Swelling Behavior of an Ethanol-Sensitive Hydrogel Immobilized on a Plasmonic Sensor Substrate

Refractive index-sensitive plasmonic sensors are suitable for the on-site detection of fluid parameters in process engineering applications. The functionalization of optically sensitive nanostructured surfaces with stimuli-responsive hydrogels enables the selective determination of parameters of complex liquids. Thereby, the degree of swelling of the hydrogel gives indications to liquid parameters like pH or molecule concentrations. In this study, the influence of the swelling degree of an immobilized ethanol-sensitive hydrogel on the sensor signal is investigated. The application of both a measuring and reference area allows differentiation of the refractive index change induced by the swelling effect from the refractive index change of the analyte due to concentration changes.