Ionic Liquid-Based Thermally Responsive Electroactive Gel for Switchable Electroanalysis

A thermally responsive poly(N-isopropyl acrylamide-co-ViEtIm[ferrocenecarboxylate anion])/Au gel (abbreviated as poly-(NIPAm-co-ViEtIm[FcCOO])/Au gel) with an electroactive function was designed and synthesized. The gel integrated copolymer poly-(NIPAm-co-ViEtImBr), ferrocenecarboxylate anion (FcCOO(-)), and Au nanoparticles (Au NPs) to achieve thermally responsive electroactivity and electrocatalytic activity. The poly(N-isopropyl acrylamide) (PNIPAm)-based poly(NIPAm-co-ViEtImBr) gel was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization with the ionic liquid monomer and the NIPAm monomer under the action of the initiator to initiate the cross-linking agent. The immobilization of the FcCOO(-) was realized via the anion-exchange reaction of the ionic liquid fragment. Au NPs were further loaded by electrostatic attraction and in situ reduction of precursor AuCl4-, thus obtaining a thermosensitive poly(NIPAm-co-ViEtIm[FcCOO])/Au gel. The PNIPAm segment provides thermal responsiveness, which can reveal or seal the electroactive FcCOO-. This indicates that the conformational change of the PNIPAm segment at different temperatures can lead to controllable switching of the electrocatalytic performance of the poly(NIPAm-co-ViEtIm[FcCOO])/Au gel/GCE. Consequently, the modified electrode also exhibited a reversible "ON-OFF" effect on the electrocatalysis of ascorbic acid (AA). The poly(NIPAm-co-ViEtIm[FcCOO])/Au gel/GCE exhibited excellent electroactivity with a linear range of 0.100-25.8 mM, detection limit of 0.0929 mM, and sensitivity of 1.87 mu A center dot cm(-2)center dot mM(-1) in the "ON" state. This kind of switchable electrocatalytic performance of the electrode is expected to be widely used in the field of intelligent electrochemical sensors and devices.