Synthesis of monodispersed silica microparticles in a microreactor for well-organized colloidal photonic crystals

Abstract

In this report, we describe the syntheses of monodispersed microparticles of silica, that is, polysilicate, in a microreactor based on Stöber method for fabrication of the well-organized colloidal photonic crystal (CPC) films with visible reflection properties. Although the bath synthesis of silica microparticles gave the relatively high coefficient of variation (CV) value of 14.1% in the particle diameter, we successfully improved the CV value from 14.1% to 5.5% by the microfluidic synthesis of silica microparticles in a flow reactor, arising from the separation of nucleation and growth processes. When we fabricated various CPC films of the silica microparticles by the vertical deposition technique, each CPC film showed a characteristic peak of Bragg reflection with a high reflectance over ~60% in the visible wavelength range. Moreover, we found that the experimental reflection spectra of CPC films have consistent with the theoretical spectra calculated by the scalar wave approximation (SWA) technique.