Ultrasensitive methyl salicylate gas sensing determined by Pd-doped SnO2

Efficient chemical warfare agents (CWAs) detection is required to protect people from the CWAs in war and terrorism. In this work, a Pd-doped SnO₂ nanoparticles-based gas sensor was developed to detect a nerve agent simulant named methyl salicylate. The sensing measurements of methyl salicylate under different Pd doping amounts found that the 0.5 at.% Pd-doped SnO₂ exhibited a significant improvement in the detection of methyl salicylate at the ppb (1 ppb = 10⁻⁹) level, and the response value to 160 ppb methyl salicylate is 0.72 at 250 °C. Compared with the pure SnO₂, the response value is increased by 4.5 times, which could be attributed to the influence of the noble metal Pd on the oxygen state and its catalytic effect. In addition, the 0.5 at.% Pd-doped SnO₂ sensor still has an obvious response to 16 ppb methyl salicylate with a response value of 0.13, indicating the lower detection limit of the sensor.     

异质复合结构纳米纤维SnO2/ZnO的制备及其气敏特性研究

采用静电纺丝法制备了多级中空结构的SnO₂纳米纤维, 然后将SnO₂纳米纤维置于90℃乙酸锌溶液中, 恒温水浴条件下, 在SnO₂纳米纤维上生长了ZnO纳米球, 形成了异质结构的SnO₂/ZnO复合纳米纤维。分别通过XRD、SEM、EDX和XPS等表征手段对异质复合纳米纤维SnO₂/ZnO材料的结构、形貌及元素含量进行了表征分析。异质结构的SnO₂/ZnO复合纳米纤维保持了SnO₂纳米纤维多级中空的纤维结构, SnO₂纳米纤维长度约为300 nm, 依附于SnO₂纤维表面的SnO₂纳米颗粒生长的ZnO纳米球直径为250~300 nm。采用静态气体测试系统对异质复合纳米纤维SnO₂/ZnO气敏元件的气敏性能进行了测试。测试结果表明: 异质复合纳米纤维SnO₂/ZnO气敏元件在最佳工作温度350℃下, 对(0.5~100)×10^-6丙酮具有优异的响应灵敏度、较好的选择性和长期稳定性。异质复合纳米纤维SnO₂/ZnO中存在于ZnO纳米球与SnO₂纳米颗粒间的N-N同型异质结导致复合材料晶界势垒高度的降低, 改善了电子与空穴的输运特性, 促使SnO₂/ZnO异质复合纳米纤维的吸附能力大大增强, 从而改善了SnO₂/ZnO元件的丙酮敏感特性。     

Au修饰SnO2复合纳米材料的制备和气敏性能

以氯金酸和乙酰丙酮氯化锡为主要材料,通过一步水热法制备了SnO₂和Au修饰的SnO₂（Au/SnO₂）纳米粒子.使用TEM、EDS、XRD和XPS等手段对样品的形貌、组成及结构进行表征,研究了两种材料对乙醇的气敏性能.结果表明,两种纳米颗粒的尺寸都比较均一,平均直径约为9-12 nm;SnO₂为四方金红石结构,Au为面心立方结构;在Au/SnO₂样品中,Au与SnO₂的重量比为2.6%,Au元素主要以Au⁰的价态存在并含有少量的Au³⁺价态;与纯SnO₂纳米粒子相比,Au修饰可显著提高气敏元件对乙醇响应的灵敏度和选择性。     

SnO2 Nanorods Prepared by Inductively Coupled Plasma-Enhanced Chemical Vapor Deposition

SnO₂ nanorods were successfully deposited on substrate by inductively coupled plasma-enhanced chemical vapor deposition (PECVD) using dibutyltin diacetate (DBTDA) as the precursor. Each of the SnO₂ nanorods in situ grown under catalyst- and template-free growth condition and without any substrate heating was found to be [110] oriented single crystal. These needle-shaped nanorods have an average diameter between 5 and 16 nm and a length of 160 to 250 nm from TEM observation. Substrate distance and RF power showed notable effects on the formation of SnO₂ nanorods.     

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.     

The preparation and gas sensitivity study of polythiophene/SnO2 composites

Nanocomposites of SnO₂ and polythiophene (PTP) were synthesized by the in situ chemical oxidative polymerization method. These nanocomposites were characterized by FTIR, transmission electron microscope (TEM), X-ray diffraction (XRD) and thermogravimetric and differential thermal analysis (TG–DTA) techniques, which proved the polymerization of thiophene monomer and the strong interaction between polythiophene and SnO₂. The composites were used for gas sensing to methanol (MeOH), ethanol (EtOH), acetone, and NO_x at different working temperature. It was found that PTP/SnO₂ materials with different PTP mass percent (1%, 5%, 10%, 20% and 30%) could detect NO_x with very higher selectivity and sensitivity at much lower working temperature than the reported SnO₂. The PTP/SnO₂ nanocomposites responded to NO_x at concentration as low as 10 ppm. PTP/SnO₂ composite containing 5 mass% PTP showed the highest sensitivity at room temperature. The sensing mechanism of PTP/SnO₂ nanocomposites to NO_x was presumed to be the effects of p–n heterojunction between PTP and SnO₂.     

Cathodoluminescence study of SnO2 powders aimed for gas sensor applications

In this paper we report on cathodoluminescence (CL) spectra of SnO₂ powders, synthesized using the wet chemical route. The analysis of influence of the modes of calcination (T_an-450–800 °C), and doping by both Pd and Pt (0.01–10.0 wt.%) on CL spectra was made. It was found that the measurement of CL spectra could be an effective research method of nanostructured metal oxides, aimed for gas sensor applications. It was established that in nanocrystalline SnO₂ the same system of energy levels, associated with radiative recombination, as in single crystalline and polycrystalline SnO₂, is retained. It was found that doping by both Pd and Pt modifies the structural properties of SnO₂ grains. Also, there is an optimum doping; near 0.1–0.2 wt.%, at which a maximum intensity of cathodoluminescence is reached. It was concluded that for low concentrations of both Pd and Pt additives in SnO₂ an improvement of the material's crystal structure is promoted, and is associated with a decrease in the non-radiating recombination rate.     

SnO2/NiO复合半导体纳米纤维的制备及气敏性能研究

采用静电纺丝技术结合化学沉淀法和高温煅烧处理,制备了具有不同Sn含量的SnO2/NiO复合半导体纳米纤维.采用扫描电子显微镜(SEM),X射线衍射仪(XRD)和能量色散X射线光谱仪(EDS)对样品的形貌,结构以及各元素含量进行表征.以乙醇为目标气体,探究SnO2/NiO纳米纤维的气体传感性质,以及Sn含量对复合纳米纤维...     

Lithographic patterning of benzoylacetone modified SnO2 and SnO2:Sb thin films

The synthesis of directly UV-photopatternable pure and antimony-doped organo-tin materials is presented. UV-photopatternability has been achieved by using the synthesized benzoylacetone modified tin and antimony 2-isopropoxyethoxides. Photopatterned pure and antimony-doped organo-tin films are crystallized by thermal annealing in order to obtain conductive SnO₂ and Sb:SnO₂ thin films. The molar ratio between benzoylacetone and metal alkoxides has to be 2 in order to obtain crack-free, good-quality structures. The effects of UV-irradiation, increasing antimony doping level and benzoylacetone concentration on the electrical properties of the single-layered films are analyzed. The highest obtained conductivity was 20 S/cm. Benzoylacetone concentration and UV-irradiation has only a negligible effect on the film electrical conductivities.     

The influence of substrate chemistry on the adhesion of electrolessly deposited Ni(P) on metal oxide coated ceramics

The adhesion of electrolessly deposited Ni(P) on alumina ceramic substrates which were coated with thin SiO₂, SnO₂, TiO₂, Al₂O₃, Y₂O₃, ZrO₂ and (In,Sn)O_x (ITO) films was studied. The adhesion was measured with the aid of the 90° peel test. Strong adhesion of Ni(P) was found for the substrates with ZrO₂ and Al₂O₃ coatings and weak adhesion for the substrates with SiO₂, TiO₂, SnO₂, Y₂O₃ and ITO coatings. The fracture path and the type of interfacial bonding were analysed using scanning electron microscopy, energy-dispersive analysis of X-rays and X-ray photoelectron spectroscopy. In the case of the strongly adhering samples, fracture took place through the metal layer and along the interface. In the case of the weakly adhering samples only interfacial failure was observed between the Ni(P) layer and the metal oxide coating. Cross-section transmission electron microscopy studies of the interfaces suggested that the differences in peel energy values are caused by differences in micromechanical interlocking at the metal oxide-Ni(P) interface. In addition, a weak boundary layer which was found to be present at the Ni(P)-alumina interface was absent in the case of the strongly adhering samples with the ZrO₂ substrate coating.     

基于Si掺杂增强光吸收提升Li2SnO3 光催化降解四环素的研究

在Li₂SnO₃中掺杂Si,研究了Si掺杂Li₂SnO₃对四环素的光催化降解性能。结果表明,对Li₂SnO₃进行等电子Si掺杂使其光学吸收带隙减小和光吸收系数增大,提高了对四环素的光催化降解效率。等电子Si掺杂Li₂SnO₃为纯相不规则块状固体,随着Si掺杂量的增加其晶格参数呈减小的趋势。Si掺杂使样品的光催化性能显著提高。Si掺杂量为10%的样品,在紫外光照射25 min后光催化降解效率为75.8%,约为母体的2倍。Si掺杂Li₂SnO₃的光催化降解行为满足赝一级动力学模型,拟合速率常数为0.02464 min^-1。在Si掺杂Li₂SnO₃的价带顶形成的Si-O键减少了光学吸收带隙,使其光吸收能力增强。Si掺杂Li₂SnO₃的光催化降解机制,属于空穴主导型。     

SnO2修饰石墨毡电极的制备及其性能表征

采用H₂O₂对石墨毡（GF）进行预处理,然后在其表面电沉积Sn,最后在120℃烘箱氧化24 h制备出SnO₂修饰的石墨毡电极。通过扫描电镜（SEM）对SnO₂修饰前后的石墨毡表面形貌进行表征,采用循环伏安法研究了SnO₂修饰后石墨毡电极的电化学性能。结果表明：SnO₂能够均匀地包覆在石墨毡表面;SnO₂修饰石墨毡后V⁴⁺/V⁵⁺电对的氧化峰的峰电流由0.0538 A增加到0.0708 A,与未处理石墨毡相比增加了31.5%,反应峰出峰持续时间提高,说明SnO₂对V⁴⁺/V⁵⁺电对电极过程具有一定的催化作用。析氧电位由1.382 V增加到了1.517 V,使电极在VOSO₄溶液中的电化学窗口变宽。     

Structural, electrical and optical characteristics of SnO2:Sb thin films by ultrasonic spray pyrolysis

Antimony-doped tin oxide (SnO₂:Sb) thin films were fabricated by an ultrasonic spray pyrolysis method. The effect of antimony doping on the structural, electrical and optical properties of tin oxide thin films were investigated. Tin(II) chloride dehydrate (SnCl₂·2H₂O) and antimony(III) chloride (SbCl₃) were used as a host and a dopant precursor. X-ray diffraction analysis showed that the non-doped SnO₂ thin film had a preferred (211) orientation, but as the Sb-doping concentration increased, a preferred (200) orientation was observed. Scanning electron microscopy studies indicated that the polyhedron-like grains observed for the non-doped SnO₂ thin films became rounder and decreased in size with the Sb-doping concentration. The lowest resistivity (about 8.4 × 10^− 4 Ω·cm) was obtained for the 3 at.% Sb-doped films. Antimony-doping led to an increase in the carrier concentration and a decrease in Hall mobility. The transmittance level in the near infrared region was lowered with the Sb-doping concentration.     

Preparation of nanocrystalline SnO2 thin film coated Al2O3 ultrafine particles by fluidized chemical vapor deposition

Fluidized chemical vapor deposition (FCVD) technology was developed for coating SnO₂ thin film on Al₂O₃ ultrafine particles. TEM and HREM analysis found that SnO₂ films with different structures were deposited by controlling the coating temperature, reactant concentration, etc. Nanocrystalline SnO₂ film was coated at 573.15 K by gas phase reaction of SnCl₄ with H₂O. EPMA and EDS studies indicated that the distribution of SnO₂ inner and outer of the agglomerates was uniform. Nucleation and film deposition were coexisted mechanism during the FCVD coating process. The fraction of SnO₂ in the composite particles increased with increasing coating temperature, SnCl₄ concentration, and coating time. The mass fraction of SnO₂ in the composite particles increased strongly with the ratio of P_H2O and P_SnCl4 at low mole ratio of H₂O with SnCl₄, but increased little under the conditions of excess H₂O with respect to SnCl₄.     

镍掺杂四氧化三钴纳米线阵列的制备及其超级电容特性

采用直流电化学沉积与高温氧化相结合的合成方法, 在氧化铝模板的辅助下, 成功制备了一种新颖的Ni掺杂的Co₃O₄纳米线阵列, 利用X射线衍射仪、扫描电镜和高分辨透射电镜等对所制备的纳米线阵列的物相和形貌进行了表征, 结果表明：所制备的Ni掺杂Co₃O₄纳米线形貌和尺寸均匀、垂直于基底排列, 纳米线的平均直径约为80 nm, 长度约为1.4 μm, 整个纳米线由纳米颗粒堆积而成, 其中Co : Ni的比例约为20 : 1。利用循环伏安和恒流充放电技术在2 mol/L的KOH电解液中对材料的电化学性能进行了测试, 结果显示所制备的纳米线阵列具有优异的电化学电容特性, 当电流密度为10 mA/cm²时, 纳米线阵列的面积比电容为173 mF/cm², 经过1000次充放电后, 比电容值仍能保持最初值的98%, 表现出良好的循环稳定性。优异的性能可归因于材料的比表面积较大以及镍掺杂后材料导电特性的提高。     

基于水热反应制备SnO2纳米棒阵列

采用水热反应制备一维SnO₂纳米棒阵列并表征其物相结构和微观形貌,研究了水热反应的核心工艺条件如前驱体浓度、反应时间、反应温度、反应次数以及前驱体中NaCl添加剂等对纳米棒阵列的生长和形貌的影响。结果表明：较低的前驱体浓度有利于制备大长径比的纳米棒;改变反应时间调控纳米棒的长度;改变反应温度和次数调控纳米棒的长度、直径和基底覆盖率;在前驱体中加入NaCl,可增强纳米棒的取向生长并降低其基底覆盖率。     

SnO2-Fe2O3复合材料应用于碳纳米管集流体对锂离子电池性能的影响

水热合成法制备纳米SnO₂-Fe₂O₃复合材料,以SnO₂-Fe₂O₃为活性物质,多壁碳纳米管（MWCNTs）导电纸代替传统铜箔作为负极集流体制作锂离子电池。采用XRD、SEM进行表征,结果显示,SnO₂-Fe₂O₃均匀嵌入到MWCNTs构建的三维导电网络的空隙中。电化学测试结果表明,SnO₂-Fe₂O₃/MWCNTs导电纸作为负极电极能够显著提高锂离子电池的循坏和倍率性能。在100 mA/g电流密度下循环30次,SnO₂-Fe₂O₃/MWCNTs导电纸电池比容量达到1 088 mAh/g,而在200 mA/g电流密度下循环200次后,SnO₂-Fe₂O₃/MWCNTs导电纸比容量能稳定保持在898 mAh/g,表现出良好的循环性能,逐渐增大充放电电流,电池的比容量有所下降但其库伦效率仍然保持在96%以上,而在高倍率（1 600 mA/g）下进行充放电时,SnO₂-Fe₂O₃/MWCNTs导电纸比容量仍然能够保持在547 mAh/g,之后再将电流密度降到100 mA/g,比容量重新回到1 000 mAh/g,SnO₂-Fe₂O₃/MWCNTs导电纸表现出十分优异的电化学性能。      

Excimer laser deposition and characteristics of tin oxide thin films

ArF excimer laser assisted chemical vapor deposition of tin oxide thin films on Si was obtained using SnCl₄ and O₂ as precursors. Experimental measurements revealed that the deposition rate increases with incident laser energy density. The composition, structure and ultraviolet-to-visible spectra of the thin films were investigated by means of XPS, SEM, XRD and a UV–Vis techniques. It was shown that SnO₂ and SnOCl₂ coexisted in the thin films, and SnOCl₂ was almost completely converted into SnO₂ after annealing. The SnO₂ thin films deposited at room temperature were amorphous in structure and the grain size of the films became larger after annealing. The transmittance of the SnO₂ thin films is above 90%, the absorption edge is 355 nm and the energy gap is 3.49 eV.     

VO2(B)/ZnO异质复合纳米棒结构的室温NH3敏感性能研究

以VO₂(B)纳米棒为内核, 利用液相生长法制备了VO₂(B)/ZnO异质复合纳米棒, 研究了ZnO生长溶液浓度对复合结构微观形貌和气敏性能的影响规律。采用扫描电子显微镜和X射线衍射仪对复合结构样品的微观形貌和结晶取向进行表征, 并测试了复合结构对NH₃的敏感性能。实验结果表明, 随着ZnO种子液浓度的增大, ZnO逐渐由纳米颗粒生长为纳米棒结构, 当ZnO种子液浓度为0.01 mol/L时, ZnO呈棒状沿径向发散生长在VO₂(B)纳米棒表面, 形成树枝状VO₂(B)/ZnO异质复合纳米棒结构, 这一结构在室温下表现出对NH₃的高灵敏度和突出的选择性, 其灵敏度最大可达5.6, 对NH₃的响应时间最短仅为2 s。在室温下表现出的优良NH₃敏感性能, 主要与高密度的VO₂(B)/ZnO异质结和树枝状结构有关。研究结果为低功耗高灵敏度NH₃气敏传感器的研制提供了重要依据。     

SnO2退火温度对钙钛矿太阳能电池性能的影响

电子传输层是钙钛矿太阳能电池的关键部分, 起到阻挡空穴、传输电子和减少电子空穴复合的作用。本研究采用低温溶液法制备SnO₂薄膜作为钙钛矿电池的电子传输层, 研究SnO₂的退火温度对电子传输层微观形貌、物理性能以及钙钛矿太阳能电池性能的影响。结果表明: 当退火温度为60、90、120和240 ℃时, SnO₂薄膜表面存在较多的孔隙; 而退火温度为150、180和210 ℃时, 薄膜表面孔隙较少。在实验温度下, 制备的SnO₂薄膜为四方相, FTO玻璃上涂覆SnO₂薄膜后其透过率要优于空白FTO玻璃的透过率。当SnO₂退火温度为180 ℃时, 薄膜的电子迁移率最高, 钙钛矿电池具有最佳的传输电阻和复合电阻, 所得电池的性能最优, 其光电转换效率为17.28%, 开路电压为1.09 V, 短路电流为20.91 mA/cm², 填充因子为75.91%。