Probing Charge Transport Kinetics in a Plasmonic Environment with Cyclic Voltammetry

Abstract

Possible modifications in electrochemical reaction kinetics are explored in a nanostructured plasmonic environment with and without additional light illumination using a cyclic voltammetry (CV) method. In nanostructured gold, the effect of light on anodic and cathodic currents is much pronounced than that in a flat system. The electron-transfer rate shows a 3-fold increase under photoexcitation. The findings indicate a possibility of using plasmonic excitations for controlling electrochemical reactions.

Figure 1

(a) Schematic of the gold nanomesh and flat gold substrate; (b) SEM (top) and the reflection spectrum (bottom) of nanomesh (taken from the sample in the electrolyte); (c) schematic of the experimental setup; and (d) typical cyclic voltammogram of iron(II) to (III) exchange in K₃[Fe(CN)₆]/KNO₃ aqueous media with the potentiodynamic sweep (flat gold, 60 mV/s, dark field).

Figure 2

(a) Cyclic voltammogram obtained using flat gold (in light and dark fields) and nanomesh gold (in light and dark fields) as working electrodes. Scan rate is shown for each electrode, 60 mV/s. (b) Oxidation–reduction peak potential in nanomesh vs v sweep rate in light and dark; (c) same in flat gold; and (d) anodic peak current vs v^1/2, experiment (points) and fitting (dashed traces). Inset: anodic (triangles) and cathodic (stars) currents in flat gold in dark.

Figure 3

Redox potential (a, b), peak-to-peak separation (c, d), and Nicholson kinetic parameter (e, f) in flat gold (top three plots) and nanomesh systems (three bottom plots). Red and green colors correspond to the data obtained under light illumination, and blue and black data are obtained in dark. Dashed traces in (e) and (f) are fitting with straight lines.