A fiber-optic evanescent wave O2 sensor based on Ru(II)-doped fluorinated ORMOSILs

A novel fiber-optic evanescent wave sensor (FOEWS) for O(2) detection based on [Ru(bpy)(3)](2+)-doped hybrid fluorinated ORMOSILs (organically modified silicates) has been developed. The sensing element was fabricated by dip-coating the optical fiber with [Ru(bpy)(3)](2+)-doped hybrid fluorinated ORMOSILs composed of n-propyltrimethoxysilane (n-propyl-TriMOS) and 3, 3, 3-trifluoropropyltrimethoxysilane (TFP-TriMOS). Fluorophores of [Ru(bpy)(3)](2+) were excited by the evanescent wave field produced on the fiber core surface and the emission fluorescence was quenched by O(2). Spectroscopic properties have been characterized by FTIR and UV-VIS absorption measurements. By using the presented hybrid fluorinated ORMOSILs, which enhances the coating surface hydrophobicity, the quenching response is increased. The sensitivity of the sensor is 7.5, which is quantified in terms of the ratio I (N2)/I (O2) (I (N2) and I (O2) represent the fluorescence intensities in pure N(2) and pure O(2) environments, respectively). The limit of detection (L.O.D.) is 0.01% (3sigma) and the response time is about 1 s. Meanwhile, the proposed FOEWS has the advantages of easy fabrication, low cost, fast response and suitable sensitivity for oxygen monitoring using a cheap blue LED as light source and coupling a miniature PMT detector directly to the optical fiber probe.