A highly conductive and transparent solution processed AZO/MWCNT nanocomposite

A solution processed aluminum-doped zinc oxide (AZO)/multi-walled carbon nanotube (MWCNT) nanocomposite thin film has been developed offering simultaneously high optical transparency and low electrical resistivity, with a conductivity figure of merit (σDC/σopt) of ~75-better than PEDOT:PSS and many graphene derivatives. The reduction in sheet resistance of thin films of pristine MWCNTs is attributed to an increase in the conduction pathways within the sol-gel derived AZO matrix and reduced inter-MWCNT contact resistance. Films have been extensively characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffractometry (XRD), photoluminescence (PL), and ultraviolet-visible (UV-vis) spectroscopy. © 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Preferential orientation growth of AIN thin films on Si (111) substrates by LP-MOCVD

Aluminum nitride (AIN) thin films were deposited on Si (111) substrates by low pressure metalorganic chemical vapor deposition system. The effects of the V/III ratios on the film structure and surface morphology were systematically studied. The chemical states and vibration modes of AIN films were characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectrometer. The optical absorption property of the AIN films, characterized by ultraviolet-visible-near infrared spectrophotometer, exhibited a sharp absorption near the wavelength of 206 mm. The AIN (002) preferential orientation growth was obtained at the V/III ratio of 10,000 and the preferential growth mechanism is presented in this paper according to the thermodynamics and kinetics process of the AIN growth.

Kinetics of dissociative water adsorption on stepped Si(001), on Si(115), Si(113), Si(5,5,12) and Si(112)

We present photoelectron spectroscopic and low energy electron diffraction measurements of water adsorption on flat Si samples of the orientations (001), (115), (113), (5,5,12) and (112) as well as on curved samples covering continuously the ranges (001)-(117) and (113)-(5,5,12)-(112). On all orientations, water adsorption is dissociative (OH and H) and non-destructive. On Si(001) the sticking coefficient S and the saturation coverage Theta(sat) are largest. On Si(001) and for small miscuts in the [110]-azimuth, S is constant nearly up to saturation which proves that the kinetics involves a weakly bound mobile precursor state. For (001)-vicinals with high miscut angles (9-13 degrees), the step structure breaks down, the precursor mobility is affected and the adsorption kinetics changed. On (115), (113), (5,5,12) and (112), the values of S and Theta(sat) are smaller which indicates that not all sites are able to dissociate and bind water. For (113) the shape of the adsorption curves Theta versus exposure shows the existence of two adsorption processes, one with mobile precursor kinetics and one with Langmuir-like kinetics. On (5,5,12), two processes with mobile precursor kinetics are observed which are ascribed to adsorption on different surface regions within the large surface unit cell. From the corresponding values of S and Theta(sat), data for structure models are deduced. (C) 1997 Elsevier Science B.V.

改进的SILAR法制备ZnO薄膜及其表征

A modified solution method, successive ionic layer adsorption and reaction(SILAR), was applied to prepare transparent zinc oxide(ZnO) film on glass substrate at (125±5) ℃ in mixed ion precursor solution. The surface morphology and crystallizations of films were analyzed by field emission scanning microscopy(FESEM) and X-ray diffraction(XRD), respectively. The optical properties of the films were studied by ultraviolet visible(UV-Vis)spectroscopy. The results show that the obtained samples are polycrystallin...中文文摘：采用一种改进的液相成膜技术——连续离子层吸附与反应(SILAR)法,用锌氨络离子[Zn(NH3)4]2+溶液作为独立的前驱体溶液,以载玻片为衬底,在(125±5)℃的温度下沉积出致密、透明的ZnO薄膜。分别用冷场发射型扫描电镜(FESEM)和X射线衍射(XRD)分析了薄膜样品的表面形貌和结晶状态,用紫外-可见分光光度计(UV-Vis spectroscopy)研究了薄膜样品的发光性能。结果表明:获得样品为六角纤锌矿结构的多晶薄膜材料沿[002]方向择优生长;样品表面均匀、致密,厚度约为550nm;在可见光波段具有高的透射率(>80%)。

Enhanced nucleation of Ag nanoparticles by vacancy-type defects in Ar-ions implanted spinel

Vacancy-type defects are introduced into magnesium aluminate spine] (MgAl2O4 (1 1 0)) by Ar-ions implantation, and then Ag-ions are implanted into the depth rich in vacancy-type defects. The ultraviolet-visible spectrometry (UV-VIS) and positron annihilation spectroscopy (PAS) are used to study the influence of vacancy-type defects on nucleation of Ag nanoparticles. After introduction of vacancy-type defects the pronounced increase of surface plasmon resonance (SPR) absorbance intensity indicates that defects enhance the nucleation of Ag nanoparticles. The PAS results reveal that vacancy-type defects provide pre-nucleating centers for Ag nanoparticles nucleation and growth. (C) 2010 Elsevier B.V. All rights reserved.

Electrochemical polymerization and characterization of polypyrrole nanowires and nanotubules

Polypyrrole nanostructure arrays, including simultaneously large quantities of nanowires and small quantities of partially filled nanotubules have been electrochemically synthesized in home-made etched ion-track polycarbonate (PC) templates. Diameter of the prepared nanostructures varies from 45 to 320 nm with their lengths up to 30 microns. Morphological studies of these nanostructures were performed by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. While optical absorption properties were studied by ultraviolet-visible-near infrared spectrophotometry (UV-vis-NIR). It has been observed that the absorption maximum of polypyrrole shifts to the longer wavelength side as the diameter of these nanostructures (nanowires and nanotubules) increases. (C) 2010 Elsevier B.V. All rights reserved.

Layer-by-layer assembly of carbon nanotubes and Prussian blue nanoparticles: A potential tool for biosensing devices

A promising method for assembling carbon nanotubes (CNTs) and poly(diallyldimethylammonium chloride) protected Prussian blue nanoparticles (P-PB) to form three-dimensional (3D) nanostructured films is proposed. The electrostatic interaction, combined with layer-by-layer self-assembly (LBL), between negatively charged CNTs and positively charged P-PB is strong enough to drive the formation of the 3D nanostructured films. Thus, prepared multilayer films were characterized by ultraviolet-visible-near-infrared spectroscopy (UV-vis-NIR), scanning electron microscopy (SEM) and cyclic voltammetry (CV).

Ag2S morphology controllable via simple template-free solution route

Different morphologies of Ag2S nano- and micro-materials, including spokewise micrometer bars, microfibers, nanowires, worm-like nanoparticles and nanopolyhedrons have been obtained controllably by a facile one-step method at room temperature. Powder X-ray diffraction (XRD), X-ray photo-electron spectroscopy (XPS) and scanning electron microscope (SEM) were employed to characterize the structure and compositions of those nanomaterials. Furthermore, ultraviolet visible (UV-vis) spectra of Ag2S with different morphologies show different spectral features.

Monitoring catalytic degradation of dye molecules on silver-coated ZnO nanowire arrays by surface-enhanced Raman spectroscopy

Catalytic degradation of organic dye molecules has attracted extensive attention due to their high toxicity to water resources. In this paper, we propose a novel method for the fabrication of uniform silver-coated ZnO nanowire arrays. The degradation of typical dye molecule rhodamine 6G (R6G), as an example, is investigated in the presence of the as-prepared silver-coated ZnO nanowire arrays. The experimental results show that such composite nanostructures exhibit high catalytic activity, and the reaction follows pseudo-first-order kinetics. Furthermore, these nanowire arrays are desirable SERS substrates for monitoring the catalytic degradation of dye molecules. Compared with traditional UV-visible spectroscopy, SERS technology can reflect more truly the catalytic degradation process occurring on the surface of the catalysts.

Electrostatic assembly of polyaniline and platinum-poly(amidoamine) dendrimers hybrid nanocomposite multilayer, and its electrocatalysis towards CO and O-2

The electrostatic layer-by-layer assembly method was successfully used in a multilayer buildup of polyaniline (PANT) and platinum nanocrystals encapsulated in the carboxyl-terminated poly(amidoamine) dendrimers (generation 4.5 G4.5COOH) (Pt-G4.5COOH NPs) on solid substrates. Multilayer growth was monitored by ultraviolet-visible (UV-vis) absorption spectroscopy. The AFM observation revealed a molecularly smooth (PANI/Pt-G4.5COOH NPs) multilayer film which is rougher and thicker than the multilayer of PANT and G4.5COOH (G4.5COOH/PANI)(m). The PANI/Pt-G4.5COOH NPs multilayers show a fast surface-confined electron-exchange process at the Au electrode in an acid solution, and remains stable, reversible and electroactive, even in neutral solution. Furthermore, the multilayers show a strong elect rocatalytic response towards CO oxidation and O-2 reduction, and the catalytic capability can be easily tuned by the control of multilayer thickness.

Interaction between La3+ and MP-11 in the physiological solution

In this paper, the interaction between La3+ and microperoxidase-11 (MP-11) in the imitated physiological solution was investigated with the electrochemical method, circular dichroism (CD) and ultraviolet-visible (UV-vis) absorption spectroscopy. It was found that the interaction ways between La3+ and MP-11 are different with increasing the molar ratio of La3+ and MP-11. When the molar ratio of La3+ and MP-11 is less than 2, La3+ mainly interacts with the metacetonic acid group of the heme group in the MP-11 molecules, causing the increase in the non-planarity of the porphyrin cycle in the heme group and the decrease in the content of the random coil conformation of MP-11. These structural changes would increase the exposure extent of the electrochemical active center of MP-11 and thus, La3+ can promote the electrochemical reaction of MP-11 and its electrocatalytic activity for the reduction of H2O2 at the glassy carbon (GC) electrode. However, when the molar ratio of La3+ and MP-11 is larger than 3, except binding to the carbonyl oxygen of the metacetonic acid group in the heme group, La3+ interacts also with the oxygen-containing groups of the amides in the polypeptide chains of the MP-11 molecules, leading to the increase in the contents of the random coil conformation in the peptide of the MP-11 molecule, comparing with that for the molar ratio of less than 2.

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 HI 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 m(2)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.

Luminescent CdSe and CdSe/CdS core-shell nanocrystals synthesized via a combination of solvothermal and two-phase thermal routes

A new solvothermal route has been developed for synthesizing the size-controlled CdSe nanocrystals with relatively narrow size distribution, and the photoluminescence (PL) quantum yields (QYs) of the nanocrystals can reach 5-10%. Then the obtained CdSe nanocrystals served as cores to prepare the core/shell CdSe/CdS nanocrystals via a two-phase thermal approach, which exhibited much higher PL QYs (up to 18-40%) than the CdSe core nanocrystals. The nanocrystal samples were characterized by ultraviolet-visible (UV-vis) absorption spectra, PL spectra, wide-angle Xray diffraction (WAXD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM).

Poly(3-dodecylthiophenes) polymerized with different amounts of catalyst

The effect of the amount of the catalyst FeCl3, used during the direct oxidation polymerization, on the structure and properties of the obtained poly(3-dodecylthiophene) (P3DDT) was investigated in this paper. Such measurements as gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) spectroscopy, thermal analysis, X-ray diffraction, infrared spectroscopy (FTIR) and ultraviolet-visible (W-vis) spectroscopy were applied. It is found that a suitable addition of FeCl3 can contribute to generate a P3DDT with greater percentage of head-to-tail head-to-tail (HT-HT) linkages, which are generally favored. The reduction of the other linkage defects helps to lengthen conjugation length, thus leading to more orderly chain packing. (C) 2000 Elsevier Science S.A. All rights reserved.

A STUDY OF THE SPECTRUM PROPERTIES AND THE PHOTOVOLTAGE RESPONSE OF NANOCRYSTALLINE ND2O3

The diffuse reflectance spectra of nanocrystalline Nd2O3 were measured in the ultraviolet-visible region, It is found that the part of f-->f transition bands were widened and red-shift occurred. The absorption tail-band in the region from 300 to 550 nm was assigned to the O-2p-->Nd-4f transition. The behavior of light-induced charge transfer and photovoltaic properties of nanocrystalline Nd2O3 were studied by the surface photovoltage spectroscopy (SPS) and electric field modulating SPS techniques. The SPS response shows two peaks at 330 nm(P-1) and 380 nm(P-2) in the UV-Vis range, The spectral features observed can be explained in terms of charge transfer and interband transition.