Development of highly sensitive [Ru(bpy)3]2+ - Based optical oxygen sensing thin films in the presence with Fe3O4 and Fe3O4@Ag NPs

Abstract Optical sensors based on chemically sensitive matrices/dyes have been used for accurate measurements of oxygen levels. In this study, the intensity-based response of highly sensitive tris(2,2′-bipyridyl) ruthenium(II) chloride [Ru(bpy)3]2+ dye to oxygen (O2) was analyzed in the polymeric ethylcellulose matrix (EC) in the presence of two magnetite forms; Fe3O4 and Fe3O4@Ag nanoparticles (NPs). Fe3O4 NPs were synthesized by flame spray pyrolysis (FSP) and then Fe3O4@Ag NPs were prepared by a core-shell coating method. Iron oxide polymorphs were characterized by using X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It was measured that the particles synthesized by the FSP technique have an average size of ˂60 nm Fe3O4, Fe3O4@Ag NPs, and 1-butyl-3-methylimidazolium tetrafluoroborate; ([BMIM][BF4]) were used as additives for enhancement of the sensitivity of the [Ru(bpy)3]2+ dye to O2 gas. The effects of these additive materials were examined by photoluminescence spectroscopy (PL). [Ru(bpy)3]2+ dye doped nanofiber in the presence with the Fe3O4@Ag NPs additive yielded higher Stern-Volmer constant (KSV) and extended linear response range when compared with the sensing slides in the presence with Fe3O4 NPs and the additive-free forms. The higher response ratio (I0/I100) was found as 3.45 for the ruthenium dye doped EC nanofiber form in the presence with Fe3O4@Ag NPs. Also, KSV values were calculated as 2.41 × 10−2 between the concentration range of 0–100% [O2]. According to our knowledge, it is the first time Fe3O4 and Fe3O4@Ag NPs were used for the enhancement of oxygen sensitivity of the ruthenium dye.