Absorption, emission and lifetimes of [2,2′ -bipyridyl]-3,3′-diol in sol-gel glasses and in polymethylmethacrylate

Spectral behaviour and quantum yields of [2,2′-bipyridyl]-3,3′ -diol (BP (OH)₂) in sol-gel glasses modified by organic sidegroups were studied and compared with the properties of BP (OH)₂ in solutions, in a plain sol-gel glass and in polymethylmethacrylate (PMMA). Fluorescence intensity of the dye in a fresh sol-gel glass is similar to that in water while the corresponding blue-shift is smaller and hints at the "cage effect". The overall spectral behaviour of the dye in organically modified sol-gel glasses is similar to that observed in some polar solvents and in PMMA, while the fluorescence intensity is higher and lifetimes are longer. This increase is ascribed to the rigidity of the silica-polymer network in these glasses.