Postdoctoral Researcher at Argonne National Laboratory
- Ph.D. in Materials Science,
University of PARIS 6 Pierre et Marie CURIE (France)
- Research interests include the synthesis of colloidal nanocrystals (QDs/metals/oxide) and heterostructure nanomaterials (semiconductor/metal), the design of organic/inorganic composite materials for photo-voltaic applications (luminescent solar concentrator). Study of structural (TEM/STEM, EXAFS) and physical properties (Photoluminescence, Magnetism) of these nanomaterials. In-situ liquid TEM investigation. Self-organization and active colloids.
Email : email@example.com
Website(French) : www.nanosciences.biz
Colloidal Nanocube Supercrystals Stabilized by Multipolar Coulombic Coupling
H. Chan, A. Demortière, L. Vukovic, P. Kral, C. Petit, 2012, ACS Nano, 6 (5), pp 4203–4213.
We explore microscopic principles governing the self-assembly of colloidal octylamine-coated platinum nanocubes solvated in toluene. Our experiments show that regular nanocubes with an edge length of lRC = 5.5 nm form supercrystals with simple cubic packing, while slightly truncated nanocubes with an edge length of lTC = 4.7 nm tend to arrange in fcc packing. We model by averaged force fields and atomistic molecular dynamics simulations the coupling forces between these nanocrystals. Our detailed analysis shows that the fcc packing, which for cubes has a lower density than simple cubic packing, is favored by the truncated nanocubes due to their Coulombic coupling by multipolar electrostatic fields, formed during charge transfer between the octylamine ligands and the Pt cores.
3D Quantitative Analysis of Platinum Nanocrystals Superlattices by Electron Tomography
I. Florea, A. Demortière, C. Petit, H. Bulou, C. Hirlimann, O. Ersen, ACS Nano, 2012, 6 (3), pp 2574–2581.
The work reported herein focuses on the 3D relative arrangement of individual platinum nanocrystals with a size of about 5 nm, and on the structure of the superlattices, they spontaneously form. Electron tomography was systematically used in this study because it allows obtaining quantitative 3D information in real space. Performing tomography in the bright-field TEM mode allowed investigating the short and long-range orderings of the nanoparticles packed as self-organized supercrystals. Systematic fcc pilings were observed with a mean lattice parameter measured to be 19.5 nm, the nature of the arrangement being controlled by the truncated octahedral morphology of platinum nanocrystals and the associated steric effects. A numerical 3D quantitative analysis of the ordering characteristics of the superlattice with a nanometer resolution has been performed that, for the first time, showed a direct correlation between single entities’ characteristics and their ordering in periodic arrays. It has been shown that the lattice parameter is different in two orthogonal directions of the fcc structure, which indicates the presence of a slightly compressed superlattice. Inside the superstructure, vacancies and axial defects were observed that would blur the occurrence of potential collective effects from the supercrystals.
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