Séminaire du LPTMS : Cyrille Hamon (LPS)


11:00 - 12:00

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Colloidal design of nanoparticles and hierarchical nanostructures

Cyrille Hamon (Laboratoire de physique des Solides)

The production of solid materials with nanoscale building blocks can be conveniently achieved by colloidal self-assembly and with a minimal synthetic effort. This presentation will revolve around elongated nanoparticles with a pentagonal base. In the first part, I will show the different methods we use to self-assemble and study NPs self-assembly. In the second part, I will focus on the self-assembly of the pentagonal NPs into low-symmetry supercrystals wherein the loss of symmetry can be understood through an analogy with the optimal packing of regular pentagons in the plane: the individual objects have rotational symmetry of order 5, but they associate in pairs which creates an inversion center. In doing so, they reduce their rotational symmetry to order 2. Assemblies are studied by X-ray scattering and electron microscopy as well as some numerical simulations reproducing the symmetry and density of the packing. Moreover, the Raman signal of molecules is enhanced in the vicinity of these assemblies, with an exaltation that depends on the exposed facet of the crystal.

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