Journal
TALANTA
Volume 99, Issue -, Pages 194-201Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.talanta.2012.05.039
Keywords
pH sensor; Fluorescence; Rhodamine; Photoinduced electron transfer; Covalent dye coupling; Click chemistry
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Funding
- Austrian Science Fund FWF [P 21192-N17]
- Spanish Ministry of Education [AT2009-0019]
- Austrian Science Fund (FWF) [P 21192] Funding Source: researchfish
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A new class of rhodamines for the application as indicator dyes in fluorescent pH sensors is presented. Their pH-sensitivity derives from photoinduced electron transfer between non-protonated amino groups and the excited chromophore which results in effective fluorescence quenching at increasing pH. The new indicator class carries a pentafluorophenyl group at the 9-position of the xanthene core where other rhodamines bear 2-carboxyphenyl substituents instead. The pentafluorophenyl group is used for covalent coupling to sensor matrices by click reaction with mercapto groups. Photophysical properties are similar to classical rhodamines carrying 2'-carboxy groups. pH sensors have been prepared with two different matrix materials, silica gel and poly(2-hydroxyethylmethacrylate). Both sensors show high luminescence brightness (absolute fluorescence quantum yield Phi(F) approximate to 0.6) and high pH-sensitivity at pH 5-7 which makes them suitable for monitoring biotechnological samples. To underline practical applicability, a dually lifetime referenced sensor containing Cr(III)-doped Al2O3 as reference material is presented. (C) 2012 Elsevier B.V. All rights reserved.
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