Effect of Lumophore and Plasticiser Concentration on The Heterogeneity of Oxygen Quenching in Thin Film Oxygen Sensors

Kinetic heterogeneity of the luminescence decay and oxygen quenching of Pt and Pd octaethylporphyrin/ethyl cellulose (OEP/EC) thin film oxygen sensors has been investigated with respect to (a) concentration of lumophore and (b) addition of plasticiser. The source of kinetic heterogeneity shown by PtOEP films under N₂ is a monomer–dimer equilibrium in which the dimer luminescence decays with k = 0.0527×10⁶ s⁻¹ and the monomer luminescence with k = 0.0101×10⁶ s⁻¹ and K _D = 790 (±20) mol dm⁻³. For PdOEP/EC films there is no detectable aggregation and luminescence decays under N₂ show good fits to single exponential curve fits at all concentrations studied. The addition of either tripbutyl phosphate or dimethylphthalate as plasticiser does not decrease kinetic heterogeneity for oxygen quenching of luminescence in the films.