The Optical Properties of Porous Opal Crystals Infiltrated with Organic Molecules

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Abstract
A fluorescent dye and a photochromic dye were infiltrated into polycrystalline samples of porous opal in order to determine the effects of opal repeat dimension on the optical properties of the dyes. These opals consist of faulted face-centered-cubic arrays of monodispersed, nanoscale SiO2 spheres. The observed absorption and fluorescence of tris(8-hydroxyquinoline) aluminum (Alq3) depended on the lattice constant of the opal. The Alq3 exhibited a blue shift of the absorption edge and a decrease of fluorescence intensity with decreasing lattice constant. Also, the stability of the photochromic behavior of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl) ethene (CMTE) increased remarkably inside the opal matrix. These characteristics are possibly due to the interaction between the nano-structure-confined dyes and the surfaces of the SiO2 spheres.