Figure 2.

Qualitative and quantitative determination of radicals formed during the photocatalytic process. A) EPR spectra recorded during the illumination of rutile Au‐TiO₂ in water with methanol for 20 min. Signals marked with an asterisk (★) belong to the oxidation product of DMPO, 5,5‐dimethyl‐2‐oxopyrroline‐1‐oxyl (DMPOX).12 Signals marked with triangles (▾) belong to the spin adduct ^.DMPO–OH, and signals marked with circles (•) belong to the spin adduct ^.DMPO–CH₂OH from methanol.13 Reaction conditions: [Au‐TiO₂]=5 g L⁻¹, [DMPO]=30 mm, [methanol]=100 mm, RT, under illumination. B) Time course of the photocatalytic umbelliferone generation from coumarin as a specific detection method for ^.OH radicals. Reaction conditions: 60 mm phosphate buffer (pH 7), [Au‐TiO₂]=5 g L⁻¹, [coumarin]=0.1 mm, [methanol]=0 (⧫) or 250 mm (▪), T=30 °C, under illumination.