Preparation of SnO2 nanowires by solvent-free method using mesoporous silica template and their gas sensitive properties

In this paper, a facile method was presented to synthesize tin dioxide (SnO2) nanowires by solvent-free method using SnCl2 x 2H2O as precursor and mesoporous silica SBA-15 as the hard template. No solvent was used in the processing. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and N2 adsorption/desorption isotherms. The results indicated that SnO2 nanowires fabricated by this method have a diameter of about 8 nm and a relatively high surface area 73.0 m2/g. The gas sensing properties of SnO2 nanowires were measured. The response and recovery time of this sensor were 6 s and 12 s, respectively. With the concentration of toluene increasing, the response of the sensor doubled increase. Compared with bulk SnO2, SnO2 nanowires showed much higher response to toluene.     

Rutile structured SnO2 nanowires synthesized with metal catalyst by thermal evaporation method

One-dimensional (1-D) nanostructures such as tubes, rods, wires, and belts have attracted considerable research activities owing to their strong application potential as components for nanosize electronic or optoelectronic devices utilizing superior optical and electrical properties. Characterizing the mechanical properties of nanostructure is of great importance for their applications in electronics, optoelectronics, sensors, actuators. Wide-bandgap SnO2 semiconducting material (Eg = 3.6 eV at room temperature) is one of the attractive candidates for optoelectronic devices operating at room temperature, gas sensors, and transparent conducting electrodes. The synthesis and gas sensing properties of semiconducting SnO2 nanomaterials have became one of important research issues since the first synthesis of SnO2 nanobelts. Considering the important application of SnO2 in sensors, these structures are not only ideal systems for fundamental understanding at the nanoscale level, but they also have potential applications as nanoscale sensors, resonator, and transducers. The structured SnO2 nanorods have been grown on silicon substrates with Au catalytic layer by thermal evporation process over 800 degrees C. The resulting sample is characterized and analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDS). The morphology and structural properties of SnO2 nanowires were measured by scanning electron microscopy and high-resolution transmission electron microscopy. The mean diameter of the SnO2 nanorods grown on Au coated silicon (100) substrate is approximately 80 nm. In addition, X-ray diffraction measurements show that SnO2 nanorods have a rutile structure. The formation of SnO2 nanowires has been attributed to the vapor-liquid-solid (VLS) growth mechanisms depending on the processing conditions. We investigated the growth behavior of the SnO2 nanowires by variation of the growth conditions such as gas partial pressure and temperature.     

Microstructural,optical and electrical investigations of large scale selenium nanowires prepared by template electrodeposition

Large scale selenium nanowires have been prepared into the pores of polycarbonate track-etched membrane by template electrodeposition. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV–Visible spectroscopy have been used to characterize as-prepared crop of selenium nanowires. XRD and FESEM studies confirmed the formation of dense crop of selenium nanowires with trigonal phase. The spectra exhibited a highly crystalline peak corresponding to (100) plane suggesting a preferential growth along [001] direction. Williamson–Hall analysis has been used to determine the crystallite size and micro strain induced due to lattice deformation. The band gap of as-prepared selenium nanowires has been found to be 1.76 eV and of the direct type of transition. The blue shift observed in the optical band gap of selenium nanowires has been attributed to quantum size effect in semiconductor nanowires. Electrical properties of selenium nanowires have been examined using two probe method and showed double diode like current–voltage characteristics. The possible reaction mechanism of the formation of selenium nanowires has also been discussed.     

Synthesis and optical properties of ZnTe single-crystalline nanowires

Single-crystalline ZnTe nanowires with the zincblende structure have been synthesized on silicon (Si) substrates via a vapor phase transport method. The ZnTe (99.99%) powders were used as the source, and 10 nm-thick thermal evaporated gold (Au) film was used as the catalyst. The as-prepared ZnTe nanowires have diameters of 30-80 nm and lengths of more than 10 microm. The products were analyzed by X-ray diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy. Optical properties of these nanowires were investigated by room-temperature Raman scattering spectrum and temperature-dependent photoluminescence measurements. The results show that the as-prepared ZnTe nanowires are of high crystal quality.     

The structure and photoluminescence properties of Bi2O3-core/SnO2-shell nanowires

Bi2O3-core/SnO2-shell nanowires have been prepared by using a two-step process: thermal evaporation of Bi2O3 powders and sputtering of SnO2. The crystalline nature of the Bi2O3-core/SnO2-shell nanowires has been revealed by high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). TEM analysis and X-ray diffraction (XRD) results indicate that the Bi2O3-core/SnO2-shell nanowires consist of pure tetragonal alpha-Bi2O3-phase momocrystalline cores and tetragonal SnO2-phase polycrystalline shells. The photoluminescence (PL) measurements show that Bi2O3 nanowires have a broad emission band centered at around 560 nm in the yellow-green region. On the other hand, the Bi2O3-core/SnO2-shell coaxial nanowires with the sputtering times of 4 and 8 min have a blue emission band centered at around 450 nm. In contrast, those with a sputtering time of 10 min have a broad emission band centered at approximately 550 nm again. The origin of this yellow-green emission from the core/shell nanowires, however, quite differs from that from Bi2O3 nanowires, i.e., it is not from the Bi2O3 cores but from the SnO2 shells.     

Self-supported supercapacitor membrane through incorporating MnO2 nanowires into carbon nanotube networks

We report on a study on the development of a self-supported membrane of carbon nanotube (CNT) mixed with MnO2 nanowires as supercapacitors. Both single-walled CNTs (SWCNTs) and multiwalled CNTs (MWCNTs) have been explored to serve as the electrically conductive networks to connect redox active MnO2 nanowires. High-quality alpha-MnO2 nanowires were synthesized using bulk alpha-MnO2 crystals as the precursor by a facile hydrothermal method. The morphology and structure of the as-prepared alpha-MnO2 nanowires were characterized by X-ray and electron diffraction, transmission electron microscopy, and scanning electron microscopy. Supercapacitor membranes were prepared by filtration of mixture solutions of MnO2 nanowires and CNTs at various ratios, forming entangled networks which are self-supported and directly used as supercapacitor electrodes without binders or backing metals. Cyclic voltammetry at various scan rates and charge--discharging measurements are used to characterize the supercapacitance of the CNT-MnO2 nanowire membranes. The specific capacitance has been found to be increased by several times over that of pure CNT membranes after incorporation of MnO2 nanowires.     

Growth of tin dioxide nanobelts via Au-catalytic VLS process

Ultra-long (several millimeters) tin dioxide SnO2 nanobelts were prepared by chemical vapor deposition at 850 degrees C. The X-ray powder diffraction (XRD) indicated that the as-prepared sample is tetragonal phase SnO2; field emission scanning electron microscopy (FESEM) reveals the as-prepared SnO2 is uniform nanobelts; transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) studies show the nanobelts is monocrystalline with width of hundreds of nanometers and growth along [101] crystal direction; X-ray energy-dispersive spectrometer (EDS) and photoluminescence (PL) spectrum were used to detail its composition and optical properties. The possible formation mechanism of these ultra-long nanobelts was also proposed on the basis of experiments.     

氧化锡纳米线的制备及其乙醇气体敏感性能

采用热蒸发法成功制备氧化锡纳米线。用X射线衍射、扫描电子显微镜和透射电子显微镜对所制备纳米线的晶格结构和表面形貌进行表征。所制材料为金红石氧化锡单晶结构,纳米线直径为50~200nm,长度为5~15μm,符合气-液-固生长机制。以氧化锡为气敏材料,制备了旁热式结构气敏元件,测试该元件对浓度范围为25×10^-6 ~500×10^-6 的乙醇气体环境的敏感性能。结果表明,该元件的最佳工作温度约为260℃;在25×10^-6 和500×10^-6 的乙醇气体中,灵敏度分别为7.54和111.01,响应时间为2~20s,恢复时间为5~33s;在测试范围内灵敏度与气体浓度具有良好的线性关系;7天内重复测量误差在5%以内,稳定性较好。     

Synthesis of plasmonic Ag@AgBr nanowires as highly efficient sunlight photocatalyst

Ag@AgBr core–shell nanowires have been synthesized through a simple method. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electronmicroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy and UV–Vis diffuse reflectance spectroscopy, were used to characterize the as-synthesized nanowires. The as-prepared Ag@AgBr photocatalyst can be used to remove the pollutants under direct sunlight. The as-prepared Ag@AgBr plasmonic photocatalysts show excellent visible-light photocatalytic performance and good reusability for decomposing organic pollutant of Rhodamine B and methyl orange dyes due to the surface plasmon resonance effect of Ag and AgBr nanoparticles. Additionally, the recycling experiment of Ag@AgBr nanowires has been done, demonstrating that Ag@AgBr nanowires have high efficiency and stability.     

超声方法合成硒纳米线（英文）

用超声的方法合成了硒纳米线.场发射扫描电镜（FESEM）结果表明产物的形貌比较均一.产物的结构通过透射电镜（TEM）和X-射线衍射仪（XRD）进行了进一步表征.TEM和XRD光谱的结果证明了所得硒纳米线为单晶结构且沿着[001]方向生长.所得硒纳米线在671nm处有一紫外光谱吸收峰,通过对光谱的计算,硒纳米线的能带为1.66eV.基于一系列的生长过程,提出了硒纳米线的生长机理：硒粉溶解溶液中产生自由硒原子;当硒原子浓度过高时,硒原子结晶形成t型硒种子;由于各向异性晶体结构,连续提供的硒原子进入结晶种子形成线性纳米结构.此外,溶解和再结晶使α型硒转化为更稳定的t型硒.超声波可以提供适当的能量来调整这动态的平衡溶解和再结晶,进一步加快这一转变.     

Decoration of Cu nanowires with chemically modified TiO2 nanoparticles for their improved photocatalytic performance

In this work, TiO₂ nanoparticles/Cu nanowires (TiO₂NPs@CuNWs) binary composites with tunable coverage of TiO₂ nanoparticles were prepared by a facile method of mixing oleic acid-modified TiO₂ nanoparticles with as-prepared Cu nanowires. Characterization studies including X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy were applied to investigate the structure and morphology of the as-synthesized TiO₂NPs@CuNWs binary composites. The photocatalytic activity of TiO₂NPs@CuNWs binary composites was examined by photodegradation of methyl orange. The enhanced photocatalytic efficiency of TiO₂NPs@CuNWs nanocomposites was ascribed to the moderate specific surface area, mesoporous structures, and the electron sink effect of the Cu nanowires. In principle, our investigation indicates that the TiO₂@Cu self-assembled nanostructures can be a promising candidate of composite photocatalysts.     

Low-temperature synthesis and optical properties of wurtzite ZnS nanowires

Single-crystal wurtzite ZnS nanowires have been synthesized via a facile solution route with polyethylene glycol-400 as inducing template at low temperature (170 °C). The as-prepared products have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy dispersive X-ray analysis (EDX). Raman and photoluminescence spectrum (PL) were used to investigate the optical properties of ZnS nanowires. The strong emission peak centered at 322 nm in PL spectrum could be attributed to the band to band transitions.     

Preparation of SnO2 nanoparticles by hard template method for high selectivity gas sensors

In this paper, SnO2 nanoparticles were synthesized by the impregnation method with SnCl2 x 2H2O as the inorganic precursor and mesoporous silica MCM-41 as the hard template. The physical and chemical properties of the products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The SnO2 nanoparticles grew into the ordered channels of MCM-41. After removing the silica template, the products exhibited good rutile structure. The gas sensing properties of the SnO2 nanoparticles were also studied. The results indicated that these SnO2 nanoparticle sensors showed high selectivity towards ethanol.     

High-performance visible-light-driven SnS₂/SnO₂ nanocomposite photocatalyst prepared via in situ hydrothermal oxidation of SnS₂ nanoparticles

SnS?/SnO? nanocomposites with tunable SnO? contents were prepared via in situ hydrothermal oxidation of SnS? nanoparticles in 0.375-4.5 mass% H?O? aqueous solutions at 180 °C for 0-12 h. The structure, composition and optical properties of the as-prepared SnS?/SnO? nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, Brunauer-Emmett-Teller (BET) surface area analysis, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and UV-vis diffuse reflectance spectra. Furthermore, their photocatalytic properties were tested for the degradation of methyl orange in water under visible light (λ > 420 nm) irradiation. It was found that the as-prepared SnS?/SnO? nanocomposites with suitable SnO? content not only demonstrated superior photocatalytic activity to both SnS? nanoparticles and physically mixed SnS?/SnO? composite nanoparticles, but also had remarkable photocatalytic stability. The tight attachment of SnO? nanoparticles to SnS? nanoparticles, which can facilitate interfacial electron transfer and reduce the self-agglomeration of two components, was considered to play an important role in achieving the high photocatalytic performances exhibited by the as-prepared SnS?/SnO? nanocomposites.     

One Pot Synthesis and Characterization of Cesium Doped SnO2 Nanocrystals via a Hydrothermal Process

The physico-chemical properties of cesium doped SnO2 nanocrystals synthesized by wet chemical method have been investigated. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), inductively coupled plasma (ICP), atomic absorption spectroscopic (AAS) analyses, UV-vis-NIR spectral studies and dielectric studies were carried out for both pure SnO2 and cesium doped SnO2 nano-samples. All samples of SnO2 did not show any metallic cluster, but the sample containing cesium as a dopant displayed significant activity. The products formed were chloride and water representing a competitive advantage from the stand point of environmental protection.     

Large scale preparation of beta-AgVO3 nanowires using a novel sonochemical route

A large number of beta-AgVO3 nanowires with diameter of 30-60 nm, and length of 1.5-3 microm have been successfully synthesized by a simple and facile low-temperature sonochemical route. The morphologies and structures of the nanowires were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning transmission electron microscopy (SEM), and thermal gravimetric analysis (TGA). Cyclic voltammetry and charge-discharge experiments were applied to characterize the electrochemical properties of the nanowires as cathode materials for lithium-ion batteries. In the initial discharge and charge process, the as-prepared beta-AgVO3 nanowires showed the initial charge and discharge capacities of 69 and 102 (mAh)/g, respectively. It is anticipated that the beta-AgVO3 nanostructures are promising cathode candidates in the application of primary lithium-ion batteries.     

Synthesis of single-crystalline silver sulfide nanowires by diffusion in porous anodic aluminium oxide template

Highly ordered single-crystalline silver sulfide (Ag₂S) nanowires have been successfully achieved directly using silver nitrate and thioacetamide (TAA) as the reactants, by diffusion in the channels of anodic aluminium oxide (AAO) membrane. The products have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The results of the research show that the as-prepared Ag₂S nanowires are monodisperse with sizes of about 50 nm in diameter, closely corresponding to the pore size of the AAO membrane. Furthermore, its photoluminescence properties and the growth mechanism are also discussed.     

Fabrication of single-crystalline gallium nitride nanowires by using alginate as template

Hexagonal gallium nitride nanowires were synthesized successfully by solvothermal method with alginate as template. The microstructure, morphologies and compositions of the as-prepared product were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM), and energy dispersive X-ray (EDX). Results suggested that the rod-like nanowires were hexagonal single-crystalline GaN growing along [001] direction. The photoluminescence spectra (PL) of the GaN revealed that the as-synthesized sample possesses excellent optical properties.     

Optical properties of zigzag twinned geometry of Zn2SnO4 nanowires

High-density single-crystalline Zn2SnO4 nanowires have been successfully synthesized by using a simple thermal evaporation method by heating a mixture of ZnO and SnO2 nano powders. The products in general contain various geometries of wires, with an average diameter of 80-100 nm. These nanowires are ultra-long, up to 100 microns. The transmission electron microscopy study showed that these nanowires exhibited zigzag twinned geometry, and grow along the (111) direction. Low-temperature photoluminescence properties of the nanowires were measured, showing a strong green emission band at about 515 nm and a weak peak corresponding to UV emission at about 378 nm, which have not been reported before.     

单分散介孔氧化硅微球的粒径可控制备

在中性醇-水体系中,采用月桂胺(DDA)为导向剂,通过调整反应物组分的剂量比,研究了具有蠕虫状介孔的单分散氧化硅微球粒径可调控行为。实验表明,当月桂胺与正硅酸乙酯的摩尔比为0.4,正硅酸乙酯的浓度范围在0.138~0.248mol/L之间,改变水/醇比例,可以实现微球粒径在50nm~1μm之间的调控。该方法简单易行,制备得到的微球尺寸均匀,单分散性好,BJH孔径在1.4nm左右。粒径可控的单分散介孔氧化硅微球,通过表面有机化修饰,可以成为改变流体流变行为的优秀添加介质。