Determination of oxygen permeabilities in thin polymer films using quenching of upconverted fluorescence in porphyrins

Abstract

Proof-of-principle is demonstrated for a method of measuring the oxygen diffusion properties of thin polymer films based on quenching of the delayed upconverted S2 fluorescence of Zn(II) meso-tetraphenylporphine (ZnTPP). Empirical oxygen diffusion coefficients and permeability coefficients for poly(vinyl alcohol) (PVA) have been computed using Stern–Volmer kinetics in the steady-state regime and a nonlinear gas solubility model in the time domain. Simplified dual-mode theory has been used to calculate crude theoretical oxygen permeability coefficients to compare with the experimental values. It is confirmed that oxygen permeability in the PVA matrix is controlled largely by the characteristics of the polymer matrix, particularly its water content and distribution.