Photosensitizers, photoinitiators and photocatalysts

Electron transfer processes involving excited transition metal photocatalysts are examined in Section 6.8.2. Reactive radical ions are usually generated from neutral 

Entry Starting material3 Product(s)3 Process Section 

---

Alternatively, light is consumed and the reaction progress is possible only under continuous light absorption this option, called catalyzed photolysis, includes photoassisted generation of a reactive form of substrate or photocatalyst. In the former the process is called catalyzed photochemical reaction, whereas in the latter either catalyst activation may lead to formation of catalyst or photoinitiator, which initiates chemical transformations but is consumed within a reaction cycle, or the catalyst reacts with substrate in its excited state (photosensitization) in both cases... 

The most essential pathways of pollutant photodegradation start from photocatalyst absorption followed by photosensitization or photoassisted reactions. The former consists in the energy or charge transfer from an excited photosensitizer to the substrate (quencher) molecule, whereas the latter results in generation of a catalyst for one cycle, called photoinitiator. To guarantee the continuity of the charge transfer reactions both photosensitizers and photoinitiators should be recycled the common practice is their regeneration by means of adequate electron donors and/or acceptors. These are not restored in a subsequent redox process but destroyed by irreversible chemical conversion thus they are called sacrificial donors and acceptors, respectively. 

Table 6.21 Photoprocesses involving photosensitizers, photocatalysts and photoinitiators...

---