a b s t r a c tThe electrochemical determination of Hg(II) at trace level using gold nanoparticles-modified glassy carbon (AuNPs-GC) electrodes is described. Starting from HAuCl 4 in NaNO 3 , gold nanoparticles (AuNPs) were deposited onto Glassy Carbon (GC) electrodes using Cyclic Voltammetry (CV). Different deposits were obtained by varying the global charge consumed during the whole electroreduction step, depending on the number of cyclic potential scans (N). AuNPs were characterized as a function of the charge using both CV in H 2 SO 4 and Field Emission Gun Scanning Electron Microscopy (FEG-SEM). The AuNPs-GC electrodes were then applied to determine low Hg(II) concentrations using Square Wave Anodic Stripping Voltammetry (SWASV). The AuNPs-GC electrodes provided significantly improved performances in Hg(II) determination compared to unmodified GC and bare Au electrodes. It was shown that the physico-chemical properties of the deposits are correlated to the performances of the AuNPs-GC electrode with respect to Hg(II) assay. The best results were obtained for four electrodeposition cyclic scans, where small-sized particles (36 ± 13 nm) with high density (73 particles lm À2 ) were obtained. Under these conditions, a linearity range from 0.64 to 4.00 nM and a limit of detection of 0.42 nM were obtained.

International audienceGold nanoparticles (AuNPs) were deposited onto glassy carbon (GC) by constant potential electrolysis (CPE) using various sets of potential and duration from -0.3 to 0.7 V and 10 to 1800 s, respectively. The physico-chemical characteristics of the as-obtained deposits were investigated by cyclic voltammetry (CV) in H2SO4, field emission gun scanning electron microscopy (FEG-SEM), and Pb underpotential deposition (UPD). Their performances towards the oxygen reduction reaction (ORR) in a NaCl-NaHCO3 (0.15 M / 0.028 M, pH 7.4) neutral solution were examined and correlated to AuNPs size and density. The best results were obtained using the deposits which exhibited a high density (555 +/- 49 µm-2) of relatively small AuNPs (25 +/- 12 nm). The Koutecky-Levich treatment was systematically applied to all the deposits in order to determine the number of electrons n exchanged for the ORR in the potential range from 0.1 to -1 V. The values of the cathodic transfer coefficients Beta n were also extracted and compared to the values reported for unmodified GC and bulk Au. A map of the Beta n values as a function of AuNPs electrodeposition potential and duration was also provided

Gold nanoparticles (AuNPs) were deposited on Glassy Carbon (GC) substrate by using three electrochemical techniques: Cyclic Voltammetry (CV), Chronoamperometry (CA) and Potentiostatic Double-Pulse (PDP). For each electrodeposition method, the resulting AuNPs-modified electrodes were characterized by CV in H 2 SO 4 and Field Emission Gun Scanning Electron Microscopy (FEG-SEM). CA was found to be the best electrodeposition mode for controlling the morphology and the density of AuNPs. The modified electrodes were used for low Hg(II) concentration detection using Square Wave Anodic Stripping Voltammetry (SWASV). AuNPs obtained by CA afforded the best amperometric response while involving the lowest amount of charge during the electrodeposition step (Q Au(III)). This analytical response is correlated to both the smallest particle size (ca. 17 nm in diameter) and the highest particle density (332 particles m −2), thus displaying high electrode effective surface area. In these optimal conditions, using a Hg(II) preconcentration time of 300 s, the nanosensor array exhibited a linearity range from 0.80 to 9.9 nM with a sensitivity of 1.16 A nM −1. A detection limit of 0.40 nM (s/n = 3) was reached.

A great challenge in the area of heavy metal trace detection is the development of electrochemical techniques and devices which are user-friendly, robust, selective, with low detection limits and allowing fast analyses. This review presents the major contribution of the French scientific academic community in the field of electrochemical sensors and electroanalytical methods within the last 20 years. From the well-known polarography to the up-to-date generation of functionalized interfaces, the different strategies dedicated to analytical performances improvement are exposed: stripping voltammetry, solid mercury-free electrode, ion selective sensor, carbon based materials, chemically modified electrodes, nano-structured surfaces. The paper particularly emphasizes their advantages and limits face to the last Water Frame Directive devoted to the Environmental Quality Standards for heavy metals. Recent trends on trace metal speciation as well as on automatic “on line” monitoring devices are also evoked.

a b s t r a c tA voltammetric microsensor has been developed for the simultaneous assay of ascorbic (AA) and uric (UA) acids in aqueous solution. The electrode surface has been modified by means of electropolymerized conductive poly(3,4-ethylenedioxythiophene) PEDOT organic films. The electrocatalytic activity of the interface was dependent on the electropolymerization parameters inducing change in the structure and the morphology of the resulting polymer. The PEDOT thickness was optimized in order to maximize the peak potential separation between both acids oxidation to more than 400 mV. By using differential pulse voltammetry (DPV), the sensitivity of the microsensor was 0.87 lA lM À1 cm À2 and 4.05 lA lM À1 cm À2 for AA and UA respectively. The later was sensible to the presence of AA in the mixture, making evidence of the catalytic mechanism of UA regeneration. The calibration curves were linear in the concentration range 5.0-300 lmol L À1 for AA and 2.0-600 lmol L À1 for UA. The detection limits were 2.5 lmol L À1 and 1.5 lmol L À1 respectively. The sensor response was unmodified in the presence of the major electroactive biomarkers. The application of the PEDOT modified microsensor to the analysis of human blood serum was evaluated.

Several attempts to attack tumours in experimental systems have been made using conjugates of chemotherapeutic agents or potent toxins with antibodies (immunotoxins). In vitro studies have been highly successful, showing target specificity of a high order in some cases. However, so far, such conjugates have been inadequate in vivo, probably for two main reasons. First, conventional heteroclonal antibodies are perhaps inappropriate, because purification by biochemical methods leaves a large amount of non-antibody gamma-globulins. The use of monoclonal antibodies may overcome this problem. Second, when whole toxins have been conjugated to antibodies there has been a strong residual nonspecific cytotoxicity due to the binding capacity of a subunit, the B-piece of the toxin. (Diphtheria toxin or ricin consist of two polypeptide subunits. The A-piece is responsible for inhibition of protein synthesis on ribosomes, and the B-piece binds to galactose residues on the cell membrane and facilitates the transmembrane passage of the A-piece.) In the present work the problem of nonspecific binding by the B-piece has been circumvented by using the A-piece only as the toxin component of immunotoxins; these immunotoxins are active both in vitro and in vivo.

International audienceElectrochemical and spectroscopic investigations were performed in order to clarify the mechanism of 4-nitrobenzene diazonium reduction on glassy carbon in protic medium. The number and nature of the electron transfer processes were found to be strongly correlated to the electrode surface state. On polished electrode two different reduction peaks were observed. Selective electrolyses realized at the corresponding potential definitely proved that the grafting process actually occurs at a potential distinct from NO2 electroreduction, this latter inducing the presence of the quasi-reversible NO/NHOH redox couple at the electrode surface. These results were confirmed by XPS analyses. Furthermore, voltammetric experiments using Fe(CN)63- showed that the electrochemical properties of the modified electrode strongly depend on the potential applied for grafting, which modulates the nitro group oxidation state. All the results suggested that the electrode functionalization was more efficient when grafting and NO2 reduction were performed separately

International audienceIntegrated (Pt/PEDOT–Pt–Ag/AgCl) and (Au/PEDOT–Pt–Ag/AgCl) electrochemical microcells (ElecCell) were elaborated for the detection of ascorbic acid, dopamine and uric acid by differential pulse voltam-metry. Specific attention was brought to the integration of poly(3,4-ethylenedioxythiophene) (PEDOT) film by electropolymerization. Gold and platinum working microelectrodes were investigated while using ethylenedioxythiophene (EDOT) electrodeposition processes in water or acetonitrile solvents. For the three antioxidant species, best (multi-)detection properties were obtained for acetonitrile-based PEDOT films deposited on gold working electrode. Thus, using integrated (Au/PEDOT–Pt–Ag/AgCl) Elec-Cell microdevices, analytical performances were determined for ascorbic acid, dopamine and uric acid, exhibiting high selectivity (oxidation potential: −40, 150 and 280 mV, respectively), linear concentration range from 0.1 to 300 ␮M, high sensitivities (0.85, 1.65 and 3.06 ␮A/␮M cm 2 , respectively) and low detection limit (0.2 ␮M, 0.1 ␮M and 0.05 ␮M, respectively)