Monitoring electrochemical dynamics through single-molecule imaging of hBN surface emitters in organic solvents

TL;DR

This paper introduces a novel single-molecule imaging technique using hBN to monitor electrochemical surface dynamics over large areas with high spatial resolution, enabling detailed analysis of analyte concentrations and reaction kinetics.

Contribution

The work demonstrates a new optical method combining single-molecule microscopy and hBN to spatially and temporally monitor electrochemical processes at the surface, surpassing traditional techniques in resolution and scope.

Findings

Linear decrease in emitters with positive voltage

Consistent electrode kinetics trends with optical data

Spectral SMLM enables multiplexed species identification

Abstract

Electrochemical techniques conventionally lack spatial resolution and average local information over an entire electrode. While advancements in spatial resolution have been made through scanning probe methods, monitoring dynamics over large areas is still challenging, and it would be beneficial to be able to decouple the probe from the electrode itself. In this work, we leverage single molecule microscopy to spatiotemporally monitor analyte surface concentrations over a wide area using unmodified hexagonal boron nitride (hBN) in organic solvents. Through a sensing scheme based on redox-active species interactions with fluorescent emitters at the surface of hBN, we observe a linear decrease in the number of emitters under positive voltages applied to a nearby electrode. We find consistent trends in electrode reaction kinetics vs overpotentials between potentiostat-reported currents and optically-read emitter dynamics, showing Tafel slopes greater than 290 mV per decade. Finally, we draw on the capabilities of spectral single molecule localization microscopy (SMLM) to monitor the fluorescent species identity, enabling multiplexed readout. Overall, we show dynamic measurements of analyte concentration gradients at a micrometer-length scale with nanometer-scale depth and precision. Considering the many scalable options for engineering fluorescent emitters with 2D materials, our method holds promise for optically detecting a range of interacting species with unprecedented localization precision.