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AQUACAT Résumé de rapport

Project ID: ICA3-CT-2002-10016
Financé au titre de: FP5-INCO 2
Pays: Spain

Reference material for photosensitized siglet molecular oxygen production measurements in solid media

Singlet molecular oxygen is a reactive oxygen species which can be efficiently generated via quenching of the excited state of a sensitizer by ground state molecular oxygen in the so-called photosensitization process. Singlet oxygen can be used for different applications, such as organic synthesis, dye bleaching, disinfection processes and photodynamic therapy.

Production of singlet oxygen by solid-supported sensitizers is often employed because the photosensitizer can be readily removed at the end of the process. In order to design the most adequate system for each application, it is essential to carry out a precise quantification of the singlet oxygen production by the supported photosensitizers. In practice, this involves measurement of the singlet oxygen production quantum yields (PHIdelta). While this issue is well solved in homogeneous media due to availability of various standards, it is far from established in heterogeneous systems.

Our research group has proposed methylene blue (MB) dyed Nafion films as a convenient reference system to quantify singlet oxygen production in solid samples. We have thoroughly characterized the production of singlet oxygen generated by MB photosensitization in films of Nafion ionomer and we have compared our results with those of two well known standards: MB in methanol and tris(2,2-bipyridyl)ruthenium(II) in acetonitrile.

We have determined singlet oxygen production quantum yields of MB in dry Nafion (PHIdelta = 0.24) and in methanol-swollen Nafion (PHIdelta = 0.49). After the characterization of the MB/Nafion system, we have concluded that Nafion films loaded with MB are homogeneous, reproducible and stable systems suitable to be used as a reference for PHIdelta determination in solid phase.

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Guillermo ORELLANA, (Department Director)
Tél.: +34-91-3944220
Fax: +34-91-3944103