ELECTROCHEMICALLY-CONTROLLED WAVE-GUIDE-COUPLED SURFACE-PLASMON SENSING

A surface plasmon resonance sensing device has been constructed, in wh ich excitation of a surface plasmon on a metal film is achieved by cou pling from light propagating in an optical waveguide. The metal film c ladding has been used as an electrode surface and it is proposed that these structures may be applied as novel optoelectrochemical sensors. Specific cationic adsorption has been monitored in potential regions w here the metal free-electron contribution is small, and the sensitivit y of this sensing technique has been deduced by comparison with ellips ometric measurements. The interfacial model used to analyse the ellips ometric results has been tested by calculating coverage by water in th e water + ethylene glycol mixture employed in the surface plasmon devi ce. The high sensitivity of this technique to adsorbed films is found to be greater than that predicted by the theoretical model described, and reasons for this discrepancy are discussed.