Hierarchically-Organized Electrochemical-Photonic Nanostructures for Studies of Single Entities - Molecules, Particles, and Beyond

Structurally regular nanopore arrays containing independently controllable annular band
nanoelectrodes are capable of manipulating optical field distributions and electrochemical potential in a
single integrated nanoscale architecture. The special characteristics of these nanopore electrode
arrays (NEAs) make it possible to address small collections of matter down to the single entity
(molecule, particle, biological cell) level using spectroelectrochemistry. These capabilities are enabled
by constructing the NEAs with a transparent bottom layer that permits optical access to the interior of
the nanopore, which effectively traps radiation in an ultrasmall volume inside the nanopore. In addition,
we have recently extended the capabilities of these structures by adding a self-organized block
copolymer (BCP) layer capable of pH- and voltage-controlled transport gating to realize hierarchically-
organized BCP@NEA structures capable of high-sensitivity electrochemical assays. Recent
experiments have utilized these strategies to investigate the behavior of single enzymes (glutathione
reductase, aldehyde dehydrogenase). As a specific example of the analytical capabilities of these
structures, incorporating aldehyde dehydrogenase (ALDH), in a voltage-gated BCP@NEA structure
enables the coupling of enzymatic oxidation of aldehydes to enable ultrasensitive voltammetric
detection with limits-of-detection (LOD) down to 1.2 ppb. Sensor utility was demonstrated by detecting
the degradation of N-oxidized SM-102, the ionizable lipid in Moderna’s SpikeVax TM vaccine, in mRNA-
1273 LNP formulation.