Proceedings Article | 21 September 2011
Proc. SPIE. 8096, Plasmonics: Metallic Nanostructures and Their Optical Properties IX
KEYWORDS: Visible radiation, Titanium dioxide, Nanoparticles, Ultraviolet radiation, Particles, Crystals, Electrons, Silver, Transmission electron microscopy, Laser crystals
Due to their surface plasmon resonance silver nanoparticles are known to absorb visible light and give glasses
various colors. Grown in mesoporous titania films, they give the material a photochromic behaviour that can be used to
produce rewritable data carriers. On the one hand, UV light forms silver nanoparticles thanks to the photo-induced
generation of electrons by titania matrix. On the other hand, visible light oxidizes the silver nanoparticles via the
photoexcitation of electrons on Ag and their stabilization by oxygen molecules. The well controlled porosity of the
mesoporous films allows to tune the nanoparticles size and to obtain, under UV illumination, homogenous distributions
of small nanoparticles embedded within the titania matrix, which color the films. As all nanoparticles absorb light
similarly, the film can then be completely bleached under exposure to a visible laser beam whose wavelength falls in the
SPR band of the particles. Therefore, CW UV and visible focused-laser radiations, respectively, can repeatedly print and
completely erase colored micropatterns within TiO2/Ag films. The paper shows patterns printed under different
conditions, deals with the reproducibility of the process and the inscription stability, and explains the nanoscale
mechanisms, including silver migration during exposures, leading to the reversible color changes on the basis of TEM,
SEM, absorption spectroscopy and Raman micro-spectroscopy characterizations. This paper also evidences that CW
laser illuminations at higher intensity locally crystallize the titania matrix and investigates the influence of the
absorption-induced heating around nanoparticles.
