光还原法制备Pd/ZnO及其光催化脱色性能研究

用光还原法制备了Pd/ZnO光催化剂(Pd/Zn原子比分别为1/100、2/100和3/100),以甲基橙为模拟有机污染物,对催化剂的光催化脱色性能进行了考察。光催化剂用 XRD、紫外-可见漫反射和表面光电压谱仪进行了表征,结果表明：当 Pd 沉积量为2/100(Pd/Zn)时电子-空恙分离效应最高,且光催化脱色活性最高;沉积Pd后ZnO在可见光区的吸收增强;高的电子-空恙分离效应有利于提高ZnO光催化活性。     

Characteristics of ZnO thin film deposited on various metal bottom electrodes

ZnO films for electronic applications were deposited by radio-frequency (rf) sputtering onto various metal bottom electrodes (Pt/Ti, W, Ni) to investigate such structural properties as crystallinity and surface morphology. The crystallinity, surface morphology and composition of the as-deposited films were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Rutherford back-scattering spectrometry (RBS), respectively. The preferred orientation and surface morphologies were strongly influenced by the type of bottom electrodes. The ZnO films with (200) texturing deposited on Pt/Ti/SiO₂/Si showed a smoother and smaller grain size than those deposited on W and Ni. The ZnO films on Pt and W electrodes exhibited compressive residual stress. This article is based on a presentation made in the 2002 Korea-US symposium on the “Phase Transformations of Nano-Materials”, organized as a special program of the 2002 Annual Meeting of the Korean Institute of Metals and Materials, held at Yonsei University, Seoul, Korea on October 25–26, 2002.     

Raman and highly ultraviolet red-shifted near band-edge properties of LaCe-co-doped ZnO nanoparticles

LaCe-co-doped ZnO nanoparticles with an average size of 20 nm were grown using a soft chemistry route. Structural investigations demonstrated that the LaCe-co-doped ZnO nanoparticles have a wurtzite structure. Oxidation and vibration state studies revealed that La and Ce ions are successfully doped into ZnO and provided evidence for the presence of a large number of defects in the crystal structure. photoluminescence properties of these nanoparticles exhibit an interesting prominent large red-shift in the ultraviolet region with the co-doping of two rare-earth metals, which makes them good prospects for use in visible high-efficiency luminescent flat displays and excellent solar light activated photocatalysts.     

A visible-light-assisted Pd/TiO2 gas sensor with carbon nanotubes electrodes for trace formaldehyde detection

Owing to the ppb-level detection standard toward the toxic and harmful gas, the detection of trace gases has become an important subject in the field of indoor environment management. However, the traditional resistive gas sensors hardly meet the requirement due to the weak signal generated by trace gas molecules that are difficult to capture. Herein, a visible-light-assisted Pd/TiO₂ gas sensor is proposed to endow the effective detection of trace formaldehyde(HCHO) gas without heatin...     

Effect of the spreading of the contact spot on the pulsed heating of electrodes

A numerical calculation of the pulsed heating of electrical contacts in a wide temperature range up to the melting point is carried out on the basis of experimental oscillograms of the electrode voltage and current. The change in the radius of the contact spot is determined taking into account the softening of the material. It is shown that even a slight spreading of the spot can lead to a significant decrease in the contact temperature. The dynamics of the heating of the contact area are analyzed, and the distributions of the temperature and heat flows are plotted.     

Multi-arc surfacing with coated electrodes

The results of investigations of the structure and properties of the deposited metal of the maraging steel of the Fe–Ni–Mo–Cr–V–Si–Ti–Al alloying system, hardened with boron compounds, are presented. The role of borides in the formation of the phase composition and the structural state of the steel in tempering is analysed. It is shown that this metal has high thermal and wear resistance. Consequently, it is recommended for hardfacing working surfaces of stamping tools.     

CO catalytic oxidation over Pd/CeO_2 with different chemical states of Pd

Three Pd/CeO₂ catalysts were,respectively,prepared by reduction–deposition and impregnation method(IMP)to investigate the effect of chemical state of Pd on CO oxidation.Two kinds of surface Pd species,namely PdO and Pd^δ+(2<δ≤4) in Pd_xCe_1-xO₂,were identified in all Pd/CeO₂ samples although their relative ratios in each sample were different.Surface Pd_xCe_1-xO₂ species were found to be very active ...     

Welding aluminium alloys with nanobeam electrodes

Investigations were carried out to develop a technology for manufacturing and application in welding aluminium alloys ‘beam’ electrodes containing as modification agents nanopowders of high-strength refractory chemical compounds. Consequently, the grain growth of the structure of the welded joint is prevented and the mechanical properties of the welded components are improved.     

Photoluminescence of MEH-PPV with ultraviolet excitation

The basic optical properties of PPV-based polymers have been extensively studied due to their potential technological applications. However, a detailed investigation of electronic processes following photoexcitation in the ultraviolet is still lacking. We report photoluminescence measurements on poly(1-methoxy-4-ethylhexyloxy-paraphenylenevinylene) – MEH-PPV in the 2.0–5.6 eV range, with excitation up to 5.6 eV. The photoluminescence spectra lineshape is independent of excitation energy. The photoluminescence efficiency is high for energies well below the absorption maximum due to near-resonant excitation of the longest conjugated segments which are responsible for the PL. It decreases strongly for excitation energies in the range 2.1–2.5 eV (up to the absorption maximum) and slightly from 2.5 to 5.6 eV. The results indicate that states excited in the ultraviolet rapidly relax nonradiatively to the lowest state, from where the usual luminescence occurs.     

MFuBSPP光度法测定钯

５，１０，１５－三（４－甲基－３－磺基苯）－２０－〔４－（５－氟尿嘧啶）丁氧基－３－磺基苯）卟啉（ＭＦｕＢＳＰＰ）是一种新的不对称性的卟啉显色剂。利用ＭＦｕＢＳＰＰ对钯的显色条件进行了研究，发现在ｐＨ４．８的醋酸一醋酸钠缓冲介质中，有抗坏血酸存在，Ｐｄ（Ⅱ）与ＭＦｕＢＳＰＰ形成灵敏度很高的１：１配合物，最大吸收波长为４１４ｎｍ，配合物的摩尔吸光系数ε＝１．５×１０＾５Ｌ·ｍｏｌ＾－１·ｃｍ＾－１，     

Air-stable all-polymer field-effect transistors with organic electrodes

Organic transistors will be one of the basic components of future plastic electronic devices as they are a precondition for the manufacture of low-cost, integrated plastic circuits (IPCs). Thus investigations on all-polymer electronics devices, i.e. electronics without any silicon and metal constituents, are of growing interest. We report here our recent results on the fabrication of all-polymer organic field-effect transistors (OFETs) comprising conductive poly(ethylenedioxythiophene)–poly(styrene sulfonic acid) PEDOT/PSS systems as electrode material, regioregular poly(3-hexylthiophene) as semiconductor, as well as polymer substrates and dielectrics. All devices were manufactured under ambient conditions by means of spin-coating and standard lithographic techniques. OFET characteristics and simple shelf lifetime tests are reported and reveal an unexpected high device stability.     

Chemical di'ssolution of oxides: Experiments with Sintered ZnO pellets and ZnO single crystals

The rate of dissolution of zinc oxide has been studied with a technique developed by Engell, in which the rate can continuously be measured as an electric current. The rate decreases with the pH in the acidic range but depends also on the type of anion present in the solution. It is enhanced by weak acids as proton donors. In the alkaline pH range, the presence of NH₃ leads to a pronounced increase of the rate which is followed by a decrease between pH 10–13. For the interpretation, a model of the kink sites at a non-polar face of the crystal is constructed and the possible steps in the dissolution process are discussed. The conclusion is that the rate determining step is the hydrolytic splitting of bonds between kink site atoms to the lattice which is catalyzed by proton donors and by molecules or ions which form ligands to the zinc atoms. The electric forces at the interface play a minor role.     

电纺丝法制备氧化锌纳米纤维

以聚乙烯醇(PVA)与乙酸锌的混合溶液为前驱体,采用静电纺丝法制得乙酸锌/PVA复合纤维,经煅烧后得到直径分布均匀的ZnO纳米纤维.对所制得的复合纤维及ZnO纳米纤维分别采用了热失重、X射线衍射、红外光谱(IR)、扫描电镜(SEM)等分析测试手段进行了表征.研究了纤维平均直径受电纺丝溶液配比的影响.     

Growth of ZnO nanorods by air annealing of ZnO films with an applied electric field

A novel method of ZnO nanorods growth is presented based on low temperature (300 °C) air annealing of ZnO film while applying an electric field (∼ 10 V/cm) parallel to the film. The films were deposited on glass substrates using a filtered vacuum arc deposition system equipped with a Zn cathode, at an arc current of 160 A, oxygen pressure of 3.2 mTorr, and deposition time of 30 s. Cu tape electrodes were applied on each end of the coated sample, and used to apply the electric field. The samples were annealed in a quartz furnace at 200, 300, 400 °C for 20 or 60 min. Each sample surface was examined using a Scanning Electron Microscope (SEM) and a High Resolution SEM (HRSEM) to study its micro- and nano-structure. The film crystallographic structure was studied using X-ray diffractometry (XRD). ZnO rods with lengths of ∼ 3 μm were observed on the samples annealed at 300 °C for 20 min with an electric field of ∼ 10³ V/m, while separated conical forms with lengths of ∼ 0.5 μm and base width of ∼ 150 nm were observed after annealing under the same conditions but without any electric field. The rod growth rate and area density were ∼ 2.0-2.5 nm/s, and ∼ 3 × 10⁷ cm^− 2, respectively.     

DTMSO的萃钯机理研究

本文讨论了环状亚砜衍生物a－十二烷－四氢噻吩亚砜（DTMSO）的萃钯机理，DTMSO在盐酸溶液中、低酸度条件下，同时存在中性溶剂络合萃取机理和离子缔合萃取机理。亚砜通过硫和氧原子与钯配合；在高配度条件下，亚砜以离子缔合萃取机理萃钯，萃合物发生亚砜PdCl^2-4的内配位转变。     

Characteristics of SiOx-cored composite nanowires with Pd shell layers

This paper describes the fabrication of Pd-coated SiO_x nanowires via a simple approach and reports the effects of subsequent thermal annealing. While the as-synthesized Pd-coated SiO_x nanowires exhibited smooth one-dimensional (1D) nanostructures, the thermal annealing induced a rough surface. X-ray diffraction, selected area electron diffraction, and lattice-resolved transmission electron microscopy coincidentally revealed that the assynthesized Pd-coated SiO_x nanowires were comprised of a cubic Pd phase, whereas annealing generated a tetragonal PdO phase. Micro-Raman spectroscopy measurements showed the presence of 630 cm⁻¹-peak, which can be assigned to the B_1g mode of single crystal PdO, whether samples had been annealed or not. Although both Pd and PdO phases did not exhibit PL emission, the PL intensity of core SiO_x nanowires has been significantly reduced by the Pd-coating, presumably due to the covering effect.     

一种性能优良的ZnO纳米线的水热法生长

以醋酸锌(Zn(CH3COO)2·2H2O)和氢氧化钠(Na(OH)2)作为实验反应前驱物,聚乙二醇(HO(CH2CH2O)13H)作为表面活性剂,采用低温水热法在60 ℃条件下,合成了不同形貌的ZnO纳米线和纳米棒材料,并对样品结构和形貌进行了XRD、SEM等分析.结果显示,ZnO纳米结构都具有六方纤锌矿结构,主要是由单晶纳米棒状组成的"菊花状"ZnO纳米団簇,団簇中的单晶在不同反应条件下合成了线形、尖细、平面等不同形貌,但主要粒子基本为棒状和菊花状.合成方法可作为制备形貌可控的金属氧化物的参考.