3,3'-二甲氧基联苯醌二亚胺与苯环和噻吩共聚物的金属配合物催化法制备及性质

Ni(Ⅱ)配合物为催化剂,具有给电子基团甲氧基的N,N'-二氯-3,3'-二甲氧基联苯醌二亚胺分别与1,4-二溴苯,2,5-二溴噻吩共聚得到了相应的聚合物:聚(3,3'-二甲氧基联苯醌二亚胺-苯)(聚合物-I)和聚(3,3'-二甲氧基联苯醌二亚胺-噻吩)(聚合物-Ⅱ).单体通过1H-NMR和红外光谱进行了表征.所得聚合物的红外光谱、紫外-可见吸收光谱以及循环伏安特性等性能进行了探讨.结果表明,聚合物-I和聚合物-Ⅱ分别在317、506、329、385、430nm处出现吸收峰.循环伏安图表明所得聚合物有一定的电化学活性.     

Large scale synthesis of polyaniline nanowires and their characterization

Polyaniline nanowires were synthesized using chemical technique. Pores in anodic alumina membrane were used as templates. Surface morphology was studied using field emission scanning electron microscopy. Structural analysis was done using X-ray diffraction and Fourier transform infrared spectroscopy. Collective I–V behaviour of polyaniline nanowires observed was nonlinear.     

Wurtzite to zinc blende phase transition in GaAs nanowires induced by epitaxial burying

We bury vertical free-standing core-shell GaAs/AlGaAs nanowires by a planar GaAs overgrowth. As the nanowires get buried, their crystalline structure progressively transforms: whereas the upper emerging part retains its initial wurtzite structure, the buried part adopts the zinc blende structure of the burying layer. The burying process also suppresses all the stacking faults that existed in the wurtzite nanowires. We consider two possible mechanisms for the structural transition upon burying, examine how they can be discriminated from each other, and explain why the transition is favorable.     

Large scale synthesis of highly pure single crystalline tellurium nanowires by thermal evaporation method

Single crystalline tellurium nanowires were successfully synthesized in large scale by a facile approach of vaporizing tellurium metal and condensing the vapor in an inert atmosphere onto a Si substrate. Tellurium was evaporated by heating at 300 degrees C at 1 torr and condensed on the Si substrate at 100-150 degrees C, in the downstream of argon (Ar) gas at a flow rate of 25 sccm for 30 min. The as-synthesized nanowires have diameters between 100-300 nm and lengths up to several micrometers. The single crystalline nanowires grew in a preferred [0001] direction. The obtained nanowires were highly pure as only tellurium metal was used in the vaporization process, and no other reagent, surfactant, or template were used for the growth. This low temperature and high-yield approach to the tellurium nanowires synthesis may facilitate its industrial production for various applications.     

Growth of doped silicon nanowires by pulsed laser deposition and their analysis by electron beam induced current imaging

Doped silicon nanowires (NWs) were epitaxially grown on silicon substrates by pulsed laser deposition following a vapour-liquid-solid process, in which dopants together with silicon atoms were introduced into the gas phase by laser ablation of lightly and highly doped silicon target material. p-n or p(++)-p junctions located at the NW-silicon substrate interfaces were thus realized. To detect these junctions and visualize them the electron beam induced current technique and two-point probe current-voltage measurements were used, based on nanoprobing individual silicon NWs in a scanning electron microscope. Successful silicon NW doping by pulsed laser deposition of doped target material could experimentally be demonstrated. This doping strategy compared to the commonly used doping from the gas phase during chemical vapour deposition is evaluated essentially with a view to potentially overcoming the limitations of chemical vapour deposition doping, which shows doping inhomogeneities between the top and bottom of the NW as well as between the core and shell of NWs and structural lattice defects, especially when high doping levels are envisaged. The pulsed laser deposition doping technique yields homogeneously doped NWs and the doping level can be controlled by the choice of the target material. As a further benefit, this doping procedure does not require the use of poisonous gases and may be applied to grow not only silicon NWs but also other kinds of doped semiconductor NWs, e.g. group III nitrides or arsenides.     

Preparation of SnS films with zinc blende structure by successive ionic layer adsorption and reaction method

Polycrystalline SnS thin films have been prepared by a modified SILAR (successive ionic layer adsorption and reaction) method, in which certain quantity of NH₄Cl was added to the cation precursor solution. The films have a novel zinc blende structure. The obtained SnS films are slightly rich in Sn component. There are small amounts of O impurity existing in the films, but no other impurity such as N or Cl is found in the films. The dark conductivity of the films is about 10^-6Ω^-1cm^-1. The polycrystalline films have a direct (forbidden) bandgap of 1.71 eV. The optical adsorption coefficient is above 10⁴ cm^-1 when the photon energy is larger than 1.4 eV.     

L-半胱氨酸诱导单晶银纳米线的快速合成及表征

采用化学还原法,以聚乙烯砒咯烷酮(PVP)为稳定剂和形貌控制剂,乙二醇为还原剂,在L-半胱氨酸诱导下,由硝酸银快速制备了银纳米线。采用紫外-可见吸收光谱、X射线衍射、扫描电子显微镜、选区电子衍射和透射电子显微镜手段对所得产物进行表征,结果表明利用L-半胱氨酸诱导可在15min内制备直径为100nm左右,长度约几百微米的银纳米线,并具有单晶结构,根据实验结果提出了可能的银纳米线快速合成机理。     

Charging effect induced by electron beam irradiation: a review

Open in a separate window     

Electrochemical synthesis of Sn doped ZnO nanowires on zinc foil and their field emission studies

Sn doped ZnO films were obtained by cathodic electrodeposition on Zn foil. The X-ray diffraction analysis revealed formation of the wurtzite phase of ZnO only. The scanning electron microscopic images showed formation of randomly oriented ZnO nanowires having diameter less than 150 nm and lengths of several micrometers. The relative atomic percentage of Sn, estimated from the energy-dispersive spectra, was found to be 0.5 and 2.0 in the post-annealed ZnO films deposited for 10 and 40 min durations, respectively. The field emission characteristics of the Sn doped ZnO nanowires are found to be appreciable in terms of the threshold field and emission current stability.     

Silver nanoparticles: Large scale solvothermal synthesis and optical properties

Silver nanoparticles have been successfully synthesized by a simple and modified solvothermal method at large scale using ethanol as the refluxing solvent and NaBH₄ as reducing agent. The nanopowder was investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-visible and BET surface area studies. XRD studies reveal the monophasic nature of these highly crystalline silver nanoparticles. Transmission electron microscopic studies show the monodisperse and highly uniform nanoparticles of silver of the particle size of 5 nm, however, the size is found to be 7 nm using dynamic light scattering which is in good agreement with the TEM and X-ray line broadening studies. The surface area was found to be 34.5 m²/g. UV-visible studies show the absorption band at ∼425 nm due to surface plasmon resonance. The percentage yield of silver nanoparticles was found to be as high as 98.5%.     

Phenomenological modeling of anisotropy induced by evolution of the dislocation structure on the macroscopic and microscopic scale

This work focuses on the modeling of the evolution of anisotropy induced by the development of the dislocation microstructure. A model formulated at the engineering scale in the context of classical metal plasticity and a model formulated in the context of crystal plasticity are presented. Images obtained by transmission-electron microscopy (TEM) show the influence of the strain path on the evolution of anisotropy for the case of two common materials used in sheet metal forming, DC06 and AA6016-T4. Both models are capable of accounting for the transient behavior observed after changes in loading path for fcc and bcc metals. The evolution of the internal variables of the models is correlated with the evolution of the dislocation structure observed by TEM investigations.     

Nanometer scale spectral imaging of quantum emitters in nanowires and its correlation to their atomically resolved structure

We report the spectral imaging in the UV to visible range with nanometer scale resolution of closely packed GaN/AlN quantum disks in individual nanowires using an improved custom-made cathodoluminescence system. We demonstrate the possibility to measure full spectral features of individual quantum emitters as small as 1 nm and separated from each other by only a few nanometers and the ability to correlate their optical properties to their size, measured with atomic resolution. The direct correlation between the quantum disk size and emission wavelength provides evidence of the quantum confined Stark effect leading to an emission below the bulk GaN band gap for disks thicker than 2.6 nm. With the help of simulations, we show that the internal electric field in the studied quantum disks is smaller than what is expected in the quantum well case. We show evidence of a clear dispersion of the emission wavelengths of different quantum disks of identical size but different positions along the wire. This dispersion is systematically correlated to a change of the diameter of the AlN shell coating the wire and is thus attributed to the related strain variations along the wire. The present work opens the way both to fundamental studies of quantum confinement in closely packed quantum emitters and to characterizations of optoelectronic devices presenting carrier localization on the nanometer scale.     

Nephron ultrastructural alterations induced by zinc oxide nanoparticles: an electron microscopic study

Due to their unique properties, zinc oxide nanoparticles (ZnO NPs) are invested in many industries, commercial products, and nanomedicine with potential risk for human health and the environment. The present study aims to focus on alterations that might be induced by ZnO NPs in the nephron ultrastructure. Male Wister Albino rats were subjected to ZnO NPs at a daily dose of 2 mg/kg for 21 days. Kidney biopsies were processed to transmission electron microscopy (TEM) and ultrastructural pathology examinations. Exposure to ZnO NPs‐induced ultrastructural alterations in the proximal convoluted tubules (PCTs) and to lesser extent in the distal ones (DCTs), while the loops of Henle were almost not affected. The glomeruli demonstrated dilatation, partial mesangial cells loss, matrix ballooning, slits filtration widening, and basement membrane thickening. Moreover, PCT revealed cytoplasmic necrosis, vacuolation, erosion, and disorganisation of the apical microvilli together with mitochondrial swelling and cristae destruction. The nuclei of the renal cells exhibited nuclear deformity, heterochromatin accumulation, and apoptotic activities. The findings indicate that ZnO nanomaterial have the potential to affect the nephron ultrastructure suggesting alteration in the kidney functions. More work is needed for better understanding the toxicity and pathogenesis of ZnO oxide nanomaterial.Inspec keywords: electron microscopy, zinc compounds, transmission electron microscopy, nanomedicine, biochemistry, diseases, cellular biophysics, biomembranes, kidney, nanofabrication, molecular biophysics, nanoparticles, II‐VI semiconductors, biomedical optical imagingOther keywords: electron microscopic study, unique properties, zinc oxide nanoparticles, ZnO NPs, nephron ultrastructure, Male Wister Albino rats, ultrastructural pathology examinations, NPs‐induced ultrastructural alterations, partial mesangial cells loss, ZnO nonmaterial, ZnO oxide nonmaterial, nephron ultrastructural alterations, kidney biopsies, time 21.0 d, ZnO     

Modifications induced by silicon and nickel ion beams in the electrical conductivity of zinc nanowires

This paper presents the modification in electrical conductivity of Zn nanowires under swift heavy ions irradiation at different fluences. The polycrystalline Zn nanowires were synthesized within polymeric templates, using electrochemical deposition technique and were irradiated with 80 MeV Si⁷⁺ and 110 MeV Ni⁸⁺ ion beams with fluence varying from 1 × 10¹² to 3 × 10¹³ ions/cm². I–V characteristics of exposed nanowires revealed a decrease in electrical conductivity with increase in ion fluence which was found to be independent of applied potential difference. But in the case of high fluence of Ni ion beam (3 × 10¹³ ions/cm²), electrical conductivity was found to increase with potential difference. The analysis found a significant contribution from grain boundaries scattering of conduction electrons and defects produced by ion beam during irradiation on flow of charge carriers in nanowires.     

Synthesis of silicon nanowires using laser ablation method and their manipulation by electron beam

Size control of silicon nanowires (SiNWs) synthesized by laser ablation of a Si target with iron or nickel as catalysts were investigated by changing the synthesis parameters such as the content of catalyst in targets and laser power during synthesis. The diameter and length of SiNWs significantly depended on the synthesis parameters, i.e. the size of SiNWs can be controlled by the synthesis parameters. Manipulation of SiNWs was also performed during the observation of scanning electron microscope. By changing the degree of charge-up for free-standing adjacent intertwined SiNWs at an edge of Si substrate, the distance and speed of opening motion of them can be controlled. This motion is probably caused by the Coulomb repulsive interaction between them.     

Large scale synthesis and characterization of Ni nanoparticles by solution reduction method

Ni nanoparticles were mass synthesized by solution reduction process successfully. The influence of the parameters on the particle size of Ni nanoparticles were studied and the referential process parameters were obtained. The morphology and structure of the synthesized Ni nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis and infrared spectroscopy (IR). The results show that Ni nanoparticles are of high purity and are covered by hydroxyethyl carboxymethyl cellulose (HECMC) layer and the mean size being about 31 nm. The magnetic measurement revealed that Ni nanoparticles are ferromagnetic.     

Large scale, highly conductive and patterned transparent films of silver nanowires on arbitrary substrates and their application in touch screens

The application of silver nanowire films as transparent conductive electrodes has shown promising results recently. In this paper, we demonstrate the application of a simple spray coating technique to obtain large scale, highly uniform and conductive silver nanowire films on arbitrary substrates. We also integrated a polydimethylsiloxane (PDMS)-assisted contact transfer technique with spray coating, which allowed us to obtain large scale high quality patterned films of silver nanowires. The transparency and conductivity of the films was controlled by the volume of the dispersion used in spraying and the substrate area. We note that the optoelectrical property, σ(DC)/σ(Op), for various films fabricated was in the range 75-350, which is extremely high for transparent thin film compared to other candidate alternatives to doped metal oxide film. Using this method, we obtain silver nanowire films on a flexible polyethylene terephthalate (PET) substrate with a transparency of 85% and sheet resistance of 33 Ω/sq, which is comparable to that of tin-doped indium oxide (ITO) on flexible substrates. In-depth analysis of the film shows a high performance using another commonly used figure-of-merit, Φ(TE). Also, Ag nanowire film/PET shows good mechanical flexibility and the application of such a conductive silver nanowire film as an electrode in a touch panel has been demonstrated.     

ZnO nanowires by pulsed laser vaporization: synthesis and properties

We report a new pulsed-laser vaporization (PLV) technique to synthesize nanowires of single-crystal ZnO having a wurtzite structure by using colloidal gold nanoparticles as seeding catalysts. The average diameter of the nanowires is approximately 13 nm, with a very narrow range of 7 to 25 nm. The nanowires are straight for the most part, with the axes parallel to the [0001] growth direction. Raman and photoluminescence spectra from the nanowires and bulk ZnO are similar except for a approximately 510 nm band in the nanowires due to oxygen vacancies. The bulk-like vibrational and electronic properties of the nanowires is due to the diameter being larger than the threshold below which quantum confinement-induced effects are expected.     

Influence of zinc precursors and surfactants on the preparation of Ag-containing materials by electron beam irradiation

Ag-Zn bimetallic nanocomposites or Ag2S precipitates were produced by irradiating a mixture of AgNO3 and Zn(NO3)2, and another mixture of AgNO3 and ZnS with an electron beam in an aqueous phase. Surfactants of poly vinyl alcohol (PVA) and poly ethylene glycol (PEG) induced a slightly different formation of particles during this process.     

Microwave-hydrothermal synthesis and structural characterization of PX-phase single-crystalline PbTiO3 nanowires by electron microscopy

PX-phase PbTiO₃ (PT) nanowires were synthesized by microwave-hydrothermal process, and their microstructures were characterized by electron microscopy. The PX-phase PT nanowires exhibit acicular morphology with diameter sizes of 20-80 nm and length over 1 µm. They tend to grow into a regular structure with parallel arrangement along their long axis in the [001] direction. Selected area electron diffraction patterns demonstrate the PX-phase PT nanowires with a 3-fold modulated periodicity along the [110] direction and a 4-fold modulated periodicity in the [001] direction. These results were also confirmed by the high-resolution transmission electron microscopy images.