Effect of Temperature on Photophysical Properties
of Polymeric Nanofiber Materials with Porphyrin Photosensitizers
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Abstract
Electrospun nanofibers possess large
surface to volume ratios,
high porosity, and good mechanical properties that are necessary for
biological applications. We prepared different types of photoactive
polymeric nanofiber materials with encapsulated or externally bound
porphyrin photosensitizers. The kinetics of formation and the decay
of both singlet oxygen O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) and porphyrin triplet states that are generated by irradiation
of nanofiber materials in an air atmosphere or in an air-saturated
aqueous solution were measured and evaluated by luminescence and transient
absorption spectroscopy in the temperature range between 5 and 60
°C. We found shortening of the O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) lifetime and a significant increase in singlet oxygen-sensitized
delayed fluorescence at higher temperatures. These photophysical data
show an increase in the diffusion coefficient for O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) with temperature, and they are consistent
with a stronger antibacterial effect of the nanofiber material on Escherichia coli at higher temperature
