Optical oxygen sensing based on luminescence quenching of platinum porphyrin dyes doped in ormosil coatings

Organically modified sol–gel films (ormosils) doped with platinum porphyrin dyes were prepared by using acid-catalyzed hydrolysis and condensation of methyl triethoxysilane (MTEOS) as precursor. The process variables like water to precursor molar ratio, acid concentration and aging time of the acid-catalyzed MTEOS-based sol were controlled to obtain ormosil coatings with good sensor properties. The effect of dopant concentration on the oxygen sensitivity was studied. The photophysical properties and decay kinetics of the coatings were studied and compared. Stern–Volmer plots for both PtOEP- and PtTFPP-doped sensor coatings were linear. The oxygen sensitivities (I0/I100) of these sensor coatings were found to be about 28 and 50 for PtTFPP and PtOEP, respectively. The ormosil coatings doped with porphyrin dyes exhibited higher oxygen sensitivity and better photostability compared to other silicone-based sensor coatings. Hence they may have good potential for surface pressure measurements in aerodynamic applications