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Title: Reduction-Triggered Self-Assembly of Nanoscale Molybdenum Oxide Molecular Clusters

A 2.9 nm molybdenum oxide cluster {Mo132} (Formula: [MoVI72MoV60O372(CH3COO)30(H2O)72]42-) can be obtained by reducing ammonium molybdate with hydrazine sulfate in weakly acidic CH3COOH/CH3COO- buffers. This reaction has been monitored by time-resolved UV-Vis, 1H-NMR, small angle X-ray/neutron scattering, and X-ray absorption near edge structure spectroscopy. The growth of {Mo132} cluster shows a typical sigmoid curve, suggesting a multi-step assembly mechanism for this reaction. The reaction starts with a lag phase period when partial MoVI centers of molybdate precursors are reduced to form {MoV2(acetate)} structures under the coordination effect of the acetate groups. Once the concentration of {MoV2(acetate)} reaches a critical value, it triggers the assembly of MoV and MoVI species into {Mo132} clusters. Parameters such as the type and amount of reducing agent, the pH, the type of cation, and the type of organic ligand in the reaction buffer, have been studied for the roles they play in the formation of the target clusters.Understanding the formation mechanism of giant molecular clusters is essential for rational design and synthesis of cluster-based nanomaterials with required morphologies and functionalities. Here, typical synthetic reactions of a 2.9 nm spherical molybdenum oxide cluster, {Mo132} (formula: [MoVI72MoV60O372(CH3COO)30(H2O)72]42), with systematically varied reaction parameters have been fully explored tomore » determine the morphologies and concentration of products, reduction of metal centers, and chemical environments of the organic ligands. The growth of these clusters shows a typical sigmoid curve, suggesting a general multistep self-assembly mechanism for the formation of giant molecular clusters. The reaction starts with a lag phase period when partial MoVI centers of molybdate precursors are reduced to form {MoV2(acetate)} structures under the coordination effect of the acetate groups. Once the concentration of {MoV2(acetate)} reaches a critical value, it triggers the co-assembly of MoV and MoVI species into the giant clusters.« less
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [1] ;  [3] ;  [4] ;  [1] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
  3. Argonne National Lab. (ANL), Argonne, IL (United States)
  4. Inst. Max Von Laue Paul Langevin, Grenoble (France)
Publication Date:
OSTI Identifier:
1324096
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 138; Journal Issue: 33; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY