Mesoporous Titania Thin Film with Highly Ordered and Fully Accessible Vertical Pores and Crystalline Walls

Abstract

We report the preparation of mesoporous titania thin films with the R$\bar 3$m pore structure derived from the Im$\bar 3$m self-assembled ordering of the titania species and an EO(106)PO(70)EO(106) triblock copolymer. The films were spin-cast and then aged at 18 degrees C at a relative humidity of 70 %, which led to the orientation of the Im$\bar 3$m structure with the [111] direction perpendicular to the substrates. The [111] body-diagonal channels became vertical channels upon calcination at 400 degrees C, thus leading to thin films with vertical channels. The pores are ordered over a large area of up to 1 mum(2). The titania films can be formed on various types of substrates. By using a titania film formed on a Pt-coated Si wafer as a template, we produced by an electrochemical-deposition technique arrays of gold nanowires, whose morphology suggests that most of the pores of the titania thin films are accessible. The pore structure of vertical channels is stable up to 600 degrees C, at which temperature the wall materials crystallize into anatase.