EFFECTS OF POLYMER MATRICES ON CALIBRATION FUNCTIONS OF LUMINESCENT OXYGEN SENSORS BASED ON PORPHYRIN KETONE COMPLEXES

The design of luminescent oxygen sensors is guided by optimizing sensi tivity and/or the form of the calibration function. Both qualities are governed by the molecular processes of luminescence quenching. To eva luate the influence of matrix effects, we prepared membranes based on oxygen-sensitive phosphorescent complexes of porphyrin ketones dissolv ed in plasticizer-free poly(vinyl chloride) (PVC) and polystyrene (PS) . In a PVC matrix, both platinum(II) and palladium(II) octaethylporphy rin ketones exhibited perfectly linear Stern-Volmer intensity plots an d almost single-exponential excited state decays. In a PS matrix, the sensitivity of palladium(II) octaethylporphyrin ketone was among the h ighest reported to date, Yet, slightly nonlinear Stern-Volmer plots an d nonexponential decays illustrate the significance of matrix effects of PS. Addition of plasticizers to PVC-based sensors allowed tuning of the oxygen sensitivity in a wide range, while the Stern-Volmer plots became pronouncedly nonlinear. For the plasticizer bis(2-ethylhexyl) a dipate, the decay profile was single-exponential in the absence but no nexponential in the presence of oxygen, which is attributed to a distr ibution of quenching rate constants.