Singlet oxygen generation under optical excitation of polytetrafluoroethylene

Abstract

Singlet oxygen together with radical reactions plays an important role in biochemistry of living organisms, and is one of the main active substances in photodynamic treatment of organs and body fluids. Along with traditional singlet oxygen photosensitizers based on biocompatible dyes, the singlet oxygen photogeneration ability of matrix materials such as organic solvents and metal oxide surfaces has recently been investigated. Despite a good compatibility with bio substances, polytetrafluoroethylene (also known under the trademark as Teflon®) remains unaddressed in these studies. Here we present our photoluminescence studies of singlet oxygen generation in polytetrafluoroethylene samples under ultraviolet and visible irradiation. We found a good singlet oxygen photogeneration with an efficiency no less and possibly exceeding it in carbon tetrachloride, a known singlet‑oxygen-retentive medium. Based on the results obtained, it is assumed that the phosphorescence of singlet oxygen is observed from the volume of polytetrafluoroethylene with direct optical excitation of oxygen adsorbed or dissolved in the structure of polytetrafluoroethylene by analogy with direct optical excitation of oxygen in the volume of various solvents. Cooling a PTFE sample down to −20 °C allows to enhance the singlet oxygen concentration in the polymer indicating the enthalpy of oxygen sorption of ΔHsorp = −1.51 kcal/mol. Our results can heighten medical interest to fluoropolymers and, in particular, to polytetrafluoroethylene making it a promising singlet oxygen generator for photodynamic uses.