Wireless radio frequency detection of greatly simplified polymeric membranes based on a multifunctional ionic liquid

In this paper, we report our ongoing investigations into the properties of poly(vinyl)chloride (PVC) based polymeric membranes incorporating the ionic liquid (IL) trihexyltetradecylphosphonium dicyanamide [P6,6,6,14][DCA] which fulfils several key functions - plasticiser, ligand and transducer dye. Upon co-ordination with Cu2+ ions, a yellow colour is generated within the membrane. Similarly exposure of a membrane to Co2+ ions produces a blue colour, whilst the IL is capable of co-ordinating both ions simultaneously, thereby generating a green optical response. Using Wireless Radio Frequency (WRF) detection however, the inherent conducting nature of these membranes can now also be exploited as a sensor signal. WRF is a novel detection technique which monitors the conductivity of a given sample wirelessly, allowing non-contact detection and measurement of IL-PVC membranes as they pass through the channel. The various co-ordinated membranes produce a discriminatory drop in the resulting signal, which is a direct function of the specific metal ion (Cu2+, Co2+ or a mixture) co-ordinated to the IL. The results of the novel WRF technique have been validated principally by electrochemical impedance spectroscopy (EIS) and also by portable x-ray fluorescence (XRF). Keywords: Ionic Liquids, Electrochemical Sensors, Polymeric Sensor