Nanoelectrode ensembles

Pore diameter Pore density Distance between Fractional Fractional 

The minimum detection limit in the voltammetric analysis on NEEs should be smaller than the value observed on the macroelectrodes, based on their fractional electrode area. Indeed, detection limits of several nM for analytes such as [(trimethylamino)methyl]ferrocene (TMAfc+) are observed with NEEs while the same species on a macroelectrode could be detected only to a minimum of several pM [71] (figure 20.4). Membranes with Au nanotubules are shown to function as 

The selective ion transport phenomenon using NEEs is exemplified in a simple experiment where a membrane separates two different solutions in a U-tube cell 

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In order to explore the effects of small electrode size, we have used the template method to prepare ensembles of disk-shaped nanoelectrodes with diameters as small as 10 nm. We have shown that these nanoelectrode ensembles (NEEs) demonstrate dramatically lower electroanalytical detection limits compared to analogous macroelectrodes. The experimental methods used to prepare these ensembles and some recent results are reviewed below. 

Nanoelectrode ensembles were prepared by electroless deposition of Au within the pores of polycarbonate membrane filters (Poretics). Filters with pore diameters of 10 and 30 nm were used [25]. The pore densities and average center-to-center distances between pores for these membranes are shown in Table 1. Multiplying the pore density (pores cm ) by the cross-... 

We have demonstrated a new method for preparing electrodes with nano-scopic dimensions. We have used this method to prepare nanoelectrode ensembles with individual electrode element diameters as small as 10 nm. This method is simple, inexpensive, and highly reproducible. The reproducibility of this approach for preparing nanoelectrodes is illustrated by the fact that NEEs given to other groups yielded the same general electrochemical results as obtained in our laboratory [84]. These NEEs display cyclic voltammetric detection limits that are as much as 3 orders of magnitude lower than the detection limits achievable at a conventional macroelectrode. 

UPD of Ag onto Au electrodes covered with SAM of alkanethiols has been described by Oyamatsu [319]. Hu et al. [320] have prepared nanoelectrode ensembles by assembling silver colloid and mercaptan on a gold electrode. 

Electrochemical interfaces modified with inorganic NPs behave as nanoelectrode ensembles. In principle, the electroanalytical detection limit at a nanoelectrode ensemble can be much lower than that at an analogous macrosized electrode because the ratio between the faradaic and capacitive currents is higher.19-23... 

Generally, inorganic NPs assembled on electrode surfaces, which behave as nanoelectrode ensembles, are not diffusionally isolated and the overall current... 

Brunetti B, Ugo P, Moretto LM et ai. Electrochemistry of phenothiazine and methylviologen biosensor electron-transfer mediators at nanoelectrode ensembles. J Electroanal Chem 2000 491 166-174. 

Menon, V.P., Martin, C.R. Fabrication and evaluation of nanoelectrode ensembles. AnaZ. Chem. 67, 1920-1928, 1995. 

Chen, C.M. Chang, GL. Lin, C.H. Performance evaluation of a capillary electrophoresis electrochemical chip integrated with gold nanoelectrode ensemble working and decoupler electrodes. J. Chromatogr. A, 2008,1194 (2), 231-236. 

The first part of this section focuses on the main characteristics and fabrication techniques used for obtaining templating membranes and depositing metal nanostructures by suitable electroless and elecuochemical procedures. Methods such as sol-gel (10-12) or chemical vapor deposition (10, 13), which have been used primarily for the template deposition of carbon, oxides, or semiconducting-based materials, will not be considered here in detail. The second part of the section focuses on the electrochemical properties of the fabricated nanomaterials with emphasis on the characteristics and applications of nanoelectrode ensembles (NEEs). 

Electrochemistry with template nanomaterials nanoelectrode ensembles... 

Nanoelectrode ensembles (NEEs) (see also Chapter 10 of this handbook) are nanotech-based electroanalytical tools which find application in a variety of fields ranging from electroanalysis to sensors (86) and electronics (7). They are fabricated by growing metal nanowires in the pores of a template, typically a PC nanoporous manbrane. The density of the pores in the template determines the number of Au-disk nanoelectrode elanents per cm of NEE surface and, correspondingly, the average distance between the nanoelectrode elements. Such electrode systems proved to be valuable tools for trace determinations and kinetics studies by simply using cyclic voltammetry (CV) (5, 69, 86, 97). 

Femmidez JL, Wijesinghe M, Zoski CG (2015) Theory and experiments for volttunmetric and SECM investigations and application to ORR electrocatalysis at nanoelectrode ensembles of ultramicroelectrode dimensions. Anal Chem 87 1066-1074... 

Zoski CG, Wijesinghe M (2010) Electrochemistry at ultramicroelectrode arrays and nanoelectrode ensembles of macro- and ultramicroelectrode dimensions. Israel J Chem 50 347-359... 

FIGURE 6.16 Fabrication of a glucose biosensor based on CNT nanoelectrode ensembles (a) Electrochemical treatment of the CNT-NEE for functionalization, (b) Coupling of the enzyme (GOx) to the functionalized CNT-NEE. (Adapted with permission from Y. Lin et al., Nano Lett. 4, 191. Copyright 2004, American Chemical Society.)... 

Jena, B.K. and Raj, CR. (2008) Gold nanoelectrode ensembles for the simultaneous electrochemical detection of... 

Nanoelectrodes have been widely used in the form of nanoelectrode arrays (NEAs) or nanoelectrode ensembles (NEEs) where individual nanoelectrodes are isolated from one another by various... 

Ugo, R, Moretto, L. M. and Vezz F. 2002. lonomer-coated electrodes and nanoelectrode ensembles as electrochemical environmental sensors Recent advances and prospects. ChemPhysChem 3 917-925. 

Lowe, R. D., Mani, R. C., Baldwin, R. P. et al. 2006. Nanoelectrode ensembles using carbon nanopipettes. Electrochem. Solid State Lett. 9 H43-H47. 

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