ABSTRACT
We describe the fabrication and characterisation of gold-coated graded index channel waveguide sensors designed for simultaneous electrochemical and surface plasmon resonance studies. The active sensing electrode area is a thin gold film between 0.5 and 5 mm in length and 200 microm wide deposited on top of a 3 microm wide waveguide which forms one arm of a Y-junction while the other arm of the Y-junction serves as a reference. Using these devices we have measured simultaneously the changes in transmittance through the device whilst carrying out cyclic voltammetry in either sulfuric or perchloric acid solution or during the deposition of an UPD layer of copper at the gold surface. In all cases we obtain stable and reproducible results which demonstrate the very high sensitivity of the devices to sub-monolayer changes occurring at the gold electrode surface. The response of these integrated optoelectrochemical devices is discussed in terms of a numerical model for the propagation of light within the waveguide structure.
ABSTRACT
Electrochemical oxidation of the surface of a thin gold film overlaid on an optical waveguide and placed in a cell containing sulfuric acid is monitored by integrated optical surface plasmon resonance (IOSPR) combined with cyclic voltammetry. Waveguide transmittance correlates well with the charge transferred to and from the electrode to oxidize and reduce the surface, with a 60% reduction in transmittance being observed for complete formation of the surface oxide. IOSPR sensors combined with electrochemical measurement and control show potential for sensitive and robust integrated multisensors for electroactive species.
