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 ΦF≈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.

The complex [Cu(xantphos)(dmp)][PF6] (dmp = 2,9-dimethyl-1,10-phenanthroline) in a nanostructured metal oxyde matrix shows better sensitivity to oxygen (KSV = 9.74 ± 0.87 kPa(-1) between 0 and 1 kPa pO2 and 5.59 ± 0.15 kPa(-1) between 0 and 10 kPa pO2) than cyclometallated iridium complexes in the same conditions.

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We describe a Hg 2+ -selective sensing film based on the incorporation of a spirocyclic phenylthiosemicarbazide rhodamine 6G derivative (called FC1) into a novel hydrophilic water-insoluble copolymer synthesized by Reverse Atom Transfer Radical Polymerization. It is demonstrated that the chemodosimeter preserves its sensing ability and displays intense fluorescence in the presence of mercury(II) after being immobilized in the novel MMA-co-HEMA water insoluble linear copolymer containing 29.6% HEMA. This paper describes the synthesis and characterization of the MMA-co-HEMA copolymer, and the careful optimization of all the instrumental and experimental variables which can affect the sensitivity of the sensing film. It responds to Hg 2+ concentrations in water between 0.9 and 12 mM, with a detection limit of 0.3 mM Hg 2+ and the response is highly selective to Hg 2+ and methylmercury. The applicability of the sensing film has been demonstrated by analysing two real samples (tap and mineral waters) obtaining recovery percentages close to 100% with RSD lower than 5%.