Phosphorescent oxygen sensors produced by spot-crazing of polyphenylenesulfide films

Phosphorescent oxygen sensors based on PtBP and PdBP dyes encapsulated in polyphenylenesulfide (PPS) films by the spot-crazing method are described. The new polymer matrix enables simple, one-step production of discrete, high-performance O₂ sensors using a low toxicity solvent 2-butanone, low overall strain (8%), low amounts of solvent and precise spatial control. The resulting nano-structured sensor materials display markedly enhanced brightness, high photo-, mechanical and chemical stability. Their structural and physico-chemical properties were characterized by differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), optical microscopy and phosphorescence lifetime imaging microscopy (PLIM). The PPS sensors show a high degree of lateral and in-depth homogeneity on the micro- and macro-scale, as revealed by confocal microscopy, linear Stern-Volmer plots and single-exponential decays. Operating in phosphorescence lifetime mode, optimised sensors show stable O₂ calibrations in the range of 0.1-100 kPa O₂, low temperature dependence (linear in the range 10-50 °C), low cross-sensitivity to humidity and high reproducibility (RSD 1.5% at 21 kPa and 0.5% at zero O₂). This technology facilitates the production of low-cost disposable O₂ sensors and their integration in large scale industrial applications such as packaging.