• nanocrystalline TiO2;
  • slow photons;
  • photonic crystals;
  • SnO2;
  • inverse opal;
  • stop-band reflection;
  • photo-catalyst


An nc-TiO2/SnO2 inverse opal composite membrane was fabricated, the photo-activity of which was significantly enhanced by utilizing both slow photons and stop-band reflection of the photonic crystal layer. The materials of the photonic crystal layer must be transparent in the area of adsorption edge of the nc-TiO2, so that SnO2, having much greater electronic band gap than TiO2, was used for the materials of the photonic crystal layer. The photonic band-gap of the SnO2 photonic crystal was designed at the semiconductor band gap of TiO2 to harvest slow photons in the interface between the SnO2 layer and the TiO2 layer. The two layer structure makes it possible to couple the stop-band reflectivity of the photonic layer to the photocatalyst. Composite membranes can improve solar energy harvesting and substantially improve photocatalysts for photolysis and photochemical degradation of environmental pollutants. © 2011 American Institute of Chemical Engineers AIChE J, 2012