| Synthesis of Nanoamorphous Germanium and Its Transformation to Nanocrystalline Germanium. | |
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MedLine Citation:
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PMID: 22228493 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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A simple reaction between a mild reducing agent such as a trialkoxysilane and Ge(IV) species such as germanium tetraalkoxides in a room-temperature water/alcohol solution produces silica-coated ultrasmall (2-3 nm) amorphous germanium nanoparticles (na-Ge/SiO(2) ). The initial reaction involves the straightforward hydrolysis and condensation of the precursors, Ge(OCH(2) CH(3) )(4) and (CH(3) CH(2) O)(3) SiH, where the reaction rate depends on the water concentration in the reaction medium. These processes can be further accelerated by adding acid to the reaction medium or carrying out the reaction at higher temperatures. At low water contents (up to 50% water/ethanol) and low acid concentrations, the reaction proceeds as a clear solution, and no precipitation is observed. The initially colorless clear solution progressively changes to pale yellow, yellow, orange, red, and finally dark red as the na-Ge particles grow. Evaporation of the solvent yields a reddish-brown powder/monolith consisting of na-Ge, embedded in an encapsulating amorphous silica matrix, na-Ge/SiO(2) . The formation of na-Ge proceeds extremely slowly and follows a first-order dependence on both water concentration and diameter of the na-Ge particles under the reaction conditions used. Annealing of the na-Ge/SiO(2) powder under an inert atmosphere at 600 °C produces ultrasmall germanium nanocrystals (nc-Ge) embedded in amorphous silica (nc-Ge/SiO(2) ). Freestanding, colloidally stable nc-Ge is obtained by chemical etching of the encapsulating silica matrix. |
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Authors:
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Omer Dag; Eric J Henderson; Geoffrey A Ozin |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-1-9 |
Journal Detail:
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Title: Small (Weinheim an der Bergstrasse, Germany) Volume: - ISSN: 1613-6829 ISO Abbreviation: - Publication Date: 2012 Jan |
Date Detail:
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Created Date: 2012-1-9 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 101235338 Medline TA: Small Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Copyright Information:
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Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
Affiliation:
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Bilkent University, Department of Chemistry, 06800 Ankara, Turkey. dag@fen.bilkent.edu.tr. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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