Bi-particulate metamaterials – METABIP

The ability of molecules and nano-objects to self-organize hierarchically up to macroscopic scale while retaining some mobility is a very powerful concept, suffice it to observe that all living organisms are made from the self-assembly of building blocks. Self-organization leads to the appearance of supplementary properties that the initial constituents do not possess. Through this supramolecular multi-scale organization and the emergence of synergetic effects, materials acquire new properties not found elsewhere and become meta-materials, literally “materials beyonds materials”, cf. the current research on optical metamaterials.
The Metabip project is a fundamental research project that aims at developping new functional architectures based on the self-assembling of mesomorphous hybrid nanoparticles, thus leading in fine to organized meta-materials simultaneously bearing magnetic, electronic and optical properties. No such system has ever been synthesized yet.
The core of these nanohybrids will be Au or Ag massive nanoparticles, Fe@Ag or Au@Ag core-shell nanoparticles, or FePt nanoparticles, coated with structuring organic ligands. All of these nanoparticles possess magnetic and/or optical properties. Ligands play a multiple role: a) stabilization of the particles ; b) induction of mesomorphism ; c) possible addition of an extra function such as photosensitivity or electron conduction. We will evidence how to built functional hybrid nano-objects with optical and/or magnetic properties, the first goal of this project.
With these nanoparticles we will then built metamaterials by combining two different sorts within the same 3D structure, a so far innovative and unseen approach. Mesomorphism will yield 3D ordered structures with a variety of organization and symmetries (lamellae, columns, bicontinuous lattices). Such assemblies may develop new properties through synergetic effects, in particular thanks to the coupling with plasmons, or electronic interactions between ligands and magnetic cores. The development of such innovative architectures is the second goal of this project. Due to their liquid-crystalline nature, these systems will potentially be collectively addressable with external electric fields, this will allow a modulation of their magnetic and/or optical properties.
Following the initial synthetic steps, the nano-objects and their assemblies will be fully characterized in terms of structure (NMR, TGA, IR, UV-vis, TEM…), mesomorphism (SAXS, DSC, POM) and properties (ESR, SQUID, spectrometries X and UV-vis,…). Near field studies (AFM, MFM, STM) will complement these studies by evaluating the physical properties of isolated objects.
In the end, the controlled production of multi-functional, multi-scale nanostructured meta-materials will be ensured. Achieving the present project will provide a unique know-how with immediate payback. Thanks to these new architectures, on the basis of our most recent work on the magnetism of gold nanoparticles, we plan to develop innovative magnetic materials. Several of the concepts and systems that we suggest are unprecedented, the preliminary results that we have validate the correctness of our approach (R.Gréget PhD thesis, 22/9/2011).