Single-particle electrochemical imaging for assessing the heterogeneous response of individual nanocrystals.

We utilize single-particle electrochemical (SPEC) imaging to resolve the redox landscapes of individual InP/ZnSe/ZnS quantum dots (QDs) in the presence of the redox mediator phenazine methosulfate (PMS). We extract a suite of intrinsic electrochemical parameters, including midpoint potentials, relative brightness changes, sensitivity slopes, rate-dependent intercepts, etc., to construct a comprehensive multi-parametric redox fingerprint for each particle. We establish a quantitative correlation between this multi-dimensional fingerprint and a particle's functional response, toward an independent chemical stimulus, such as dopamine. This correlation-based approach allows us to use electrochemical signatures as a diagnostic tool to evaluate the functional heterogeneity and the readiness of nanocrystals, providing a new paradigm for linking fundamental electrochemical properties to single-particle performance in complex systems.