Surface plasmon resonance enhanced ellipsometric analysis for monitoring of cobalt electrochemical reaction in solution

Cobalt-based ion selective electrode (ISE) is one of the key methods for phosphate detection. In this paper, surface plasmon resonance (SPR) enhanced ellipsometric analysis method has been used to monitor the electrochemical reaction process at Co ISE sensor surface and the mass consumption of sensitive electrode membranes. An Au–Co bilayer film is designed as optical detection interface. In order to obtain detectable reflection intensity variation with Co thickness, Au film and Co film thickness are optimized at TM polarization state. According to the calculation results, 50 nm Au film is formed on glass substrate by electron beam evaporation. Then cobalt film with thickness of about 20 nm is grown on gold film by electrochemical deposition method. Ellipsometric measurements were performed at SPR angle 59°. The consuming process of Co film reacting with dissolved oxygen in deionized water has been obtained by monitoring the change of reflection intensity.