Surface plasmon resonance fibre-optic sensor for gas detection

Surface plasmon resonance (SPR) is a powerful technique for direct sensitive (bio)chemical detection. In this work, a surface plasmon resonance fibre-optic sensor has been developed allowing sensitive remote detection. A 50 nm thick silver film is deposited by thermal evaporation onto the silica core of the optical fibre. To protect the silver from oxidation, self-assembled monolayers (SAMs) of long-chain alkanethiols are used. For detecting gas and vapours, the surrounding dielectric medium consists of polyfluoroalkylsiloxane, deposited on the modified metallic film. Halogenated hydrocarbons such as trichloroethylene, carbon tetrachloride, chloroform and methylene chloride have been tested with detection limits of 0.3, 0.7%, 1 and 2%, respectively. Moreover, both the response time and the desorption time are less than 2 min.