We present a method for the production of nanoelectrodes using focussed ion beam techniques (FIB). The electrodes utilise nanometric holes milled in a silicon nitride based pasivation layer, followed by wet etching of a silicon oxide based pasivation layer, to expose an underlying gold electrode. After functionalisation using a surface assembled monolayer and an electrochemically grown polypyrrole, these gold nanoelectrodes have been tested, via cyclic voltammetry, in the detection of [Fe(CN)6]4−/3− ions. The nanoelectrodes will be used to investigate the electrical properties of nanometric biological specimen.

By using the metallacarborane [Co(C2B9H11)(2)](-), [1](-), as a doping anion, PPy materials can be made 300-500 mV more resistant to overoxidation. These materials are written as PPy/[A]to indicate a noncovalency between the anion and the PPy and have a clear overoxidation resistance limit, ORL, so that once this is surpassed the material becomes permanently nonelectroactive or dead. On the contrary if [Co(C2B9H11)(2)](-) chemically bonded to pyrrole through a spacer and then is copolymerized with pyrrole the resulting material, PPy-[1sp], has an electroactive behavior similar to PPy/[A] so that once an apparent ORL is reached the PPy-[1sp] becomes electroinactive but, very importantly, in few hours recovers the electroactivity. The situation is so attractive that even in the case that the overoxidation threshold was surpassed the system would react to restore itself. In this paper we demonstrate that [1](-) not only enhances the overoxidation resistance but that, if grafted to the PPy strand, the applied voltage that can sustain the new material can go far beyond the overoxidation limit of the compositionally similar material with, however, no anion grafting. These properties are due to grafting of the metallacarborane to the PPy and have not been observed before. This behavior is not a consequence of the anion grafting to the PPy but depends on the nature of the anion.

A novel dithiomacrocycle (4-phenyl-11-decanoyl-1,7-dithia-11-azacyclotetradecane-4-sulfide) has been synthesized and used as a new ionophore in order to develop a plasticized poly(vinyl chloride) membrane for copper ion detection. The performance of these novel planar copper(II)-selective potentiometric microelectrodes was investigated using potentiometric measurements. The developed microelectrodes exhibits a good linear response of 29.5±1mV per decade within the concentration range of 1.0×10−6 to 1.0×10−2M (r=0.9995) of Cu2+. The detection limit was determined as 5.62×10−7M and the selectivity coefficients for possible interfering cations were evaluated. The microelectrodes are suitable for use with aqueous solutions of pH 3.5–6.0 and were found to be insensitive to the nature of the anions used in the sample.

The development of novel potassium-ion selective microelectrodes using microfabrication technologies and electrochemical polymerization is described. The microelectrode is based on electropolymerized polypyrrole films, doped with cobaltabis(dicarbollide) ions ([3,3′-Co(1,2-C2B9H11)2]), as an internal solid contact layer between the platinum surface and the polymeric sensing membrane. The ion selective membranes, which are based on a plasticized PVC membrane, contain 1,3-(di-4-oxabutanol)-calix[4]arene-crown-5 as a novel potassium ionophore, and are deposited on top of a layer of the conducting PPy[3,3′-Co(1,2-C2B9H11)2]. The response of the microelectrode was linear with a Nernstian slope of 51±2mVdecade−1 over a K+ ion concentration range of 6×10−6 to 1×10−1M, with a detection limit of 1.8×10−6M. The microelectrode is suitable for use within the pH range of 3–11. The electrode could be used for at least one month without a considerable alteration in its potential.

Planar sodium-selective potentiometric microelectrodes with a conducting polymer (polypyrrole doped with cobaltabis(dicarbollide) ions ([3,3′-Co(1,2-C2B9H11)2]−)) as solid contact layer between the polymeric sensitive membrane and the platinum substrate have been constructed. The p-tert-butylcalix[4]arene ethyl ester was used as ionophore for sodium recognition. The microelectrode shows a linear response for Na+ concentrations between 3.0×10−6 and 1.0×10−1M with a Nernstian slope of 58.65±2mV per decade and a detection limit of 1.45×10−6M. The response time was 14s, and the electrode is suitable for use within the pH range of 3–10.

The influence of weakly coordinating anions with different shapes and substituents has been studied to get the overoxidation resistance limit of the material, ORL. The anions utilized are derivatives of [Co(C2B9H11)2]−, [B12H12]2− and [B12H11NH3]−. The following tendencies have been established (1) boron cluster monoanions are to date the anions that offer the highest stability to overoxidation of PPy doped materials (2) the ORL stability of the material can not be attributed only to the shape of the cluster (3) monoanionic clusters are far superior than dianionic to get an ORL rise (4) cluster charge density reduction results in ORL rise as has been observed in [Co(C2B9H11)2]− after incorporation of electron-withdrawing substituents with no electron back-donation (5) globular, rigid and large monoanions are less suitable for enhanced ORL values than elongated and non-rigid species (6) adequate anion's substitution produce a rise in the ORL of the material, thus polyether side-arms are beneficial with [Co(C2B9H11)2]−, whereas, T-shaped methylaryl groups are appealing in [B12H11NH3]− based materials, respectively, (7) substituents on the anions usually imply higher difficulty in the materials' growth. The high boron contents in these materials has permitted to learn on the fate of the doping anions during the overoxidation process. There is a built-up of the concentration of the doping anion in the electrolyte near surface area, whereas, a depletion is observed in the nearest inner layers.