Electrochemical Responses and Electrocatalysis at Single Au Nanoparticles

Abstract

Steady-state electrochemical responses have been obtained at single Au nanoparticles using Pt nanoelectrodes. A Au single-nanoparticle electrode (SNPE) is constructed by chemically immobilizing a single Au nanoparticle at a SiO(2)-encapsulated Pt disk nanoelectrode, which was previously modified by an amine-terminated silane. The Au SNPE has been characterized by transmission electron microscopy, underpotential deposition of Cu, and steady-state cyclic voltammetry. It has been found that the presence of a single Au nanoparticle enhances the electron transfer from the Pt nanoelectrode to the redox molecules, and the voltammetric response at the Au SNPE depends on the size of the Au nanoparticle. The Au SNPE has been utilized to examine the oxygen-reduction reaction in a KOH solution to explore the feasibility of measuring the electrocatalytic activity at a single-nanoparticle level. It has been shown that the electrocatalytic activity of single Au nanoparticles can be directly measured using SNPEs, and the electrocatalytic activity is dependent on the size of the Au nanoparticles. This study can help to understand the structure-function relationship in nanoparticle-based electrocatalysis.

Tuning the Size of Gold Nanoparticles with Repetitive Oxidation-reduction Cycles

“…The same holds true for AuNP with a nominal diameter of 20 nm, although the rate of charge decay with respect to the scan number was considerably slower than for 4 nm AuNP ( Figure 3B). Also, the cathodic and anodic peak potentials measured for both 4 nm and 20 nm AuNP were shifted relative to the bulk gold oxidation ( Figure S4, Supporting Information).Such sizedependent AuNP oxidation potential shifts were observed in previous studies [11,12] using surface attached particles and suggested a theoretical model based on free energy changes with the metal surface area.…”

“…[12] Linker usage was avoided when AuNP are physisorbed using a drop-casting to screen printed [13] or glassy carbon electrodes, [14] that enabled to register particle size-dependent charge-transfer responses. A direct charge exchange between the freely diffusing nanoparticles and the ultramicroelectrode was also demonstrated recently, [14,16,17,18,19,20] despite low diffusion coefficients of nanoparticles in solution.…”

Scanning Electrochemical Microscopy of Individual Catalytic Nanoparticles

“…[9][10][11][12][13][14][15] The landing experiments provided more information about transport processes and collision dynamics, the size distribution and concentration of NPs than electron transfer (ET) or catalytic activities. The problems in NP immobilization experiments [13][14][15] include difficulties in characterizing the geometry of the nanoelectrode/NP system, significant background current produced by the underlying electrode surface, and poorly defined NP shape if it is formed in situ by electrodeposition. …”

Fabrication and characterization of gold nanohole electrode arrays

“…Plasma enhanced chemical vapour deposition [11], chemical etching [5], self-assembly of gold nanoparticles have also been used to fabricate nanoelectrodes [12].…”