In2O3 Thin Films Obtained Through a Chemical Complexation Based Sol-Gel Process and Their Application as Gas Sensor Devices

A new approach is presented for preparing In₂O₃ thin films starting from inorganic precursors, based on a very simple but effective modification of the usual precipitation-peptization process. Indium nitrate was dissolved in methanol and In³⁺ ions were chelated with acetylacetone before adding concentrated base to the resulting solution. Such a route allowed obtaining long-term stable sols, from which films could be deposited on glass substrates by spin-coating. Furthermore, the films exhibited a very good adhesion and uniformity, without any need for adding additives to the solution. The modification of the In precursor was confirmed by thermal analysis, while XRD studies revealed that the films prepared with the modified route result in smaller In₂O₃ grains compared to the traditional precipitation-peptization process. Optical reflectance measurements on the films further highlighted the difference between the two processes. Gas-sensing tests carried out on the films deposited onto alumina substrates in the temperature range between 100 and 400°C showed that faster responses are obtained at temperatures higher than 250°C. The response value (R/R ₀, where R is the electrical resistance of the sensor in the test gas and R ₀ that in dry air) to 100 ppb ozone is remarkably high: it is equal to 1500 for In₂O₃ with a response time of about 1 minute. The recovery time is about 10 minutes.     

Revealing the Chemical State of Palladium in Operating In2O3 Gas Sensors: Metallic Pd Enhances Sensing Response and Intermetallic InxPdy Compound Blocks It

The sensing response of metal oxides activated with noble metal nanoparticles is significantly influenced by changes to the chemical state of corresponding elements under operating conditions. Here, a PdO/rh-In₂O₃ consisting of PdO nanoparticles loaded onto rhombohedral In₂O₃ was studied as a gas sensor for H₂ gas (100–40000 ppm in an oxygen-free atmosphere) in the temperature range of 25–450 °C. The phase composition and chemical state of elements were examined by resistance measurements combined with synchrotron-based in situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy. As found, PdO/rh-In₂O₃ undergoes a series of structural and chemical transformations during operation: from PdO to Pd/PdH_x and finally to the intermetallic In_xPd_y phase. The maximal sensing response (R_N2/R_H2) of ∼5 ⋅ 10⁷ towards 40000 ppm (4 vol %) H₂ at 70 °C is correlated with the formation of PdH_0.706/Pd. The In_xPd_y intermetallic compounds formed around 250 °C significantly decrease the sensing response.     

WO3纳米材料的H2S气敏特性

用于检测微量H2S气体的SnO2元件具有相当高的灵敏度,但响应—恢复时间较长,选择性的提高也受限制。本文用化学沉淀法合成了xwt.%SiO2-WO3(x=0,3,5,10,15)纳米粉体,研制出一系列烧结型气敏元件,工作温度为180℃,掺杂量为5％的气敏元件对H2S有很高的灵敏度和选择性,响应—恢复快,而且工作温度较低,有较好的应用价值。     

Gas Sensing Properties of Co3O4-loaded SnO2 to Ethanol and Acetone

A series of Co3O4-loaded SnO2 nanocomposite thick films were prepared by grinding, screen-printing and sintering at 700 ±C for 3 h. XRD data showed the nanocomposite thick films were rutile structure of SnO2 and cubic Co3O4. The composite films were found to exhibit good response to alcohol and acetone at 300 ±C. The film went through a sharp sensitivity maximum at 5 mol%CoO4=3 with a change in Co3O4 content. At 300 ±C, the maximum sensor response to alcohol and acetone, each 1000 ppm in air, was 301 and 235, respectively, which was about 7 and 5 times as large as that of the pure SnO2 respectively. The selectivity to alcohol and acetone over H2 and CO also was promoted by the addition of Co3O4 to SnO2. The mechanism of such strong promotion of sensor response (electronic sensitization) is discussed.     

常压水热法合成玉米棒状In_2O_3及其性能研究

以In(NO_3)_3·4.5H_2O和(NH_2)_2CO为原料,采用常压水热法于95℃反应22 h制得氧化铟(In_2O_3)前驱物氢氧化铟,于600℃煅烧2 h合成了In_2O_3粉体,其结构、形貌及性能经紫外-可见(UV-Vis)光谱、X-射线衍射(XRD)、拉曼光谱和扫描电镜(SEM)表征。以甲基橙为目标降解物,研究了In_2O_3粉体的光催化活性。结果表明:In_2O_3粉体为体心立方晶系方铁锰矿结构和亚稳相刚玉六方结构的混合体,In_2O_3的UV-Vis谱图中出现了明显的蓝移。当In(NO_3)_3·4.5H_2O和(NH_2)_2CO物质的量比为1∶7时,In_2O_3粉体中出现了玉米棒状结构,棒状体长度约为500 nm,直径约150 nm;该棒状结构的In_2O_3对甲基橙有较好的光催化活性,在紫外光照射6.5 h后甲基橙的降解率为69.7%。     

Ce掺杂In_2O_3纳米纤维的制备及其三乙胺气敏性能(英文)

用简单有效的静电纺丝法制备了Ce掺杂的In2O3纳米纤维材料.采用X射线衍射(XRD)、透射电子显微镜(TEM)、高分辨率透射电子显微镜(HRTEM)和扫描电子显微镜(SEM)对合成样品的晶体结构和形貌进行了表征.结果显示,此纤维材料的平均直径约为90nm,长度达到几十个微米.气敏性能测试结果表明,4%(w)Ce掺杂的In2O3纳米纤维对三乙胺的灵敏度最高,该气敏元件对3μL·L-1三乙胺的灵敏度达到2.6,响应时间为5s,恢复时间约为6s,且具有较好的选择性.     

Preparation of Sol-Gel Nano-Composites Containing Copper Oxide and Their Gas Sensing Properties

Sol-gel derived composite materials were prepared with nano-sized copper particles in silica matrix. Nano-sized oxide coatings were grown on the nano-particles of copper by subjecting the composites to a controlled oxidation treatment at different temperatures. The current response of samples with oxide layers of different thickness were studied at fixed temperatures in the range 350–450°C in the presence of different concentrations of CO and NO₂. The nano-composites were sensitive to both the gases. The operating temperature and the oxide thickness were found to have significant effect on the sensing properties.     

Optical Gas Sensing Properties of Silica Film Doped with Cobalt Oxide Nanocrystals

SiO₂ sol-gel films doped with cobalt oxide nanocrystals have been fabricated. The nanocrystals precipitate in the glass film at 500_°C, while the film is still porous. The nanocomposite films showed a reversible change in the optical transmittance when exposed to CO in the 250 < < 850 nm range. The effects of the residual porosity and testing temperature have been studied. The gas sensing properties of the cobalt oxide nanocrystals doped films are compared with those of nickel oxide nanocrystals doped silica film, previously reported.     

p-CuO/n-In_2O_3异质结纳米纤维的制备及气敏特性

以电纺In_2O_3纳米纤维为模版,通过溶剂热法构建了p-CuO/n-In_2O_3异质结纳米纤维.采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)等方法对所得材料的形貌和结构进行表征.结果表明,CuO纳米颗粒可以均匀地负载在超细In_2O_3纳米纤维表面;随着反应液中乙酸铜浓度的增加,负载的CuO纳米颗粒密度也逐渐增加.通过制备旁热式气敏器件对复合纳米纤维材料的气敏特性进行了研究.结果表明,与纯In_2O_3纳米纤维相比,p-CuO/n-In_2O_3异质结纳米纤维对H_2S气体具有较高的灵敏度和较低的工作温度.     

有机二元酸-水体系中In(OH)_3/In_2O_3微纳材料的制备与表征

本文利用系列有机二元酸-水体系作为制备In(OH)3纳米晶体介质,采用低温水热法成功制备了不同形貌和尺寸的In(OH)3为纳材料。利用扫描电镜(SEM)、透射电镜(TEM)、X-射线衍射(XRD)、傅立叶红外光谱仪(FT-IR)和拉曼光谱仪(Raman)等手段分别对材料的形貌、结构和物相等进行了表征与分析。实验结果表明,通过本研究方法,在己二酸水体系中可以得到较均一的尺寸在300-400 nm范围的In(OH)3球形粒子,而在癸二酸水体系中则得到棒状和片状混杂的In(OH)3纳米颗粒。样品在450°C条件下焙烧4 h后,可获得相应的具有良好形貌继承性的In2O3微纳材料。     

基于CoFe2O4表面催化发光的硫化铵气体传感器研究

基于铁酸钴(CoFe₂O₄)纳米材料催化硫化铵的氧化反应产生化学发光的现象, 建立了一种检测空气中痕量硫化铵的催化发光气体传感器. 在对合成的3种材料的催化发光性质进行比较的基础上, 对分析方法条件进行了优化, 其结果表明: 在检测波长400 nm、反应温度306 ℃、载气流速400 mL/min的最优条件下, 可测定的硫化铵浓度的线性范围为0.13～13 mg/L (r＝0.9951, n＝9), 检出限为0.04 mg/L (3σ), 对1.3 mg/L的硫化铵连续平行测定8次, 其相对标准偏差为1.8%. 此外, 考察了相同浓度的常见挥发性有机物的干扰情况, 其结果表明该传感器具有很好的选择性. 连续60 h通过1.3 mg/L的硫化铵, 发光强度无明显降低, 相对标准偏差小于5%, 表明此传感器使用寿命长. 并将该传感器成功用于人工合成样品的分析, 回收率为94.7%～103.9%.     

Electrochemical Glyphosate Sensor Based on Hybrid Material SiO2/Sm2O3/Carbon Modified with Meldola Blue

In this work, we have proposed an electrochemical sensor for the detection of pesticides by using a ceramic composite with a SiO₂ surface modified with Sm₂O₃ nanoparticles and C-graphite (SSMG), obtained by the sol-gel process and immobilized by adsorption in Meldola Blue cationic dye (MB). The composite was called (SSMG/MB), which was characterized by spectroscopic, electrochemical techniques, Fourier-transform infrared spectroscopy, and Cyclic Voltammetry. The proposed sensor was applied for the glyphosate electrochemical detection, using Differential Pulse Voltammetry, and, under optimized parameters has presented the linear response for the pesticide in the concentration range from 0.99 to 7.94 (μmol L⁻¹; R²=0.9963; n=8). The calculated values for the detection limit and the quantification limit were 0.15 and 0.49 μmol L⁻¹, respectively. Therefore, the new electrochemical sensor based on SiO₂, NPsSm₂O_3, C-graphite, and MB hybrid material was developed for the first time for glyphosate determination, which has demonstrated high potential for the development of new hybrid devices for environmental control.     

基于氧化钛-氧化钇粉体催化发光甲醛气体传感器的研究

研究了甲醛在TiO2-Y2O3(质量比为3∶1)粉体表面催化发光行为,发现基于这种催化剂的气体传感器对甲醛的检测具有高灵敏度和较强的选择性。在波长490 nm处进行定量分析,催化发光强度与甲醛浓度在一定范围内呈良好的线性关系,其线性范围为0.08~40 mL/m3(r=0.9991,n=6);检出限为0.03 mL/m3(S/N=3)。外来物质如环己烷、正己烷、三氯甲烷、苯、乙醇、甲醇、乙醛、氨、水蒸气等与甲醛共存时,除了乙醇和氨分别引起干扰外,水蒸气与其它气体不干扰测定。该传感器工作时间可达80 h以上,是一种长寿命的、性能稳定的气体传感器,并成功地实现了对甲醛的实时在线检测。     

氧化铟掺杂对ZnFe2O4半导体气敏性能的影响

用化学共沉淀法在ＺｎＦｅ２Ｏ４中掺入Ｉｎ２Ｏ３．Ｘ射线衍射分析证实，Ｉｎ２Ｏ３与ＺｎＦｅ２Ｏ３之间没有新相生成，晶格常数有微小变化．掺入Ｉｎ２Ｏ３降低了ＺｎＦｅ２Ｏ４的电导，改变了该系列材料的导电机制，提高了材料对乙醇的敏感性和选择性，而且缩短了材料的响应时间     

Preparation of size‐controlled In2O3 nanoparticles

Highly crystalline and monodisperse In₂O₃ nanoparticles were successfully prepared by thermal decomposition of In(dipy)₃Cl₃·2H₂O in oleylamine and oleic acid under inert atmosphere. The size of In₂O₃ nanoparticles could be readily tuned from 10–15 nm to 40–50 nm, depending on the molar ratio of precursor to combined solvent in the reaction system. As‐synthesized In₂O₃ nanoparticles have a center‐body cubic structure as characterized by powder X‐ray diffraction and selected‐area electron diffraction. Transmission electron microscopy images showed that In₂O₃ nanoparticles have a narrow size distribution. A relatively strongly PL peak centered at 378 nm could be clearly seen when 10–15 nm In₂O₃ nanoparticles redispersed in cyclohexane were excited at 275 nm at room temperature. Copyright © 2007 John Wiley & Sons, Ltd.     

Gas Sensing Properties of In2O3and Au-doped In2O3Films for Detecting Carbon Monoxide in Air

Catalytic and sensing properties of several metal oxides in the reaction of CO oxidation and in the sensor detection of CO in air have been studied and compared to each other. Indium oxide has been found to be the most sensitive and possessing a relatively low catalytic activity in the oxidation of CO. Possible reasons for the high activity of the indium oxide sensor matrix are discussed. The promoting effect of Au and Pd doping of In₂O₃in the detection of CO in air has been studied, and a mechanism explaining the enhanced sensor response of Au-doped In₂O₃has been proposed. A change in humidity has no significant effect on the sensor response of Au-doped In₂O₃in the detection of CO in air.     

二氧化锡气体传感器快速检测挥发性有机化合物

论述了将SnO2气体传感器作为便携式气相色谱检测器,重点是挥发有机化合物(VOCs)检测方法的可行性研究。SnO2气体传感器的动态范围103;最小检测浓度(苯)8.12×10-4g/L、面积重现性<6%,取得了较满意的结果。对SnO2气体检测器的加热电压、温度特性和快速检测指标作了基本分析和考察,最后将SnO2气体传感器和FID检测器进行了初步比较。实验表明,将其作为专用便携色谱检测器,可以基本满足快速分析应用的要求。     

Enhancement of Activity of SnO2-doped In2O3/Al2O3 Catalyst for NO Reduction with Propene in the Presence of H2O and SO2

The selective catalytic reduction of nitrogen oxides by hydrocarbons (HC-SCR) has attracted much attention as an efficient way to remove NO in the presence of excess oxygen1-2. The metal oxides are the most promising catalysts for the SCR of NO because of their high activity and selectivity3-5. In the previous work, the metal oxides such as Ag, Sn, In, Co supported on alumina for NO reduction were investigated6-8, however, the HC-SCR is usually suppressed in the presence of H2O and S…