Stochastic On-Chip Detection of Subpicomolar Concentrations of Silver Nanoparticles

Abstract

We introduce the stochastic amperometric detection of silver nanoparticles on-chip using a microelectrode array. The technique combines the advantages of parallel and low-noise recordings at individually addressable microelectrodes. We demonstrate the detection of subpicomolar concentrations of silver nanoparticles with a diameter of 10 nm at sampling rates in the kilohertz regime for each channel. By comparison to random walk simulations, we show that the sensitivity of a single measurement is mainly limited by adsorption of nanoparticles at the surface of the chips and the measurement time.

Time-Resolved Detection of Surface Oxide Formation at Individual Gold Nanoparticles: Role in Electrocatalysis and New Approach for Sizing by Electrochemical Impacts

“…This typically involves monitoring the current-time (I-t) transients associated with the stochastic collision of NPs from a (dilute) colloidal solution with a collector electrode, with the detected current arising from either: (i) a heterogeneous electron-transfer reaction taking place at the NP surface (e.g., electrocatalytic amplification [3][4][5][6] ); or (ii) the electro-dissolution of the NP itself. 7,8 In this contribution, we introduce a third approach to investigate the dynamic interaction between metal NPs and a collector electrode, in which the detected current arises from NP surface oxidation, as is shown schematically in Figure 1a for the case of an Au NP. This measurement is much more challenging than the (volumetric) anodic oxidation of metal NPs 7,8 , due to the smaller charges involved and much faster timescale of the process, but opens up new prospects for detecting noble metals and analyzing the formation of surface oxides, which can greatly influence (retard or accelerate) electrocatalysis.…”

Impact and oxidation of single silver nanoparticles at electrode surfaces: one shot versus multiple events

“…32 It is further important to note that in many reports on impact coulometry, little information was given about signal amplification, sampling time and the data processing carried out to interpret NP impact current transients; these critical factors have only recently begun to be reported. 33,34 …”

“…Electrochemical oxidation of single Ag NPs of 10 nm in diameter has produced current magnitudes of 1 to 10 pA and anodic dissolution transient durations of 2–3 ms by using carbon fiber (CF) 20 and Pt 34 UMEs, but the use of a cut-off filter 20 or signal averaging 34 compromised the ability to probe short-time stripping events. In addition, the electrochemical oxidation of Ag NPs of 100 nm in diameter has led to peak currents spanning from 30–200 pA, 21 on the one hand, to 0.5–10 nA, 18 on the other, with an identical experimental configuration save for the use of different equipment to record the transients.…”

Tracking motion trajectories of individual nanoparticles using time-resolved current traces

“…Over the past several decades, examples of single NP electrochemical measurements include electrocatalytic amplification 20–23 and electrochemical oxidation 23–25 of single metal oxide or metal NPs by detecting the current transients as individual NPs collide with a UME. Considerable experimental and theoretical effort has been devoted to studying the shape and statistical properties of these transients, which have significant practical applications for analyzing the size, structure, and catalytic characteristics of individual NPs.…”