Dynamic Nanoparticle‐Substrate Contacts Regulate Multi‐Peak Behavior of Single Silver Nanoparticle Collisions

Abstract

Single nanoparticle collision (SNC) technology has attracted increasing attention to explore single nanoparticle electrochemistry. By improving the temporal resolution of electrochemical recording, several recent studies have uncovered the intermittent electron transfer processes during the SNC of single silver nanoparticles. The electrode current curve displayed multiple current peaks that were completely separated, instead of a single peak. In the present work, we employed surface plasmon resonance microscopy to monitor the collision and oxidation processes of single silver nanoparticles. Simultaneous optical and electrochemical recordings provided comprehensive capability to correlate the physical movement of nanoparticles (from optical signal) and the electron transfer activity (from electrochemical signal). While previous studies hypothesized the physical detachment of nanoparticles from the electrode due to electrostatic repulsion or Brownian motion, the optical imaging revealed that nanoparticles often remained in physical touch with the electrode even though no electron transfer was occurring. These results demonstrated that the electrical contact between nanoparticle and electrode, which could be rather stochastic due to thermal motion and micro-convection, played critical roles in regulating the multi-peak behavior of single silver nanoparticles.In the past several decades, nanoparticles (NPs) have found a wide range of applications in many different areas, including electrocatalysis, electrochemical sensing and fuel cells, because of their unique structure-dependent properties. [1][2][3] The electrochemical properties of NPs are dependent strongly on their size, shape and surface states. [4][5][6] Because of the inherent heterogeneity of NPs in terms of both structure and activity, single NP electrochemistry has been emerging rapidly due to its capability for resolving the electrochemical activity at single NP level and for offering another opportunity to establish the structure-activity relationship in a bottom-up manner. [7][8][9] In order to achieve this goal, a new strategy has emerged rapidly in the field of nanoelectrochemistry, namely single nanoparticle collision (SNC). [10][11][12] This method has received widespread attention once proposed because it is simple, speedy, cost-effective and because it can detect the electrochemical response of a large number of individual NPs. The key factor in identifying a single collision event was the use of an ultramicroelectrode (UME) as the working electrode, which not only decreased the collision frequency, but also greatly reduced the background noise. In collision experiments, the frequency of collision, the magnitude and shape of the current response can provide rich information about NPs, including size distribution, concentration, and diffusion coefficient. [13][14][15] Many groups have conducted intensive explorations in this field and achieved a series of remarkable research results. [16][17][18][19][20][21] Based on the different mechanisms, SNC ...

Emerging Optical Microscopy Techniques for Electrochemistry

“…3D optical tracking of Ag NPs near a polarized interface revealed intermittent NP-electrode interactions associated with partial oxidation events (72,74). This supports the hypothesis of multistep Ag→Ag + electrodissolution, first established from high-frequency current traces and attributed to stochastic electrical disconnection (75). Under conditions favoring Ag + precipitation, a time lag is observed between the injection of electrochemical charges and the dissolution of optically probed NPs, highlighting solid phase conversion (e.g., to oxide, halide, or thiocyanate crystals (72,73,(76)(77)(78)).…”

Exploring dynamic interactions of single nanoparticles at interfaces for surface-confined electrochemical behavior and size measurement

“…This distinct phenomenon was explained by the fact that AgNP partially oxidized in one stochastic collision and tended to oxidize incrementally during the repeated multicollision processes at the solution −electrode interface 13 . Although the combination of stochastic collision electrochemistry with scanned nanoprobe microscopies 19,20 or optical-based techniques 21 was introduced as a new tool for real-time analysis of the electrochemical reaction mechanism/kinetics of individual NPs with high spatial and temporal resolution 22,23 , it remains an open and challenging issue to elucidate how nanoscale particles interact with an electrode interface to clearly understand the dynamic electrochemical processes of such particles [24][25][26] .…”

Optical Nanoimpacts of Dielectric and Metallic Nanoparticles on Gold Surface by Reflectance Microscopy: Adsorption or Bouncing?

“…In principle, these situations may be differentiated optically. The optical monitoring, in 3D [11][12][13][14] by holography or in 2D by SPR [7,8,55,56], of the reaction did not show such significant NP escape but rather that the NP stays close by (< 300 nm) to the electrode surface until its complete dissolution. On one hand, these experiments then suggest that if NPs are partially dissolved, allowing their desorption, they may not be evacuated in the solution, at least with the Brownian dynamics of a freely diffusing NP.…”