Browsing by Author "Alp S."

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    Photophysical and photochemical characteristics of an azlactone dye in sol-gel matrix; a new fluorescent pH indicator
    (2003) Ertekin K.; Karapire C.; Alp S.; Yenigül B.; Içli S.
    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 (Qf=0.296) and fluorescence emission lifetime (τf=0.47 ns) compared to Qf=0.0027-0.0025 and τf=0.02-0.03 ns for solutions in MeCN and THF. The acidity constant of DPO was 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. © 2002 Elsevier Science Ltd. All rights reserved.
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    Glucose sensing employing fluorescent pH indicator: 4-[(p-N,N-dimethylamino)benzylidene]-2-phenyloxazole-5-one
    (2005) Ertekin K.; Cinar S.; Aydemir T.; Alp S.
    The proton sensitive azlactone derivative; 4-[(p-N,N-dimethylamino) benzylidene]-2-phenyloxazole-5-one (DPO) exhibits high quantum yield, excellent photostability, and high molar absorptivity in a sol - gel matrix. In this work, two different DPO containing constructions were tested and evaluated as glucose sensors. In the first, both glucose oxidase (GOx) and azlactone derivative were incorporated into a single tetraethylorthosilicate (TEOS) based sol - gel phase. In the second, TEOS and 3-aminopropyltriethoxysilane (APTEOS) containing dye-doped sol - gel layer was covered with GOx entrapped sol - gel (the two-layer configuration). The monolayer configuration has the fastest response time (τ90 = 20 s) but suffers from leaching upon prolonged use. Response time and dynamic working range of the cross-linking agent containing two-layer configuration are 40 s and 0.1-15 mM glucose, respectively. The resulting glucose sensor was characterized by high sensitivity, low interference from acidogenic species, and a working lifetime of at least 90 days. © 2004 Elsevier Ltd. All rights reserved.