Bridged EGFET Design for the Rapid Screening of Sorbents as Sensitisers in Water-Pollution Sensors

We further simplify the most ‘user-friendly’ potentiometric sensor for waterborne analytes, the ‘extended-gate field effect transistor’ (EGFET). This is accomplished using a ‘bridge’ design, that links two separate water pools, a ‘control gate’ (CG) pool and a ‘floating gate’ (FG) pool, by a bridge filled with agar-agar hydrogel. We show electric communication between electrodes in the pools across the gel bridge to the gate of an LND150 FET. When loading the gel bridge with a sorbent that is known to act as a sensitiser for Cu2+ water pollution, namely, the ion exchanging zeolite ‘clinoptilolite’, the bridged EGFET acts as a potentiometric sensor to waterborne Cu2+. We then introduce novel sensitisers into the gel bridge, the commercially available resins PurometTM MTS9140 and MTS9200, which are sorbents for the extraction of mercury (Hg2+) pollution from water. We find a response of the bridged EGFET to Hg2+ water pollution, setting a template for the rapid screening of ion exchange resins that are readily available for a wide range of harmful (or precious) metal ions. We fit the potentiometric sensor response vs. pollutant concentration characteristics to the Langmuir–Freundlich (LF) model which is discussed in context with other ion-sensor characteristics.