Luminescence of rhodamine B doped in silica films by evaporation-induced self-assembly

Abstract

Rhodamine B was embedded in a matrix of mesoporous silica films by the sol-gel method. A precursor sol containing tetraethoxysilane, ethanol, surfactant cetyltrimethylammonium bromide (CTAB), water, rhodamine B and acid catalyst was prepared by sol-gel. Depositing the precursor sol on a substrate wherein evaporation of solvent and water causes the formation of mesostructured films on the substrate surface by evaporation-induced self- assembly process. The nanocomposites films were obtained by embedded rhodamine B in the pores of mesoporous silica films. The mesoporous film was characterized by XRD and TEM, UV-VIS-NIR. The luminescence was measured and a red shift in the peak of the luminescence spectra compared with rhodamine B in the film and rhodamine B in water was observed, which may be interpreted as reflecting a decrease in the dipole moment of the exited molecule. The results show the luminescence action of rhodamine B in nanopores approach to single molecule's. This relates to the restriction of nanopores to organic molecules. The degree of aggregation decreases for the mesoporous silica films may be regarded as a hydroxylic, relatively polar environment, less polar than water although controversy still exists on the role of water in causing aggregation.