Fluorescent polyurethane nanofabrics: a source of singlet oxygen and oxygen sensing

Polyurethane (PUR) nanofabrics based on nanofibers of average diameters in the range of 250-110 nm with different meso-tetraphenylporphyrin (TPP) loading (0.01-5 wt %) were prepared by an electrospinning process. The oxygen quenching of excited states and singlet oxygen-sensitized delayed fluorescence (SODF) of TPP were studied at different oxygen pressures. We found that TPP in PUR matrix is present in monomeric state, and it is easily accessed by oxygen. Analysis of the kinetics of the TPP triplet, singlet oxygen, and SODF indicates that repopulation of TPP fluorescent state includes reaction of singlet oxygen with TPP triplets. The integrated SODF achieved more than 20% of the prompt fluorescence for nanofabric loaded with 5 wt % TPP. The dependence of SODF intensity on the TPP concentration in nanofibers is nearly quadratic.