Voltage‐Gated Nanoparticle Transport and Collisions in Attoliter‐Volume Nanopore Electrode Arrays

Abstract

Single nanoparticle analysis can reveal how particle‐to‐particle heterogeneity affects ensemble properties derived from traditional bulk measurements. High‐bandwidth, low noise electrochemical measurements are needed to examine the fast heterogeneous electron‐transfer behavior of single nanoparticles with sufficient fidelity to resolve the behavior of individual nanoparticles. Herein, nanopore electrode arrays (NEAs) are fabricated in which each pore supports two vertically spaced, individually addressable electrodes. The top ring electrode serves as a particle gate to control the transport of silver nanoparticles (AgNPs) within individual attoliter volume NEAs nanopores, as shown by redox collisions of AgNPs collisions at the bottom disk electrode. The AgNP‐nanoporeis system has wide‐ranging technological applications as well as fundamental interest, since the transport of AgNPs within the NEA mimics the transport of ions through cell membranes via voltage‐gated ion channels. A voltage threshold is observed above which AgNPs are able to access the bottom electrode of the NEAs, i.e., a minimum potential at the gate electrode is required to switch between few and many observed collision events on the collector electrode. It is further shown that this threshold voltage is strongly dependent on the applied voltage at both electrodes as well as the size of AgNPs, as shown both experimentally and through finite‐element modeling. Overall, this study provides a precise method of monitoring nanoparticle transport and in situ redox reactions within nanoconfined spaces at the single particle level.

Nanoconfinement Effect for Signal Amplification in Electrochemical Analysis and Sensing

“…A similar gating behavior was used to investigate nanoparticle transportation and in situ redox reactions at the single-particle level using a top ring electrode (Figure 8B). [96] The top ring electrode served as a particle gate to control the transport of silver nanoparticles (AgNPs), while the bottom disk electrode provided a nanoconfined space for AgNP redox collisions. Because of attoliter-scale nanoconfinement, nanoparticles entering the nanopores displayed collision dynamics that differed from the planar ultramicroelectrodes.…”

“…[91] Copyright 2019, The Royal Society of Chemistry. [96] Copyright 2018, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. C) NEAs cooperate with SERS to monitor single Ag Raman-sentinel nanoparticles.…”

“…B) Schematic drawing of nanoparticle transport and in situ redox reactions in nanoconfined spaces. Reproduced with permission [96]. Copyright 2018, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.…”

Monitoring Simultaneous Electrochemical Reactions with Single Particle Imaging

“…[10] Electrochemical studies at the single particle level are of great interest because they reveal particle-to-particle heterogeneity and provide an understanding of the underlying mechanisms that may be hidden in ensemble electrochemical measurements. [14][15][16][17][18][19][20][21][22][23][24] Recently, Zhang et al [25] . [14][15][16][17][18][19][20][21][22][23][24] Recently, Zhang et al [25] .…”

Electrochemical determination of surface area-to-volume ratio for metal nanoparticle analysis.

“…132 With DLS, the signal is usually dominated by larger NPs and the analysis can be susceptible to interference from luminescent species. 133 18,21,139,140,141 or translocation through a nanopore. 142,143 The peak spacing corresponding to the quantized double-layer charging of MP-AgNSs (Monolayer protected Ag NSs) 144 in a differential pulse voltammogram correlated to the capacitance, and hence the radius of the NSs.…”