Monomeric Germanium(II) Amides Bearing β-Diketiminato Ligands: Synthesis, Structural Characterization, and Thermal Properties

Germanium(II) compounds featuring β-diketiminate-type ligands are attractive for applications as nanoparticle precursors, imaging agents, and components of electronic devices. In this work, we report the synthesis of β-diketiminatogermanium(II) amides LGe(NHPh) [1, L = {HC(CMeN–2,4,6-Me3C6H2)2} – ], LGe(4-NHPy) (2), LGe(2-NHPy) (3), and LGe(2-NHPy) (4), L = {HC(CMeN–2,6-iPr2C6H3)2} – ], which were obtained by the reaction of a low-valent organogermanium halide (LGeCl or LGeCl) with a lithium salt of the respective aromatic amine (LiNHPh) or aminopyridine [Li(4-NHPy) and Li(2-NHPy)]. Compounds 1–4 were characterized with several techniques such as melting point, FTIR, 1H and 13C NMR spectroscopy, elemental analysis, X-ray diffraction, and thermogravimetric analysis (TGA). Compounds 1–3 and 4 crystallized in the orthorhombic (space group Pnma) and monoclinic (space group P21/c) crystal systems, respectively. In all cases, the geometry around the central germanium atom was highly tetrahedrally distorted. According to TGA data, 1–4 do not sublime intact but rather exhibit thermal decomposition.Universidad de Costa Rica/[804-B2-A59]/UCR/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Electroquímica y Energía Química (CELEQ)UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Químic

Cluster Lenses

Clusters of galaxies are the most recently assembled, massive, bound structures in the Universe. As predicted by General Relativity, given their masses, clusters strongly deform space-time in their vicinity. Clusters act as some of the most powerful gravitational lenses in the Universe. Light rays traversing through clusters from distant sources are hence deflected, and the resulting images of these distant objects therefore appear distorted and magnified. Lensing by clusters occurs in two regimes, each with unique observational signatures. The strong lensing regime is characterized by effects readily seen by eye, namely, the production of giant arcs, multiple-images, and arclets. The weak lensing regime is characterized by small deformations in the shapes of background galaxies only detectable statistically. Cluster lenses have been exploited successfully to address several important current questions in cosmology: (i) the study of the lens(es) - understanding cluster mass distributions and issues pertaining to cluster formation and evolution, as well as constraining the nature of dark matter; (ii) the study of the lensed objects - probing the properties of the background lensed galaxy population - which is statistically at higher redshifts and of lower intrinsic luminosity thus enabling the probing of galaxy formation at the earliest times right up to the Dark Ages; and (iii) the study of the geometry of the Universe - as the strength of lensing depends on the ratios of angular diameter distances between the lens, source and observer, lens deflections are sensitive to the value of cosmological parameters and offer a powerful geometric tool to probe Dark Energy. In this review, we present the basics of cluster lensing and provide a current status report of the field.Comment: About 120 pages - Published in Open Access at: http://www.springerlink.com/content/j183018170485723/ . arXiv admin note: text overlap with arXiv:astro-ph/0504478 and arXiv:1003.3674 by other author

Materials Chemistry

The 2nd edition of Materials Chemistry builds on the strengths that were recognized by a 2008 Textbook Excellence Award from the Text and Academic Authors Association (TAA). Materials Chemistry addresses inorganic-, organic-, and nano-based materials from a structure vs. property treatment, providing a suitable breadth and depth coverage of the rapidly evolving materials field. The 2nd edition continues to offer innovative coverage and practical perspective throughout. After briefly defining materials chemistry and its history, seven chapters discuss solid-state chemistry, metals, semiconducting materials, organic "soft" materials, nanomaterials, and materials characterization. All chapters have been thoroughly updated and expanded with, for example, new sections on ‘soft lithographic’ patterning, ‘click chemistry’ polymerization, nanotoxicity, graphene, as well as many biomaterials applications. The polymer and ‘soft’ materials chapter represents the largest expansion for the 2nd edition. Each chapter concludes with a section that describes important materials applications, and an updated list of thought-provoking questions. The appendices have also been updated with additional laboratory modules for materials synthesis and a comprehensive timeline of major materials developments. Appropriate for junior/senior undergraduate students, as well as first-year graduate students in chemistry, physics, or engineering. Materials Chemistry may also serve as a reference to industrial researchers. The author chose depth over breadth, resulting in deep, detailed prose. The strenghts of this book are its illustrations and color graphics, as well as up-to-date references and examples. 'Choice Reviews Online', 2008 on Materials Chemistry 1st edition

Damage-Free Removal of Residual Carbon in a Dielectric Barrier Discharge (DBD) Plasma for Carbothermal-Synthesized Materials

In this work, we demonstrate damage-free removal of residual carbon in a dielectric barrier discharge (DBD) plasma for carbothermal-synthesized materials, such as CaAlSiN₃:Eu²⁺ phosphors, SnSb alloy anode materials, and TiN ceramic powders. The efficiency of residual carbon removal and the damaging effects of the plasma for treated materials are investigated in detail, with carbothermal-synthesized CaAlSiN₃:Eu²⁺ phosphors being used as an example. Results show that the residual carbon in carbothermal-synthesized CaAlSiN₃:Eu²⁺ phosphors could be removed effectively within a DBD plasma generator, resulting in the significant improvement of luminescent properties. The damage-free character of this DBD plasma decarburization process to phosphors is revealed, showing amazing superiority over the traditional high-temperature decarburization route. These results offer an attractive strategy for the removal of residual carbon for various carbothermal-synthesized materials with finely controlled compositions

Novel g‑C₃N₄/CoO Nanocomposites with Significantly Enhanced Visible-Light Photocatalytic Activity for H₂ Evolution

Novel g-C₃N₄/CoO nanocomposite application for photocatalytic H₂ evolution were designed and fabricated for the first time in this work. The structure and morphology of g-C₃N₄/CoO were investigated by a wide range of characterization methods. The obtained g-C₃N₄/CoO composites exhibited more-efficient utilization of solar energy than pure g-C₃N₄ did, resulting in higher photocatalytic activity for H₂ evolution. The optimum photoactivity in H₂ evolution under visible-light irradiation for g-C₃N₄/CoO composites with a CoO mass content of 0.5 wt % (651.3 μmol h^–1 g^–1) was up to 3 times as high as that of pure g-C₃N₄ (220.16 μmol h^–1 g^–1). The remarkably increased photocatalytic performance of g-C₃N₄/CoO composites was mainly attributed to the synergistic effect of the junction or interface formed between g-C₃N₄ and CoO