Reversible Long-Range Assemblies in Gold Nanoparticles – Liquid Crystal Composites: Molecular Dynamics of the Gold Capping Layer

J. Milette, V. Toader, L.-P. Scheffer, R.B. Lennox, L. Reven
McGill University, CA

Keywords: nanoparticles, liquid crystal, assembly


Highly miscible mesogenic ligand capped gold nanoparticles (AuNPs) [1] that produce reversible long-range assemblies in nematic and smectic liquid crystal (LC) [2-3] were recently developed by our group. At the isotropic-to-nematic phase transition of cyanobiphenyl based liquid crystal, AuNP networks are formed with controllable dimension and topology. The molecular interactions driving the assembly and detected by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy are presented in this paper. The chain mobility of the ligand shell at the gold surface was found to play a key role in the nanocrystal miscibility and to be higher for the mix monolayer AuNPs. The orientational orders of the selectively deuterated LC matrix and AuNP ligands, each separately followed by variable temperature deuterium NMR as a function of particle concentration, were also observed to be strongly correlated [4]. The mechanism of the nanoparticle structure formation is attributed to the coupling of the AuNP ligands to the LC matrix, inducing an isotropic-nematic biphasic state.