Nanoelectrodes, nanoelectrode arrays and their applications

Abstract

This review deals with the topic of ultrasmall electrodes, namely nanoelectrodes, arrays of these and discusses possible applications, including to analytical science. It deals exclusively with the use of nanoelectrodes in an electrochemical context. Benefits that accrue from use of very small working electrodes within electrochemical cells are discussed, followed by a review of methods for the preparation of such electrodes. Individual nanoelectrodes and arrays or ensembles of these are addressed, as are nanopore systems which seek to emulate biological transmembrane ion transport processes. Applications within physical electrochemistry, imaging science and analytical science are summarised.

Electrochemical Behavior of Nanoelectrode Ensembles in the Ionic Liquid [BMIm][BF4]

“…Such a theoretical current is 5 -6 times larger than the experimental value, above reported. A possible explanation of this discrepancy is that the nanoelectrodes are partially recessed so that Equation 2 [32] should be used instead of Equation 1.…”

Electroanalysis at discrete arrays of gold nanowire electrodes

“…[36] This improvement in the capacitive behaviour achieved at nanowire electrodes is due to the nanoscale critical dimensions of the electrode, at which the thickness of the analyte diffusion profiles and the electrolyte double layer are comparable, resulting in reducing charging due to much faster mass transport and reduced solution resistance. [5,8,35] This in turn greatly improves the signal-to-noise (S/N) ratios achievable at nanoelectrodes when compared to conventional electrodes.…”

“…[7,8] In electrochemistry, work at very small (sub-micrometre) electrode sizes at silicon substrates, has mainly been restricted to electrochemically favourable geometries, such as nanodisks, nanopores and short inlaid nanobands. [5,[9][10][11][12][13] However, when employed as discrete electrodes, these structures can have extremely low measurable signals (typically < 100 pA) [8,14,15] and require large electrode numbers in array format (> 10 x 10) to realise reasonable measureable currents, i.e. in the nanoAmpere range.…”

“…[1][2][3][4] Enhanced electrochemical sensitivity arises from improved mass transport of the nanoscale electrodes offering the potential for kinetic measurements of faster electrochemical processes. [5] Other advantages include: shorter response times, lower RC constants, low analyte depletion and greatly reduced sample volumes. [6] Finally, smaller electrodes dimensions should enable nanosensors to be fabricated at high density, at technologically relevant substrates, such as at a silicon chip, thus yielding much higher information-generating capability per device.…”

Interdigitated 50 nm Ti electrode arrays fabricated using XeF2enhanced focused ion beam etching

“…The progress in fabrication methods for nanostructures made in the last few years opens the door for new applications in fields such as biotechnology [1] and microelectrochemistry [2][3][4], as well as microelectronics [5]. Interdigitated electrode arrays (IEAs) of micrometric dimensions and nanometric gaps and widths offer various advantages compared to micrometric IEAs.…”