Self-Assembly and Integration of Ordered, Robust, Three-Dimensional Gold Nanocrystal/Metal Oxide Superlattices

We report the synthesis of a new nanocrystal (NC) mesophase through self-assembly of water-soluble NCmicelles with soluble silica. The mesophase comprises gold nanocrystals arranged within a silica matrix in a facecentered-cubic lattice with cell dimensions that are adjustable through control of the nanocrystal diameter and/or the alkane chain lengths of the primary alkanethiol stabilizing ligands or the surrounding secondary surfactants. Under kinetically controlled silica polymerization conditions, evaporation drives self-assembly of NCmicelles into ordered NC/silica thin film mesophases during spin-coating. The intermediate NC-micelles are watersoluble and of interest for bio-labeling. The robust, 3-D NC mesophase solids are of interest for development of collective optical and electronic phenomena, and, importantly, for the integration of nanocrystal arrays into device architectures. Initial experiments on a MOS capacitor fabricated with an ordered gold NC/silica ‘oxide’ demonstrated charge storage on the gold nanocrystals and discharge behavior dominated by electron transport within the ordered gold nanocrystal array.