Preparation of fusion materials based on ionic liquids and cationic gold nanoparticles

Abstract

Fusion materials based on cationic gold nanoparticles mixed with ionic liquids were prepared. An anion exchange of the surface-capping ligand on the gold nanoparticles from a halogen anion to bis(trifluoromethanesulfonyl)amide (Tf 2 N) in an aqueous solution afforded nanoparticles showing infinite miscibility with Tf 2 N-based ionic liquids. The thermal decomposition temperature of the gold nanoparticle was elevated by 100 °C after the anion-exchange process. The ionic liquid-like structure of the surface-capping ligand with Tf 2 N anions led to a glassy solid material with a densely packed assembly of nanoparticles, in which a portion of nanoparticles formed superlattices. A fusion material of ionic liquid and gold nanoparticles with a gold content as high as 40 wt% was obtained by the co-solvent evaporation method using acetone. The stable dispersion of gold nanoparticles in the fusion materials with a high gold content was confirmed by the clear appearance of the plasmon absorption of gold nanoparticles in an optical microscopic image, as well as in an absorption spectrum. The use of an ionic liquid-based monomer yielded a gold nanoparticle-ionic liquid polymer composite, in which the gold nanoparticles showed a high thermal stability.