有序介孔SnO_2的制备及其气敏特性的研究

以SBA-15为硬模板,利用浸渍法将SnCl2担载到介孔孔道中,通过控制反应温度和反应环境合成SnO2/SBA-15复合材料,用NaOH溶液除去SBA-15模板,制备具有与SBA-15反转结构的介孔SnO2;通过XRD,TEM和N2吸脱附的表征,证明所制备的SnO2具有有序的介孔结构和较大的比表面积;对乙醇敏感特性进行了初步探讨。     

纳米SnO_2/SiO_2复合材料的制备及其对H_2气敏性研究

采用锡粒氧化法合成纳米二氧化锡(SnO2),并以KH-550为改性剂,对纳米二氧化锡进行表面化学修饰,制得SnO2/SiO2复合材料,研究了不同条件下制得的SnO2/SiO2复合材料对H2的气敏性能。实验结果表明较佳的SnO2/SiO2复合材料制备工艺条件为:室温条件下,改性剂与纳米二氧化锡质量百分比为9%,在甲苯溶剂中反应3h。制备的SnO2/SiO2复合材料对1000ppm H2的气体灵敏度为37.506。     

Sol-Gel法制备纳米SnO2掺杂PMMA透明复合材料

采用溶胶-凝胶法制备SnO2的乙醇溶液胶体,在140℃条件下,获得乙醇修饰的无定形纳米SnO2,将该纳米SnO2溶于甲基丙烯酸甲酯(MMA)单体中,聚合制备得到SnO2/PMMA复合材料.采用X衍射(XRD)、傅立叶红外(FTIR)、示差扫描量热-热重法联用(DSC-TG)、粒度仪和透射电镜(TEM)等方法对纳米SnO2、纳米SnO2乙醇溶液及其SnO2/PMMA复合材料进行分析表征.扫描电子显微镜(SEM)对实验获得的透明的SnO2/PMMA复合材料进行了分析,表明纳米SnO2能够较好的分散在PMMA中.     

纳米SnO2/TiO2复合粉体制备及其红外特性研究

以溶胶-凝胶方法制备纳米SnO2/TiO2复合粉体,并用XRD、TEM等方法对其进行了表征,给出了相关的工艺参数.研究了纳米SnO2及SnO2/TiO2复合材料的红外吸收特性.结果表明,本文制备的纳米SnO2/TiO2复合材料在4000～1500cm-1和1000～400cm-1范围内有较好的红外吸收.     

介孔硅基WO3纳米颗粒薄膜室温气敏元件特性

采用双槽电化学腐蚀法在p＋单晶硅片表面制备介孔硅层（meso-PSlayer）,然后用对向靶磁控反应溅射法在介孔硅表面沉积WO3纳米颗粒薄膜,在干燥空气中于400℃下保温4h进行退火热处理,制备出介孔硅基WO3纳米颗粒薄膜（WO3-PS）室温气敏元件.利用扫描电子显微镜（SEM）分析介孔硅层及WO3-PS的表面形貌,通过X射线衍射（XRD）研究WO3的结晶状态,测试WO3-PS气敏元件在室温下对NO2、NH3的气敏性能,并探讨了WO3-PS气敏元件的工作机理.实验结果表明,在介孔硅表面沉积WO3纳米颗粒薄膜可使介孔硅的气敏性能显著提高,其中在室温下对10×10^-6NO2的灵敏度由5提高至56,大大提高了介孔硅的灵敏度,并降低了其响应/恢复时间,提高了对NO2的选择性.     

介孔炭材料及介孔炭/氧化硅复合材料对大分子有机污染物的吸附

介孔炭材料与活性炭相比具有较大的孔体积和孔径,高的比表面积以及规则的孔道结构,而介孔炭/氧化硅复合材料兼顾了活性炭与介孔材料的优点,因此在吸附大分子有机污染物方面有很好的应用前景。笔者综述了近年来介孔炭,负载/修饰后的介孔炭,介孔炭/氧化硅复合材料的制备和最新研究进展。在制备方面,根据其制备机理的不同可分为硬模板法和软模板法,制备出有序的介孔炭与介孔炭/氧化硅复合材料。在应用方面,重点介绍了介孔炭材料和介孔炭/氧化硅复合材料对大分子有机污染物的吸附性能。进而对介孔炭/氧化硅复合材料在吸附方面的应用进行了展望。     

聚吡咯/SnO2复合材料气敏性能研究

采用化学氧化聚合法合成了聚吡咯(PPy),并通过机械共混法制备了PPy/SnO2/PVA复合薄膜材料,研究其在室温下对乙醇和丙酮气体的敏感性。结果表明:PPy/SnO2/PVA材料随着SnO2的增加表现出较好的选择性,响应和恢复时间缩短,灵敏度下降。当SnO2为40%时,PPy/SnO2/PVA对乙醇气体响应时间比PPy/PVA缩短了65%,恢复时间缩短了68%,而灵敏度下降了39%,材料的稳定性得到提高。PPy/SnO2/PVA复合材料在乙醇和丙酮气体中显示出不同的气敏性和响应恢复时间,但灵敏度相差不大。膜厚易导致材料灵敏度降低和响应、恢复时间变长。此外,该类气敏复合材料具有良好的重复性、稳定性。     

室温条件下-(CH2)3NH2修饰的介孔分子筛MCM-41的合成与表征

在室温条件下,以3-氨丙基三乙氧基硅烷为前驱体,使有机官能团-CH2CH2CH2NH2修饰了硅铝介孔分子筛MCM-41(Si/Al=35),制备了无机-有机复合材料MCM-(CH2)3NH2.并通过XRD,DTA-TGA,FTIR,N2吸附-脱附对复合材料MCM-(CH2)3NH2进行了表征.     

真空浸渍制备膨胀石墨基C/C复合材料及其甲醛吸附性能

以蔗糖为炭源,磷酸为活化剂,采用真空浸渍法经炭化、活化制得膨胀石墨基C/C复合材料.采用SEM、氮气吸脱附法、TG和TEM等测试手段,研究了磷酸/蔗糖质量比(Xp)、蔗糖浓度对复合材料孔结构和比表面积的影响,利用FTIR和Boehm滴定法对复合材料表面的化学官能团进行表征,并考察了C/C复合材料对甲醛的吸附能力.结果表明:膨胀石墨基C/C复合材料含有大量的微孔、一定量的介孔和大孔,表面含有丰富的含氧官能团,有利于对甲醛极性分子的吸附.在Xp=1.0、蔗糖溶液浓度为30％(质量分数)时所制得的膨胀石墨基C/C复合材料比表面积最高,达到2112m2/g,孔容为1.08 mL/g,其对甲醛的吸附量为854mg/g,较同工艺制备的活性炭提高了26.9％.     

插入NiCr合金层对SnO2/Ag/SnO2多层结构透明导电薄膜热稳定性的影响

室温下通过磁控溅射技术制备了SnO2/Ag/SnO2(SAS)、SnO2/Ag/NiCr/SnO2(SANS)和SnO2/NiCr/Ag/NiCr/SnO2(SNANS)三类多层膜.采用X射线衍射(XRD)、原子力显微镜(AFM)、霍尔效应测量仪和紫外-可见分光光度计研究了大气和真空退火温度与薄膜结构、形貌和透明导电性...     

Synthesis of mesoporous tin oxide and its application as a LNG sensor

The nanostructured SnO2 gas sensor with Au electrodes and Pt heater has been fabricated as one unit via screen printing process. The gas sensor was tested for CH4 sensing behavior at 350 degrees C in the concentration range of 500-10,000 ppm. Those mesoporous SnO2 sensors exhibited the similar sensoring properties in CH4 and CO detection. The fast speed of response and high sensitivity were obtained for mesoporous tin oxide sensor as compared to non-porous one.     

Enhanced catalytic activity of ultrathin CuO islands on SnO/sub 2/ films for fast response H/sub 2/S gas sensors

H/sub 2/S gas-sensing properties of a novel SnO/sub 2/-CuO structure consisting of ultrathin (/spl sim/10 nm) CuO dotted islands (600 /spl mu/m diameter) on 120-nm thick, sputtered SnO/sub 2/ film are compared with a pure SnO/sub 2/ and a SnO/sub 2/-CuO bilayer sensor. The SnO/sub 2/-CuO-dotted sensor exhibited a high sensitivity of 7.3/spl times/10/sup 3/ at a low operating temperature of 150/spl deg/C. A fast response time of 14 s for 20 ppm of H/sub 2/S gas and a recovery time of 118 s under flowing air have been measured. The electronic interaction due to modulation of the space charge regions between the distributed p-type CuO islands on the n-type SnO/sub 2/ thin-film surface and the presence of adsorbed oxygen on the SnO/sub 2/ support have been analyzed. Dissociated hydrogen available from the CuO-H/sub 2/S interaction spills over and its chemical interaction with the adsorbed oxygen on the SnO/sub 2/ surface is found to play a dominant role in the observed fast response characteristics.     

Ultrahigh-sensitive tin-oxide microsensors for H/sub 2/S detection

Ultrahigh-sensitivity SnO/sub 2/-CuO sensors were fabricated on Si(100) substrates for detection of low concentrations of hydrogen sulfide. The sensing material was spin coated over platinum electrodes with a thickness of 300 nm applying a sol-gel process. The SnO/sub 2/-based sensors doped with copper oxide were prepared by adding various amounts of Cu(NO/sub 3/)/sub 2/.3H/sub 2/O to a sol suspension. Conductivity measurements of the sensors annealed at different temperatures have been carried out in dry air and in the presence of 100 ppb to 10-ppm H/sub 2/S. The nanocrystalline SnO/sub 2/-CuO thin films showed excellent sensing characteristics upon exposure to low concentrations of H/sub 2/S below 1 ppm. The 5% CuO-doped sensor having an average grain size of 20 nm exhibits a high sensitivity of 2.15/spl times/10/sup 6/ (R/sub a//R/sub g/) for 10-ppm H/sub 2/S at a temperature of 85/spl deg/C. By raising the operating temperature to 170/spl deg/C, a high sensitivity of /spl sim/10/sup 5/ is measured and response and recovery times drop to less than 2 min and 15 s, respectively. Selectivity of the sensing material was studied toward various concentrations of CO, CH/sub 4/, H/sub 2/, and ethanol. SEM, XRD, and TEM analyses were used to investigate surface morphology and crystallinity of SnO/sub 2/ films.     

Fabrication of a room-temperature NO2 gas sensor based on WO3 films and WO3/MWCNT nanocomposite films by combining polyol process with metal organic decomposition method

Polyol process was combined with metal organic decomposition (MOD) method to fabricate a room-temperature NO₂ gas sensor based on a tungsten oxide (WO₃) film and another a nanocomposite film of WO₃/multi-walled carbon nanotubes (WO₃/MWCNTs). X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the structure and morphology of the fabricated films. Comparative gas sensing results indicated that the sensor that was based on the WO₃/MWCNT nanocomposite film exhibited a much higher sensitivity than that based on a WO₃ film in detecting NO₂ gas at room temperature. Microstructural observations revealed that MWCNTs were embedded in the WO₃ matrix. Therefore, a model of potential barriers to electronic conduction in the composite material was used to suggest that the high sensitivity is associated with the stretching of the two depletion layers at the surface of the WO₃ film and at the interface of the WO₃ film and the MWCNTs when detected gases are adsorbed at room temperature. The sensor that is based on a nanocomposite film of WO₃/MWCNT exhibited a strong response in detecting very low concentrations of NO₂ gas at room temperature and is practical because of the ease of its fabrication.     

Development of a detection sensor for lethal H2S gas

The gas which may be lethal to human body with short-term exposure in common industrial fields or workplaces in LAB may paralyze the olfactory sense and impose severe damages to central nervous system and lung. This study is concerned with the gas sensor which allows individuals to avoid the toxic gas that may be generated in the space with residues of organic wastes under 50 degrees C or above. This study investigates response and selectivity of the sensor to hydrogen sulfide gas with operating temperatures and catalysts. The thick-film semiconductor sensor for hydrogen sulfide gas detection was fabricated WO3/SnO2 prepared by sol-gel and precipitation methods. The nanosized SnO2 powder mixed with the various metal oxides (WO3, TiO2, and ZnO) and doped with transition metals (Au, Ru, Pd Ag and In). Particle sizes, specific surface areas and phases of sensor materials were investigated by SEM, BET and XRD analyses. The metal-WO3/SnO2 thick films were prepared by screen-printing method. The measured response to hydrogen sulfide gas is defined as the ratio (Ra/R,) of the resistance of WO3ISnO2 film in air to the resistance of WO3/SnO2 film in a hydrogen sulfide gas. It was shown that the highest response and selectivity of the sensor for hydrogen sulfide by doping with 1 wt% Ru and 10 wt% WO3 to SnO2 at the optimum operating temperature of 200 degrees C.     

SnO/SnO2 heterojunction: an alternative candidate for sensing NO2 with fast response at room temperature

The SnO₂-based family is a traditional but important gas-sensitive material. However, the requirement for high working temperature limits its practical application. Much work has been done to explore ways to improve its gas-sensing performance at room temperature (RT). For this report, SnO₂, SnO, and SnO/SnO₂ heterojunction was successfully synthesized by a facile hydrothermal combined with subsequent calcination. Pure SnO₂ requires a high operating temperature (145 °C), while SnO/SnO₂ heterojunction exhibits an excellent performance for sensing NO₂ at RT. Moreover, SnO/SnO₂ exhibits a fast response, of 32 s, to 50 ppm NO₂ at RT (27 °C), which is much faster than that of SnO (139 s). The superior sensing properties of SnO/SnO₂ heterojunction are attributed to the unique hierarchical structures, large number of adsorption sites, and enhanced electron transport. Our results show that SnO/SnO₂ heterojunction can be used as a promising high-performance NO₂ sensitive material at RT.     

Synthesis and mechanism study of mesoporous SnO2/SiO2 composites

Mesoporous SnO2/SiO2 composite particles (Si/Sn < or = 0.25) sustainable to calcination up to 600 degrees C have been fabricated using a stepwise sol-gel technique on nonionic surfactant template (tetradecylamine, TDA). The newly designed preparation method involved the pre-formation of SnO2 sol solution from SnCl4. Subsequently, SnO2 nanocrystals were covered by the silicate species (from the hydrolysis of tetraethylorthosilicate, TEOS) in a pH controlled colloidal solution. Upon mixing with the surfactant solution, mesophase composite was obtained. After the removal of templates at various temperatures (400 to 600 degrees C), worm-like mesoporous SnO2/SiO2 with large specific surface area and pore volume as high as 362 m2/g and 0.33 cc/g were obtained, respectively. High thermal stability is mainly due to the effective inhibition of SnO2 crystal growth (mean crystallite size <30 A) by the amorphous SiO2 species at the grain boundaries. Formation of mesoporous silicate skeleton such as M41S family material was prevented. The obtained materials maintain the relatively narrow pore size distribution typically in the range of 30 to 70 A. Relations between material properties and key synthesis parameters (i.e. TDA/Si/Sn molar ratio and calcination temperature) were investigated by TGA, wide/small-angle X-ray scattering, (HR)TEM, BET, and FTIR techniques. Mechanisms on the mesostructure formation and crystal growth inhibition were also proposed with detailed discussion.     

Novel fabrication of an SnO(2) nanowire gas sensor with high sensitivity

We fabricated a nanowire-based gas sensor using a simple method of growing SnO(2) nanowires bridging the gap between two pre-patterned Au catalysts, in which the electrical contacts to the nanowires are self-assembled during the synthesis of the nanowires. The gas sensing capability of this network-structured gas sensor was demonstrated using a diluted NO(2). The sensitivity, as a function of temperature, was highest at 200?°C and was determined to be 18 and 180 when the NO(2) concentration was 0.5 and 5?ppm, respectively. Our sensor showed higher sensitivity compared to different types of sensors including SnO(2) powder-based thin films, SnO(2) coating on carbon nanotubes or single/multiple SnO(2) nanobelts. The enhanced sensitivity was attributed to the additional modulation of the sensor resistance due to the potential barrier at nanowire/nanowire junctions as well as the surface depletion region of each nanowire.     

SnO-SnO2 modified two-dimensional MXene Ti3C2Tx for acetone gas sensor working at room temperature

Acetone,as widely used reagents in industry and laboratories,are extremely harmful to the human.So the detection of acetone gas concentrations and leaks in special environments at room temperature is essential.Herein,the nanocomposite combining SnO-SnO2 (p-n junction) and Ti3C2Tx MXene was successfully synthesized by a one-step hydrothermal method.Because of the existence of a small amount of oxygen during the hydrothermal conditions,part of the p-type SnO was oxidized to n-type SnO2,forming in-situ p-n junctions on the surface of SnO.The hamburger-like SnO-SnO2/Ti3C2Tx sensor exhibited improved acetone gas sensing response of 12.1 (Rg/Ra) at room temperature,which were nearly 11 and 4 times higher than those of pristine Ti3C2Tx and pristine SnO-SnO2,respectively.Moreover,it expressed a short recovery time (9 s) and outstanding reproducibility.Because of the different work functions,the Schottky barrier was formed between the SnO and the Ti3C2Tx nanosheets,acting as a hole accumulation layer (HALs) between Ti3C2Tx and tin oxides.Herein,the sensing mechanism based on the formation of hetero-junctions and high conductivity of the metallic phase of Ti3C2Tx MXene in SnO-SnO2/Ti3C2Tx sensors was discussed in detail.     

基于ZIF8/rGO的高性能NO2室温传感器

二氧化氮气体是一种常见的大气污染物, 对自然环境和人类健康造成严重的危害, 开发检测该类有毒有害气体的高效检测设备势在必行。新型复合薄膜气体传感器可以在常温下对二氧化氮进行高选择性、高灵敏度检测, 为自然环境和人类健康保驾护航。本工作采用化学沉淀法和超声法制备了多孔、高比表面积的ZIF8/还原氧化石墨烯(ZIF8/rGO)复合材料, 以此为气敏材料构建NO₂传感器, 并系统研究了其在室温下对NO₂的气敏性能, 进一步探讨了ZIF8/rGO气敏传感器感应NO₂的可能机理。气敏实验结果表明：ZIF8/rGO气敏传感器对50×10^-6 NO₂的响应达到34.77%, 是纯rGO气敏传感器的3.2倍。ZIF8/rGO传感器在4个可逆循环测试中表现出较好的可重复性, RSD(Relative Standard Deviation)为3.9%。此外, ZIF8/rGO传感器表现出优秀的长期稳定性(RSD为2.5%)、选择性和低的检出限(3.8×10^-8)。室温下灵敏感应NO₂的气敏性能主要归因于ZIF8的多孔结构和超大的比表面积以及rGO的优越性能。本工作将为ZIF8/rGO作为气敏材料检测有毒有害的NO₂气体提供新思路。