Effect of lanthanides on the spectral-luminescence properties and photoresistance of organic dyes in silicate sol-gel films

A sol-gel method is used to synthesize silicate films dyed in the sol stage with rhodamine C or methylene blue and further doped with cerium or lanthanum. It is shown that this sort of doping leads to a reduction in the peak intensity and a change in the shape of the S ₁←S ₀ band of the dyes, as well as to a shift in this band in a direction that depends on the H₂O: Si(OC₂H₅)₄ ratio. At the same time, the photoresistance of the rhodamine C molecules increases. The observed spectral changes are explained by the formation of supramolecules that include organic molecules, rare earth ions, and elements from the structural grid of the film, while the enhanced photoresistance is explained mainly by strengthening of the T ₁→S ₀ transitions in the dye. Fiz. Tverd. Tela (St. Petersburg) 41, 1979–1984 (November 1999)