Microwave hydrothermal synthesis and photocatalytic properties of ZnWO4 nanorods

Cd²⁺‐doped ZnWO₄ nanorods have been synthesized at 200 °C with microwave hydrothermal method, using Zn(NO₃)₂·6H₂O, Na₂WO₄·2H₂O and CdCl₂ as raw materials. The effects of Cd²⁺ doping contents on the structure and morphology of the product were studied. The results show that Cd²⁺ doping into the crystal lattice of ZnWO₄ nanopowder makes the powder orientationally grow along (010), (110) and (200) crystal planes to form the nanorods. The bigger Cd²⁺ doping contents are, the more obviously ZnWO₄ nanorods grow. Meanwhile, the nanopowder is gradually transformed from monoclinic phase into the orthogonal phase. As the charge transference medium between the interfaces, Cd²⁺ restrains the combination of holes and electrons. After doped, the photocatalytic properties of ZnWO₄ nanorods are increased. When Cd²⁺ doping content is 20%, the Cd²⁺‐doped ZnWO₄ nanorods showed the highest degradation rate up to 98% in 2 h.     

水热法合成SnO2金红相纳米柱晶体

本文采用水热法,以SnCl4·5H2O为前驱物,NaOH为矿化剂,在180℃,填充度为68;,通过加入不同量的NaOH,调节溶液pH值分别为2、4、11,合成了三种具有不同形态的金红相SnO2纳米晶体.其中在较高浓度的酸或强碱环境下合成了具有清晰结构,长100nm、直径10nm的SnO2纳米柱体.     

Synthesis and field emission properties of SnO2 nanowalls

SnO₂ nanowalls were synthesized on silicon substrate by the thermal chemical vapor transport method at a low temperature of around 650 °C under atmospheric pressure. The microstructure and morphology of the SnO₂ nanowalls were evaluated by using scanning electron microscopies and X‐ray diffraction. Room temperature photoluminescence spectra of the nanowalls showed a broad emission band centering at about 530 nm. Field emission measurements demonstrated that the nanowalls possessed good performance with a turn‐on field of ∼3.5 V/μm and a threshold field of ∼6.1 V/μm. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure and humidity sensing properties of SnO2 zigzag belts

A novel method was developed for synthesizing ultralong SnO₂ zigzag belts with the assistance of CuO powder. The crystalline structure and morphology of SnO₂ zigzag belts were characterized using x‐ray diffraction, scanning electron microscopy and transmission electron microscopy. The growth mechanism of the ultralong SnO₂ zigzag belts and the catalytic behavior of the copper were discussed. The humidity sensor based on as‐synthesized product shows high sensitivity and fast response time due to unique structure of the SnO₂ zigzag belts with large surface‐to‐volume ratio. It can be found that the resistance of the SnO₂ materials decreases obviously with increasing relative humidity (RH) at room temperature (26 °C). The results demonstrate that these SnO₂ nanostructures are potential to be used as effective and high performance humidity sensors. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Controllable synthesis of TiO2 nanoparticles employing substrate/dielectrophoresis/sol‐gel

Due to size‐dependent catalytic selectivity, the size and special morphology are of great importance to applications of TiO₂. The synthesis method of size and morphology control has been in need of innovation. In this study, TiO₂ nanoparticles(TiO₂‐NPs) with well‐defined morphology and homogenous size were synthesized using a novel method, in which bamboo substrate, dielectrophoresis (DEP) technology and a sol‐gel process were combined(substrate/ DEP/ sol‐gel). Powder X‐ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used to characterize the TiO₂‐NPs. Further study showed that, with this combined method, the size and the uniformity of TiO₂‐NPs can be controlled by changing the voltage of DEP. The number and arrangement of TiO₂ nanorods can be controlled by changing the voltage. Substrate/ DEP/ sol‐gel proved to be an efficient way to form special morphologies of TiO₂‐NPs. A visible‐light catalytic activity experiment showed that among three preparation methods, the substrate/ DEP/ sol‐gel method made TiO₂‐NPs with the highest catalytic activity for degradation of methyl orange. TiO₂‐NPs produced by the DEP/ sol‐gel process presented higher catalytic activity than TiO₂‐NPs produced by only a sol‐gel process.     

Preparation,structure, and photoluminescence properties of Ga2O3/SnO2 coaxial nanowires

Ga₂O₃/SnO₂ coaxial nanowires were synthesized by thermal evaporation of GaN powders and then atomic layer deposition of SnO₂. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) analysis results indicate that the Ga₂O₃ cores and the SnO₂ shells of the coaxial nanowires after thermal annealing are single crystals with monoclinic and simple orthorhombic structures, respectively, although the SnO₂ shells are amorphous before annealing. Our results also show that photoluminescence (PL) emission can be enhanced by thermal annealing in an H₂/N₂ atmosphere. EDX concentration profile suggests that the enhancement in the bluish green emission is due to the increase in the concentration of the Ga vacancies in the cores during the H₂/N₂ annealing. On the other hand, a red emission is newly formed while the bluish green emission is degraded by annealing in an oxygen or nitrogen atmosphere (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

SnO2/石墨分级纳米异质结构的合成及其电化学性能研究

以石墨为基底,五水合四氯化锡为锡源,氢氧化钠为沉淀剂,采用一步水热法合成了SnO2/石墨分级纳米异质结构.利用FESEM、XRD、EDS、Raman等对SnO2/石墨分级纳米异质结构进行了形貌、结构和成分表征.研究发现,结晶良好的SnO2纳米线首先组装成SnO2纳米棒,纳米棒进一步组装成直径约450 nm的花状结构,并...     

Morphology‐photocatalytic properties‐growth mechanism for ZnO nanostructures via microwave‐assisted hydrothermal synthesis

ZnO nanostructures with various morphologies including rod‐like, sheet‐like, needle‐like and flower‐like structures were successfully synthesized via a fast and facile microwave‐assisted hydrothermal process. Reaction temperature, reaction time and the addition of NaOH were adjusted to obtain ZnO with different morphologies. Scanning electron microscopy(SEM), transmission electron microscope(TEM), X‐ray diffraction (XRD) and ultraviolet spectrophotometer (UV) were used to observe the morphology, crystal structure, ultraviolet absorption and photocatalytic activity of the obtained ZnO. The results indicated that growth rate of ZnO nanostructure along [001] direction was more sensitive to temperature compared with those along [101] and [100] directions. The competition between anionic surfactant and OH⁻ played an important role in the formation of ZnO with various morphologies. Flower‐like ZnO had better ultraviolet absorption property and excellent photocatalytic activity than ZnO in the other morphologies. On the basis of the above results, a possible growth mechanism for the formation of ZnO nanostructures with different morphologies was described.     

Electrospinning synthesis and photocatalytic property of CaFe2O4/MgFe2O4 heterostructure for degradation of tetracycline

CaFe₂O₄/MgFe₂O₄ nanowires with heterostructure had been successfully synthesized by electrospinning method. The obtained samples were systematically characterized by scanning electron microscopy (SEM), X‐Ray diffraction (XRD), UV–Vis diffuse reflectance spectra (UV‐Vis DR) and Environment scanning electron microscopy (ESEM). The novel CaFe₂O₄/MgFe₂O₄ nanowires exhibit an enhanced photocatalytic activity for degrading of tetracycline (TC) under visible light. Compared with bare CaFe₂O₄ or MgFe₂O₄ samples, the prepared CaFe₂O₄/MgFe₂O₄ (Ca:Mg:Fe = 3:2:10) composited nanowires show the best photocatalytic performance with a degradation efficiency of 40% after 150 min reaction time. This enhancement is attributed to the heterostructure of CaFe₂O₄/MgFe₂O₄ nanowires, which effectively repress the recombination of photo‐generated electrons and holes. Based on heterostructure and energy band positions, the enhancement of mechanism under visible‐light enhances the photocatalytic activity.     

Multi‐factors on photocatalytic properties of Y‐doped Bi2WO6 crystallites prepared by microwave‐hydrothermal method

Different contents of Y‐doped Bi₂WO₆ crystallites were synthesized by a microwave‐hydrothermal method. The photocatalytic properties with different contents of Y‐doped Bi₂WO₆ crystallites were studied. The Y‐doped Bi₂WO₆ crystallites were also characterized by XRD, EDX, SEM and UV‐vis DRS and the multi‐factors on photocatalytic properties of Y‐Doped Bi₂WO₆ crystallites were discussed. The results indicate that Y³⁺ replacing Bi³⁺ enters into the Bi₂WO₆ lattice, producing a degree of Bi₂WO₆ lattice distortion. It also has an impact on the crystallinity of Bi₂WO₆ and the band gap is from 2.49 eV to 2.71 eV. The photocatalytic results show that when the content of Y doping becomes 10%, the degradation rate of rhodamine B is above 90% after 40 min irradiation, which shows that doping the proper rare earth ions is conducive to the photocatalytic properties of Bi₂WO₆ crystallites.     

CuO-NiO/SnO2光催化剂的制备、表征及产氢性能

采用溶胶-凝胶法制备纳米SnO2,通过浸渍法制备CuO-NiO/SnO2光催化材料,采用XRD、UV-Vis DRS、TEM及HRTEM对其结构、形貌及光吸收性能进行表征。在紫外灯照射下,以无水乙醇为电子给体,详细考察了CuO掺杂量、NiO掺杂量、乙醇浓度等对SnO2光催化产氢性能的影响。研究结果表明:5%CuO-7%NiO/SnO2的光催化产氢性能最佳,约是同条件下纯SnO2产氢性能的2.8倍;最优乙醇浓度约为1.2 mol/L。     

One‐step green synthesis by organic molten salt method and optical properties of CdS nanosheets

Cadmium sulfide (CdS) nanosheets were synthesized by an environment friendly, “green” organic molten salt (OMS) method at 220 °C. The as‐synthesized products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS), respectively. The XRD results reveal that the as‐synthesized CdS nanosheets are of the hexagonal wurtzite structure and the CdS nanosheets grow along the c‐axis. The SEM results indicate that the diameters and thickness of the CdS nanosheets are about 20–40 nm and 5–10 nm, respectively. The optical properties of the CdS nanosheets were investigated by ultraviolet–visible (UV‐Vis) spectroscopy and photoluminescence (PL) spectroscopy. The ultraviolet–visible spectrum exhibits two excitonic peaks with a step‐like absorption and the photoluminescence spectrum shows a green emission peak centered at around 524 nm. A possible growth mechanism of CdS nanosheets was discussed.     

自掺杂SnO2微球的水热合成及其可见光催化性能

本研究采用水热法,以柠檬酸为螯合剂,通过控制n(Sn⁴⁺)/n(Sn²⁺)的数值,合成了由具有丰富氧空位的SnO₂纳米晶体组装成的微球。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶红外光谱(FT-IR)、X射线光电子能谱(XPS)及UV-Vis漫反射光谱对SnO₂纳米微球进行表征分析,结果表明:在酸性水热条件和柠檬酸的螯合作用下,二氧化锡纳米晶体聚集形成微球;在Sn⁴⁺/Sn²⁺摩尔比例为3:7时,其微球尺寸最小,整体分散性较好;同时适量二价锡离子的掺杂使得该样品氧空位浓度达到最佳,氧空位的存在将使得样品光吸收范围拓展至可见光,因而该样品显示出较强的可见光催化效率,在8 min内完全降解甲基橙。     

电子和空穴注入对氮掺杂SnO2材料光电性能的影响

采用基于密度泛函理论的线性缀加平面波(FLAPW)方法研究了电子、空穴对N掺杂SnO2光电性能的影响,结果表明注入空穴比注入电子的Sn16O31N体系禁带宽度减小了0.02 eV,比未注入电子、空穴的Sn16O31N体系变窄了0.04 eV,导带也相对展宽,体系呈现出半金属特性,SnO2材料导电性能有所提高.注入空穴的体系光学特性也发生了较大的变化,其吸收系数、能量损失函数及折射率在低能区域低于本征和电子注入体系,整个体系的态密度向低能方向移动发生了红移,吸收边变宽,体系的光学响应增大.     

Structural and optical properties of TiO2:SnO2 thin films prepared by sol gel method

ABSTRACT

TiO₂:SnO₂ thin films were deposited on glass substrates, by using sol gel spin coating method with different ratio (3%, 5% and 7%) at 3200 rpm, to study their effect on different properties of TiO₂: SnO₂ thin films. The structural and optical properties of films have studied for different ratio. These deposited films have been characterized by various methods such as X-Ray Diffraction (XRD), Ultra Visible spectroscopy. The (XRD) can be used to identify crystal structure of as deposited films. The Transmission spectra have shown the transparent and opaque parts in the visible and UV wavelengths.     

Ti/SnO2-IrO2电极的制备及其电化学降解对氯苯酚

电化学氧化法降解水中毒性有机物具有低碳、节能、清洁等优点,该技术的关键是开发高效、稳定、价格低廉的阳极。本文采用热分解法制备了Ti/SnO₂-IrO₂电极,对电极进行表征和电化学性能分析,并降解了对氯苯酚。考察不同因素(电流密度、目标污染物初始浓度、Cl^-浓度)对降解效果的影响。结果表明,Ti/SnO₂-IrO₂电极具有较长的寿命和良好的电化学性能。当电流密度为20 mA·cm^-2,对氯苯酚初始浓度为300 mg/L,Cl^-浓度为1 000 mg/L时,化学需氧量(COD)去除率可达89.02%,同时电极具有较低的能耗0.596 kWh·g^-1,表现出优异的催化性能。该电极具有一定的工业应用前景。     

Hydrothermal synthesis of anatase flower‐like nanostructures for photocatalytic degradation of dye

Flower‐like hierarchical nanostructures of titanium dioxide (TiO₂) have been synthesized in large scale by a facile and controlled hydrothermal and after annealing process. The morphologies of flower‐like hierarchical nanostructures are formed by self‐organization of several tens of radially distributed thin flakes with a thickness of several nanometers holding a larger surface area. The materials are characterized by Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). The ultraviolet photocatalytic degradation of R6G dyes has been studied over this flower‐like hierarchical nanostructures and the activity is compared with that of commercial P25 TiO₂ under same conditions. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

SnO2/氮掺杂石墨烯纳米复合材料的制备及其电化学性能研究

采用温和的水热法在氧化石墨烯(GO)片层上原位生长纳米SnO2颗粒, 通过氨水调节体系pH值并对石墨烯进行掺氮,成功制备出了SnO2/氮掺杂石墨烯(N-rGO)和SnO2/石墨烯(rGO)纳米复合材料,并对它的电池和电催化性能进行研究.XRD和SEM等分析结果表明,SnO2颗粒均匀地分布在N-rGO和rGO表面,粒径分别为50 nm和100 nm左右.进一步的TEM结果表明,SnO2颗粒是由更细小的粒径为5~7 nm SnO2颗粒所组成的二次团聚体.半电池性能测试结果表明:在100 mA/g电流密度下,SnO2/N-rGO和SnO2/rGO的可逆容量分别为901 mAh/g、756 mAh/g,比同等条件下纯的纳米SnO2高6.0和4.9倍;在2 A/g的高电流密度放电情况下, SnO2/N-rGO和SnO2/rGO的放电比容量分别可以达到619 mAh/g和511 mAh/g,表现出优异的倍率性能.电催化性能测试表明:SnO2/N-rGO的催化活性要高于SnO2/rGO,催化氧还原反应(ORR)主要按照四电子转移过程进行,为非铂催化剂的研究提供了一个新的思路.     

Studies on optical properties of polycrystalline SnO2:Sb thin films prepared using SnCl2 precursor

Optical properties of spray deposited antimony (Sb) doped tin oxide (SnO₂) thin films, prepared from SnCl₂ precursor, have been studied as a function of antimony doping concentration. The doping concentration was varied from 0‐4 wt.% of Sb. All the films were deposited on microscope glass slides at the optimized substrate temperature of 400 °C. The films are polycrystalline in nature with tetragonal crystal structure. The doped films are degenerate and n‐type conducting. The sheet resistance of tin oxide films was found to decrease from 38.22 Ω/□ for undoped films to 2.17 Ω/□ for antimony doped films. The lowest sheet resistance was achieved for 2 wt.% of Sb doping. To the best of our knowledge, this sheet resistance value is the lowest reported so far, for Sb doped films prepared from SnCl₂ precursor. The transmittance and reflectance spectra for the as‐deposited films were recorded in the wavelength range of 300 to 2500 nm. The transmittance of the films was observed to increase from 42 % to 55 % (at 800 nm) on initial addition of Sb and then it is decreased for higher level of antimony doping. This paper investigates the variation of optical and electrical properties of the as‐deposited films with Sb doping. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

水热法合成SnO2金红相纳米柱和亚微米晶体

本文采用水热法,以SnCl4·5H2O为前驱物,在180℃,填充度为68;,反应时间8h,强酸环境条件下合成了SnO2纳米金红相晶体,直径约为5～10nm,长30～100nm.加入一定量的NaOH,调节溶液pH值为强碱性(pH=11),同样条件下也合成了SnO2金红相纳米柱晶体,长200nm、直径10～20nm.提高水热反应的温度为430℃,矿化剂为3mol/L NaOH,反应时间24h,合成了亚微米金红相SnO2晶体,最大线度为300nm.