RESUMO
Single-entity collisional electrochemistry (SECE), a subfield of single-entity electrochemistry, enables directly characterizing entities and particles in the electrolyte solution at the single-entity resolution. Blockade SECE at the traditional solid ultramicroelectrode (UME)/electrolyte interface suffers from a limitation: only redox-inactive particles can be studied. The wide application of the classical Coulter counter is restricted by the rapid translocation of entities through the orifice, which results in a remarkable proportion of undetected signals. In response, the blocking effect of single charged conductive or insulating nanoparticles (NPs) at low concentrations for ion transfer (IT) at a miniaturized polarized liquid/liquid interface was successfully observed. Since the particles are adsorbed at the liquid/liquid interface, our method also solves the problem of the Coulter counter having a too-fast orifice translocation rate. The decreasing quantal staircase/step current transients are from landings (controlled by electromigration) of either conductive or insulating NPs onto the interface. This interfacial NP assembly shields the IT flux. The size of each NP can be calculated by the step height. The particle size measured by dynamic light scattering (DLS) is used for comparison with that calculated from electrochemical blocking events, which is in fairly good agreement. In short, the blocking effect of IT by single entities at micro- or submicro-liquid/liquid interface has been proven experimentally and is of great reference in single-entity detection.
RESUMO
Single-entity collisional electrochemistry (SECE) can capture physicochemical information at the single entity level. In the present work, we systematically studied in-situ generation and detection of single anionic ionosomes via SECE combined with a miniaturized interface between two immiscible electrolyte solutions (ITIES). Ionosome is an ionic-bilayer encapsulated nanoscopic water cluster/droplet that carries a net charge. Discrete spiky ionic currents were observed upon collisions/fusions of individual F- or Cl- -ionosomes with a positively polarized micro-ITIES. This fusion process was proved to follow the bulk electrolysis model. With this method, some essential factors such as concentration and charge density of the hydrated anions, and the interfacial area, were revealed. It demonstrates that anionic ionosomes share a common theoretical framework with their counterparts (i. e., cationic ionosomes, like Li+ -ionosomes). This work will spur the advancements in a myriad of fields, including such as the colloid and interface science, micro- and/or nanoscale electrochemistry, and electrophysiology and brain sciences.
