Discrete O₂ sensors produced by a spotting method on polyolefin fabric substrates

New solid-state phosphorescent oxygen sensors produced by solvent spotting on hydrophilic polyolefin fabrics are described. The method comprises of a simple spotting of dye solution, followed by a short post-treatment of water washing and baking (<4 h), resulting in sensors with uniform distribution of dye molecules in a discrete spot. The resulting sensors exhibited high brightness, optimal lifetime signals (27-31 μs at 21 kPa and 49-53 μs at 0 kPa O₂), quasi-linear Stern-Volmer plots and temperature dependence. Compared to the commercial O₂ sensors (PS coating on the micro porous support), the new polyolefin-based sensors performed well, showing good wettability and fast response time in liquid (3 min for wetlaid and 7 min for spunbond PP vs. 32 min for the reference). The homogeneity of the sensors was confirmed by microscopic analysis using PLIM (phosphorescence lifetime imaging). Both sensors exhibit cross-sensitivity to humidity which is investigated in this paper through the use of confocal microscopy.