Controlled self-assemblies of clay silicate platelets by organic salt modifier

Abstract

We observed unique cubic microstructures and hierarchical dendrite formation from clay silicate platelet self-piling. The fundamental units of silicate platelets with dimensions of ca. 80 × 80 × 1 nm were previously prepared from natural clay stacks. By ionic exchange with the hydrochloride salt of diethylene glycolamine, the platelets could be connected with polar organic moieties. The self-piling of these silicate platelets generated cubic arrays of 1–4 μm in size that differed from the rod-like microstructures of 10–60 μm in length and 0.5–1.5 μm in diameter for non-modified platelets. The cubic self-assemblages were characterized to be hollow in structure by energy dispersive X-ray spectrometry for elemental analysis, scanning electron microscopy, and transmission electron microscopy. Dendrite arrays were further observed over a large area of a millimeter square, indicating high regularity of the cube unit interconnection. Both charge attraction and organic interaction had shifted the platelet piling directions, favoring 3-D cubes and further facilitating the formation of hierarchical dendrites.