Preparation of ordered porous SnO 2 films by dip-drawing method with PS colloid crystal templates

Abstract

Ordered macroporous SnO 2 thin films were fabricated by using colloid crystal template of polystyrene (PS) spheres. Efficient dip-drawing method was used in both PS template assembly and the fabrication of porous structure. The PS templates were orderly assembled on clean glass substrates through colloid crystallization of monodisperse PS latex spheres, which were synthesized by an emulsion polymerization technique. The porous SnO 2 thin films were prepared through filling SnO 2 precursor sol into the spaces among the close-packed PS templates, and then annealing at 500 °C to remove the PS spheres and form SnO 2 crystal wall. The forming mechanism of PS templates through dip-drawing method was explained based on three driving forces existing in the assembly processes. The SnO 2 sol concentration and PS sphere size had important effects on formation of ordered porous structure The X-ray diffraction (XRD) spectra indicated the thin film was rutile structure and consisted of nanometer grains. The transmittance spectrum showed that optical transmittance kept above 80% beyond the wavelength of 440 nm. Optical band-gap of the porous SnO 2 film was 3.68 eV.