The role of topological defects liquid crystal materials the organization of nanoparticles

The optical properties of nanoparticles are directly related to their small size and to the electromagnetic coupling that takes place between the nanoparticles. When they are a few nanometres apart this coupling can significantly modify these properties. The community now knows how to synthesize, often in solution, a great diversity of nanoparticles, with various sizes, shapes and natures inducing the implementation of optical properties also varied. How to induce an organization of nanoparticles where the coupling between nanoparticles would be driven homogeneously to the nearest subnanometer over the entire sample from a solution of nanoparticles dispersed in a solvent? To answer this question, researchers from the INSP Physical Chemistry and Surface Dynamics team have studied the confinement of gold nanospheres in liquid crystal topological defects. They demonstrated the concentration-controlled formation of 1D (chains) or 2D (hexagonal arrays) nanoparticle networks, oriented along a single pre-defined direction on the substrate, which is otherwise difficult to achieve by other methods.


Caption: Evolution of the anisotropy of light absorption by gold nanoparticles (absorption wavelength for a parallel polarization as a function of the absorption wavelength for a perpendicular polarization) when the nanoparticle concentration increases. The GISAXS signal presented for the 2D network in reflection geometry highlights the characteristic diffraction rods of a hexagonal 2D network.

« From Chains to Monolayers : Nanoparticle Assembly Driven by Smectic Topological Defects »
Syou P’Heng Do, Missaoui Amine, Alessandro Coati, Delphine Coursault, Haïfa Jeridi, Andrea Resta, Nicolas Goubet, Michal M. Wojcik, Arnaud Choux, Sébastien Royer, Emrick Briand, Bertrand Donnio, Jean Louis Gallani, Brigitte Pansu, Emmanuel Lhuillier, Yves Garreau, David Babonneau, Michel Goldmann, Doru Constantin, Bruno Gallas, Bernard Croset and Emmanuelle Lacaze
Nano Letters, Volume : 20 1598–1606 (2020)