a b s t r a c tEnsembles of copper nanowire electrodes (CuWNEEs) are prepared via electrodeposition in track-etched polycarbonate membranes. Three different preparation methods are compared showing that the better results in terms of sensor durability and reproducibility are achieved by pre-sputtering a thin gold film on the templating membrane and attaching it to a supporting electrode by exploiting the adhesion property and ionic conductivity of a thin Nafion interlayer. SEM-EDS analyses together with double layer charging currents measurements indicate that these arrays are formed by copper nanowires with 400 nm diameter, 10 m length distributed with a spatial density of 1 × 10 8 nanowires/cm 2 . The voltammetric reduction of nitrate at CuWNEEs is characterized by a well-resolved cathodic peak at approximately −0.680 V vs Ag/AgCl, whose current scales linearly with the nitrate concentration in the 10-400 M range. The limit of detection (LOD) achieved by simple linear sweep voltammetry is in the 1.7-3.0 M range, depending on the CuWNEE preparation method, such LOD values being among the lowest reported up to now in the literature. The possibility to use CuWNEEs in chloride and nitrite containing water samples is demonstrated.

In this contribution we report on results from an optimization study of SU-8 photoresist derived carbon electrodes. SU-8 derived carbon tends to be glassy in nature, however, based on the exact pyrolysis strategy and other fabrication parameters employed one can obtain a range of electrical, electrochemical and thermal properties related to the variation of the graphitic content of the thus obtained carbon. Hence, in order to obtain electrodes that emulate or improve upon the performance of commercially available glassy carbon (GC) electrodes, the right choice of pyrolysis conditions, and fabrication parameters such as the polymer patterning method, the nature of the substrate, polymer precursor film thickness and dimensions of the electrodes are all important. Carbon electrodes made employing a variety of pyrolysis times and pyrolysis end temperatures, film thicknesses and substrates are investigated by cyclic voltammetry of a redox probe ([Fe(CN) 6 ] 4− ), resistance measurements and spectroscopic analysis (Raman and XRD). SU-8 derived carbon electrodes displayed a wide potential stability window even in acidic media comparable to that of commercially available GC electrodes. Finally, these electrodes were applied to the simultaneous detection of traces of Cd(II) and Pb(II) through anodic stripping voltammetry and detection limits as low as 0.7 and 0.8 μgL −1 were achieved.

The results of a study on the determination of trace levels of arsenic with nanoelectrode ensembles (NEEs) are reported. In order to lower the detection limit and to increase the number of performable analysis for each NEE, the right choice of the supporting electrolyte concentration and electroanalytical parameters were optimized. The electrochemical behavior of As(III) at NEEs was studied at first by cyclic voltammetry, while trace concentrations of As(III) were determined by anodic stripping square wave voltammetry. The method is characterized by a detection limit as low as 5 ng/L (65 pM) after 3 min preconcentration at À0.4 V. Finally, NEEs were applied to trace As analysis in real samples such as certified seawater samples.

A study on the simultaneous determination of Ni(II) and Co(II) dimethylglyoximates (Ni-DMG and Co-DMG) through adsorptive cathodic stripping voltammetry at an in situ bismuth-modified gold electrode (Bi-AuE) is reported. The key operational parameters, such as Bi(III) concentration, accumulation potential and accumulation time were optimized and the morphology of the Bi-microcrystals deposited on the Au-electrode was studied. The BiAuE allowed convenient analysis of trace concentrations of solely Ni(II) or of Ni(II) and Co(II) together, with cathodic stripping voltammograms characterized by well-separated stripping peaks. The calculated limit of detection (LOD) was 40 ng L À1 for Ni(II) alone, whereas the LOD was 98 ng L À1 for Ni(II) and 58 ng L À1 for Co(II), when both metal ions were measured together. The optimized method was finally applied to the analysis of certified spring water (NIST1640a) and of natural water sampled in the Lagoon of Venice. The results obtained with the BiAuE were in satisfactory agreement with the certified values and with those provided by complementary techniques, i.e., ICP-OES and ICP-MS.