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The air–water interface has traditionally been employed to prepare particle assemblies and films of metals and semiconductors. The interface between water and an organic liquid, however, has not been investigated sufficiently for possible use in preparing nanocrystals and thin films of materials. In this article, we demonstrate the use of the liquid–liquid interface as a medium for preparing ultrathin films of metals, chalcogenides and oxides. The method involves the reaction at the interface between a metal-organic compound in the organic layer and an appropriate reagent for reduction, sulfidation, etc. in the aqueous layer. Some of the materials discussed are nanocrystalline films of gold, CuS, CuSe, CuO, and Cu(OH)2 formed at the liquid–liquid interface. The results reported in this article should demonstrate the versatility and potential of the liquid–liquid interface for preparing nanomaterials and ultrathin films and encourage further research in this area.
Molecular oxygen adsorbed on (110) and polycrystalline Cu surfaces has been investigated by UPS, XPS, AES, HREELS and LEED. Molecularly adsorbed O2 on the (110) surface shows the characteristic three-peak HeII spectrum due to πg, πu and σg orbitals, accompanied by an O-O stretching frequency at 660 cm-1. On the polycrystalline Cu surface, adsorbed O2 shows the three peak HeII spectra with a considerably smaller separation between the πu and σg band and two O-O stretching bands at 610 and 880 cm-1. O2 adsorbed on the Cu(110) surface gives rise to a (1×1) LEED pattern and characteristic Kπ∗π∗ transition in the Auger spectrum.
In YBa2Cu3–yGayO7–δ, Ga can be substituted at the Cu(1) site up to y= 0.1 without change in structure, but this is accompanied by a slight decrease in the hole concentration and Tc; the same is true when Y is partly substituted by Ca, as in Y1–xCaxBa2Cu3–yGayO7–δ(0.0<x⩽0.2). When one Ba is replaced by Sr as in YBaSrCu3–yGayO7–δ, however, Ga can be substituted at the Cu(1) site to a much greater extent (up to y= 0.6). In this system, Ga substitution changes the structure from orthorhombic to tetragonal, unlike in YBa2Cu3–yGayCu3O7–δ. Both the hole concentration and Tc decrease with an increase in y and the material becomes non-superconducting for y> 0.2. The y= 0.3 and 0.4 compositions show metal–semiconductor transitions at 60 and 120 K, respectively, while the y= 0.6 composition is a semiconductor. When Y is partly substituted by Ca as in Y1–xCaxBaSrCu3–yGayO7–δ, the material is superconducting even when y= 0.3. All these Ga-substituted cuprates are in the underdoped region and accordingly Tc increases with increase in hole concentration.
The formation energies of Schottky defects in the CsCl (Pm3m) and the NaCl (Fm3m) structures of CsCl are found to be 1·4 and 2·0 eV respectively. The ground-state interaction energies between Sr2+Cs+ and the V–Cs+ in the Pm3m and Fm3m phases are ca. 0·45 and 0·35 eV respectively. The cation migration energies in CsCl are affected by the incorporation of K+, Rb+ or Br–. The formation energy of Schottky defects in the solid solutions of CsCl with KCl or RbCl is low (1·4 eV) in the Pm3m phase, but attains a much higher value (2 eV) at compositions where the Fm3m structure gets stabilized.
Reaktiver als Silber‐und Nickelmetall sind Kleine Cluster aus diesen Elementen, wie Reaktivitätsstudien mit O 2 sowie H 2 S und CO zeigen. So ist zum Beispiel die Spaltung von O 2 an kleinen Ag‐Clustern bevorzugt, und der Anteil der O 2 ‐Moleküle, die gespalten werden, hängt nicht, wie bei größeren Clustern und Silbermetall, von der Temperatur ab. Die Änderung der Reaktivität ist dann am größten, wenn der Übergang vom Metall zum Isol tor vollzogen wird‐ein für die heterogene Katalyse wichtiger Befund.
The energies of association between a divalent anion impurity and an anion vacancy in KCI have been evaluated fro three associated states. Distribution of these I′CI-V′CI pairs has been worked out over the temperature range 300-1000°K.
Electron-energy-loss spectra, recorded from ultramicro quantities (<10–12 g), reveal L2,3 edges the energy and intensity of which vary systematically with oxidation state in a series of transition metal oxides; the first ever evidence for structure-sensitive features in oxygen K-edges is reported.
ADVERTISEMENT RETURN TO ISSUEPREVArticlePhysical chemistry of high-temperature oxide superconductors [Erratum to document cited in CA110(24):223296s]T. V. Ramakrishnan and C. N. R. RaoCite this: J. Phys. Chem. 1989, 93, 26, 8388Publication Date (Print):December 1, 1989Publication History Published online1 May 2002Published inissue 1 December 1989https://pubs.acs.org/doi/10.1021/j100363a028https://doi.org/10.1021/j100363a028research-articleACS PublicationsRequest reuse permissionsArticle Views32Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts
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Metal nanoparticles of varying sizes can be prepared by physical as well as chemical methods. They exhibit many fascinating properties, the size-dependent metal to nonmetal transition being an important one. Metal nanoparticles capped by thiols can be organized into ordered one-, two- and three-dimensional structures and these structures have potential applications in nanodevices. In this context, organization of arrays of metal nanoparticles with a fixed number of atoms assumes significance.
Oxygen atoms in the middle CuO layer of YBa2Cu3O7 consisting of strings of corner-connected (CuO4)∞ units are shown to be crucial for superconductivity. Importance of hole-hole pairing giving rise to OO bonds is also indicated.
