Synthesis and characterization of ultrathin WO3 nanodisks utilizing long-chain poly(ethylene glycol)

Metal oxide nanostructures hold great potential for photovoltaic (PV), photoelectrochemical (PEC), and photocatalytic applications. Whereas thin films of various materials of both nanoparticle and nanorod morphologies have been widely investigated, there have been few inquiries into nanodisk structures. Here, we report the synthesis of ultrathin WO3 nanodisks using a wet chemical route with poly(ethylene glycol) (PEG) as a surface modulator. The reported nanodisk structure is based on the interaction of the nonionic 10000 g/mol PEG molecules with tungsten oxoanion precursors. The WO3 nanostructures formed are dominated by very thin disks with dimensions on the nanometer to micrometer scale. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images reveal the structures to have dimensions on the order of 350-1000 nm in length, 200-750 nm in width, and 7-18 nm in thickness and possessing textured single-crystalline features. A number of analytical techniques were used to characterize the WO3 nanodisks, including selected-area electron diffraction (SAED), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), Raman scattering spectroscopy, UV-visible spectrophotometry, and cyclic voltammetry (CV). The growth of the WO3 nanodisks was inhibited in the [010] crystal direction, leading to ultrathin morphologies in the monoclinic crystal phase. The large flat surface area and high aspect ratio of the WO3 nanodisks are potentially useful in PEC cells for hydrogen production via direct water splitting, as has been demonstrated in a preliminary experiment with external bias.     

A low-temperature, soft chemistry method for the synthesis of zirconia nanoparticles in thermally evaporated fatty amine thin films

We demonstrate the synthesis of zirconia nanoparticles in a lipid matrix by a simple, low temperature beaker-based process. This is accomplished by electrostatic entrapment of ZrF6(2-) ions within thermally evaporated octadecylamine (ODA) thin films followed by the low-temperature in situ hydrolysis of the entrapped metal ion complexes. The zirconia particles thus formed were of the monoclinic phase and were fairly monodisperse with particles of average size 40 nm. The zirconia crystallites appeared to exhibit preferred orientation indicating epitaxial growth of the crystals within the lipid matrix. The formation of zirconia nanoparticles in the lipid matrix was investigated using quartz crystal microgravimetry (QCM), optical absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques.     

Large-scale synthesis of tungsten oxide nanofibers by electrospinning

We show in this communication that large-scale synthesis of orthorhombic WO3 nanofibers can be obtained via a simple electrospinning method. The morphology and the crystal structure are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), FTIR, X-ray diffraction patterns (XRD) and X-ray photoelectron spectra (XPS) spectra. SEM and TEM images showed that the diameter of the obtained WO3 nanofibers is between 100 and 500 nm. The structure of the obtained WO3 nanofibers was characterized by FTIR, XRD, and XPS spectra. The photoluminescence of the obtained WO3 nanofibers were also investigated.     

煅烧温度对阳极氧化WO3多孔薄膜的形貌及光电化学性能的影响

采用一步式阶跃电压加压方法,在NH4F/(NH4)2SO4电解质溶液中对W片进行阳极氧化处理制备了WO3多孔薄膜,通过后续热处理温度的控制,制备了性能规律性变化的WO3多孔纳米薄膜材料.用场发射扫描电镜(FE-SEM)、X射线衍射(XRD)分析等手段考察了热处理温度对氧化钨晶体结构和形貌影响的规律,在450°C以下的煅烧温度下,薄膜保持50-100nm孔径;通过对光电化学性质、光催化降解甲基橙动力学行为的研究,考察了不同热处理温度对WO3多孔薄膜光电转换性能影响的规律.研究表明,450°C煅烧处理后的WO3薄膜在500W氙灯光源照射及1.2V偏压下,光电流密度达到5.11mA·cm-2;340及400nm单色光辐射下光电转换效率(IPCE)值分别达到87.4%及22.1%.电化学交流阻抗谱显示,450°C煅烧处理后的WO3薄膜表现出最佳的导电率及最小的界面电荷转移电阻.实验结果证明,高结晶度的多孔结构是WO3薄膜具有高光电转换效率的主要因素,控制热处理温度是实现薄膜具有高孔隙率、完整结晶度、低电阻的重要手段.     

Highly sensitive WO3 hollow-sphere gas sensors

In this paper, we describe how WO(3) hollow spheres have been synthesized in solution phase by the controlled hydrolysis of WCl(6) using novel carbon microspheres as the templates. All of the products were characterized by X-ray powder diffraction (XRD), scanning electronic microscopy (SEM), and transmission electron microscopy (TEM). The as-synthesized spheres had large diameters of about 400 nm and thin shells of about 30 nm composed of numerous small nanocrystals. Prompted by the porous structure and small crystal size of the shell wall, we constructed WO(3) hollow-sphere gas sensors and found that these sensors had good sensitivity to alcohol, acetone, CS(2), and other organic gases.     

一种新的WO3纳米管的制备方法

一维纳米材料因可用来构造高性能纳米器件的结构单元而成为纳米材料研究的热点．目前的研究重点集中在材料的制备和结构性能表征方面,已发展了多种制备方法,主要有模板法、V-L-S法、L-L-S法和V-S法等,其中阳极氧化铝(AAO)模板法是制备一维材料的好方法．AAO模板的制备工艺已相当成熟,     

Nd3+:NaLa(WO4)2晶体的生长和光学性质

Nd3+:NaLa(WO4)2 crystals with a dimension up to 7 mm were grown from a high temperature solution using a double-crucible method. Scanning electron microscopy observations of the crystals showed that there were no small cracks on the surface of the crystals although they underwent two phase transitions when cooling down from high temperatures. X-ray diffraction studies indicated that the as-obtained product is pure low- temperature tetragonal Nd3+:NaLa(WO4)2. The absorption and fluorescence spectra for Nd3+:NaLa(WO4)2 were measured at room temperature. The absorption band at 804 nm has a wide full-width half maximum of 23 nm whose origin is discussed. The absorption and emission cross sections were calculated to be 7.24*10-20 cm2 at 804 nm and 6.54*10-20 cm2 at 1057 nm, respectively.     

Synthesis and evaluation of bis-β-diketonate dioxotungsten(VI) complexes as precursors for the photodeposition of WO3 films

In this paper non-stoichiometric tungsten oxide thin films have been successfully prepared by direct UV irradiation of bis-β-diketonate dioxotungsten(VI) precursor complexes spin-coated Si(1 0 0) substrates. Photodeposited films were characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) and the surface morphology examined by Atomic Force Microscopy (AFM). The results of XRD analysis showed that the as-photodeposited WO_3−x films are amorphous and have a rougher surface than thermally treated films. Post-annealing of the films in air at 500 °C transforms the sub-oxides to a monoclinic WO₃ phase.     

A scanning electron and atomic force microscopy study of the surface morphology and composition of CsI films as affected by evaporation rate and humid-air exposure.

Evaporation rate and subsequent exposure to humid air affect the surface morphology and composition of cesium iodide (CsI) films and, in turn, their photoemissive efficiency when used as photocathodes. The surface morphology and elemental composition of 300-nm-thick CsI films grown at two different rates (1 nm/s and 0.04 nm/s), both freshly evaporated and after 24-h exposure to humid air were investigated by means of atomic force microscopy and scanning electron microscopy/electron diffraction spectroscopy. The CsI film freshly evaporated at a slow rate exhibited a granular surface presenting circular holes or craters where the CsI material was moved from the center to the boundaries. After 24-h exposure to humid air, this film coalesced in large grain showing a marked increase of surface roughness. Conversely, the CsI film grown at a fast rate mostly retained its original surface uniformity and homogeneity with no presence of holes and craters after 24-h exposure to humid air. Further, surface roughness and average peak height decreased, but the surface coalesced in large grains spaced by small fractures where the CsI coverage was almost lost. In conclusion, the films grown at a fast evaporation rate were affected by 24-h exposure to humid air less than those grown at a slow rate, and are thus expected to possess a greater long-term stability.     

WO3/TiO2 复合纤维的制备及储能光催化性能

以钛酸正丁酯为前驱体, 采用静电纺丝技术制得了纯锐钛矿TiO2纤维, 并以其为基质, 通过水热法制备了具有异质结构的WO3/TiO2复合纤维. 利用X射线衍射仪(XRD)、 扫描电子显微镜(SEM)、 能量色散光谱仪(EDS)、 透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等对样品的结构和形貌进行了表征. 以罗丹明B的脱色降解为模型反应, 考察了样品的光催化性能和储能光催化性能. 结果表明, 花状WO3微球包裹在TiO2纤维上, 得到了具有异质结构的WO3/TiO2复合纤维光催化剂. WO3与TiO2复合有利于光生载流子的输运和分离, 增强了体系的量子效率, 提高了光催化活性. WO3/TiO2 复合纤维经光照处理后, 在黑暗条件下显示出储能光催化特性.     

Synthesis and electrochemical study of novel Pt-decorated Ti nanowires

We report on a facile approach to fabricate free-standing Ti nanowires and Pt-decorated Ti nanowires via a one-step environment-friendly and template-free process. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) spectroscopy were employed to characterize the synthesized nanowires, showing that highly dense Ti nanowires with diameters of ～45 nm were directly grown on the Ti substrate and that the Pt nanoparticles coated onto the surface of Ti nanowires were uniform and ultrafine (～3 nm). Our electrochemical studies reveal that the active surface area of the Pt-decorated Ti nanowires is over 265 times larger than that of a polycrystalline Pt electrode and that the Pt-decorated Ti nanowires exhibit much higher activity for electrochemical oxidation of methanol compared to the polycrystalline Pt electrode.     

Elemental composition analysis of silicon carbonitride thin films by energy dispersive spectroscopy

Specific features of elemental composition analysis of silicon carbonitride thin films by energy dispersive spectroscopy (EDS) are considered. The films were preliminarily examined by IR spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron (SEM) and atomic force microscopy (AFM), and X-ray diffraction analysis using synchrotron radiation (SR-XRD) to acquire data on their chemical and phase composition, crystalline structure and surface morphology. The effect of film thickness, substrate material and electron beam energy on the results of energy dispersive analysis was investigated.     

Synthesis of thin dense titania films via an aqueous solution-gel method

Nanostructured titanium dioxide films have been reported to be used in many applications ranging from optics and solar energy devices to gas sensors. This work describes the synthesis of nanocrystalline titania films via an aqueous solution-gel method. The thin films are deposited by spin coating an aqueous citratoperoxo-Ti(IV)-precursor solution onto a silicon substrate. The influence of processing parameters like Ti⁴⁺ concentration and crystallization temperature on the phase formation, crystallite size and surface morphology of the films is studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Furthermore, the effect of successive layer deposition on the film thickness of the resulting films is studied by means of cross sectional SEM. SEM and TEM micrographs clearly show that, after optimization of the process parameters, thin, smooth, dense nanocrystalline films are synthesized in a reproducible manner. The films are composed of 15–20 nm grains. At higher crystallization temperatures (600, 650°C) also larger particles (40–70 nm) are present. XRD data reveal that a phase pure anatase film is formed at 450°C. Crystallization temperatures equal to or higher than 600 °C however give rise to the formation of both the anatase and rutile crystalline phases. The smoothness of the films is proved by their very low rms surface roughness (≤1.1 nm) measured by AFM.     

Structural and spectroscopic studies of LaPO4:Ce/Tb@LaPO4@SiO2 nanorods: Synthesis and role of surface coating

Highly fluorescent LaPO₄:Ce/Tb@LaPO₄@SiO₂ (core/shell/Si) nanorods(NRs) were fabricated with an average length 100 nm by co-precipitation process at low temperature. X-ray diffraction (XRD), Transmission electron microscopy (TEM), energy dispersive X-ray analysis, Fourier transform infrared, optical absorption and photoluminescence spectral techniques were applied to investigate the crystal structure, phase purity, morphology, surface chemistry and optical properties of the as-prepared samples. XRD results confirmed the formation of highly crystalline with single phase, monoclinic type structure. TEM image illustrates the poly-dispersed, narrow size distributed, irregular size rod-shaped nanostructures, with mean diameters of 20 nm and average lengths up to 140 nm. FTIR spectral analysis confirmed the silica surface modification. The comparative emission spectral study shows highest luminescence intensity of core/shell NRs, due to a reduction in nonradiative transition rate. The emission intensity enhancement proves that growing of an inert LaPO₄ layer on the surface of luminescent core-NRs was an effective way to suppress surface related quenching mechanism. These well crystalline, highly aqueous soluble along with extraordinary colloidal stability core/shell/Si NRs were extremely suitable material in fluorescent bio-labeling applications.     

Sn掺杂ZnO纳米针的结构及其生长机制(英文)

利用包括磁控溅射和热氧化的两步法在Si(111)衬底上制备了Sn掺杂ZnO纳米针.首先用磁控溅射法在Si(111)衬底上制备Sn:Zn薄膜,然后在650℃的Ar气氛中对薄膜进行热氧化,制备出Sn掺杂ZnO纳米针.样品的结构、成分和光学性质采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)、能量散射X射线(EDX)谱和光致发光(PL)光谱等技术手段进行分析.结果表明,制备的样品为具有六方纤锌矿结构的单晶Sn掺杂ZnO纳米针,Sn掺杂量为2.5%(x,原子比),底部和头部直径分别为200-500 nm和40 nm,长度为1-3μm,结晶质量较高.室温光致发光光谱显示紫外发光峰比纯ZnO的发光峰稍有蓝移,这可归因于能谱分析中探测到的Sn的影响.基于本实验的实际条件,简单探讨了Sn掺杂ZnO纳米针的生长机制.     

不同形貌WO3的水热合成及其在水处理中的应用研究

三氧化钨(WO₃)以其较窄的带隙,成为继二氧化钛(TiO₂)之后颇具发展潜力的n型半导体光催化剂.本文采用水热合成法,通过调控反应参数,如原料组成、沉淀时间等,合成了不同形貌和晶型的WO₃;采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶变换红外光谱(FT-IR)、氮气吸附-脱附(N₂ adsorption-desorption)等表征了所合成的WO₃产品,发现原料组成、沉淀时间等条件对WO₃的晶型和形貌都有影响;研究了所合成的WO₃产品去除水中亚甲基蓝染料污染物的性能,结果表明,所制备的WO₃对水中亚甲基蓝具有较好的去除效果,去除率可达97%.     

Electrodeposition of high-pressure-stable bcc phase bismuth flowerlike micro/nanocomposite architectures at room temperature without surfactant

Three-dimensional (3D) bismuth flowerlike micro/nanocomposite architectures were successfully prepared on Cu substrates by electrochemical self-assembly in aqueous solution at room temperature. The morphology, crystal structure, and composition were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). Results show that the synthesized 3D architectures are built with dozens of two-dimensional (2D) single crystal nanoscaled petals, which are high-pressure-stable bcc phase Bi. The thickness of the 2D petals is about 60 nm. The effects of the concentration of Bi³⁺ ions and the electric potential gradient on the evolution of the Bi flowerlike micro/nanocomposite architectures are discussed.     

混合溶剂热合成BaFBr∶Eu~(2+)微纳米晶及其性能表征

通过水和乙醇的混合溶剂热方法制备了不同形貌和粒径的BaFBr∶Eu2+微纳米晶.研究了不同反应条件对产物的影响,初步提出了产物的形成机制.用场发射扫描电镜(FE-SEM)、高分辨透射电子显微镜(HRTEM)、X射线粉末衍射(XRD),荧光光谱(PL)对BaFBr∶Eu2+进行了表征.结果表明:反应温度、时间及十六烷基三甲基溴化铵(CTAB)用量对产物物相、形貌及粒径有显著影响;制备的BaFBr∶Eu2+经退火后有优越的发光性能:用280nm光激发,在390nm处有对应于Eu2+4f65d12(t2g)→4f78(S7/2)跃迁的强发射峰,是计算机辐射成像板(Imaging Plate)中X射线存储荧光粉潜在可应用材料,本文为优质高效X射线存储荧光材料的可控制备提供了简洁的路径.     

Development of nanoscale inhomogeneities during drying of sol-gel derived amorphous lead zirconate titanate precursor thin films

The structural evolution of sol-gel derived lead zirconate titanate (PZT) precursor films during and after physical drying was investigated by transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), selected area electron diffraction (SAED), and time-resolved X-ray diffraction (XRD). Films were deposited from initial 0.3 mol/dm(3) precursor sols with varying hydrolysis ratios. Zr-rich grains of 1-10 nm size, embedded in a Pb-, Zr-, and Ti-containing amorphous matrix were found in as-dried films. The Zr-rich regions were crystalline at hydrolysis ratios [H(2)O]/[PZT] < 27.6, and amorphous at ratios > 100. X-ray diffraction analysis of PZT and zirconia sols revealed that the crystalline nanoparticles in both sols are identical and are probably composed of nanosized zirconium oxoacetate-like clusters. This study demonstrates that time-resolved X-ray diffraction combined with electron energy loss spectroscopy mapping is a powerful tool to monitor the nanoscale structural evolution of sol-gel derived thin films.     

Structural properties of lithium thio-germanate thin film electrolytes grown by radio frequency sputtering

In this study, lithium thio-germanate thin film electrolytes have been successfully prepared by radio frequency (RF) magnetron sputtering deposition in Ar gas atmospheres. The targets for RF sputtering were prepared by milling and pressing appropriate amounts of the melt-quenched starting materials in the nLi(2)S + GeS(2) (n = 1, 2, and 3) binary system. Approximately 1 μm thin films were grown on Ni coated Si (Ni/Si) substrates and pressed CsI pellets using 50 W power and 25 mtorr (～3.3 Pa) Ar gas pressures to prepare samples for Raman and Infrared (IR) spectroscopy, respectively. To improve the adhesion between the silicon substrate and the thin film electrolyte, a sputtered Ni layer (～120 nm) was used. The surface morphologies and thickness of the thin films were determined by field emission scanning electron microscopy (FE-SEM). The structural properties of the starting materials, target materials, and the grown thin films were examined by X-ray diffraction (XRD), Raman, and IR spectroscopy.