Coffee stain-driven self-assembly of mesoporous rings

Coffee stain-driven self-assembly is a general non equilibrium phenomenon which leaves ring-like structures upon evaporation of a colloidal droplet; we have used mesoporous monodispersed beads to form rings with a particular close packed monolayer structure. The mesoporous beads have been characterized by transmission electron microscopy which has revealed a porous radial structure with pores of around 3 nm in diameter. During evaporation the mesoporous beads are driven to organize in circular rings which show a 2D long-range ordered structure in the outer part. Arrays of mesoporous rings have been easily produced by casting small colloidal droplets on silicon and soda-lime glass substrates, after solvent evaporation, the rings are stable towards washing with variety of solvents. Absorption of fluorescent molecules into the mesoporous rings has been preliminary studied for lithography-free fabrication of micro sensing arrays. The rings have been used as functional “pits” for droplets containing fluorescent analyte. After removal of the droplets, the rings showed a strong fluorescence resulting from the analyte absorption.

Mesoporous monodispersed beads have been self-assembled through coffee stain effect to form rings with a close packed 2D hexagonal monolayer structure. The mesoporous rings have been tested as a device for absorbing fluorescent probe molecules.Figure optionsDownload as PowerPoint slideHighlights
► Stain effect was used to self-organize mesoporous monodispersed beads.
► Mesoporous ring arrays were obtained by evaporation of colloidal droplets.
► Absorption of fluorescent dye into the rings was studied for fabrication of sensing arrays.