The role of interparticle and external forces in nanoparticle assembly

The past 20 years have witnessed simultaneous multidisciplinary explosions in experimental techniques for synthesizing new materials, measuring and manipulating nanoscale structures, understanding biological processes at the nanoscale, and carrying out large-scale computations of many-atom and complex macromolecular systems. These advances have led to the new disciplines of nanoscience and nanoengineering. For reasons that are discussed here, most nanoparticles do not 'self-assemble' into their thermodynamically lowest energy state, and require an input of energy or external forces to 'direct' them into particular structures or assemblies. We discuss why and how a combination of self- and directed-assembly processes, involving interparticle and externally applied forces, can be applied to produce desired nanostructured materials.     

Hierarchical assembly of ultranarrow alkylamine-coated ZnS nanorods: a synchrotron surface X-ray diffraction study

The packing of anisotropic ultranarrow nanoparticles ( r 相似文献   

Orientated CNT‐polypropylene nanocomposite films made from extruded monofilaments

In this study, a method for making an orientated polymer nanocomposite film was developed. Melt‐drawn nanocomposite monofilaments of isotactic polypropylene and acicular nanofillers, i.e. carbon nanotubes (CNT) or vapor grown carbon nanofibers (VGCF), were prepared and characterized from the aspect of polymer chain orientation, mechanical properties, and overall morphology. A marked improvement in mechanical properties was observed as a function of the addition of CNT, increasing draw down ratio (DDR) and annealing. Nanocomposite films were prepared from drawn monofilaments by hot‐pressing under low pressure in order to maintain the orientation of the monofilaments. Wide angle X‐ray diffraction showed a high degree of residual orientation in the films. Electron microscopy (high‐resolution scanning electron microscopy, transmission electron microscopy) unexpectedly revealed that the CNT‐matrix interface is amorphous. However, differential scanning calorimetry found no measurable influence of the CNT on the overall crystallinity as determined by the enthalpy of melting of the matrix. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Complex investigation of electronic structure transformations in Lead Sulphide nanoparticles using a set of electron spectroscopy techniques

It has been reported recently that kinetic energy of photoelectrons emitted from core levels decreases with decreasing of the nanocrystal size. This phenomenon is called the size shift. The size shift value is the same for donor and acceptor in the compound. The present work is aimed on the explanation of this phenomenon. Crystals of lead sulfide PbS with different size from 50 to 350 nm were grown by chemical bath deposition (CBD) technique from alkaline solution onto Si and GaAs substrates. The morphology and size of crystals were analyzed by high resolution scanning electron microscopy (HRSEM). Complex electron spectroscopy investigations of electronic structure were carried out. In recent experiments X-ray photoelectron spectroscopy (XPS) was used for determination of Pb 4f, and S 2p electronic level positions and their size shifts. To explain the observed dependences in this work, we applied the following methods: analysis of PbS valence band (VB) and Pb 5d electronic level structure in the range ∼0-30 eV by XPS, high resolution electron energy losses spectroscopy (HREELS) for analysis of band gap transformations and work function measurements by Kelvin probe microscopy for the contact potential difference (CPD). The influence of work function increasing, widening of the band gap, transformations in VB and inter-level energy distances with decreasing of nanocrystal size on the size shift function ΔE(R) is discussed.     

Jewish Nationalism,European Colonialism and Modernity: The Origins of the Israeli Public Housing System

Since the middle of the 19th century, housing the growing number of Jews immigrating to Palestine demanded resources that were not available to all immigrants. Housing projects were initiated either by Jewish philanthropists or building associations established by leaders of local communities. Numbers of immigrants rose sharply with the increasing involvement of the Zionist national movement in Palestine and the establishment of the British Mandatory regime. Most houses were built then by the private sector, widening the gap among different socio-economic groups. Only after the 1948 war and the termination of the colonial regime, was the newly established State of Israel able to initiate large-scale housing projects, due to its control of former Arabowned lands. The distribution of those lands raised conflicts between different sectors of the Israeli society, such as in the following two cases of public housing projects initiated in the Tel Aviv metropolitan area.     

Microstructure and corrosion resistance of alloys of the Mg-Zn-Ag system

New alloys of the Mg-Zn-Ag system are studied. The capacity for precipitation hardening and mechanical properties of extruded Mg-Zn alloys are determined depending on the degree of their alloying with silver. The microstructure of the alloys is studied with the help of light and electron microscopes; the grain sizes are measured before and after the extrusion. The hardness and the mechanical properties of extruded alloys are determined after single and double aging.     

Material and electrical properties of electroless Ag-W thin film

Thin Ag-W films were prepared on Si (100) substrate and on metal (Ag and Co) seed layers by electroless technology for ULSI applications. The thin film electrical and physical parameters were studied as a function of the film composition. The thin film composition depends on the electroless bath formula. The role of the tungsten in silver matrix was studied via measurements of the film microhardness and thermal stability as function of the composition. The Ag-W films, thicker than 200 nm, exhibited a specific electrical resistivity of about 2μΩ* and a reflectivity larger than 90%. These films have not corroded in air at temperatures up to 200°C (thermal stable). Therefore, we assume that silvertungsten films can be used for applications where reliable conducting thin films is required, such as packaging and interconnects for microelectronics.     

Pelvic splenosis mimicking endometriosis, causing low abdominal mass and pain

Splenosis is the heterotopic autotransplantation of splenic tissue that usually follows traumatic splenectomy. The clinical significance of these splenic implants and the need for surgical removal is debatable. A case of a 35 year old woman, with post-traumatic splenectomy presenting with low abdominal pain and pelvic mass is reported. Laparoscopic removal of the pelvic splenic implants dispelled all complaints.     

Reliability and validity of the Family Eating and Activity Habits Questionnaire

Morphological and cytochemical studies have suggested that maturation ameloblasts participate in protein loss by absorbing and degrading enamel proteins as the enamel matures. Several immunocytochemical and autoradiographic studies have suggested other possible explanations for the presence of enamel matrix proteins in maturation ameloblasts. The weakness of these autoradiographic studies is the uncontrolled distribution of systemically injected radioactive amino acids, making it impossible to trace the source of the visualized intracellular isotope. This study used a localized technique to control the targets of the applied isotope and to identify enamel matrix proteins in the maturation ameloblasts with more confidence about their origin. The amount of labelled enamel protein was higher in maturation ameloblasts than transitional ameloblasts. When cycloheximide, a protein-synthesis inhibitor, was applied, there was no effect on the amount of labelled protein in the maturation ameloblasts. These findings support the hypothesis that maturation ameloblasts actively resorb and degrade enamel matrix proteins during enamel formation in the mandibular incisor of the rat.