Scanning Electrochemical Microscopy with Gold Nanotips: The Effect of Electrode Material on Electron Transfer Rates

Abstract

The disk-type, polished Au nanoelectrodes were prepared, characterized, and used as tips in the scanning electrochemical microscope (SECM). Kinetic parameters were measured for several rapid heterogeneous electron transfer (ET) reactions and compared to those obtained previously at Pt nanoelectrodes. The kinetics of most investigated ET processes were found to be independent of the electrode material. In contrast to the previously reported results, the rate constant of hexaammineruthenium(III) reduction was somewhat higher at Pt than at Au electrodes in different electrolyte solutions. This finding suggests that this reaction exhibits some degree of nonadiabaticity.

Electrochemistry at highly oriented pyrolytic graphite (HOPG): lower limit for the kinetics of outer-sphere redox processes and general implications for electron transfer models

“…For Ru(NH 3 ) 6 3+/2+ on Au and Pt, k 0 was considered to be statistically higher on Pt (17.0 ± 0.9 cm s -1 ) than on Au (13.5 ± 2 cm s -1 ). 103 However, it should be pointed out that although SECM with nanoelectrodes provides much higher mass transport than other techniques, 101 enabling the measurement of ultra-fast electrode kinetics, such measurements require great care, as nanoelectrodes may be damaged easily by electrostatic discharge and electrochemical etching. 106 This type of damage is not necessarily manifest in the SECM or the steady-state voltammetric response.…”

Electrochemistry at Nanoscale Electrodes: Individual Single-Walled Carbon Nanotubes (SWNTs) and SWNT-Templated Metal Nanowires

“…electrodes with at least one dimension in the sub-100 nm regime, for both the quantification of fast electron transfer (ET) kinetics [1][2][3][4][5][6] and electroanalysis. 4,7 The most popular NSEs are based on tapered or etched metal wires encapsulated by a variety means to produce disk or conical electrodes.…”

“…The latter is likely to be a consequence of the adsorption of products and/or the formation of Prussian blue 31,32 during the course of the experimental measurement. Although Fe(CN) 6 4-/3-is used as a couple for investigating many electrode geometries, it is known to be a rather complex couple showing non-ideal redox behavior 30,33 and such effects become very noticeable in these measurements due to the very high fluxes to the NW electrodes. 2) solution at a 70 nm Au NW electrode, at 100 mV s -1 , using a microcapillary with R c = 21 µm and R m = 24 µm.…”

Methods of photoelectrode characterization with high spatial and temporal resolution

“…UMEs having 1-25 mm diameter tips are routinely employed, and are commercially available, although UME tips as small as 10 nm have been demonstrated. 59,60 SECM thus offers exciting opportunities to study photoelectrode materials and architectures with nano-scale heterogeneities, but the complexity of these measurements often increases substantially at the nano scale. [61][62][63] Because SECM is typically operated with tip/substrate separation distances that are approximately 1-2 times the tip radius, operating a nano-scale UME at constant Z-position requires that a sample be extremely flat in order to maintain a constant tip/ substrate separation distance.…”