Periodically ordered meso- and macroporous SiO2 thin films and their induced electrochemical activity as a function of pore hierarchy

Silica thin films with variable pore hierarchy (different combinations of small meso-, large meso-, and macropores) were produced via evaporation induced self-assembly in a one-pot synthesis. A suitable block copolymer and an ionic liquid served as porogens for the generation of different types of mesopores whereas polymethylmethacrylate particles were used as macrotemplate. The silica architectures were characterized by various state-of-the-art techniques, such as 2D-SAXS, TEM, SEM, AFM, krypton and nitrogen sorption. Moreover, electrochemical functionalization was utilized as a tool to study the hierarchy-property relationship. Thus, hierarchically porous films prepared on FTO-coated glass were post-synthetically silylated and electro-chemically active ferrocene groups subsequently grafted onto the pore walls. Cyclic voltammetry was used to monitor the induced electrochemical activity as a function of variations in the pore hierarchy. It turned out that multimodal pore systems possess a relatively higher electrochemical response due to better connection between the pores and higher surface area.