Silicone Films for Optical Oxygen Sensing

The importance of molecular oxygen sensing is unquestionable, given the role this species plays in nature. According to the required application field, different sensor types have been developed through the years, whether for measurements in the gas-phase or in liquids [82-84]. From the very beginning, silicones have been present in the fabrication of oxygen sensors. The amperometric Clark electrode for waterborne Oj measurements, developed in 1956, was basically formed 

Concerning the indicator dyes and bearing in mind that the dynamic quenching process of the indicator (electronic) excited state by is described by the Stern-Volmer 

A good oxygen sensing material requires luminescent indicators with moderate to high emission quantum yields (4)) and long excited state Hfetimes in the absence of oxygen for maximum sensitivity [103]. 

Among the most commonly used indicator dyes for doping silicone films are ruthenium(II) complexes with polyazaheterocyclic chelating hgands [33] and metallo-porphyrins [104]. These compounds possess unique photochemical and photophysical characteristics such as large separation between the absorption and emission bands and 

L6pez-Gejo et al. [37] have carried out a detailed study of the aforementioned microenvironments by fluorescence lifetime imaging microscopy (FLIM), where it was shown that addition of hydrophihc silica filler increases both the solubility of in the silicone film and the concentration of the indicator dye. Nevertheless, if the dye payload is raised, it becomes too concentrated, and phenomena such 

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