Spontaneous Preparation of Monodispersed, Structural Colored, Spherical Particles by Rotational Stirring

Abstract When rotational stirring was applied to an electrically neutral aqueous suspension containing negatively charged, monodispersed silica fine particles and a positively charged polyelectrolyte, monodispersed, spherical particles with a size of several hundred micrometers were obtained. Conditions such as the rotational stirring speed, solute concentration, and total suspension amount were examined to clarify the conditions under which the monodispersed, spherical particles can be obtained. Spherical particles with a uniform size were obtained because the solutes create aggregates by electrostatic interactions, and the flow of the suspension from rotational agitation disperses the aggregates. Additionally, the obtained monodispersed, spherical particles contained monodispersed silica fine particles in submicron size aggregates with short‐range order. We found that monodispersed, spherical particles with a vivid structural color could be prepared by incorporating a small amount of a black substance in the spherical particles. Because monodispersed, spherical particles with various colors can be created using silica, polymer, and carbon, which are non‐toxic materials, they may be useful as new, environmentally safe pigments.