title: N3-dye-induced visible laser anatase-to-rutile phase transition on mesoporous TiO2 films.
abstract: Titanium dioxide has been extensively used in photocatalysis and dye-sensitized solar cells, where control of the anatase-to-rutile phase transformation may allow the realization of more efficient devices exploiting the synergic effects at anatase/rutile interfaces. Thus, a systematic study showing the proof of concept of a dye-induced morphological transition and an anatase-to-rutile transition based on visible laser (532 nm) and nano/micro patterning of mesoporous anatase (Degussa P25 TiO(2)) films is described for the first time using a confocal Raman microscope. At low laser intensities, only the bleaching of the adsorbed N3 dye was observed. However, high enough temperatures to promote melting/densification processes and create a deep hole at the focus and an extensive phase transformation in the surrounding material were achieved using 1s laser pulses of 25-41 mW/cm(2), in resonance with the MLCT band. The dye was shown to play a key role, being responsible for the absorption and efficient conversion of the laser light into heat. As a matter of fact, the dye is photothermally decomposed to amorphous carbon or to gaseous species (CO(x), NO(x), and H(2)O) under a N(2) or O(2) atmosphere, respectively.
authors.affiliation: Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, Butanta, CEP 05508-000, São Paulo, SP, Brazil.
authors.forename: André L A
authors.initials: AL
authors.lastname: Parussulo
authors.forename: Manuel F G
authors.initials: MF
authors.lastname: Huila
authors.forename: Koiti
authors.initials: K
authors.lastname: Araki
authors.forename: Henrique E
authors.initials: HE
authors.lastname: Toma