title: Chemical growth and photochromism of silver nanoparticles into a mesoporous titania template.
abstract: Elaboration of mesoporous titanium oxide film supporting silver nanoparticles is described. Mesoporous titanium oxide films are characterized by TEM analysis. Titania films are infiltrated with a silver salt solution and chemical reduction treatments are performed using either a NaBH(4) or a formaldehyde solution. Infiltrated films are then characterized by TEM, SEM, AFM, UV-visible spectroscopy, X-ray diffraction, and Rutherford Backscattering Spectrometry (RBS). The utilization of a mesoporous titania substrate allows to control the nanoparticle size and the interparticle distance. RBS experiments provide the evidence that NaBH(4) treatment induces a strong accumulation of silver nanoparticles in the subsurface of the layer, while formaldehyde treatment induces the formation of silver nanoparticles embedded into almost the whole depth of the titania film. Large silver nanocrystals are also formed at the film surface whatever the reducer used. A broad visible absorption band related to the surface plasmon resonance (SPR) is obtained in both cases and is strongly red-shifted compared to the SPR obtained for silver nanoparticles inside a silica matrix. Moreover, irradiation with visible light causes the photooxidation of silver nanoparticles by titania and a complete discoloration of the material. The photooxidation is related to a drastic decrease in the silver nanoparticle size and is found to be reversible, particularly in the case of the material obtained by the formaldehyde reduction.
authors.affiliation: Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, Université Claude Bernard, Lyon 1, 43 Boulevard 11 novembre 1918, 69622 Villeurbanne, France. laurence.bois@univ-lyon1.fr
authors.forename: Laurence
authors.initials: L
authors.lastname: Bois
authors.forename: Fernand
authors.initials: F
authors.lastname: Chassagneux
authors.forename: Yann
authors.initials: Y
authors.lastname: Battie
authors.forename: François
authors.initials: F
authors.lastname: Bessueille
authors.forename: Laurent
authors.initials: L
authors.lastname: Mollet
authors.forename: Stéphane
authors.initials: S
authors.lastname: Parola
authors.forename: Nathalie
authors.initials: N
authors.lastname: Destouches
authors.forename: Nelly
authors.initials: N
authors.lastname: Toulhoat
authors.forename: Nathalie
authors.initials: N
authors.lastname: Moncoffre