TiO2表面电子结构及其光催化活性

利用ＨＣｌ和ＨＣｌＯ４对不同方法制备的ＴｉＯ２进行了表面修饰,发现经强酸修饰后ＴｉＯ２的光催化活性有明显提高,其中ＨＣｌ的修饰效果好于ＨＣｌＯ４。     

Reductive dissolution of ferrihydrite by ascorbic acid and the inhibiting effect of phospholipid

The interaction of ascorbic acid with ferrihydrite nanoparticles with and without adsorbed phospholipid has been investigated with atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), density functional theory (DFT) cluster calculations, and batch geochemical methods. Both batch geochemical rate measurements and in situ AFM showed that ferrihydrite particles dissolved in the presence of ascorbic acid over a period of hours. The area-normalized dissolution rate derived from AFM measurements of isolated ferrihydrite particles was relatively constant over the period of dissolution and was faster than the dissolution rate derived from batch reaction methods. Results from ATR-FTIR interpreted in view of theoretical calculations suggested that exposure of ferrihydrite to ascorbic acid led to an adsorbed monodentate ascorbate surface complex. Ferrihydrite dissolution was suppressed if particles were exposed to an organic lipid prior to or during exposure to ascorbic acid. AFM analysis of the lipid layer showed that its thickness was close to 7 nm, the expected value for lipid assembled into a bilayer structure.     

Effect of molecule-substrate interaction on thin-film structures and molecular orientation of pentacene on silver and gold

Evaporated pentacene thin films with thicknesses from several nm to 150 nm on gold and silver substrates have been studied by ultraviolet photoelectron spectroscopy (UPS), near-edge X-ray absorption fine structure (NEXAFS), scanning tunneling microscopy (STM), and atomic force microscopy (AFM). It was found that pentacene thin-film structures, particularly their molecular orientations, are strongly influenced by the metal substrates. UPS measurements revealed a distinct change in the valence band structures of pentacene on Au compared to those on Ag, which is attributed to the different packing between adjacent molecules. Using NEXAFS, we observed 74+/-5 degrees and 46+/-5 degrees molecular tilt angles on Ag and Au, respectively, for all measured thicknesses. We propose that pentacene molecules stand up on the surface and form the "thin-film phase" structure on Ag. On Au, pentacene films grow in domains with molecules either lying flat or standing up on the substrate. Such a mixture of two crystalline phases leads to an average tilt angle of 46 degrees for the whole film and the change in valence band structures. STM and distance-voltage (z-V) spectroscopy studies confirm the existence of two crystalline phases on Au with different conducting properties. z-V spectra on the low conducting phase clearly indicate its nature as "thin-film phase".     

Synthesis and Optical Properties of Mn2+-Doped ZnS Nanoparticles in Solutions and Coatings

Mn2+-doped ZnS nanoparticles with different Mn-doping concentrations stabilized by hydroxypropyl cellulose (HPC) have been synthesized in ethanolic solutions and coatings. Their optical and structural properties have been characterized by means of UV-vis spectroscopy, luminescence spectroscopy, high resolution transmission electron microscopy (HRTEM) and small angle X-ray scattering (SAXS). Solutions and coatings exhibit a strong luminescence at 590 nm when excited with UV light showing that Mn2+ is incorporated into the ZnS nanoparticles. The highest luminescence intensity is obtained with an Mn2+ concentration of 2 mol%. HRTEM and SAXS investigations show that the particles are crystalline and are 3 ± 0.5 nm in size. Irradiation of the coatings with UV light leads to a photochemical oxidation of the particles, as shown by the decreasing absorption of the coating with irradiation time and a blue shift of the absorption maximum. Furthermore, the luminescence intensity first strongly increases and then decreases completely with UV-irradiation time. Both phenomena can be explained by the photochemical oxidation of the particles.     

Morphology-controllable synthesis and characterization of single-crystal molybdenum trioxide

Molybdenum trioxide nanobelts and prism-like particles with good crystallinity and high surface areas have been prepared by a facile hydrothermal method, and the morphology could be controlled by using different inorganic salts, such as KNO3, Ca(NO3)2 , La(NO3)3, etc. The possible growth mechanism of molybdenum trioxide prism-like particles is discussed on the basis of the presence of H+ and the modification of metal cations. The as-prepared nanomaterials are characterized by means of powder X-ray diffraction (PXRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transformation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and ultraviolet and visible spectroscopy (UV-vis). TEM and HRTEM micrographs show that the molybdenum trioxide nanobelts and prism-like particles have a relatively high degree of crystallinity and uniformity. BET specific surface areas of the as-prepared molybdenum trioxide nanocrystals are 67-79 m2 g-1. XPS analysis indicates that the hexavalent molybdenum is predominant in the nanocrystals. UV-vis spectra reveal that the direct band gap energy of the annealed molybdenum trioxide prism-like particles shows a pronounced blue shift compared to that of bulk MoO3 powder. Interestingly, molybdenum trioxide nanobelts exhibit a red shift under this condition.     

Metallic ReO3 nanoparticles

ReO3 nanoparticles in the diameter range of 8.5-32.5 nm have been prepared by decomposition of the Re2O7-dioxane complex under solvothermal conditions and characterized by X-ray diffraction, electron microscopy, optical spectroscopy, and scanning probe microscopy. The nanoparticles have the cubic (Pm3m {221} space group) structure with the lattice parameter increasing with decreasing size. The particles are metallic and show a plasmon band around 520 nm, which becomes blue-shifted with a decrease in size. The metallicity of the nanoparticles is also confirmed by tunneling conductance measurements. The nanoparticles show paramagnetic or diamagnetic behavior depending on the size, with evidence for superparamagnetism at low temperatures when the size is small.     

Synthesis, characterization and optical band gap of NiO nanoparticles derived from anthranilic acid precursors via a thermal decomposition route

This study focuses on the preparation and characterization of single phase NiO nano particles. Four nickel anthranilic acid complexes were synthesized by the semi-solid phase reaction method as precursors for the preparation of NiO nanoparticles via a solid-state decomposition procedure at 700 °C. Thermogravimetric analysis (TGA) was applied to determine the thermal behavior of the precursors and the temperature at which the precursors decompose leaving the oxide. The crystalline structures of the products were investigated by X-ray diffraction (XRD), the morphology of particles by SEM and TEM. The particles size was determined by STM, and the average particle size was found to be 8 nm. Electronic spectra were used to clarify qualitatively the change in absorption band positions on changing the particle size of NiO. The optical band gap of the NiO nanoparticles was calculated and indicated a direct transition. The values of the optical band gap of NiO nanoparticles increase as the particle size decreases.     

Synthesis of hafnium oxide-gold core-shell nanoparticles

Developing cheap composite nanoparticle systems that combines a high dielectric constant with good conductivity is important for the future of the electronic industry. In this study, two different sizes, 7.3 ± 2.2 and 5.6 ± 1.9 nm, of HfO(2)@Au core-shell nanoparticles are prepared by using a high-temperature reduction method. The core-shell nanoparticles are characterized by powder X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), and UV-visible absorption spectroscopy. HfO(2) exhibits no absorption in the visible region, but the HfO(2)@Au core-shell nanoparticles show a plasmon absorption band at 555 nm that is 25 nm red-shifted as compared to pure gold nanoparticles. According to transmission electron microscopy and energy dispersive X-ray analysis, the HfO(2) particles are coated with approximately three atomic layers of gold.     

Nanoscale electrocrystallisation of Sb and the compound semiconductor AlSb from an ionic liquid

Aluminium antimonide nanoclusters with an apparent band gap energy of 0.92 +/- 0.2 eV have been electrodeposited from the neutral ionic melt AlCl3-1-butyl-3-methylimidazolium chloride {AlCl3-[C4mim]+Cl-} at room temperature and have been characterized in-situ by electrochemical scanning tunneling microscopy (STM) and spectroscopy (STS).     

First Preparations and Characterization of Conductive Polymer Crystalline Nanoneedles

Single crystalline nanoneedles of three families of the most studied conductive organic polymers - polythiophene, polyaniline and polypyrrole - were synthesized for the first time using an interfacial polymerization process that takes place with simultaneous crystallization. As the crystal growth is concurrent with polymerization, more ordered crystal packing can be expected. Most of the bulk conducting-polymer systems studied contains regions that are inhomogeneous. Single nanocrystals of conducting polymers have not been reported, although needle-shaped bulk crystals of the quarterphenyl cation radical salt have previously been studied. The investigation of processes in a nanodomain of a single crystal is critical in ascertaining the inherent electronic properties of polymer nanoelements. The organic conductive nanoneedles were characterized using TEM, HRTEM, electron diffraction, EDS, and EPR to establish their crystal structure and composition. Scanning tunneling microscopy/spectroscopy (STM/STS) investigation were conducted to examine their electronic behaviors, leading to the discovery of a field-induced conductance switching with response times on the millisecond level. The switch voltages are in the range of 3 to 4 volts in STM experiments, consistent with the trend of the band gap of the three polymers. The organic conductive nanoneedles with nano-tip having high density of mobile electron may serve as interesting elements for nanoscale electronics.     

Conformational study of CdS nanoparticles prepared by ultrasonic waves

CdS nanoparticles of about 5 nm in size have been prepared with the aid of ultrasound irradiation to ethylenediamine solution of cadmium acetate dehydrate and elemental S in presence of 1-decanthiol under air and normal laboratory conditions. X-ray diffraction (XRD) and selected area electron diffraction (SAED) studies indicate that the products are nanocrystallites in hexagonal structure. High resolution transmission electron microscopy (HRTEM) image reveals that lattice fringes are clearly visible, conforming their crystallinity with lattice space of 0.27 nm corresponding to (1 0 2) plane of hexagonal CdS. Energy-dispersive X-ray analysis (EDAX) shows that the product are entirely pure and atomic percentage ratio of Cd to S is about 53:47. UV–vis absorption spectroscopy of the as prepared nanoparticles reveals an energy band gap of about 3.8 eV compared to 2.42 eV corresponding to its bulk value; a blue shift of about 1.38 eV, which is understood as quantum size effect due to confinement of electron and hole in a small volume.     

Effect of titania structure on the properties of its supported copper oxide catalysts

A facile and rapid microwave irradiation method was explored for the synthesis of bismuth phosphate (BiPO(4)) nanostructures with various morphologies and phases in different solvents. The BiPO(4) products were characterized by powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflection spectroscopy (DRS). The effect of the solvents on the formation of the BiPO(4) nanostructures was discussed on the basis of experimental results. The different BiPO(4) nanostructures exhibited different optical properties, BET surface areas and photocatalytic activities on the degradation of methyl orange (MO) under UV and visible light irradiation. The experimental results suggested that the photocatalytic activity was closely relative with the crystalline phase and band gap of BiPO(4). Hexagonal BiPO(4) nanoparticles with narrow band gap showed the highest photocatalytic performance.     

One-step in situ synthesis of NHx-adsorbed rhodium nanocrystals at liquid-liquid interfaces for possible electrocatalytic applications

Nearly monodisperse rhodium nanoparticles with adsorbed NH(x) were synthesized at the CCl(4)-water interface. The presence of NH(x)-adsorbed species was confirmed by energy-dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS) studies. The synthesis of controlled size 2-38 nm rhodium particles was studied as a function of reducing agent concentration by transmission electron microscopy (TEM). HRTEM confirmed the formation of rhodium nanoparticles having fringe spacing consistent with reported Rh (111) planes. The continuity of these films over an area of 1×1 μm was revealed by atomic force microscopy (AFM) studies. The electrocatalytic application of these nanostructure Rh-NH(x) thin films for formaldehyde oxidation in 0.5M NaOH was investigated by cyclic voltammetry. The Rh nanoparticles formed by the present strategy are expected to be useful for other catalytic applications also.     

ZnS nanosheets: Egg albumin and microwave-assisted synthesis and optical properties

ZnS nanosheets were prepared via egg albumin and microwave-assisted method. The phases, crystalline lattice structures, morphologies, chemical and optical properties were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscope(FE-SEM), selected area electron diffraction (SAED), Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy and fluorescence(FL) spectrometer and growth mechanism of ZnS nanosheets was investigated. The results showed that all samples were pure cubic zinc blende with polycrystalline structure. The width of ZnS nanosheets with a rectangular nanostructure was in the range of 450–750 nm. The chemical interaction existed between egg albumin molecules and ZnS nanoparticles via the amide/carboxylate group. The band gap value calculated was 3.72 eV. The band at around 440 nm was attributed to the sulfur vacancies of the ZnS nanosheets. With increasing volumes of egg albumin, the photoluminescence (PL) intensity of ZnS samples firstly increased and then decreased, attributed to concentration quenching.     

Adsorption-site-dependent electronic structure of catechol on the anatase TiO2(101) surface

The adsorption of catechol (1,2-benzendiol) on the anatase TiO(2)(101) surface was studied with synchrotron-based ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy (XPS), and scanning tunneling microscopy (STM). Catechol adsorbs with a unity sticking coefficient and the phenyl ring intact. STM reveals preferred nucleation at step edges and subsurface point defects, followed by 1D growth and the formation of a 2 × 1 superstructure at full coverage. A gap state of ～1 eV above the valence band maximum is observed for dosages in excess of ～0.4 Langmuir, but such a state is absent for lower coverages. The formation of the band gap states thus correlates with the adsorption at regular lattice sites and the onset of self-assembled superstructures.     

溶剂热法制备球状Cu2ZnSnS4纳米晶及其表征

通过简单的溶剂热法合成了锌黄锡矿结构的Cu2ZnSnS4(CZTS)纳米晶,使用L-半胱氨酸作硫源和络合剂,以金属氯化物作前驱体,在180°C下反应16h成功获得了CZTS微球.使用X射线衍射(XRD)仪,场发射扫描电子显微镜(FESEM)、能量色散谱(EDS)、高分辨透射电子显微镜(HRTEM)、多功能X射线光电子能谱仪(XPS)、紫外-可见(UV-Vis)分光光度计对产物的物相、结构、形貌及光学性能进行表征.结果表明:所得的产物为纯相锌黄锡矿结构的CZTS纳米颗粒,CZTS微球直径为400-800nm,并可观察到微球是由大量厚度约20nm的纳米片构成;将CZTS颗粒均匀分散在异丙醇中,测试后估算其禁带宽度约1.58eV,与薄膜太阳能电池所需的最佳禁带宽度相近.并对其形成机理进行了初步探讨.     

类牙釉状丝胶蛋白/羟基磷灰石复合材料的合成及表征

采用化学沉淀法合成了丝胶蛋白(SS)/羟基磷灰石(HAP)复合材料, 并研究了矿化时间对复合材料的影响. X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、透射电镜(TEM/HRTEM)和扫描电镜(SEM)表征结果表明: 在较短的矿化时间内, 合成的SS/HAP为直径约20 nm的复合颗粒; 随着矿化时间的延长, 这些复合颗粒能够沿轴方向组装并融合成类牙釉结构的较大晶体. 文章讨论了其可能的组装机制.     

Thermal behavior and film formation from an organogermanium polymer/nanoparticle precursor

In situ high-resolution transmission electron microscopy (HRTEM) was used to investigate the effect of heating on an organo-Ge polymer/nanoparticle composite material containing 4-8 nm diameter alkyl-terminated Ge nanoparticles. The product was obtained from the reduction of GeCl4 with Na(naphthalide) with subsequent capping of the -Cl surface with n-butyl Grignard reagent. The in situ HRTEM micrographs show that the product undergoes significant changes upon heating from room temperature to 600 degrees C. Two pronounced effects were observed: (i) Ge nanoparticles coalesce and remain crystalline throughout the entire temperature range, and (ii) the organo-Ge polymer acts as a source for the in situ formation of additional Ge nanoparticles. The in situ-formed Ge nanoparticles are approximately 2-3 nm in diameter. These in situ-formed nanoparticles (2-3 nm) are so dense that, together with the original ones, they build up an almost continuous crystalline film in the temperatures between 300 and 500 degrees C. Above 480 degrees C, melting of the in situ formed Ge nanoparticles (2-3 nm) is observed, while nanoparticles greater than 5 nm remain crystalline. After cooling to room temperature, the 2-3 nm Ge nanoparticles recrystallized.     

Synthesis and electron holography studies of single crystalline nanostructures of clathrate-II phases K(x)Ge136 and Na(x)Si136

Crystalline nanosized particles of clathrate-II phases K(x)Ge(136) and Na(x)Si(136) were obtained from a dispersion of alkali metal tetrelides in ionic liquids based on DTAC/AlCl(3), which were slowly heated to 120-180 °C. The nanoparticles are bullet-shaped with typical dimensions of about 40 nm in width and 140-200 nm in length. Detailed structure investigations using high-resolution transmission electron microscopy (HRTEM) and electron holography reveal the crystallinity and dense morphology of the clathrate nanorods.     

Solvent-stabilized oxovanadium phthalocyanine nanoparticles and their application in xerographic photoreceptors

A stable organic sol of solvent-stabilized oxovanadium phthalocynine (VOPc) nanoparticles with excellent photoconductivity was successfully prepared by ultrasonificating a prepared nanoscopic VOPc powder in1,2-dichloroethane (C(2)H(4)Cl(2)) without any additive. These solvent-stabilized VOPc nanoparticles have a size distribution from 2 to 20 nm with an average diameter of 4.6 nm. The VOPc concentration of these organic sols could be as high as 100 g/L. The nanoscopic VOPc particles were well-dispersed in an insulating polycarbonate (PC) resin, resulting in single-layered photoreceptors with high surface charge durability in the dark and excellent photoconductivity. Based on the light-assisted scanning tunneling microscopy (STM) measurements, the charge transport mechanism of these photoreceptors was ascribed to light-induced enhancement of electron tunneling through the VOPc-nanoparticle/insulator junctions.