Effect of gelation and ball milling on the optical absorption and emissionof macrilon yellow dye molecules trapped in silica prepared by the sol-gelmethod

Organic dye molecules (macrilon yellow) were embedded into silicon dioxide matrix by the sol-gel method. Optical measurements at room temperature of a bsorption and emission were performed at different steps of the gelation pr ocess, starting when the suspension was liquid and finishing when it got th e solid state. Optical absorption spectra show the dependence with gelation process and with the milling process. The intensity of the absorption band at 420 nm increases with the viscosity of the suspension. This effect is m ore important for the milled suspension, working with the same pigment conc entration. The gelation and the milling processes also affect the emission spectra. The emission spectra has two bands centered at about 520 and 560 n m. During gelation the relative intensity of the band at about 560 nm incre ases respect the band at about 520 nm. The emission band of the sample made with milled suspension is three times more intense than that of the not mi lled suspension. (C) 2000 Elsevier Science B.V. All rights reserved.