Figure 5.

Photosensitized RF-mediated oxidation mechanisms. Upon activation by light, RF is excited to a singlet state of higher energy (1RF*), followed by intersystem crossing to an excited triplet state (3RF*). 3RF* can be involved in a photosensitized oxidation process of Type I or Type II. In the Type I mechanism, RF transfers the energy to a substrate (S) and generates RF* free radical species that interact with molecular oxygen in the ground state to yield oxidation products. In the Type II mechanism, RF transfers the energy to molecular oxygen in the ground state to generate the more reactive singlet molecular oxygen (¹O₂). The latter, in reaction with S, leads to the final oxidation products (according to [135]).