Cooperative Electric Alignment of Colloidal Graphene Oxide Particles with Liquid Crystalline Niobate Nanosheets

Abstract

Binary colloids of morphologically different two particle species cause phase separation containing liquid crystalline phases. Although electric alignment of colloidal nanosheets has been investigated for the colloidal systems consisting of single nanosheet species, that of binary nanosheet colloids has scarcely been examined. We report herein the electric alignment of aqueous binary colloids composed of niobate (NB) nanosheets from K₄Nb₆O₁₇ and commercially available graphene oxide (GO) platelets. The NB–GO binary colloids show multiphase coexistence involving liquid crystalline phases induced by the NB nanosheets, whereas the employed GO particles do not contribute to the liquid crystallinity. The NB nanosheets in the binary colloids are electrically aligned in parallel to an AC voltage (1 kV cm⁻¹ peak to peak, 50 kHz) applied to the sample. When the concentration of GO in the binary colloids is low enough, the GO particles are also electrically aligned although they hardly respond to electric field in the absence of NB nanosheets. Combined optical microscopy of bright-field, polarized, and fluorescence observations demonstrates that isolated GO particles are dragged by the aligning motion of the NB nanosheets forming liquid crystalline domains. The results indicate that collective motions of colloidal nanosheets can make participation of isolated particles.