title: New fluorescent pH sensors based on covalently linkable PET rhodamines.
abstract: 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 Φ(F)≈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 Al(2)O(3) as reference material is presented.
authors.affiliation: Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, Stremayrgasse 9, A-8010 Graz, Austria.
authors.forename: Daniel
authors.initials: D
authors.lastname: Aigner
authors.forename: Sergey M
authors.initials: SM
authors.lastname: Borisov
authors.forename: Francisco J Orriach
authors.initials: FJ
authors.lastname: Fernández
authors.forename: Jorge F
authors.initials: JF
authors.lastname: Fernández Sánchez
authors.forename: Robert
authors.initials: R
authors.lastname: Saf
authors.forename: Ingo
authors.initials: I
authors.lastname: Klimant
mesh_terms: D004579:Electron Transport; D005456:Fluorescent Dyes / Q000737:chemistry*; D054879:Halogenation; D006863:Hydrogen-Ion Concentration; D055668:Photochemical Processes; D012235:Rhodamines / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D012235:Rhodamines; D014867:Water