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The objective of this paper is the study of the electrochemical oxidation and subsequent polymerisation of 1,3-dihydroxybenzene, 3-aminophenol and 1,3-phenylenediamine at pH 7. These related monomers were subsequently utilised by the authors in the production of pinhole free masks for the construction of features on gold surfaces of nanometer dimensions (neutral pH was required due to the use of biological templates). It is shown that whilst the electrochemical oxidation of 1,3-phenylenediamine is very similar to that of 3-aminophenol, it is quite dissimilar to that of 1,3-dihydroxybenzene and this can be attributed to the lack of interaction between the substituents on the ring due to their meta orientation. This behaviour can be correlated with differences in the HOMO values of the molecules as calculated using Crystal98. X-ray photoelectron spectroscopy was used to characterise the polymer films and their thin layer nature.

This paper describes studies of a combined electrochemical/acoustic wave sensor for detection of metal ions in aqueous solutions. The sensor is based upon surface complexation of the metal ions at thiodisuccinic acid (TDS) functionalised self-assembled monolayer (SAM) modified electrodes on 10 MHz AT-cut quartz resonators, functioning as a quartz crystal microbalance (QCM). The SAM-modified electrodes were employed for the detection of Cd(II) ions in single and mixed metal ion solutions, with Pb(II) or Cu(II) as the interferants. Acoustic determination was based on the QCM frequency change associated with the binding to the surface-immobilised ligand of metal ions as a function of their concentration. Frequency response data were acquired under emersed and immersed conditions for ligand binding to the Au electrode and, subsequently, metal ion binding to the ligand. In the latter case, the data were interpreted according to a range of isotherms, of which the Temkin isotherm was found empirically best to describe the concentration dependence. The acoustic wave data yielded information on equilibrium binding stoichiometry and energetics. The extent of metal ion binding was also determined by coulometric assay (upon reduction to the zero-valent metal) after transfer to metal ion-free electrolyte solution. XPS studies of surface-bound metal-TDS ligand complexes confirmed the binding stoichiometry obtained from the electrochemical and acoustic wave responses, and provided information on the ligand–substrate binding and bound analyte oxidation state.

The electrochemical quartz crystal microbalance (EQCM) has been used to study overall ion and solvent transfers in surface-immobilized [Os(bipy)2(PVP)10Cl]+ films exposed to aqueous p-toluenesulphonic acid solutions. Crystal impedance measurements were used to identify situations where the observed frequency response was dominated by changes in the viscoelastic characteristics of the films. Unfunctionalized pyridine moieties can be protonated (pKaapp = 2.9 ± 0.1), leading to pH-dependent film properties. The characteristics of films at open circuit and accompanying Os(II)/Os(III) redox switching were studied. In both cases, viscoelastic effects are observed at low and high electrolyte concentrations; at very low and intermediate concentrations the Sauerbrey equation can be used to interpret the frequency response. Even when the layer is non-rigid, isotopic substitution experiments show that solvent transfer accompanies redox switching. The film thickness dependence of the frequency response to redox switching is greater when the films are exposed to aqueous p-toluenesulphonic acid than to perchloric acid.

Electrochemical quartz crystal microbalance (EQCM) measurements were used to study redox-induced changes in the ion and solvent content of polybithiophene/polyxylylviologen (PBT/PXV) bilayers. Experimental measurements were taken under slow scan voltammetric conditions in 1 mol dm −3 tetraethylammonium perchlorate + CH 3 CN. Outer (PXV) layer redox conversion occurs only at potentials where the inner (PBT) layer becomes conducting. On the relatively long time-scales employed, bilayer mass changes are dominated by perchlorate anion transfer (ejection on PXV 2+ reduction and entry on PXV 0 oxidation), with relatively little solvent transfer. The mass-charge characteristics of PBT/PXV bilayer and PXV single-layer films are relatively similar, despite their very different mass-potential characteristics.