STABILIZATION OF A SURFACE-PLASMON RESONANCE (SPR) OPTICAL-FIBER SENSOR WITH AN ULTRA-THIN ORGANIC FILM - APPLICATION TO THE DETECTION OF CHLORO-FLUORO-CARBON (CFC)

Surface plasmon resonance (SPR) is a powerful technique for direct sen sitive (bio) chemical detection. This phenomenon can be used to measur e the refractive index of either bulk chemical samples or chemically s ensing thin layers. In this work, a SPR fibre optic sensor has been de veloped. A 50 nm thick silver film is deposited by thermal evaporation onto the silica core of the optical fibre. To protect silver from oxi dation, the evaporated silver film was covered with self-assembled mon olayers (SAMs) of long-chain alkanethiols (1-octadecanethiol). To char acterize these SAMs, silver films evaporated onto macroscopic glass su rfaces as test samples and several techniques such as contact angle me asurements (sessile drop method), X-ray photoelectron spectroscopy (XP S) and atomic force microscopy (AFM) were used. In the subsequent step , a chemically sensing thin layer (polyfluorosiloxane) was deposited o nto the thiol surface. In such a configuration the SPR fibre optic sen sor was able to detect a few percent of chloro-fluoro-carbon (CFC) vap ours. (C) 1997 Elsevier Science S.A.