(Digital Presentation) Catalytic Interruption Mitigates Edge Effects in the Characterization of Heterogeneous, Insulating Nanoparticles

Single entity electrochemistry encompasses a broad collection of techniques that are used to detect and characterize single, freely diffusing analytes in solution1,2. A particular scheme in this field, “blocking” nanoimpacts, has expanded the scope of electrochemistry to the study of redox-inert materials. Here, as a particle adsorbs, it prevents charge exchange between the microelectrode with a freely diffusing electroactive redox mediator. The interpretation of these blocking results, however, is often complicated by “edge effects,” in which enhanced mass transport to the edges of microelectrodes leads to uneven current distributions3,4. To overcome this problem we introduce here the use of electrochemical amplification5. That is, we employ electrocatalytic amplification to drive a current increase, moving the rate limiting step in current generation away from the electrode surface, reducing the geometric impact of the electrode’s edges. Finite element simulations indicate that the rapid chemical kinetics introduced by this approach contributes to the amplification of the electronic signal to restore analytical precision and reliability detect and characterize the heterogeneity of nanoscale electro-inactive materials. Using this approach, which we have termed “electrocatalytic interruption,” we achieve significantly improved precision in the determination of particle size distributions.6 References Quinn, B. M.; van’t Hof, P. G.; Lemay, S. G. Time-Resolved Elec-trochemical Detection of Discrete Adsorption Events. J. Am. Chem. Soc. 2004, 126 (27), 8360–8361. https://doi.org/10.1021/ja0478577. Bard, A. J.; Faulkner, L. R. Electrochemical Methods: Fundamentals and Applications, 2nd ed.; Wiley: New York, 2001. Compton, R. G.; Banks, C. E. Understanding Voltammetry (Third Edition); World Scientific, 2018. Deng, Z.; Elattar, R.; Maroun, F.; Renault, C. In Situ Measurement of the Size Distribution and Concentration of Insulating Particles by Electrochemical Collision on Hemispherical Ultramicroelectrodes. Anal. Chem. 2018, 90 (21), 12923–12929. https://doi.org/10.1021/acs.analchem.8b03550. Bonezzi, J.; Boika, A. Deciphering the Magnitude of Current Steps in Electrochemical Blocking Collision Experiments and Its Implica-tions. Electrochimica Acta 2017, 236, 252–259. https://doi.org/10.1016/j.electacta.2017.03.090. Chung, J.; Hertler, P.; Plaxco, K.W.; Sepunaru, L. J. Am. Chem. Soc. 2021, https://doi.org/10.1021/jacs.1c04971. Figure 1