Distributed Bragg reflectors from colloidal trilayer flake solutions

Abstract

The fabrication of highly reflective inorganic distributed Bragg reflectors (DBRs) from aqueous solutions of colloidal flakes is demonstrated. Our approach involves the deposition of compact or mesoporous TiO2-SiO2-TiO2 trilayers onto a patterned sacrificial layer. A subsequent etch-release of the patterned flakes into water results in a colloidal flake solution. Drops of this flake-containing solution are then deposited onto another substrate, where they self-assemble into stacks upon solvent evaporation. This method gives rise to high quality DBRs in a much quicker fabrication process compared to previously established methods and produces ordered DBRs of high reflectivity. Changing compact for mesoporous assemblies, the produced DBRs can be used for environmental refractive index sensing. The presented approach may open the way for the on-demand integration of stimuli-responsive DBRs into microfluidic and fiber-end sensing applications or allow the integration of highly reflective colloidal flakes with light emission and detection technologies.