Optical properties of BBOT-doped silica films prepared via sol-gel processing

Optical and photoluminescent properties of an 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene (BBOT) silica films are reported here. The materials were prepared via a sol-gel process in combination with dioxane as a co-solvent. The doped silica can be uniformly dispersed as a visibly transparent film, which displays bright blue photoluminescence from the film. Excited state of BBOT was found to have an increased polarity as a bathochromic shift was observed when the solvent polarity increased. This acted as a probe to monitor the interactions within the BBOT-doped silica matrices. A strong interaction was found between the silica and the BBOT molecules through the Stoke's shift and the broadening in the spectra. However, the shift in photoluminescence as increased in concentrations was due to the aggregation or micro-crystallization of the dopant. No distinct concentration quenching was observed in the concentration range studied. This investigation demonstrated that the silica prepared via sol-gel process might be used as an excellent host for organic light-emitting materials. This opens a new route to prepare novel materials in combination with the excellent stability of inorganic materials and the tunability of the organics. (c) 2006 Elsevier B.V. All rights reserved.