pH Sensor Based on Supramolecular Host–Guest Interactions and an Organic Field-Effect Transistor with a Magnetic Carbon Gate Electrode

A robust electrolyte-gated organic field-effect transistor (EGOFET) able to respond to pH in the range 1–10 is reported. This is realized by exploiting the pH-dependent supramolecular host–guest complexation of imidazole/β-cyclodextrin (β-CD). The sensing protocol is performed by incubating magnetic nanoparticles functionalized with β-CD with imidazole solutions at different pHs and trapping them in a magnetic carbon electrode. Such an electrode is then implemented as gate contact in the EGOFET. At higher pH, the complexation is more favored, resulting in a negative shift of the device transfer characteristics. Remarkably, the carbon gate electrode can be polished and reused and the devices show high stability and reproducibility.