Photophysical and photochemical characteristics of an azlactone dye in sol-gel matrix;: a new fluorescent pH indicator

The photophysical and photochemical properties of an azlactone derivative, 4-(p-N,N-dimethylaminophenylmethylene)-2-phenyl-5-oxazolone, (DPO) in a sol-gel matrix have been examined, The fluorescence quantum yield, radiative lifetime, fluorescence lifetime, fluorescence rate constant and singlet energy values of the DPO dye were determined in a modified tetraethyl orthosilicate (TEOS) solid matrix by absorption and emission spectroscopy and obtained data were compared with the results of measurements in acetonitrile (MeCN) and tetrahydrofuran (THF) solution. The sol-gel matrix enhanced the fluorescence quantum yield (Q(f) = 0.296) and fluorescence emission lifetime (tau(f) = 0.47 ns) compared to Q(f) = 0.0027-0.0025 and tau(f) = 0.02-0.03 ns for solutions in MeCN and THF. The acidity constant of DPO vas found to be as pKa = 5.1 in the transparent sol-gel matrix. The dye doped sol-gel exhibited a pH sensitivity in pH range 3.0-7.0. (C) 2002 Elsevier Science Ltd. All rights reserved.