title: The relationship between photocatalytic activity and photochromic state of nanoparticulate silver surface loaded titanium dioxide thin-films.
abstract: Anatase titania thin-films were prepared by a modified spray-pyrolysis method. Glass substrates were coated at room temperature with an aerosol-spray of a titania sol-gel solution and then annealed at 500 °C to form rough, transparent, crystalline thin-films of anatase TiO(2). Silver nanoparticles were deposited on the surface of these films by a photo-assisted deposition method; films were dip-coated in methanolic solutions of silver nitrate salt and then photo-irradiated for 5 h with UVC light. The AgNO(3) concentration was adjusted to create an array of films with varying silver loadings. The films displayed photochromism; changing colour to orange-brown in UV-light to colourless under white light. The rates of photochromic change, when subjected to four different lighting conditions (UVC, UVA, white light and dark), were analysed by UV-visible spectroscopy. By assessing the photocatalytic activity to these light sources it was found that the initial photochromic state of the material had a profound effect on the films photocatalytic ability. This effect was more pronounced in the more concentrated silver loaded films; where significant enhancements in photoactivity occurred when reactions were initiated from the photo-reduced state. The mode of improved photocatalysis was attributed to the photo-generated electron trapping by silver nanoparticles, which stabilised photo-generated holes and drove photo-oxidation processes. We believe this is the first study in which the relationship between the photochromic state of a thin-film and its subsequent photocatalytic activity is reported.
authors: Materials Chemistry Research Centre, Department of Chemistry, University College London, 20 Gordon Street, London, UK WC1H 0AJ.
authors: Andreas
authors: A
authors: Kafizas
authors: Charles W
authors: CW
authors: Dunnill
authors: Ivan P
authors: IP
authors: Parkin
mesh_terms: D002384:Catalysis; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D018625:Microscopy, Atomic Force; D055668:Photochemical Processes; D012834:Silver / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D014025:Titanium / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D012834:Silver; D014025:Titanium