Self-assembly oxygen sensing thin film based on a Ru(ii) complex covalently grafted to porous anodized alumina oxide (AAO) templates

Abstract

A novel functional Ru(bpy)₂(phen-NH₂)(PF₆)₂ complex (bpy = bipyridyl, phen-NH₂ = 5-amine-1,10-phenanthroline) is covalently bonded to an anodized alumina oxide (AAO) template through a “soft bridge” of 3-glycidoxypropyltrimethoxysilane (GPMS). This can form an oxygen sensor with the structure [Ru(bpy)₂(phen-NH)/GPMS/AAO]. This oxygen sensing thin film was characterized using scanning electron microscopy (SEM) and fluorescence spectrophotometry. A series of cluster structures were observed on the surface of the AAO, the Ru(bpy)₂(phen-NH₂) fluorophore which was uniformly dispersed. The film proved to have good oxygen quenching properties owing to the great interaction between the fluorophore and molecular oxygen. Finally, a Stern–Volmer plot of the [Ru(bpy)₂(phen-NH)/GPMS/AAO] thin film shows a good linearity with a fitting parameter R² of 0.9948 when the oxygen concentration is 0%–80%, and the sensitivity rises to 10.47, which is 7.5 times greater than that of oxygen sensors based on sol–gel methods. A short response/recovery time of 7 s/15 s was achieved, which is almost 100% faster than that of sol–gel methods with the same fluorophore. When stored in the ambient air of the laboratory, there was no significant drift in intensity after 6 months. These characteristics result in the thin film of [Ru(bpy)₂(phen-NH)/GPMS/AAO] being a promising candidate for sensitive oxygen sensors.