One-dimensional assembly of silica nanospheres mediated by block copolymer in liquid phase.

Colloidal silica spheres and their assembly processes are encountered in nature and numerous technological applications. We report here a novel and facile method to prepare highly anisotropic one-dimensional (1D) arrays of silica nanospheres (SNSs) in the liquid phase. Uniform-sized SNSs ca. 15 nm in size assemble into a 1D chain-like structure in the presence of a commercially available block copolymer. The 1D assembly in the liquid phase is evident from Cryo-TEM observations and time-dependent turbidity measurement of the suspension. The mode of the assembly has been systematically controlled by the concentration of the block copolymer, pH of the suspension, and the concentration of a salt added to the system. These results suggest the importance of the balance between electrostatic repulsion and block copolymer-mediated attractive interaction that are operative between particles in the formation of 1D array.