Conductive Ionogel for the Study of Charge Transport through SAM-based Junctions in Aqueous Solution

The urgency about the application of large-area molecular junction into aqueous environments has garnered significant attention, driven by the necessity for biomolecular testing under physiological conditions and the monitoring of chemical reactions in solutions. In this study, we synthesized a conductive ionogel as top electrode to measure the electrical properties of self-assembled monolayers (SAMs). The SAMs for test are with different terminal groups including -COOH, -CH3 and -F, exhibiting distinct affinities with water molecules. The variation in current density for each SAM can be attributed to the amount of water molecules between the electrode and SAMs. The electrical tests conducted in buffer solutions indicate that our tunneling process is dominated by electrons rather than ions, laying the foundation for testing biomolecules in physiological environments. We utilized ionogel electrodes for testing molecular junctions based on myoglobin and conducted temperature-dependent experiments with excellent repeatability. The exploration of ionogel electrodes contributes to our ability to conduct more complex measurements like rapid testing or drug screening, particularly in aqueous environments.