Recessed Nanoelectrodes for Nanogap Voltammetry

Abstract

Exploration of electrochemical properties of nanoconfined species is an area of active interest. In this Communication, recessed Pt nanoelectrodes were prepared by controlled electrochemical etching and evaluated by combination of voltammetry and atomic force microscopy. The effects of ac frequency and ac voltage on the etching process are discussed. Voltammetry was carried out in the nanogap between the etched nanoelectrode and the planar substrate surface. Peak‐shaped steady‐state voltammograms were obtained with a low concentration of supporting electrolyte and fitted to the theory, pointing to the influence of the electrical double layer on transport of a charged redox species within the confined space.

Identifying Nanoscale Pinhole Defects in Nitroaryl Layers with Scanning Electrochemical Cell Microscopy

“…As we observed no peaks in the voltammograms, we were satisfied with the approximation of the pinhole as flat however in the case of thicker surface films in addition to a characteristic pinhole radius, the depth of the pinhole will play a significant role. A steady state current will still be observed however a peak could emerge due to a thin‐layer‐cell type electrolysis of species in the cylindrical pinhole or a depression in the limiting current as is the case for recessed nano‐ and microelectrodes …”

“…A steady state current will still be observed however a peak could emerge due to a thin-layer-cell type electrolysis of species in the cylindrical pinhole or a depression in the limiting current as is the case for recessed nano-and microelectrodes. [40] The capability to identify pinhole surface defects in a partially passivated surface can have significant implications but perhaps one of the more readily apparent case is corrosion and protective coatings. Pinhole defects in protective films such as polymeric or conversion coatings can be significantly detrimental due to pitting corrosion, which can lead to a breakdown of structural integrity or leaching of potentially toxic metal ions (especially problematic in implants).…”

A few key theoretical issues of importance in modern molecular electrochemistry

“…New nanofabrication methods have been recently developed to create nanochannels with interelectrodes gaps of precise dimensions in the tens of nanometers range in hope to evaluate in more details the stochastic properties of a redox molecules [12][13][14][15]. More interestingly in view of the subject of this perspective is the fact that such nano-gap electrochemical cells allowed investigating the effect of diffuse layer electrical fields on the meaning of electron transfer (ET) kinetics [16][17][18][19][20][21], as well as the consequences of adsorption of one member of the investigated redox couple [22], while these effects are difficultly interpreted when observed under classical electrochemical conditions.…”

“…Presumably, this is the source of the uncommon effects related to the composition of the electrolytes cited above [16][17][18][19][20][21]. We therefore strongly believe that this problem of single molecule electrochemistry should be precisely investigated theoretically before any hope of using these approaches to unravel electrochemical properties beyond investigations related to the stochastic nature of fundamental electrochemical laws [11,12,27].…”

Single Cylindrical Nanopore Electrodes: Surface Functionalization, Unusual Voltammetry, and Size‐Exclusion Properties

“…The steady‐state voltammetric behavior and electrostatic‐gated transport properties of such conically shaped nanopore electrodes were investigated carefully. Mirkin and Sun fabricated and characterized recessed nanoelectrode/nanopore electrode by slightly etching platinum nanodisk electrode, which have been used to study electrochemical reaction in TLC ,,. However, the electrochemical behaviors using conically shaped nanopore electrodes with micrometers developed by White et al.…”