Synthesis and growth mechanism of CuO nanostructures and their gas sensing properties

CuO nano-particles, nano-rods, nano-sheets and nano-flowers were synthesized by the hydrothermal routes with copper salts under different additions. The obtained samples were characterized by X-ray diffraction and scanning electron microscopy. We investigated the effects of precursors on the formation of CuO with different morphologies and proposed their possible formation mechanisms. In addition, the obtained CuO nano-flowers are found to show better sensing performances than the other three low-dimensional CuO nanostructures. Our results also demonstrate that gas sensing properties of nanocrystals can be significantly improved by tailoring shape and morphology of the nanocrystals. The CuO nano-flowers may hold substantial promise in low-dimensional gas-sensing applications.     

Facile fabrication and enhanced gas sensing properties of ZnSnO3/NiO heterostructures

Journal of Materials Science: Materials in Electronics - The sensing performance of gas sensitive materials can be improved by adjusting their microstructure and electronic structure. In this work,...     

Synthesis of nestlike ZnO hierarchically porous structures and analysis of their gas sensing properties

Nestlike 3D ZnO porous structures with size of 1.0-3.0 μm have been synthesized through annealing the zinc hydroxide carbonate precursor, which was obtained by a one-pot hydrothermal process with the assistance of glycine, Na(2)SO(4), and polyvinyl pyrrolidone (PVP). The nestlike 3D ZnO structures are built of 2D nanoflakes with the thickness of ca. 20 nm, which exhibit the nanoporous wormhole-like characteristic. The measured surface area is 36.4 m(2)g(-1) and the pore size is ca. 3-40 nm. The unique nestlike 3D ZnO porous structures provided large contacting surface area for electrons, oxygen and target gas molecules, and abundant channels for gas diffusion and mass transport. Gas sensing tests showed that the nestlike 3D ZnO porous structures exhibit excellent gas sensing performances such as high sensitivity and fast response and recovery speed, suggesting the potential applications as advanced gas sensing materials.     

WO3掺杂NiO纳米材料的VOCs气敏性能

制备掺杂WO_3的NiO纳米粉体材料并测量了材料的VOCs气敏性能。XRD分析表明,WO_3掺杂使NiO粉体中出现新相NiWO_4。随着WO_3掺杂量增多,NiO的衍射峰半高宽明显宽化,WO_3掺杂抑制了热处理过程中NiO晶粒的长大。50×10~(-6)浓度二甲苯、甲醛、甲苯和乙醇等气体中的测量结果说明,WO_3掺杂明显提高了NiO材料的VOCs气体灵敏度,对二甲苯的最佳掺杂量是5%,最大灵敏度为26.4,响应时间4s;对甲醛的最佳掺杂量是10%,最大灵敏度是4.67,响应时间6s。     

花状SnO2的制备及其气敏特性的研究

以乙二醇(C2H6O2)为有机溶剂,采用溶剂热法制备了花状SnO2纳米材料,并将制备的SnO2制成旁热式气敏元件.通过XRD,SEM等测试手段对SnO2纳米材料进行了表征,并初步分析了气敏元件对丙酮的敏感机理.制备的SnO2材料是由粒径约为10 nm的颗粒有规则的堆叠而成的直径约为3～4μm的花瓣清晰的多孔分级花状结构.研究发现,气敏元件对丙酮气体有很好的响应灵敏度.在最佳工作温度(350℃)时,检测的丙酮体积分数最低为1×10-6.对100 ppm丙酮的响应及恢复时间分别为40和50 s.且气敏元件对丙酮气体的响应灵敏度远高于对苯、甲苯、甲醇、甲醛、氨等气体的响应灵敏度.     

网状纤维结构氧化镍的制备及其气敏性能

p型半导体金属氧化物作为气敏材料具备响应快速、选择性高的特点,用于气体传感器的制备与开发。静电纺丝法可制备具有丰富气体吸附位点的网状结构材料,增强材料的气体敏感特性。以聚乙烯吡咯烷酮(PVP)、四水合乙酸镍为原料,采用静电纺丝法制备具有网状纤维结构的p型半导体氧化镍。通过X射线衍射、扫描电镜、X射线光电子能谱和比表面积测试等分析技术对材料的结构、形貌、组成和比表面等性能进行表征,并对其气敏性能进行测定,考察煅烧温度对材料气敏性能的影响。结果表明:煅烧温度为500℃时获得的氧化镍组装成气体传感器,在工作温度为250℃时,该元件对50mg/L丙酮气体表现出快速响应特性(响应时间为5s)、良好选择性和稳定性。     

Structure and CO gas sensing properties of electrospun TiO2 nanofibers

Titanium dioxide (TiO₂) nanofibers were fabricated by electrospinning a hybrid solution, which is a mixture of the TiO₂ sol precursor, polymer, and solvent. The structure and gas sensing properties of TiO₂ nanofibers were investigated. By calcining at 600 °C, the polymeric components were decomposed and a multi-layered random network structure of TiO₂ nanofibers was obtained. Polycrystalline TiO₂ nanofibers consist of tetragonal anatase and rutile TiO₂ phases. The diameter ranged from 400 nm to 500 nm and the grain size was about 15 nm. The TiO₂ nanofibers-based sensor exhibited response to CO concentration as low as 1 ppm at 200 °C.     

Synthesis and ethanol sensing properties of Fe-doped SnO2 nanofibers

Fe-doped SnO₂ nanofibers are synthesized through an electrospinning method and characterized by scanning electron microscopy and transmission electron microscopy. The sensor fabricated from these nanofibers exhibits high sensitivity and rapid response/recovery to ethanol at 300 °C. The sensitivity is up to 15.3 when the sensor is exposed to 100 ppm ethanol, and the response and recovery time is about 1 and 3 s, respectively. The linear dependence of the sensitivity on the ethanol concentration is observed in the range of 10-300 ppm. These results demonstrate that Fe-doped SnO₂ nanofibers can be used as the sensing material for fabricating high performance ethanol sensors.     

Synthesis and gas sensing properties of novel SnO2 nanorods

We report the microstructures and gas sensing properties of two novel SnO₂ nanorods prepared by hydrothermal method with the utilizing of cetyltrimethylammonium bromide and polyethylene glycol. The structures and morphologies of the dense and porous nanorods were characterized by means of powder X-ray diffraction and scanning electron microscopy. The gas sensing performances towards ethanol of the two samples were investigated. The results show that the porous SnO₂ nanorods display excellent gas response to ethanol, indicating SnO₂ as a potential gas sensing material for broad applications.     

纺丝法制备多级SnO2纳米纤维及其气敏特性研究

为了提高SnO2的气敏性能,以PVP为有机溶剂,采用静电纺丝法制备了多级结构的SnO2纳米纤维,利用XRD,SEM和TEM等技术对材料的结构、形貌进行了表征,并制备了SnO2旁热式气敏元件.采用静态气体测试系统对SnO2元件进行了气敏测试.在工作温度300℃时,对0.5~50 ppm甲醛进行了气敏测试.测试结果表明:SnO2气敏元件对甲醛气体具有优异的响应灵敏度,快速的响应及响应恢复特性、较好的选择性.采用静电纺丝制备的多级结构SnO2纳米纤维对甲醛表现出良好的气敏特性.     

纳米片状NiO的合成及电容性质

采用沉淀法在500℃下草酸溶液中合成了NiO纳米片。以扫描电子显微镜(SEM)、X射线衍射仪(XRD)、循环伏安曲线和充放电曲线等表征了所得NiO的形态、晶体结构和电化学性质。结果表明,所得到的NiO纳米片长度为100～150nm,宽度为30～50nm。NiO的纯度高,晶体结构为六方相。并且纳米片的形态和晶格常数随合成温度的改变而变化。由于纳米片形貌大大增加了表面氧化镍的比率,所得NiO纳米片具有较好的电容性质,循环伏安曲线包含两对较强的氧化还原峰,比电容量为157.89F/g。     

Pt掺杂SnO2花状纳米结构的合成及其气敏性能的研究

用原位掺杂法制备了Pt/SnO2花状纳米结构.通过控制反应源物中n(Pt4+)/n(Sn4+)比率,可以获得不同Pt掺杂量的复合纳米结构.采用SEM、XRD、TEM和Raman光谱对样品的形貌、结构等进行了分析,并测试了材料的NH3气体敏感性能.结果表明,Pt掺杂的SnO2纳米花大小约为2μm,由平均直径为180nm,...     

Free-standing ZnO-CuO composite nanowire array films and their gas sensing properties

A modified hydrothermal method was developed to synthesize ZnO-CuO composite nanostructures. A free-standing film made of ZnO-CuO nanostructures was assembled on the surface of the hydrothermal solution with a smooth surface on one side and a spherical surface on the other side. The structure, growth mechanism and the optical properties of the composite nanostructures were studied. Structural characterizations indicate that the composite nanostructure mainly consisted of two single-crystal phases of CuO and ZnO. The sensitivity for CO gas detection was significantly improved for the composite CuO-ZnO nanostructure film. This method offers a possible route for the fabrication of free-standing nanostructure films of different functional composite oxides.     

Transport properties of hybrid nanoparticle-nanowire systems and their application to gas sensing

Experimental data and theoretical modelling of the I-V characteristics of a gas sensor constructed from a mat of Au nanoparticle-coated GaN nanowires are presented. The principal mechanism for the response of the gas sensor to methane is explained in terms of the formation of a depletion layer within the nanowires due to the presence of the gold nanoparticles. The depth of the depletion layer is modulated by the potential induced by the physisorption of gas molecules onto the Au nanoparticles. A statistical model of the temperature-dependent I-V characteristics of bare and Au nanoparticle-decorated mats of GaN nanowires based on Poisson's equation has been used to determine the depth of the depletion layers of the nanowires. The room-temperature carrier concentration for the GaN nanowires was determined to be approximately 2.2 × 10(17)?cm(-3). The induced potential due to methane physisorption onto the Au nanoparticles that decorate the GaN nanowires was determined to be approximately -37?mV.     

Microwave hydrothermal synthesis of nanoporous cobalt oxides and their gas sensing properties

In this paper, the precursors were synthesized by microwave hydrothermal method using Co(NO₃)₂·6H₂O as raw material, CO(NH₂)₂ and KOH as precipitants, respectively. The precursors and calcined products were characterized by XRD, FESEM, and BET-BJH. The results show that both constituent and synthetic condition can determine the products morphology. When using KOH as precipitant, hollow Co₃O₄ nanorings were obtained whose precursor was synthesized at 140 °C for 3 h and calcined at 500 °C in air for 2 h. While using CO(NH)₂, Co₃O₄ like-nanochains were obtained whose precursor was synthesized at 110 °C for 1 h and calcined at 420 °C in air for 2 h, and Co₃O₄ nanosheets were obtained while their precursor was synthesized at 140 °C for 3 h and calcined at 500 °C in air for 2 h. The sensitivity test of Co₃O₄ to alcohol reveals that the hollow Co₃O₄ nanorings show the best sensitivity, porous Co₃O₄ like-nanochains are superior to that of the porous nanosheets.     

氧化石墨烯的制备及其对NH3的敏感特性研究

石墨烯独特的原子结构赋予其电学、热学、力学等方面的优异性能,在诸多领域具有广泛的应用。氧化石墨烯不仅具有石墨烯结构特点,而且具有大量的含氧官能团,增强了对气体的吸附能力,更适合应用于气敏传感器。通过改进的Hummer方法制备了片状多层氧化石墨烯,并对不同浓度的NH3进行敏感特性测试。结果表明氧化石墨烯对NH3具有良好的响应,在(1.5～3.5)×10-4范围内呈线性关系。     

三维网状结构WO_3纳米材料的合成、表征及气敏性能

以鸡蛋壳内膜为模板,通过简单环保的液相浸渍技术结合热处理工艺制备了具有蛋膜分级结构特征的WO3纳米材料。利用XRD、SEM等测试手段,对其物相、结构进行了表征。测试了材料对H2S的气敏性能,探讨了煅烧温度、工作温度以及气体浓度对材料气敏性能的影响。结果表明700℃热处理条件下得到的材料对3.0×10-5 H2S的灵敏度高达687,且响应时间很短,材料的灵敏度与气体浓度呈现良好的线性关系。     

CO gas sensing of Pd-doped ZnO nanofibers synthesized by electrospinning method

Pure and Pd-doped ZnO nanofibers were synthesized by electrospinning method, and characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The diameters of the fibers annealed at 600 °C range from 70 to 160 nm. Compared with pure ZnO nanofiber sensor, the Pd-doped ZnO nanofiber sensor exhibits improved sensing properties to CO at 220 °C. Moreover, this sensor processes considerable sensitivity to low concentration CO in the range of 1-20 ppm with good selectivity. The response and recovery times are in the range of 25-29 s and 12-17 s, respectively. The sensing mechanism is also discussed.