Integrated optical surface plasmon resonance for electrochemically addressed layers
This thesis reports on the development of the first integrated optical surface plasmon resonance sensor that combines an optical and electrochemical interrogating technique in sensing electrochemically addressed layers over a gold film. This device brings together the advantages of the analytical technique of surface plasmon resonance and of cyclic voltammetry on a single chip that exhibits portability, miniaturisation capability and compatibility with optical fibre. The integrated optical chip allows the potential introduction of a large number of sensing pads on a single chip thus allowing the acquisition of precise information about a test compound while simultaneously monitoring different test compounds in the same sensing area. The integrated optical surface plasmon resonance (IOSPR) devices fabricated were applied in the study of the oxidation of gold and the removal of the oxide layer in real time. The optical response to the oxidation process was similar to those reported in the literature using ellipsometry and or reflectance spectroscopy. Here the IOSPR device performed better, giving transmittance changes of 60 % in response to the formation of an oxide film. The introduction of a monolayer of copper onto the gold surface of the device via the underpotential deposition process was monitored for the first time using the surface plasmon technique. Here the response and performance of the device was compared with other reported studies in the literature, which combined an optical and electrochemical technique for similar analysis. The IOSPR device performed better with 10 % change in transmittance in comparison to a change of 1 % reported for reflectance measurements. Comparisons were also made with those predicted by a numerical waveguide model. The feasibility of potential applications in biological analysis was demonstrated by applying the device in analysing the adsorption and desorption of thiol and phospholipid layers onto the sensing surface of the device.