Optical solid-state oxygen sensors using metalloporphyrin complexes immobilized in suitable polymeric matrices

Porphyrins based on platinum(II) (PtOEP), palladium(II) (PdOEP) octaethylporphyrin and Ru(II) (RuOEP) octaethylporphyrin pyridyl carbonyl are immobilized in poly(ethylene glycol)ethyl ether methacrylate (pPEGMA) solid matrices, which possess two different average molecular weights. The phosphorescence quenching by molecular oxygen in the resulting sensors is studied. Our results point out that PdOEP-based devices exhibit higher sensitivity towards O2 but have a lower photostability than PtOEP samples. Whereas, RuOEP shows evident photodegradation and poor sensitivity compared to the other lumophores tested. A comparison between the polymeric supports having distinct viscosity shows that the less viscous medium produces better performances of the resulting device. In particular, the decreasing average molecular weight, than the viscosity, of the polymer produces effects quite similar to those obtained with the use of a plasticizer. Finally, all systems analyzed in this work exhibit linear Stern-Volmer response and similar slopes are found at different emission wavelengths, suggesting that the chromophores are quite homogeneously dispersed in pPEGMA.