Copper(I) complexes as alternatives to iridium(III) complexes for highly efficient oxygen sensing

Cu(i) complexes outperforming Ir(iii) complexes for optical oxygen sensing are demonstrated, which creates new opportunities for low cost sensors.</p

New fluorescent pH sensors based on covalently linkable PET rhodamines

Financial support from the Austrian Science Fund FWF (Project no. P 21192-N17) and from the Spanish Ministry of Education (Joint Project no. AT2009-0019) is gratefully acknowledged. The authors thank the Institute of Organic Chemistry, Graz University of Technology, particularly Jana Rentner, MSc for kind support in performing LC-MS. Furthermore, we thank Johann Pichler, Institute of Inorganic Chemistry, Graz University of Technology, for acquiring 19F-NMR spectra, as well as Sarah Schiller and Stefan Schobesberger.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.Austrian Science Fund (FWF) P 21192-N17Spanish Government AT2009-001