花状硫化铜级次纳米结构的制备及可见光催化活性研究

本实验以氯化铜 (CuCl₂·2H₂O) 和二硫化碳(CS₂)为原料, 以乙二醇(C₂H₆O₂) 为溶剂, 通过溶剂热法成功制备了具有可见光活性的花状硫化铜(CuS) 级次纳米结构. 并利用X射线粉末衍射技术(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM) 等技术对其进行了表征, 利用紫外可见吸收光谱(Uv-vis)分析了其光学性能, 并以甲基橙为目标降解物对其可见光催化活性进行了研究. 结果表明: 花状CuS级次纳米结构具有很高的可见光催化活性, 与体相CuS粉末相比有很大的提高, 在自然光照射下对甲基橙的降解率可以达到100%. 同时本文对花状级次纳米结构的形成机理进行了分析. 关键词： 硫化铜 溶剂热 级次纳米结构 光催化     

Synthesis and optical properties of ZnO nanorods on indium tin oxide substrate

ZnO nanorods with uniform diameter and length have been synthesized on an indium-tin oxide (ITO) substrate by using a simple thermal evaporation method which is suitable to larger scale production and without any catalyst or additives. The samples were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-vis (UV-vis) absorption spectrum, photoluminescence (PL) spectrum and Raman spectrum. The single-phase ZnO nanorods grow well-oriented along the c-axis of its wurtzite structure on ITO substrate. The ZnO nanorods shows sharp and strong UV emission located at 380 nm without notable visible light emission in the PL spectrum, which suggests the good crystallinity of the nanorods, which was also testified by their Raman spectrum. The photodegradation of methylene orange (MO) in aqueous solution reveals that the well-arranged c-axis growth of ZnO nanorods possess evidently improved photocatalytic performance and these properties enable the ZnO nanorods potential application in UV laser.     

Electronic structure of fluorinated and hydrogenated beryllium monoxide nanostructures

Using first‐principles calculations, we investigate the chemical functionalizations of beryllium monoxide (BeO) nanostructures by the fluorine and hydrogen atoms. We find that the hydrogenation weakens the Be–O bonds and causes the instability of semihydrogenated nanosheets, while the fluorination is energetically favorable and forms a stable semifluorinated conformation. More importantly, the semifluorinated BeO sheet exhibits an intrinsic half‐metallic behavior, which is robust with a large half‐metal gap and a high Curie temperature above room temperature. By the same strategy of fluorination, the half‐metallicity can also be achieved in the one‐dimensional BeO nanotubes and nanoribbons. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of High Quality CdS Nanorods by Solvothermal Process and their Photoluminescence

Large-scale cadmium sulfide (CdS) nanorods with high quality were successfully synthesized by solvothermal method using ethylenediamine (en) aqueous as solvent. The as-obtained product was investigated by X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FE-SEM), ultraviolet–visible (UV–Vis) spectrum and photoluminescence (PL) spectrum. The length and width of the CdS nanorods were in the range of 1–2 μm, 30–40 nm, respectively. XRD analysis revealed that the crystal structure of the product was hexagonal phase. Photoluminescence measurement showed that the nanobelts have two main emission bands around 470 and 560 nm, which should come from the higher-level transition and the intrinsic transition, respectively.     

单原子层FeS半导体纳米片及其光催化还原二氧化碳应用

采用简单的溶剂热法制备了厚度约为1.16 nm单层超薄FeS纳米片,其具有涵盖从近紫外至近红外的太阳光谱波段的优异光学吸收性能和干净均一的表面,显微图像显示其具有超薄的片状结构,晶面结构清晰,物相测定证实合成的超薄FeS纳米片为单硫铁矿相,物性测定及理论计算显示超薄FeS纳米片具有半导体的电子能带结构,电子迁移率高,全光谱光催化CO₂还原到CO的产率约为260μmol·g^-1·h^-1,且具有很好的光催化稳定性,该研究为地球储量丰富的铁基材料应用于能源转化领域提供了可行的方向.     

Template-free sonochemical synthesis of flower-like ZnO nanostructures

Flower-like ZnO nanostructures have been successfully synthesized via a facile and template-free sonochemical method, using zinc acetate and potassium hydroxide as reactants only. The as-synthesized flower-like ZnO nanostructures were composed of nanorods with the width of ∼300–400 nm$\sim 300\text{–}400\text{nm}$ and the length of ∼2–3 μm$\sim 2\text{–}3\text{μm}$. The structures, morphologies and optical properties of the as-prepared products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscopy, UV-Vis spectrophotometry and Raman-scattering spectroscopy. A plausible formation mechanism of flower-like ZnO nanostructures was studied by SEM which monitors an intermediate morphology transformation of the product at the different ultrasonic time (t=80,90,95,105, and 120 min$t=80,90,95,105\text{, and}120\text{min}$).     

Synthesis of ZnO nanostructures with controlled morphology and size in ionic liquids

Nanostructured ZnO has been synthesized by a hydrothermal route, using different ionic liquids (ILs) as the morphology templates. The morphology of ZnO changes from rod-like to star-like and flower-like in different ILs. A 3D nano/micro structure ZnO with unique flower-like morphology has been synthesized via the assembly of dicationic IL and [Zn(OH)₄]²⁻. The flower-like pattern was obtained in the presence of IL 1. The flower-like ZnO structure has a hexagonal prism, with a hexagonal pyramid on the tip, and diameter of ~444 nm. While the ZnO prepared in IL 2, shows uniform rod-like shape with a diameter of 91 nm, star-like morphology consisting of nanorods with diameter of ~109 nm was formed in IL 3. The XRD, SEM, and PL spectra have been employed for characterization of the synthesized ZnO nano structures.     

Synthesis of dendritic silver nanostructures by means of ultrasonic irradiation

In this paper, a simple and effective route for the synthesis of silver dendritic nanostructures by means of ultrasonic irradiation has been developed. Well-defined silver dendritic nanostructures were obtained by sonicating the aqueous solution of 0.04 mol/L silver nitrate with 4.0 mol/L isopropanol as reducing agent and 0.01 mol/L PEG400 as disperser for 2 h. The effects of the irradiation time, the concentration of Ag⁺ and the molar ratio of PEG to AgNO₃ on the morphology of silver nanostructures were discussed. The structures of the obtained samples were characterized by transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray powder diffraction (XRD), and the chemical composition of the dendrites was examined by energy-dispersive X-ray spectrum (EDS).     

过渡金属硫化物纳米晶的溶剂热合成与表征

以硝酸钴（Co(NO3)2•6H2O）、硝酸铁（Fe(NO3)3•6H2O）和硫脲为原料,在同一混合溶剂（乙二醇和水）中通过控制两种溶剂的比例（1:2; 4:1）,利用溶剂热法在180℃分别恒温制备了硫化钴（CoS1.097）和硫化铁（Fe3S4）两种纳米晶。用X-射线衍射（XRD）、透射电镜（TEM）对样品组成、粒径和表面形貌进行了表征,荧光光谱对其荧光性质进行了测量。结果表明,所得样品分别为六方相的CoS1.097和立方相的Fe3S4纳米粉末。在此基础上,对影响两种纳米晶形成的主要因素进行了初步的分析和讨论。     

Synthesis,characterization, and effect of concentration variation on metal oxide nanostructures

Zinc oxide (ZnO) has been successfully synthesized by an anodization method, and it has been fabricated through anodization method with different concentration of zinc nitrate. The element composition, surface inspection, structural, and morphological features of the products are depend on the concentration of zinc nitrate. At lower concentration (0.01M), SEM image shows ZnO nanowires with average width of about 30 and 50 nm. With increase in the concentration of zinc nitrate from 0.01 to 0.05 M, the nanowires change into the nanosheets with average width of about 0.5 and 1.5 μm. For samples (0.1 M) exhibits nanodots, morphology was composed of hundreds of nanosheets with thickness is about 90 nm on average. When the concentration increases to 0.2 M, the nanodots trench became bigger with diameter about 1.2–2.0 μm. When the concentration of zinc nitrate is 0.3 M, the average diameter of nanodots is about 2–2.5 μm. The trench of nanosheets becomes thinner and shorter, but the number of nanosheets increases with diameter 20–50 nm. The formation of nanowires, nanodots, and nanosheets nanostructures is also believed to result from actions on concentration of zinc nitrate as an aquas medium. The EDX result shows the atomic percentage (at.%) of the oxygen increased when the concentration of zinc nitrate increased. The pattern of EDX indicates that the ZnO nanostructures are composed of Zn, O, and Al. They represent Al composition in the sample because the anode using the aluminum rod during experiment.     

Photoluminescence properties of various CVD-grown ZnO nanostructures

We have studied systematically room-temperature photoluminescence (PL) properties of many nanostructured ZnO samples grown by chemical vapour deposition (CVD). Their PL spectra consist of two emissions peaked in the ultraviolet (UV) and green regions. The relative intensity of these emissions depends on the excitation energy density, size and morphology of ZnO nanostructures. Based on the excitation-density dependence of the integrated intensity ratio of UV-to-green emission, we could classify PL spectra of ZnO nanostructures into three groups characteristic of size and morphology. Our study also reveals that with increasing excitation density, the UV-peak position shifts slightly towards longer wavelengths while the green emission around 514-520 nm is almost unchanged. This green-luminescence emission is dominant when the nanostructure sizes range from 20 to 200 nm, which is related to a large surface-to-volume ratio.     

Morphology engineering of ZnO nanostructures

Nanosized ZnO structures were grown by atmospheric pressure metalorganic chemical vapor deposition (APMOCVD) in the temperature range 200–500 °C at variable precursor pressure. Temperature induced evolution of the ZnO microstructure was observed, resulting in regular transformation of the material from conventional polycrystalline layers to hierarchically arranged sheaves of ZnO nanowires. The structures obtained were uniformly planarly located over the substrate and possessed as low nanowires diameter as 30–45 nm at the tips. The observed growth evolution is explained in terms of ZnO crystal planes free energy difference and growth kinetics. For comparison, the convenient growth at constant precursor pressure on Si and SiC substrates has been performed, resulting in island-type grown ZnO nanostructures. The demonstrated nanosized ZnO structures may have unique possible areas of application, which are listed here.     

Splitting the surface wave in metal/dielectric nanostructures

We investigate a modified surface wave splitter with a double-layer structure, which consists of symmetrical metallic grating and an asymmetrical dielectric, using the finite-difference time-domain (FDTD) simulation method. The metal/dielectric interface structure at this two-side aperture can support bound waves of different wavelengths, thus guiding waves in opposite directions. The covered dielectric films play an important role in the enhancement and confinement of the diffraction wave by the waveguide modes. The simulation result shows that the optical intensities of the guided surface wave at wavelengths of 760-nm and 1000-nm are about 100 times and 4～5 times those of the weaker side, respectively, which means that the surface wave is split by the proposed device.     

Tin oxide nanocubes, and tin-core/tin oxide-shell nanostructures, with and without a hollow interior

A number of nanoscale tin oxide structures including 2–5 nm tin oxide hollow nanoparticles, 3–5 nm tin oxide nanocubes, 80–120 nm tin-core/tin oxide-shell nanocubes, and hollow tin oxide nanocubes, have been prepared from phenanthroline (phen)-capped Sn nanoparticles. Transmission electron microscopy revealed the existence of a hollow interior in the tin-core/tin oxide-shell nanostructures. It is believed that the low melting Sn core was hollowed out by electron beam irradiation of the sample during microscopy. The 2–5 nm tin oxide hollow nanoparticles and 80–120 nm tin oxide hollow nanocubes had thin but stable shells capable of preserving the integrity of the large cavity within.     

Synthesis of different gold nanostructures by solar radiation and their SERS spectroscopy

In this article, a simple and novel photochemical synthesis of different gold nanostructures is proposed using solar radiation. This method is rapid, convenient and of low cost, and can be performed under ambient conditions. By adjusting the concentration of sodium acetate (NaAc), different morphologies of the products can be easily obtained. Without NaAc, the products obtained are mainly polyhedral gold particles; lower concentration of NaAc (0.05 and 0.1 M) accelerates the formation of flowerlike gold nanostructures; while higher concentration of NaAc (0.5 M) facilitates the formation of a variety of gold nanowires and nanobelts. It is found that the morphology change of gold nanaostructures is the result of the synergistic effect of poly(diallyl dimethylammonium) chloride (PDDA), Ac⁻ ions, and the pH value. In addition, the different gold nanostructures thus obtained were used as substrates for surface‐enhanced Raman scattering (SERS) with p‐aminothiophenol (p‐ATP) as the probe molecule. In comparison, the flowerlike gold nanostructures show stronger SERS effect than the other gold nanostructures, which is associated with their unique geometrical shapes providing highly localized electromagnetic (EM) field for the optical enhancement to the probe molecules. These gold nanostructures, with different geometrical shapes, might have potential applications in the areas of photonics, optoelectronics and optical sensing. Copyright © 2009 John Wiley & Sons, Ltd.     

Sb2Te3 纳米结构的制备与表征

以室温热电性能优异的传统热电材料Sb₂Te₃为研究对象,利用化学气相沉积法制备Sb₂Te₃单晶纳米结构,并研究其生长机理.实验结果表明,不加催化剂时Sb₂Te₃易生长成六方纳米盘,在金催化剂条件下定向生长成纳米线.Sb₂Te₃的形貌与其晶体结构和生长机理有关.Sb₂Te₃为三角结构,Sb和     

表面纳米结构的自组装生长

无论是对低维基本物理以及其中新奇量子现象的探索与认识,还是微电子工业水平的持续发展,都迫切地需要掌握一种能够精确、可靠地操控表面纳米结构的方法.自组织生长,即粒子聚集时由于介观尺度力场或受限运动作用而导致的自发有序现象,在原子尺度上可以实现对纳米结构的精确控制,而在介观尺度上又可以调节这些微观结构单元的组织构型.文章结合作者近年来在表面纳米结构生长与物理性质研究方面所做过的工作,从自组织生长的原理出发,介绍了对金属纳米线、有序分子薄膜以及合金量子点阵列生长进行人工操控的方法.     

表面纳米结构的自组装生长

无论是对低维基本物理以及其中新奇量子现象的探索与认识,还是微电子工业水平的持续发展,都迫切地需要掌握一种能够精确、可靠地操控表面纳米结构的方法.自组织生长,即粒子聚集时由于介观尺度力场或受限运动作用而导致的自发有序现象,在原子尺度上可以实现对纳米结构的精确控制,而在介观尺度上又可以调节这些微观结构单元的组织构型.文章结合作者近年来在表面纳米结构生长与物理性质研究方面所做过的工作,从自组织生长的原理出发,介绍了对金属纳米线、有序分子薄膜以及合金量子点阵列生长进行人工操控的方法.     

Effects of annealing temperature on morphologies and optical properties of ZnO nanostructures

The effects of annealing temperature on the morphologies and optical properties of ZnO nanostructures synthesized by sol–gel method were investigated in detail. The SEM results showed that uniform ZnO nanorods formed at 900 C. The PL results showed an ultraviolet emission peak and a relatively broad visible light emission peak for all ZnO nanostructures sintered at different temperature. The increase of the crystal size and decrease of tensile stress resulted in the UV emission peak shifted from 386 to 389 nm when annealing temperature rose from 850 to 1000 C. The growth mechanism of the ZnO nanorods is discussed.     

Optics of anisotropic nanostructures

The analytical formalism of Rokushima and Yamakita [J. Opt. Soc. Am. 73, 901–908 (1983)] treating the Fraunhofer diffraction in planar multilayered anisotropic gratings proved to be a useful introduction to new fundamental and practical situations encountered in laterally structured periodic (both isotropic and anisotropic) multilayer media. These are employed in the spectroscopic ellipsometry for modeling surface roughness and in-depth profiles, as well as in the design of various frequency-selective elements including photonic crystals. The subject forms the basis for the solution of inverse problems in scatterometry of periodic nanostructures including magnetic and magneto-optic recording media. It has no principal limitations as for the frequencies and period to radiation wavelength ratios and may include matter wave diffraction. The aim of the paper is to make this formalism easily accessible to a broader community of students and non-specialists. Many aspects of traditional electromagnetic optics are covered as special cases from a modern and more general point of view, e.g., plane wave propagation in isotropic media, reflection and refraction at interfaces, Fabry-Perot resonator, optics of thin films and multilayers, slab dielectric waveguides, crystal optics, acousto-, electro-, and magneto-optics, diffraction gratings, etc. The formalism is illustrated on a model simulating the diffraction on a ferromagnetic wire grating.