Sculpting Silica Colloids by Etching Particles with Nonuniform Compositions.

We present the synthesis of new shapes of colloidal silica particles by manipulating their chemical composition and subsequent etching. Segments of silica rods, prepared by the ammonia catalyzed hydrolysis and condensation of tetraethylorthosilicate (TEOS) from polyvinylpyrrolidone loaded water droplets, were grown under different conditions. Upon decreasing temperature, delaying ethanol addition, or increasing monomer concentration, the rate of dissolution of the silica segment subsequently formed decreased.

Self-assembly of colloids with liquid protrusions.

A facile and flexible synthesis for colloidal molecules with well-controlled shape and tunable patchiness is presented. Cross-linked polystyrene spheres with a liquid protrusion were found to assemble into colloidal molecules by coalescence of the liquid protrusions. Similarly, cross-linked poly(methyl methacrylate) particles carrying a wetting layer assembled into colloidal molecules by coalescence of the wetting layer.