Electrostatic-Gated Kinetics of Rapid Ion Transfers at a Nano-liquid/Liquid Interface

Abstract

Charge (ion and electron)-transfer reactions at a liquid/ liquid interface are critical processes in many important biological and chemical systems. An ion-transfer (IT) process is usually very fast, making it difficult to accurately measure its kinetic parameters. Nanoliquid/liquid interfaces supported at nanopipettes are advantageous approaches to study the kinetics of such ultrafast IT processes due to their high mass transport rate. However, correct measurements of IT kinetic parameters at nanointerfaces supported at nanopipettes are inhibited by a lack of knowledge of the nanometer-sized interface geometry, influence of the electric double layer, wall charge polarity, etc. Herein, we propose a new electrochemical characterization equation for nanopipettes and make a suggestion on the shape of a nano-water/1,2-dichloroethane (nano-W/DCE) interface based on the characterization and calculation results. A theoretical model based on the Poisson−Nernst−Planck equation was applied to systematically study how the electric double layer influences the IT process of cations (TMA + , TEA + , TPrA + , ACh + ) and anions (ClO 4 − , SCN − , PF 6 − , BF 4 − ) at the nano-W/DCE interface. The relationships between the wall charge conditions and distribution of concentration and potential inside the nanopipette revealed that the measured standard rate constant (k 0 ) was enhanced when the polarity of the ionic species was opposite to the pipette wall charge and reduced when the same. This work lays the right foundation to obtain the kinetics at the nano-liquid/liquid interfaces.

Artificial Funnel Nanochannel Device Emulates Synaptic Behavior

“…With nanofluidic technologies, by designing the geometry of the nanoconfined spaces and the type of solutions, it is possible to regulate the ion transfer behaviors to be symmetric or asymmetric ion transfer. 19 Through structural design, we constructed a nanoscale tip and a microscale transition structure, where the interfacial ion transfer at the tip causes ion hysteresis and the mass transport at the microscale transition structure guarantees that the reaction is controlled by the interfacial ion transfer and generates significant current. 49 The device is fabricated using MEMS technology (Figure S1), which has the advantages of integration and wafer-level fabrication.…”

“…The fluid-based bionic nervous system, having the same carrier as that of biological nervous system and being compatible with the biological solution environment, capable of breaking the information barriers between biological and machine interfaces, has become a new research trend. − Owing to the unique structural and transport properties, numerous novel transport phenomena of ions and molecules have been unveiled in nanofluidics. − Inspired by biological systems, by mimicking the structure, switching mechanism, and ionic transport modality as biological synapses, big breakthroughs have been made in iontronic artificial synapses. − Currently, bionic nanofluidic neuromorphic devices, utilizing mechanisms such as ion concentration polarization, − switching of ion channels, , movement of liquid/liquid (L/L) interfaces, − the form of filaments between two electrodes, − alteration of ion aggregation states, , and adsorption properties of ions on channel walls, , have been developed. Utilizing various ions as signal carriers, these approaches not only regulate ion and fluid transport behavior but also mimic various ion transport phenomena encountered in life activities and generate signals that resemble the electrophysiological signals of the human brain in nanofluidic devices.…”