(176c) Columnar Self-Assembly of Nanodisks

Size- and shape-monodisperse CuS nanodisks, 5 nm thick and 15 nm in diameter, were synthesized by arrested precipitation. The nanodisks are sterically-stabilized and dispersible in organic solvents. The disks were found to self-assemble into a columnar phase when drop cast from a concentrated dispersion. The columnar organization consists of disks stacked into columns, which are hexagonally close-packed. The columnar structure was confirmd by imaging (TEM and SEM) and small angle X-ray scattering (SAXS). Time-dependent synchrotron SAXS measurements showed the evolution of the columnar phase as the particles were drop cast from a dispersion onto a substrate. Grazing incidence SAXS (GISAXS) measurements confirmed the columnar order of the disks and also that that columns are ordered perpendicular to the substrate with the disk faces flat on the surface. This is the first observation of columnar order of disk-like colloidal particles in this small size range that we are aware of.