1,3-diphenylisobenzofuran (DPBF), a colorimetric agent that reacts with singlet oxygen to produce a colorless product, was used to detect 1O2 production. Fabric samples (3 cm × 3 cm) were first soaked with 10 mL ethanol for 30 min to remove any leachable thionine, and were then placed in the bottom of a 10 mL beaker containing 5 mL 150 mM DPBF solution in ethanol. The sample was illuminated by a handheld laser (532 nm, 85 ± 1 mW/cm2; HTPOW Laser Limited) for 10 min, and the UV–visible spectrum of the solution was recorded every 2 min at 410 nm.