In situ derivatisation of solid contact poly(3,4-ethylenedioxythiophene) transducers for ion-selective electrodes through “click” chemistry

Abstract

The ion-to-electron transducing layer is an essential part of the solid-contact ion-selective electrode, mostly responsible for providing a stable signal readout. Among available materials such as redox probes, carbon-based materials or nanomaterial, redox polymers are a transducer of choice owing to their ability to be solvent cast or electropolymerized reproducibly, thereby ensuring inter-electrode repeatability. Although the number of commercially available redox polymer is gradually increasing, those used in ion-selective electrode as transducing layer must be synthetically modified in most cases to achieve a sufficient degree of hydrophobicity to avoid the formation of a water layer at the transducer – membrane interface. We present here a versatile solution to generate a wide range of transducers using an azide modified derivative of 3,4-ethylenedioxythiophene, EDOT-N3. In this approach, the polymer is generated through dynamic electropolymerisation and then its surface is modified by taking advantage of the high yield “click” reaction between the azide group and an alkyne. We show that before subjecting the polymer to the “click” reaction the choice of supporting electrolyte is critical to generate a polymer suitable to be used as transducer in ion-selective electrodes. Alkyl chains ranging from 6 to 18 carbon atoms and a plasticiser-like moiety were grafted to the polymer backbone to demonstrate the increase in the hydrophobic properties of the surface layer and performance as transducer. Water contact angles up to 156.6° were obtained, indicating super-hydrophobic properties.