1,720,981 research outputs found
Insight into the formation of hollow silver nanoparticles using a facile hydrothermal strategy
No full textA facile hydrothermal approach is used to synthesize hollow silver nanoparticles, labeled as hAgNPs, involving an initial formation of metal complexes from Ag+ ion precursors and dodecylamine in a water/ethanol mixture at room temperature and a subsequent reduction in an autoclave at elevated temperature. A number of characterization techniques are used to characterize the structure and chemical composition of the as-formed hAgNPs, and to understand the mechanism behind the formation. The notable simplicity renders this synthetic approach promising for creating hAgNPs on a large scale for a given technological application, and the mechanistic understanding may provide new opportunities to design and fabricate other hollow nanostructures. (C) 2015 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved
RSC Adv.
No full textCarbon-supported palladium nanoparticles (NPs) with hollow interiors (hPdNPs/C) are fabricated via a facile approach. In this strategy, core-shell NPs with an Ag core and an Ag-Pd alloy shell (Ag@Ag-Pd) are first synthesized in oleylamine by a galvanic replacement reaction between Ag seed particles and Pd2+ ion precursors. Then the core-shell Ag@Ag-Pd NPs are loaded on the XC-72 carbon supports and refluxed in acetic acid to remove the original organic surfactant. The carbon-supported core-shell Ag@Ag-Pd NPs are subsequently agitated in saturated Na2S or NaCl solution for 24 h to eliminate the Ag component from the core and shell regions, leading to the formation of hPdNPs/C. Specifically, the hPdNPs/C generated by NaCl treatment exhibit superior catalytic activity and durability for formic acid oxidation reaction (FAOR) and oxygen reduction reaction (ORR), compared with the commercial Pd/C catalysts from Johnson Matthey, mainly due to the high electrochemically active surface areas (ECSAs) of the hollow structure, whereas the hPdNPs/C obtained by Na2S treatment display very poor catalytic performance due to the serious poisoning induced by S2- adsorption.Carbon-supported palladium nanoparticles (NPs) with hollow interiors (hPdNPs/C) are fabricated via a facile approach. In this strategy, core-shell NPs with an Ag core and an Ag-Pd alloy shell (Ag@Ag-Pd) are first synthesized in oleylamine by a galvanic replacement reaction between Ag seed particles and Pd2+ ion precursors. Then the core-shell Ag@Ag-Pd NPs are loaded on the XC-72 carbon supports and refluxed in acetic acid to remove the original organic surfactant. The carbon-supported core-shell Ag@Ag-Pd NPs are subsequently agitated in saturated Na2S or NaCl solution for 24 h to eliminate the Ag component from the core and shell regions, leading to the formation of hPdNPs/C. Specifically, the hPdNPs/C generated by NaCl treatment exhibit superior catalytic activity and durability for formic acid oxidation reaction (FAOR) and oxygen reduction reaction (ORR), compared with the commercial Pd/C catalysts from Johnson Matthey, mainly due to the high electrochemically active surface areas (ECSAs) of the hollow structure, whereas the hPdNPs/C obtained by Na2S treatment display very poor catalytic performance due to the serious poisoning induced by S2- adsorption
Heterogeneous nanocomposites of silver selenide and hollow platinum nanoparticles toward methanol oxidation reaction
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Making use of the electronic coupling between different domains in composite nanomaterials is an effective way to enhance the activity of electrocatalysts. Herein, we demonstrate the preparation of nanocomposites consisting of silver selenide (Ag2Se) and platinum (Pt) nanoparticles with a hollow interior by combining the inside-out diffusion of Ag in core-shell Ag-Pt nanoparticles with the synthesis of highly active hydrophobic Se species. In specific, the Ag2Se-hPt nanocomposites are found to have superior activity and stability for methanol oxidation reaction in an acidic condition due to the strong electronic coupling effect between semiconductor and metal domains. This strategy may provide a greener and less expensive way to the large-scale synthesis of Pt-based nanocomposites, and might be used to generate other heterogeneous nanomaterials with technological importance. (C) 2016 Elsevier B.V. All rights reserved.</p
Nano Res.
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Noble metal nanoparticles with hollow interiors and customizable shell compositions have immense potential for a wide variety of applications. Herein, we present a facile, general, and cost-effective strategy for the synthesis of noble metal nanoparticles with hollow structures, which is based on the inside-out diffusion of Ag in solid-state core-shell nanoparticles. This approach starts with the preparation of core-shell nanoparticles with Ag residing in the core region, which are then loaded on a solid substrate and aged in air to allow the inside-out diffusion of Ag from the core region, leading to the formation of monometallic or alloy noble metal nanoparticles with a hollow interior. The synthesis was carried out at room temperature and could be achieved on different solid substrates. In particular, the inside-out diffusion of Ag calls for specific concern with respect to the evaluation of the catalytic performance of the Ag-based core-shell nanoparticles since it may potentially interfere with the physical and chemical properties of the core-shell particles.
Noble metal nanoparticles with hollow interiors and customizable shell compositions have immense potential for a wide variety of applications. Herein, we present a facile, general, and cost-effective strategy for the synthesis of noble metal nanoparticles with hollow structures, which is based on the inside-out diffusion of Ag in solid-state core-shell nanoparticles. This approach starts with the preparation of core-shell nanoparticles with Ag residing in the core region, which are then loaded on a solid substrate and aged in air to allow the inside-out diffusion of Ag from the core region, leading to the formation of monometallic or alloy noble metal nanoparticles with a hollow interior. The synthesis was carried out at room temperature and could be achieved on different solid substrates. In particular, the inside-out diffusion of Ag calls for specific concern with respect to the evaluation of the catalytic performance of the Ag-based core-shell nanoparticles since it may potentially interfere with the physical and chemical properties of the core-shell particles.</p
Formation of composite dimers consisting of Ag2S and hollow structured Pd nanoparticles
No full textUnderstanding the mechanism for the production of composite dimers, which often exhibit new properties not present in their individual components due to the electron transfer across the nanometer contact at the interface, is undoubtedly important. Herein, with the assistance of a small amount of [AD] PO4, an organic soluble ionic liquid, core-shell Ag@Ag-Pd nanoparticles with an average size of 28.2 nm are successfully prepared, which serve as templates for the subsequent synthesis of dimeric nanocomposites consisting of Ag2S and hollow structured Pd nanoparticles (Ag2S-hPd) by converting the Ag component in the core-shell particles into Ag2S with elemental sulfur. Specifically, the large size of the core-shell nanoparticles allow us to observe clearly the ripening of Ag2S to a single site on the surface of the remnant hollow structured Pd nanoparticles, which elucidates the mechanism accounting for the formation of Ag2S-hPd composite dimers instead of core-shell nanostructures with a hollow Pd core and a continuous Ag2S shell, although the transformation from Ag to Ag2S occurred uniformly on the surface of the remnant hollow Pd particles. Electrochemical measurements demonstrate that the dimeric Ag2S-hPd nanocomposites display better electrocatalytic behavior for formic acid oxidation than commercial Pd/C catalysts due to the strong electronic coupling between the semiconductor and noble metal domains in the nanocomposites
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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