One-pot synthesis of intestine-like SnO2/TiO2 hollow nanostructures

In the present study the intestine-like binary SnO₂/TiO₂ hollow nanostructures are one-pot synthesized in aqueous phase at room temperature via a colloid seeded deposition process in which the intestine-like hollow SnO₂ spheres and Ti(SO₄)₂ are used as colloid seeds and Ti-source, respectively. The novel core (SnO₂ hollow sphere)-shell (TiO₂) nanostructures possess a large surface area of 122 m²/g (calcined at 350 °C) and a high exposure of TiO₂ surface. The structural change of TiO₂ shell at different temperatures was investigated by means of X-ray diffraction and Raman spectroscopy. It was observed that the rutile TiO₂ could form even at room temperature due to the presence of SnO₂ core and the unique core-shell interaction.     

Microwave-assisted synthesis and investigation of SnO2 nanoparticles

Microwave technique was adopted for preparation of tin dioxide nanoparticles with particles size ranging from 10 to 11 nm within 10 min. The formation of monocrystalline SnO₂ nanoparticles was confirmed by the XRD (X-Ray Diffraction) and TEM (Transmission Electron Microscopy) as well as with SAED (Selected Area Electron Diffraction) analysis. The structure of the SnO₂ crystal was found to be Cassiterite type tetragonal structure. The FT-IR results further supported the formation of tin dioxide from tin hydroxyl group without any post annealing. The samples were further characterized by thermo gravimetric analysis (TGA), electrical resistance measurements and photoluminescence spectrum.     

Preparation of porous SnO2 helical nanotubes and SnO2 sheets

We report a surfactant-free chemical solution route for synthesizing one-dimensional porous SnO₂ helical nanotubes templated by helical carbon nanotubes and two-dimensional SnO₂ sheets templated by graphite sheets. Transmission electron microscopy, X-ray diffraction, cyclic voltammetry, and galvanostatic discharge–charge analysis are used to characterize the SnO₂ samples. The unique nanostructure and morphology make them promising anode materials for lithium-ion batteries. Both the SnO₂ with the tubular structure and the sheet structure shows small initial irreversible capacity loss of 3.2% and 2.2%, respectively. The SnO₂ helical nanotubes show a specific discharge capacity of above 800 mAh g⁻¹ after 10 charge and discharge cycles, exceeding the theoretical capacity of 781 mAh g⁻¹ for SnO₂. The nanotubes remain a specific discharge capacity of 439 mAh g⁻¹ after 30 cycles, which is better than that of SnO₂ sheets (323 mAh g⁻¹).     

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.     

High pressure synthesis of Cu2GeO4 with hausmannite structure

Copper(II)metagermanate, CuGeO₃, decomposes at high pressure to rutile-type GeO₂ and Cu₂GeO₄. Very small single crystals of Cu₂GeO₄ can be obtained by direct high pressure synthesis from CuOGeO₂ mixtures. The compound has a distorted spinel structure (Hausmannite structure, space group $\text{I}\text{4}{}_1\text{amd}$) with $\text{a}\text{= 5.593}\text{A}\text{?}$, $\text{c}\text{= 9.396}\text{A}\text{?}$, Z = 4.     

Silver layer instability in a SnO2/Ag/SnO2 trilayer on silicon

Trilayers of SnO₂/Ag/SnO₂ deposited on oxidized Si (100) substrates at room temperature become unstable after annealing at 100 °C and 200 °C, exhibiting five phenomena - formation of internal Ag hillocks, cracking of the top SnO₂ layer above internal Ag hillocks, penetration of Ag/Ag grain boundaries by SnO₂ leading to grain pinch-off, formation of Ag whiskers and islands on the free surface of the SnO₂ through the cracked top layer, and void formation in the Ag layer. The possible driving forces and evolution path for the observed instabilities resulting from thermal expansion mismatch stresses and the reduction in interfacial energy are discussed.     

Characterizations of SnO2 and SnO2:Sb thin films prepared by PECVD

Structural characterizations of tin oxide (SnO₂) thin films, deposited by plasma-enhanced chemical vapor deposition (PECVD), were investigated with scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results show that the films are porous, the crystalline structure transforms from crystalline to amorphous phase as deposition temperature changes from 500°C to 200°C, and the chemical component is non-stoichiometric (Sn:O is 1.0716 prepared at 450°C with a value of O₂ flow 3.5 l/min). Sheet resistance of the thin films decreases with increasing of deposition temperature. Whereas, sheet resistance increases with increasing of oxygen flow. Tin oxide doped with antimony (SnO₂:Sb) thin films prepared by same method have a better selectivity to alcohol than to carbon monoxide; the maximum sensitivity is about 220%. The gas-sensing mechanism of SnO₂ thin films is commentated.     

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.     

反应液加入H2O2制备本征SnO2高阻薄膜

在反应液中加入H2O2,用超声喷雾热分解技术制备了SnO2高阻薄膜.结合XRD图谱,方块电阻测试,透光率测试以及Tauc曲线分析的结果,发现反应液中加入H2O2制备的SnO2薄膜,膜质较好,样品在(200)晶面有明显的择优取向;电阻率有明显提高,为12～13 Ω·cm;透光率与一般的透明导电膜并没有很大差别.     

Facile synthesis of SnO2 nanograss array films by hydrothermal method

SnO₂ nanograss array films (SNAFs) were synthesized on indium tin oxide glass substrates by hydrothermal method. The effects of preparing conditions such as precursor concentration, reaction temperature and growth time on the formation of the SNAFs have been investigated in detail by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction and photoluminescence spectrum. It is shown that the precursor concentration plays an important role in determining the morphology of the prepared SnO₂. The average diameter, length and growth rate of the SNAFs can be controlled to some extent by varying growth time. The reaction temperature has also influence on the growth rate of SNAFs. Moreover, the growth mechanism of the SNAFs was also discussed. Room-temperature photoluminescence spectra were further carried out to investigate their optical properties.     

Template-free synthesis of SnO2 nanostructural hollow spheres covered by nanorods

In the present work, SnO₂ nanostructural hollow spheres have been successfully synthesized in the absence of template by a simple synthetic route, and their surfaces were covered by nanorods. The synthesized nanostructural hollow spheres covered by nanorods were further characterized by XRD, SEM and TEM measurements. The diameter of SnO₂ hollow spheres and the thickness of shells are found to be ca. 150-200 and 20-30 nm, respectively. The size of the nanorod is found to be ca. 5 nm, and the length up to tens of nanometers. Based on a series of experimental results, an oxidizing-aggregating-Ostwald ripening model has been proposed for the formation of SnO₂ nanostructural hollow spheres.     

Preparation of antimony-doped SnO2 nanocrystallites

The antimony-doped SnO₂ nanocrystallite was synthesised by the co-precipitation reaction and subsequent calcination from the antimony(III) chloride and tin(IV) chloride. The crystal size, pore size distribution and properties of the nanocrystalline powders were examined by differential thermal analysis, thermogravimetric analysis, X-ray diffraction and desorption isotherm(Barrett-Joyner-Halenda method). Calcination of the precipitate powder at 650°C led to the formation of Sb-SnO₂ nanocrystallite of ∼6 nm in crystal size. Most of the pores in the nanocrystallite are about 5-10 nm in diameter. Effect of doped antimony on the crystal size of the nanocrystallite is discussed.     

In-situ preparation of TiO2/SnO2 nanocrystalline sol for photocatalysis

A novel preparation method to synthesize TiO₂/SnO₂ nanocrystalline sol under mild conditions was presented. Ti(OC₄H₉)₄ used as a precursor was hydrolyzed in the rutile SnO₂ nanocrystalline sol, and in-situ formed TiO₂/SnO₂ nanocrystalline sol. The crystal structure, morphology and photocatalysis performance of samples were investigated. The results show that the additional rutile SnO₂ nano grains serve as heterogeneous crystal nucleus and exhibite the inducing effect on TiO₂ grains growth, thus leading to the changes in crystalline phase and particle morphology. In addition, the photoluminescence (PL) spectra analysis indicates that TiO₂/SnO₂ composite structure induces a better charge separation, and thus the photocatalytic activity of TiO₂/SnO₂ sol is increased significantly compared with TiO₂ sol.     

正交结构LiGaS2的合成及表征

为了获得高纯单相LiGaS2多晶原料,采用LiGa与S化合法合成LiGaS2,并与传统的单质直接合成法相对比.利用垂直长石英管作为反应器,采用X射线衍射和Raman光谱对其结构进行表征,同时利用差热–热重分析和紫外光谱对其热性能和光学性能进行研究.研究表明:采用LiGa与S化合法可以获得单相、均一的LiGaS2多晶材料;LiGaS2中的Li–S键平均力常数为fLi-S=16.0 N/m,Ga–S键平均力常数为fGa-S=39.6 N/m;LiGaS2多晶料的熔点为1 020℃,温度低于1 100℃,样品很稳定,没有分解现象;白色样品、黄色样品和灰色样品的紫外吸收边分别为323,435和496 nm.     

Investigation into real-time pressure sensing properties of SnO2, TiO2, and TiO2/ZnO thick films with interdigitated electrodes

The pressure sensing properties of nanocomposite SnO₂, TiO₂, and TiO₂/ZnO thick film capacitors with interdigitated electrodes are investigated. To form the dielectric layers, the metal oxides powders were respectively mixed with isopropanol, wet ball milled for 24 h, then the mixtures were dried at 120 °C and further the powders were placed under 2 tonnes of pressure to form pellets, which were fired at 1250 °C (rate of 5 °C/min) in a vacuum of 6 × 10⁻³ mbar for 5 h, followed by cooling (rate of 3 °C/min). After firing, the resultant nanopowders were mixed with 7 wt.% of polyvinyl butyral (binder) and suitable amount of ethylenglycolmonobutylether (solvent) to form the pastes. These were screen-printed over the Ag electrodes on alumina substrates to form SnO₂, TiO₂, and TiO₂/ZnO capacitor pressure sensors accordingly. The evaluation of pressure sensing properties of these sensors was performed using a HP 4192A Impedance Analyser, which recorded the changes in the values of the capacitances under different mechanical stresses. At the applied load of 5 kPa, the response times of 2.5 s, 5.6 s and 4 s were recorded for SnO₂, TiO₂, and TiO₂/ZnO sensors, respectively. In addition to instant response times, these pressure sensors have the advantage of being reusable, as their electrical properties were restored to the original value after annealing for 2 h at 80 °C. Moreover, one year later after the initial testing, the sensors were still operational and produced similar time responses to pressure.     

Nanocrystalline SnO2 and Au:SnO2 thin films prepared by direct current magnetron reactive sputtering

Nanocrystalline pure and gold doped SnO₂(Au:SnO₂) films were prepared on unheated glass substrates by dc magnetron reactive sputtering and, subsequently, the as deposited films were annealed in air. The films structure, surface morphology, photoluminescence, electrical and optical properties were investigated. After annealing the as deposited SnO₂ films, crystallinity increased and the surface roughness decreased. The intensity of PL peaks increases sharply with the annealing temperature. The optical transmittance of the films was around 89% after annealing the as deposited SnO₂ films at 450 °C. The as deposited Au:SnO₂ films show better crystallinity than the as deposited SnO₂ films, the average grain size was around 4.4 nm. The emission peaks of Au:SnO₂ films are slightly blue shifted as compare to undoped SnO₂ films. The Au:SnO₂ films show the lowest electrical resistivity of 0.001 Ωcm with optical transmittance of 76%, after annealing at 450 °C.     

TiO2 coated SnO2 nanosheet films for dye-sensitized solar cells

TiO₂-coated SnO₂ nanosheet (TiO₂-SnO₂ NS) films about 300 nm in thickness were fabricated on fluorine-doped tin oxide glass by a two-step process with facile solution-grown approach and subsequent hydrolysis of TiCl₄ aqueous solution. The as-prepared TiO₂-SnO₂ NSs were characterized by scanning electron microscopy and X-ray diffraction. The performances of the dye-sensitized solar cells (DSCs) with TiO₂-SnO₂ NSs were analyzed by current-voltage measurements and electrochemical impedance spectroscopy. Experimental results show that the introduction of TiO₂-SnO₂ NSs can provide an efficient electron transition channel along the SnO₂ nanosheets, increase the short current density, and finally improve the conversion efficiency for the DSCs from 4.52 to 5.71%.     

Effect of SnO2 on the photocatalytical properties of TiO2 films

TiO₂/SnO₂ thin films with different tin atomic percentages were successfully prepared on glass substrates by the spray pyrolysis method from an alcoholic solution of TiO[C₅H₇O₂]₂ with different concentrations of SnCl₄. The TiO₂/SnO₂ thin films prepared at 450 °C presented the anatase phase in polycrystalline configuration from %Sn = 0 in the starting solution up to %Sn = 20, at higher tin content the films present an amorphous configuration. The resulting thin films have a homogeneous surface structure with some porosity. The photocatalytical properties of the films were evaluated with the degradation of methylene blue. The products of the degradation reaction were identified by ¹H nuclear magnetic resonance and the film properties were studied by atomic force microscopy, scanning electron microscopy, UV–Vis spectroscopy, and X-ray diffraction.     

新型SnO2/WO3双层薄膜NO2敏感性能研究

采用射频磁控反应溅射锡(Sn)靶和钨(W)靶的方法制备了SnO2/WO3双层薄膜材料,通过XRD和XPS实验研究了双层薄膜的物相结构和组份,结果表明,SnO2/WO3双层薄膜经过热处理后形成了SnWO4化合物.在此基础之上,制作了相应的NO2气体敏感薄膜传感器,研究了双层薄膜传感器的制备工艺参数及工作条件对传感器性能的影响,研究了传感器的敏感特性,包括灵敏度、选择性、响应恢复等特性.结果表明,传感器对NO2气体有较好的敏感性,对其他干扰气体不敏感.     

Photocatalytic degradation of pendimethalin over Cu2O/SnO2/graphene and SnO2/graphene nanocomposite photocatalysts under visible light irradiation

The Cu₂O/SnO₂/graphene (CSG) and SnO₂/graphene (SG) nanocomposite photocatalysts were prepared by simple sol-gel growth method, and characterized by Fourier transform infrared spectra (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) measurements, respectively. The photocatalytic efficiency of catalysts were evaluated by degradation of pendimethalin under visible light irradiation (λ > 420 nm), which conformed that CSG and SG exhibited better photocatalytic activity than SnO₂ or graphene alone. An effort has been made to correlate the photoelectro-chemical behavior of these samples to the rate of photocatalytic degradation of pendimethalin.