Improved Singlet Oxygen Detection Sensitivity in Electron Spin Resonance Using a Spin-trap Agent Incorporated into a Water-soluble Polymer Film

2,2,6,6-Tetramethyl-4-piperidinol (TEMP) is a spin-trap agent for electron spin resonance (ESR) that is usually employed in solution. However, in this study, TEMP is mixed with hydroxypropyl methylcellulose (HPMC) to form a film for the detection of singlet oxygen in vacuo. The ESR intensity achieved is 3.3 times higher than that for a previously reported polyvinyl alcohol film. Furthermore, the diffusion of singlet oxygen into HPMC is shown to follow Fick's law, having a diffusion coefficient of ≈2.5 × 10−8 cm2 s−1.