Optimizing Sol−Gel Infiltration and Processing Methods for the Fabrication of High-Quality Planar Titania Inverse Opals

We developed a simple sol−gel chemistry-based opal infiltration method for the fabrication of high-quality planar titania photonic crystals. Polystyrene synthetic opals were infiltrated with a hydrophobic and air/moisture-stable liquid titania precursor. The high stability and hydrophobicity of the titania precursor enabled a new “lift-off/turn-over” backfilling technique that after calcination gives planar titania inverse opals with a flat and completely open surface, without the need for additional processing steps to remove any excess surface coating of the backfilling material. We also compare two different infiltration strategies and their influence on the structural and photonic properties. The obtained inverse opals display excellent photonic properties as evidenced by the presence of first-, second-, and third-order Bragg reflection peaks in accordance with theoretical photonic band structure calculations.