Narrow-range optical pH sensors based on luminescent europium and terbium complexes immobilized in a sol gel glass

The metal-based emission of a series of luminescent europium and terbium co mplexes incorporating an aromatic chromophore is rendered pH-dependent eith er through perturbation of the aryl singlet or triplet energy or by modulat ing the degree of quenching of the lanthanide excited state. Systems exhibi ting each of these pathways have been incorporated in thin-film sot gel mat rixes and evaluated as pH sensors in static and flow analyses at constant i onic strength. pH-dependent intensity or ratiometric methods, for emission or excitation spectra, have been defined for lanthanide complexes incorpora ting substituted phenanthridine (pK(a)* from ca. 6.8 to 7.2) or 6-cyanophen anthridine-2-sulfonyl chromophores (pK(a) similar to 7.14 in human serum so lution) (lambda (exc) 365 nm, phiH(2)O = 7.2%).