Voltammetry at the Nanoscale

The transfer of a probe ion across nano-ITIES arrays has been characterized voltammetrically. For instance, static IT voltammetry at the nano-ITIES array templated by a y-alumina membrane was used to determine membrane porosity. In this work, a nanoscale interface was formed at the orifice of each nanopore filled with the aqueous solution of a probe ion (tetraethylammonium, TEA ) in contact with the external organic solution (Fig. 17a). Potential sweep rates were chosen such that the mass transport of the probe ion during the forward potential sweep was controlled by the linear diffusion confined within nanopores (Fig. 17b). The resultant peak current based on TEA transfer depends on the total area of the nanoscale... 

These nanoporous electrodes can be utilized for the same type of electrochemical studies as planar electrodes but have some distinct differences in electrochemical response due to their nanoscale geometry. The kinetics at the electrode surface can be significantly altered as the pore sizes are often on the same scale as the electrical double layer thickness and thus overlapping double layers can be achieved. Voltammetric responses of nanoporous electrodes are distinctly different from their nonporous counterparts as the surface features can provide acceleration of proton or electron transfer steps of electrochemical reactions. " Despite these differences in electrochemical response, nanoporous electrodes are often utilized to perform chronoamperometry and voltammetry to achieve the detection of various electroactive analytes. 

In these cases, the double layer and the diffusion layer are no longer straightforwardly decoupled, and so electric fields, altered overpotentials and population differences in the double layer are likely to affect the voltammetry in a manner which would not occur for electrochemistry at a larger electrode. Therefore, nanoscale electrochemistry requires consideration of the double layer and is theoretically more demanding to interpret, as well as opening the door to a number of interesting phenomena. 

In a series of voltammetric experiments on nanoscale dendrimers, C. Ama-tore et al. discussed interesting nanoscale effects in single molecule voltammetry [ChemPhysChem 2 (2001) 130]. Fourth-generation PAMAM (polyamidoamide) dendrimers modified with 64 Ru(II) redox sites at their surface were adsorbed onto a platinum substrate the dendrimer molecule has a radius of approximately 5 nm (see Fig. 11.2). 

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