Figure 1.
Jablonski diagram for PDT. In type I reactions, the triplet photosensitizer will transfer an electron to 3O2 react with molecular targets to produce radical species, or alternatively interact directly with the acceptor, [A], without oxygen mediation. In type II reaction, the energy is transferred from the triplet photosensitizer to ground state molecular oxygen (3O2), creating reactive singlet oxygen (1O2).