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High Resolution Physical Characterization of Single Metallic Nanoparticles
Published on: June 28, 2019
Molybdenum-oxide based unique polyprotic nanoacids showing different deprotonations and related assembly processes in
Melissa L Kistler1, Tianbo Liu, Pierre Gouzerh
1Department of Chemistry, Lehigh University, 6 E. Packer Ave., Bethlehem, Pennsylvania 18015, USA.
Dalton Transactions (Cambridge, England : 2003)
|June 30, 2009
Summary
Three Keplerate-type molybdenum-oxide clusters self-assemble into blackberry structures. Their assembly depends on surface charge density, pH, and solvent, with variations observed between vanadium, chromium, and iron clusters.
Area of Science:
- Supramolecular Chemistry
- Inorganic Chemistry
- Materials Science
Background:
- Keplerate-type molybdenum-oxide clusters are nanoscale structures with potential applications in materials science.
- These clusters exhibit unique polyprotic acid behavior due to external water ligands.
- The self-assembly of these clusters into larger structures is influenced by their surface properties.
Purpose of the Study:
- To investigate the solution-based self-assembly processes of three Keplerate-type clusters: {Mo72V30}, {Mo72Cr30}, and {Mo72Fe30}.
- To understand how variations in the non-molybdenum metal centers (V, Cr, Fe) affect cluster self-assembly.
- To correlate cluster surface charge density and ligand lability with the formation of supramolecular structures.
Main Methods:
- Synthesis and characterization of {Mo72V30}, {Mo72Cr30}, and {Mo72Fe30} clusters.
- Solution-based studies involving varying pH and solvent composition (aqueous and mixed water/organic).
- Observation and analysis of self-assembly into blackberry-type structures.
Main Results:
- All three clusters self-assemble into blackberry-type structures, with diameters around 2.5 nm.
- {Mo72Cr30} and {Mo72Fe30} exhibit similar self-assembly behavior in aqueous solution, driven by partial deprotonation of external water ligands.
- {Mo72V30} clusters, with fewer external water ligands and a net negative charge, form blackberry structures only in mixed solvents, with size dependent on organic solvent content.
Conclusions:
- The self-assembly of Keplerate clusters is tunable via pH and solvent properties, directly related to surface charge density.
- Differences in the number and lability of external water ligands significantly impact self-assembly pathways, particularly for the {Mo72V30} cluster.
- Comparative studies reveal general principles governing the self-assembly of polyoxometalate clusters into complex supramolecular architectures.
