posted on 2021-11-04, 17:35authored byJulia Chung, Phoebe Hertler, Kevin W. Plaxco, Lior Sepunaru
Blocking electrochemistry, a subfield
of nanochemistry, enables
nondestructive, in situ measurement of the concentration,
size, and size heterogeneity of highly dilute, nanometer-scale materials.
This approach, in which the adsorptive impact of individual particles
on a microelectrode prevents charge exchange with a freely diffusing
electroactive redox mediator, has expanded the scope of electrochemistry
to the study of redox-inert materials. A limitation, however, remains:
inhomogeneous current fluxes associated with enhanced mass transfer
occurring at the edges of planar microelectrodes confound the relationship
between the size of the impacting particle and the signal it generates.
These “edge effects” lead to the overestimation of size
heterogeneity and, thus, poor sample characterization. In response,
we demonstrate here the ability of catalytic current amplification
(EC′) to reduce this problem, an effect we term “electrocatalytic
interruption”. Specifically, we show that the increase in mass
transport produced by a coupled chemical reaction significantly mitigates
edge effects, returning estimated particle size distributions much
closer to those observed using ex situ electron microscopy.
In parallel, electrocatalytic interruption enhances the signal observed
from individual particles, enabling the detection of particles significantly
smaller than is possible via conventional blocking electrochemistry.
Finite element simulations indicate that the rapid chemical kinetics
created by this approach contributes to the amplification of the electronic
signal to restore analytical precision and reliably detect and characterize
the heterogeneity of nanoscale electro-inactive materials.