Convective self-assembly to deposit supported ultra-thin mesoporous silica films

Abstract

For practical consideration in applying mesoporous films for sensors, it is ideal to fabricate thinner films to achieve fast transport and therefore rapid response. Here we report a new, facile method to deposit mesoporous silica films with thickness less than 100 nm through combining convective self-assembly and surfactant/silica self-assembly. Through an interfacial capillarity defined in the wedge between two substrates, a meniscus of solutions containing silicate, surfactant, alcohol, and water is formed. While the solvent evaporates during the film formation, the solution from the bulk droplet spreads to the drying region, enriching the surfactant/silica concentration at the edge of the meniscus by the convective flux of solvent. The continuous evaporation, spreading, and enriching induce surfactant and silica self-assembly in the bulk droplet to form an ordered surfactant/silica liquid crystal mesophase film. After calcination, supported ultra-thin films are formed containing interconnected mesopore channels with high surface areas. The combined self-assembly process relies on the evaporation of the solvents to form ordered mesostructures, which enables the deposition of patterned films and ultimately makes this combined technique ideal for device fabrication.