利用PT100型金属铂电阻温度特性,使用三线制接法,采用STC12C5A16S2型单片机芯片对温度信号进行采集。使用工业上常用的RS485总线作为温度传输的通讯方式,以提高信息传输的可靠性。通过在高低温环境下实验,验证了该温度采集系统的可行性。