Photochromism of spiropyran nanocrystals embedded in sol-gel matrices.
Spectroscopic and kinetic properties of a new photochromic medium, consisting of nanocrystals of spyropyran molecules (1,3-dihydro-1,3,3,5',6',pentamethyl-spiro[2H-indole-2,2'-[2H]pyrano [3,2-b]pyridinium] iodide) embedded in an organo-silicate sol-gel film, are presented and compared to microcrystals obtained by slow evaporation of a solvent. High photoconversion efficiencies for both kinds of crystals have been observed. In microcrystals, the photomerocyanine form absorbs at 570 nm with a fading rate of 5 h, in nanocrystals the photomerocyanine form absorbs at 535 nm with a fading rate of 41 h. Therefore, the crystalline structure of nanocrystals is different from the microcrystal one.
Spagnoli
Sylvie
S
Laboratoire de Spectrométrie Physique, Université Joseph Fourier, CNRS, BP 87, 38402, St Martin d'Hères Cedex, France. spagnoli@spectro.ujf-grenoble.fr
Block
Dominique
D
Botzung-Appert
Estelle
E
Colombier
Isabelle
I
Baldeck
Patrice L
PL
Ibanez
Alain
A
Corval
Anne
A