Foto personale

Laura PIGANI

Department of Chemical and Geological Sciences

Pigani, Laura; VASILE SIMONE, Giuseppe; Foca, Giorgia; Ulrici, Alessandro; Masino, Francesca; Cubillana Aguilera, L.; Calvini, Rosalba; Seeber, Renato ( 2018 ) - Prediction of parameters related to grape ripening by multivariate calibration of voltammetric signals acquired by an electronic tongue - TALANTA - n. volume 178 - pp. da 178 a 187 ISSN: 0039-9140 [Articolo in rivista (262) - Articolo su rivista]
Abstract

An electronic tongue (ET) consisting of two voltammetric sensors, namely a poly-ethylendioxythiophene modified Pt electrode and a sonogel carbon electrode, has been developed aiming at monitoring grape ripening. To test the effectiveness of device and measurement procedures developed, samples of three varieties of grapes have been collected from veraison to harvest of the mature grape bunches. The derived musts have been then submitted to electrochemical investigation using Differential Pulse Voltammetry technique. At the same time, quantitative determination of specific analytical parameters for the evaluation of technological and phenolic maturity of each sample has been performed by means of conventional analytical techniques. After a preliminary inspection by principal component analysis, calibration models were calculated both by partial least squares (PLS) on the whole signals and by the interval partial least squares (iPLS) variable selection algorithm, in order to estimate physico-chemical parameters. Calibration models have been obtained both considering separately the signals of each sensor of the ET, and by proper fusion of the voltammetric data selected from the two sensors by iPLS. The latter procedure allowed us to check the possible complementarity of the information brought by the different electrodes. Good predictive models have been obtained for estimation of pH, total acidity, sugar content, and anthocyanins content. The application of the ET for fast evaluation of grape ripening and of most suitable harvesting time is proposed.

Zanardi, C.; Zanfrognini, B.; Morandi, S.; Terzi, F.; Pigani, L.; Pasquali, L.; Seeber, R. ( 2018 ) - Synthesis, spectroscopic and electrochemical characterization of Co(II)-terpyridine based metallopolymer - ELECTROCHIMICA ACTA - n. volume 260 - pp. da 314 a 323 ISSN: 0013-4686 [Articolo in rivista (262) - Articolo su rivista]
Abstract

A new oligothienyl-based metallopolymer including Co(terpyridine)2complex units is synthesised by electrochemical oxidation of the relevant monomer. The chemical structure of the polymer chains and the electronic interaction between the organic portions and the metal centres are investigated by spectroscopic (X-rays photoelectron spectroscopy included), electrochemical, and spectroelectrochemical techniques. Thanks to the low potential of the Co(III)/Co(II) redox couple in the Co(terpyridine)2complex and to the presence of oligothienyl spacer, strong electron interaction between the organic backbone and the metal centres have been demonstrated.

Ruggeri, Stefano; Miles, Emily; Poletti, Fabrizio; Pigani, Laura; Zanardi, Chiara; Zanfrognini, Barbara; Corsi, Elia; Dossi, Nicolò; Seeber, Renato; Terzi, Fabio ( 2018 ) - Voltammetric behaviour of Cu alloys toward hydrogen peroxide and organic species - ELECTROCHEMISTRY COMMUNICATIONS - n. volume 90 - pp. da 56 a 60 ISSN: 1388-2481 [Articolo in rivista (262) - Articolo su rivista]
Abstract

he communication reports on the electrocatalytic properties exhibited by five Cu alloys (Cu-Zn, Cu-Sn, Cu-Ni, Cu-Zn-Ni, Cu-Al) and of pure Cu, Ni and Al in the reduction or oxidation of a number of representative species. A prototypical strong oxidising agent, namely hydrogen peroxide, and some of the most important oxidisable species, namely methanol, ethanol, and formaldehyde, are tested. Both cathodic and anodic processes are facilitated by using specific alloys in the case of strong oxidants and different organic molecules, respectively.

Ruggeri, Stefano; Terzi, Fabio; Zanfrognini, Barbara; Corsi, E.; Dossi, N.; Zanardi, Chiara; Pigani, Laura; Seeber, Renato ( 2017 ) - Electroanalytical determination of soluble Mn(II) species at high concentration levels - ELECTROCHIMICA ACTA - n. volume 240 - pp. da 108 a 113 ISSN: 0013-4686 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Glassy carbon electrodes have been successfully employed for the determination, by differential pulse voltammetry, of Mn(II) ions dissolved in aqueous solutions. In particular, a simple and fast procedure also suitable for on-line or at-line process control has been developed. Statistical analysis of the results obtained reveals that the procedure can be adopted in the range 0.59–57.30 mM Mn(II). The electrochemical responses are repeatable and reproducible. Repeatability is testified by the lack of variation of peak current values calculated from 20 subsequent scans carried out at the maximum explored concentration (relative standard deviation <1%). Reproducibility of the responses is supported by the data from the responses on three different electrodes. The proposed procedure does not require any pre-concentration of Mn species at the electrode surface or de-aeration of the solution. By adopting the developed procedure for the analysis, the GC electrode demonstrates to be suitable also for application in real matrices, namely solutions from spent battery recycling; in particular the results from the present electrochemical method are not significantly different from those obtained through inductively plasma coupled mass spectrometry. Interference from other metal species, such as Zn(II) and Fe(III), is negligible. This result is particularly meaningful, since the experimental conditions chosen, implying particularly high concentrations of heavy metals, are representative of those adopted in recovery and recycle processes of Mn species from batteries.

Toniolo, Rosanna; Dossi, Nicolò; Svigelj, Rossella; Pigani, Laura; Terzi, Fabio; Abollino, Ornella; Bontempelli, Gino ( 2016 ) - A Deep Eutectic Solvent-based Amperometric Sensor for the Detection of Low Oxygen Contents in Gaseous Atmospheres - ELECTROANALYSIS - pp. da 757 a 763 ISSN: 1040-0397 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The possibility of adopting deep eutectic solvents (DESs) instead of room temperature ionic liquids (RTILs) in membrane-free electrochemical gas probes was estimated by first evaluating the performance of ethaline as electrochemical medium. This very easily prepared DES was chosen as prototype since it displays high conductivity and fairly modest viscosity, comparable with those of RTILs usually adopted in electrochemical measurements. Its electrostability window at Au, Pt and GC electrodes was first detected, together with diffusion coefficients displayed in this medium by ferrocene in the range 2.0-26.5°C, it being adopted as prototype analyte in view of its well known electrochemical behavior and high enough solubility in ethaline. These diffusion coefficients were then used to infer viscosity values of ethaline at all temperatures considered, by exploiting the Stokes-Einstein equation. Even though ferrocene diffusion coefficients turned out to be remarkably lower than those displayed in usual aprotic solvents, they were fairly higher than those usually found in electrochemical measurements conducted in RTILs, thus pointing out that the use of DESs as solvents adhering to electrode surfaces for assembling electroanalytical gas sensors could be advantageous. On these bases, a conveniently assembled DES-based probe was tested for the electrochemical detection of low oxygen contents in cooled atmospheres. The quite satisfactory results found indicated that the drawback affecting DESs, consisting in the low values of diffusion coefficients displayed by dissolved analytes, can be overcome by using thin enough DES layers and resorting to a high sensitive detection approach such as amperometry under flow conditions. In fact, good sensitivities were found at all temperatures considered (2.0-26.5°C), accompanied by a low detection limit (ca. 0.1% v/v).

Pigani, Laura; Rioli, Cristina; Foca, Giorgia; Ulrici, Alessandro; Seeber, Renato; Terzi, Fabio; Zanardi, Chiara ( 2016 ) - Determination of polyphenol content and colour index in wines through PEDOT-modified electrodes - ANALYTICAL AND BIOANALYTICAL CHEMISTRY - n. volume 408 - pp. da 1 a 10 ISSN: 1618-2642 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Poly(3,4-ethylenedioxythiophene)-modified electrodes have been used for the estimation of the polyphenolic content and of the colour index of different samples of wines. Synthetic wine solutions, prepared with different amount of oenocyanins, have been analysed spectrophotometrically and electrochemically in order to find a correlation between the total polyphenolic content or colour index and the current peak. The regression curves obtained have been used as external calibration lines for the analysis of several commercial wines, ranging from white to dark red wines. In this way, a rapid estimation of the total polyphenolic content and of the colour index may be accomplished from a single voltammetric measurement. Furthermore, principal component analysis has also been used to evaluate the effect of total polyphenolic content and colour index on the whole voltammetric signals within a selected potential range, both for the synthetic solutions and for the commercial products.

Zanardi, Chiara; Pigani, Laura; Maccaferri, Giulio; Degli Esposti, Micaela; Fabbri, Paola; Zannini, Paolo; Seeber, Renato ( 2016 ) - Development of a redox polymer based on poly(2-hydroxyethyl methacrylate)for disposable amperometric sensors - ELECTROCHEMISTRY COMMUNICATIONS - n. volume 62 - pp. da 34 a 37 ISSN: 1388-2481 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Membranes based on poly(2-hydroxyethyl methacrylate), chemically modified with ferrocene functionalities, are proposed as novel coatings for the development of disposable amperometric sensors. They are mass-produced on an inert support through an UV photo-induced polymerization, forming self-standing films that can be transferred on an electrode surface. Thanks to the characteristic of the functionalized methacrylate matrix to rapidly and reversibly swell by incorporation of large amounts of water, the ferrocene moieties are in intimate contact with the electrolytic solution. They can activate effective electrocatalytic processes that can be exploited in the field of amperometric sensing. The performance of the methacrylate coating with respect to the determination of hydroquinone benchmark analyte has been tested both in a static solution and in a flux cell.

Palacios-Santander, J.M.; Terzi, F.; Zanardi, C.; Pigani, L.; Cubillana-Aguilera, L.M.; Naranjo-Rodriguez, I.; Seeber, Renato ( 2016 ) - Electrocatalytic and antifouling properties of CeO2-glassy carbon electrodes - JOURNAL OF SOLID STATE ELECTROCHEMISTRY - n. volume 20 - pp. da 3125 a 3131 ISSN: 1432-8488 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Binary metal oxides with different degrees of covalent/ionic character of the oxygen-metal bond are tested as a partial coating of glassy carbon electrode surfaces. The electrocatalytic and antifouling properties of the resulting bicomponent electrode systems are analysed in view of possible applications in different fields of electrochemistry, such as electroremediation and electroanalysis. Based on the performance with respect to oxidation of ascorbic acid, as to sensitivity, repeatability of the responses, and activation of electrocatalytic oxidation, CeO2 has been preferred. This same electrode system has been further studied in respect to a trickier electrochemical process, namely the anodic oxidation of a chlorophenol derivative, which induces massive passivation of bare electrode surfaces. The effectiveness of the bicomponent electrode system in anodic oxidation of 2,4,6-trichlorophenol has been ascertained, over a wide range of concentrations, by comparison with pure glassy carbon surfaces.

Seeber, Renato; Pigani, Laura; Terzi, Fabio; Zanardi, Chiara ( 2015 ) - Amperometric sensing. A melting pot for material, electrochemical, and analytical sciences - ELECTROCHIMICA ACTA - n. volume 179 - pp. da 350 a 363 ISSN: 0013-4686 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The critical review discusses the key points of the main blocks leading to the development and use of an amperometric sensing system. On the one side, most attention is paid to the electrode materials that may potentially induce impressive progresses in the performance of the device. On the other side, comparable room is given to the remaining parts constituting the sensing system as a whole, from tests in different solutions to problems arising from data processing. All these steps require care and knowledge of the manifold branches of science and technology that concur to realise and use the device at best. However, some of these aspects are too often underestimated, also due to the different scientific origin of researchers or analysts who are directly involved. The discussion is centred on both the virtues of amperometric sensing systems and on the limits they present. The last are especially evidenced, in order to induce full consciousness of the complexity and interdisciplinary features of this kind of analytical tools. Exemplificative literature dealing with the issues dealt with is cited and critically inserted in the frame of the overall picture.

Zanardi, Chiara; Pigani, Laura; Seeber, Renato; Terzi, Fabio; Arduini, Fabiana; Cinti, Stefano; Moscone, Danila; Palleschi, Giuseppe ( 2015 ) - Carbon Black/Gold Nanoparticles Composite for Efficient Amperometric Sensors - SENSORS - n. volume 319 - pp. da 159 a 163 ISBN: 9783319096162 ISSN: 1876-1100 [Contributo in Atti di convegno (273) - Relazione in Atti di Convegno]
Abstract

A screen-printed electrode (SPE) modified with a carbon black and Au nanoparticles bilayer was developed and proposed as an amperometric sensor for ascorbic acid quantification in pharmaceutical products and for dopamine estimation in the presence of large excess of ascorbic acid. Electrochemical investigations highlight the performances of the resulting modified electrode with respect to SPEs modified with a single component of the nano-composite.

Zanardi, Chiara; Ferrari, Erika; Pigani, Laura; Arduini, Fabiana; Seeber, Renato ( 2015 ) - Development of an Electrochemical Sensor for NADH Determination Based on a Caffeic Acid Redox Mediator Supported on Carbon Black - CHEMOSENSORS - n. volume 3 - pp. da 118 a 128 ISSN: 2227-9040 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Screen-printed electrode (SPE) modified with carbon black nanoparticles (CB) has been tested as a new platform for the stable deposition of caffeic acid (CFA) on the electrode surface. The electrochemical performance from varying the amount of CFA/CB composite has been tested with respect to NADH determination. The electrocatalytic activity of CFA/CB has also been compared with that of SPEs modified by a single component of the coating, i.e., either CFA or CB. Finally, glycerol dehydrogenase, a typical NADH-dependent enzyme, was deposited on the CFA/CB coating in order to test the applicability of the sensor in glycerol determination.

Terzi, Fabio; Zanfrognini, Barbara; Ruggeri, Stefano; Maccaferri, Giulio; Pigani, Laura; Zanardi, Chiara; Seeber, Renato ( 2015 ) - Ti metal electrode as an unconventional amperometric sensor for determination of Au(III) species - ANALYTICAL AND BIOANALYTICAL CHEMISTRY - n. volume 407 - pp. da 983 a 990 ISSN: 1618-2642 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The control of the noble metal concentration is crucial in order to increase the efficiency of hydrometallurgic processes in mining and in the recovery of precious materials from electronic waste. The present study is devoted to the development of an effective procedure for the quantification of Au(III) species dissolved in aqueous solutions, similar real complex matrices included. In particular, a novel electrode system based on Ti has been studied. This electrode material is still poorly investigated in the framework of electroanalysis, despite its lack of sensitivity to common interfering species, such as oxygen; hence, the determination of metal species can be carried out without performing deaeration of the solution. In addition, the interfering effect due to the presence of other heavy metal ions, such as Ag, Fe and Pb, has been minimised by a proper choice of the conditions adopted for the amperometric measurements. Ti electrodes exhibit reproducible electrochemical responses, even in the presence of high concentration of organic fouling species typical of biosorption processes.

Pigani, Laura; Seeber, Renato; Alessandro, Bedini; Enrico, Dalcanale; Michele, Suman ( 2014 ) - Adsorptive-Stripping Voltammetry at PEDOT-Modified Electrodes. Determination of Epicatechin - FOOD ANALYTICAL METHODS - n. volume 7 - pp. da 754 a 760 ISSN: 1936-9751 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The food industry has a direct interest to bitter-tasting substances, either for the identification of negative off-flavors or for the monitoring of organoleptic quality. Polyphenols (such as catechins and epicathechins) are among the main molecular components responsible for the bitter taste of coffee/cocoa/chocolate-based products. The electrochemical detection of epicatechin through adsorptive stripping voltammetry on poly(3,4-ethylenedioxythiophene)-modified Pt electrodes has been investigated. The accumulation conditions were defined in order to record repeatable and reproducible electrochemical signals. Calibration plots were built in the 0.2-2.5 ppm concentration range of epicatechin in phosphate buffer solutions, pH 7. Preliminary tests in aqueous extraction solutions of biscuits containing different percentages of cocoa were performed; they confirmed, in principle, the effectiveness of the device and of the procedure proposed for the epicatechin determination by simple extraction from complex food matrices

Terzi, F.; Zanfrognini, B.; Pelliciari, J.; Pigani, L.; Zanardi, C.; Seeber, R. ( 2014 ) - Amperometric Determination of Strong Oxidising Species Through Titanium Electrode Systems - Sensors and Microsystems - Springer International Publishing basel CHE) - n. volume 268 - pp. da 77 a 81 ISBN: 9783319006833 ISSN: - [Contributo in Atti di convegno (273) - Relazione in Atti di Convegno]
Abstract

The amperometric determination of strong oxidising species has been carried out through an unusual electrode material, namely, Ti. In particular the study involves H2O2 and HClO, even at high concentration levels. A complex real matrix, such as an industrial detergent, containing high H 2O2 concentrations, has been taken as a meaningful study case to check the effectiveness of the electrode system and procedure proposed.

Pigani, L.; Seeber, R.; Bedini, A.; Dalcanale, E.; Suman, M. ( 2014 ) - Determination of Polyphenols in Bakery Food Matrices with New Detection Methods - Sensors and Microsystems - Springer International Publishing * DEU) - n. volume 268 - pp. da 459 a 462 ISBN: 9783319006833 ISSN: - [Contributo in Atti di convegno (273) - Relazione in Atti di Convegno]
Abstract

The food industry is continuously looking for reliable methods useful to standardize different control parameters and has a direct interest into bitter‐tasting substances, either for the identification of negative off‐flavors or for the monitoring of a desired organoleptic quality. The exploitation of dedicated panel tests for sensory purposes is useful, but it suffers from limitations related to subjectivity, reproducibility, and number of analysis per day (Profile Attribute Analysis). On the contrary, sophisticated analytical solutions, such as HPLC, need trained personnel and are often too expensive or time consuming. The target of the present research work is the development of alternative techniques potentially able to detect taste molecular markers in bakery commodities, with particular attention to polyphenol detection. In particular, two different analytical approaches were developed and compared to a reference LC-MS protocol in order to detect the polyphenol concentration inside real food matrices like biscuits: FT-NIR and electroanalytical methods.

Terzi, Fabio; Pigani, Laura; Zanardi, Chiara; Zanfrognini, Barbara; Seeber, Renato ( 2014 ) - Development of Nanostructured Electrode Coatings for Amperometric Sensors - Lecture Notes in Electrical EngineeringSensors - Springer Science + Business Media New York USA) - n. volume 162 - pp. da 43 a 48 ISBN: 9781461438595; 9781461438601 | 9781461438601 ISSN: - [Contributo in Atti di convegno (273) - Relazione in Atti di Convegno]
Abstract

The goal of the communication is to illustrate the main advantages of the use of nanostructured materials as electrode modifiers in the frame of electroanalysis. Particularly meaningful examples extracted from the activity of the research group are discussed. The aim is to evidence the main properties of the single material and the synergic activity deriving from the combination of different materials in hybrids or composites electrode modifiers.

Terzi, Fabio; Pigani, Laura; Zanardi, Chiara; Zanfrognini, Barbara; Ruggeri, Stefano; Maccaferri, Giulio; Seeber, Renato ( 2014 ) - Novel electrode systems for amperometric sensing: the case of titanium - Optics and Photonics for Counterterrorism, Crime Fighting, and Defence X; and Optical Materials and Biomaterials in Security and Defence Systems Technology XI - n. volume 9253 [Contributo in Atti di convegno (273) - Relazione in Atti di Convegno]
Abstract

fter working for years on organic materials, e.g., polythiophenes and relevant composites with metal nanoparticles, we shifted our attention to unusual metals, chosen as candidates to effective amperometric sensing on the basis of the atomic structure and crystalline properties. The present contribution aims at proposing an electrode material rarely employed in electroanalysis, namely Ti. We have experimented that the peculiar nature of Ti leads to electrochemical behavior quite different with respect to the conventional electrode materials, including those based on TiO2 (nano) particles. Our work focuses on the determination of strong oxidizing species, namely H2O2 and HClO, and noble metal ions, namely Au(III). Strong oxidizing species are commodity chemicals employed in a number of different industrial processes, in which usually high concentration levels should be monitored. The procedures proposed have been successfully applied also in complex matrices, such as detergent samples. As to Au(III) determination, it also constitutes a crucial tool in order to increase the efficiency of hydrometallurgic processes and of the recovery of precious materials from electronic waste. Ti electrodes allow the determination of dissolved Au species in the presence of other metal ions. In any cases the electrodes exhibit reproducible and repeatable electrochemical responses, even in the presence of high concentration of organic fouling species typical of bio-sorption processes.

Fabio Terzi; Jonathan Pelliciari; Barbara Zanfrognini; Laura Pigani; Chiara Zanardi; Renato Seeber ( 2013 ) - Behaviour of Ti electrode in the amperometric determination of high concentrations of strong oxidising species. - ELECTROCHEMISTRY COMMUNICATIONS - n. volume 34 - pp. da 138 a 141 ISSN: 1388-2481 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The study of the capabilities of an unusual electrode material, namely, Ti, is presented: the amperometric determination of species showing responses that, on different materials, cannot be often profitably exploited, is proposed. H2O2 and HClO are successfully analysed, even at high concentrations. In similar conditions, which are quite common in industrial environments, these strong oxidising species are determined by time-consuming, off- or at-line, and multistep procedures. A complex real matrix, such as an industrial detergent, containing high H2O2 concentrations, has been taken as a meaningful study case to check the effectiveness of the electrode system and procedure proposed.

Chiara Zanardi; Luca Ferrari; Barbara Zanfrognini; Laura Pigani; Fabio Terzi; Stefano Cattini; Luigi Rovati; Renato Seeber ( 2013 ) - Development of a Sensor System for the Determination of Sanitary Quality of Grapes. - SENSORS - n. volume 13 - pp. da 4571 a 4580 ISSN: 1424-8220 [Articolo in rivista (262) - Articolo su rivista]
Abstract

An instrument for the automatic quantification of glycerol in grapes has been developed. We verify here that this analyte can be taken as a benchmark of a serious disease affecting the grapevines, namely Botrytis cinerea. The core of the instrument is an amperometric biosensor consisting of a disposable screen printed electrode, generating the analytical signal thanks to a bi-enzymatic process involving glycerol dehydrogenase and diaphorase. The full automation of the analysis is realised by three micropumps and a microprocessor under control of a personal computer. The pumps allow the correct and constant dilution of the grape juice with a buffer solution also containing [Fe(CN)6]4- redox mediator and the injection of NAD+ cofactor when the baseline signal reaches a steady state; the instrument leads to automated reading of the analytical signal and the consequent data treatment. Although the analytical method is based on an amperometric technique that, owing to heavy matrix effects, usually requires an internal calibration, the analyses indicate that a unique external calibration is suitable for giving accurate responses for any grapes, both white and black ones.

Davide Vanossi;Laura Pigani;Renato Seeber;Paolo Ferrarini;Pietro Baraldi;Claudio Fontanesi ( 2013 ) - Electropolymerization of ortho-phenylenediamine. Structural characterisation of the resulting polymer film and its interfacial capacitive behaviour - JOURNAL OF ELECTROANALYTICAL CHEMISTRY - n. volume 710 - pp. da 22 a 28 ISSN: 1572-6657 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The physico-chemical characteristics of thin poly-(orth o-phenylenediamine) (PPD) films, obtained by electrochemical oxidation of the relevant monomer, are investigated using electrochemical, morpholog-ical and spectroscopic techniques. In particular, cyclic voltammetry and electroche mical impedance spec-troscopy (EIS) techniques are used to collect information concerning the redox, conductivity and double layer capacitance properties of the PPD film. AFM imaging and Raman spectroscopy results are exploited to characterize the film structure. In this respect, Raman spectra of two possible PPD oligomers are cal-culated at the B3LYP/6-311G level of the theory.

Fabio Terzi;Jonathan Pelliciari; Chiara Zanardi; Laura Pigani; Antti Viinikanoja; Jukka Lukkari; Renato Seeber ( 2013 ) - Graphene-modified electrode. Determination of hydrogen peroxide at high concentrations. - ANALYTICAL AND BIOANALYTICAL CHEMISTRY - n. volume 405 - pp. da 3579 a 3586 ISSN: 1618-2642 [Articolo in rivista (262) - Articolo su rivista]
Abstract

A gold electrode partially coated by graphene multilayer is developed and tested with respect to high concentrations of hydrogen peroxide. The effective use of conventional electrode materials for the determination of such an analyte by anodic oxidation or cathodic reduction is prevented by the occurrence of adsorptions fouling the electrode surface. This prevents reliable and repeatable voltammetric curves for being recorded and serious problems arise in quantitative analysis via amperometry. The gold–graphene electrode is shown to be effective in quantitative evaluation, by cathodic reduction, of hydrogen peroxide at concentration levels that are of interest in an industrial. Acid, neutral, and basic pH values have been tested through correct adjustment of a Britton Robinson buffer. The experiment s have been performed both by cyclic voltammetry and with amperometry at constant potential in unstirred solution. The latter technique has been employed in drawing a calibration linear plot. In particular, the performances of the developed electrode system have been compared with those of both pure gold and pure graphene electrode materials. The bi-component electrode was more sensitive; co-catalytic action by the combination of the two components is hypothesised. The system is stable over many potential cycles, as checked by surface-enhanced Raman spectra recorded over time.

F. Terzi; B. Zanfrognini; C. Zanardi; L. Pigani; R. Seeber ( 2012 ) - Electroreduction of chloramines through novel electrode materials - ELECTROANALYSIS - n. volume 24 - pp. da 833 a 841 ISSN: 1040-0397 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Novel electrode materials have been developed and applied to the determination of chloramines by amperometric methods. In particular, a thin layer of a conducting polymer, namely poly(3,4-ethylenedioxythiophene) (PEDOT) has been tested for the first time in the presence of chloramines. Significant improvements in the performance of the modified electrodes are obtained by using composite materials based on differently encapsulated Au nanoparti-cles and PEDOT. The resulting electrode system exhibits repeatability and reproducibility of the voltammetric re-sponses, as well as low limit of detection and high sensitivity in the determination of monochloramine, as testified by the cyclic voltammetric curves and the calibration plots obtained by a rotating disk electrode.

Marco Calderisi;Alessandro Ulrici;Laura Pigani;Alberto Secchi;Renato Seeber ( 2012 ) - Experimental design-based strategy for the simulation of complex gaseous mixture spectra to detect drug precursorsOptical Materials and Biomaterials in Security and Defence Systems Technology IX - Optical Materials and Biomaterials in Security and Defence Systems Technology IXOptical Materials and Biomaterials in Security and Defence Systems Technology IX - Conference Proceedings SPIE Bellingham, Washington USA USA) - n. volume 8545 [Contributo in Atti di convegno (273) - Relazione in Atti di Convegno]
Abstract

In the frame of the EU project CUSTOM, a new sensor system for the detection of drug precursors in gaseous samples is being developed, which also includes an External Cavity-Quantum Cascade Laser Photo Acoustic Sensor (ECQCLPAS). In order to define the characteristics of the laser source, the optimal wavenumbers within the most effective 200 cm-1 range in the mid-infrared region must be identified, in order to lead to optimal detection of the drug precursor molecules in presence of interfering species and of variable composition of the surrounding atmosphere. To this aim, based on simulations made with FT-IR spectra taken from literature, a complex multivariate analysis strategy has been developed to select the optimal wavenumbers. Firstly, the synergistic use of Experimental Design and of Signal Processing techniques led to a dataset of 5000 simulated spectra of mixtures of 33 different gases (including the 4 target molecules). After a preselection, devoted to disregard noisy regions due to small interfering molecules, the simulated mixtures were then used to select the optimal wavenumber range, by maximizing the classification efficiency, as estimated by Partial Least Squares – Discriminant Analysis. A moving window 200 cm<sup>-1</sup> wide was used for this purpose. Finally, the optimal wavenumber values were identified within the selected range, using a feature selection approach based on Genetic Algorithms and on resampling. The work made will be relatively easily turned to the spectra actually recorded with the newly developed EC-QCLPAS instrument. Furthermore, the proposed approach allows progressive adaptation of the spectral dataset to real situations, even accounting for specific, different environments.

Pigani, Laura; Zanfrognini, Barbara; Seeber, Renato ( 2012 ) - PEDOT modified microelectrodes. Preparation, characterisation and analytical performances - ELECTROANALYSIS - n. volume 24 - pp. da 1340 a 1347 ISSN: 1040-0397 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Poly(3,4-ethylenedioxythiophene) (PEDOT) modified microelectrodes were prepared by electropolymerisation of therelevant monomer from CH3CN and H2O solutions. The electrochemical behaviour of the obtained coatings wasinvestigated by cyclic voltammetry in both organic and aqueous media. The anodic responses obtained for a typicalbenchmark analyte such as ascorbic acid have been chosen in order to test the different coatings; calibration curves havebeen built up in order to evaluate the repeatability of the response and reproducibility of the realised sensing system.Moreover, the ability of the modified microelectrodes to work in low conductivity media has been studied, and exploratorytests in dense food matrix have been performed

L. Pigani; A. Culetu; A. Ulrici; G. Foca; M. Vignali; R. Seeber ( 2011 ) - PEDOT modified electrodes in amperometric sensing for analysis of red wine samples - FOOD CHEMISTRY - n. volume 129 - pp. da 226 a 233 ISSN: 0308-8146 [Articolo in rivista (262) - Articolo su rivista]
Abstract

A poly(3,4-ethylendioxythiophene) modified electrode has been considered as a potentially useful amperometric sensor to use either alone or in the frame of a set of sensors bearing complementary information, i.e. within an electronic tongue. The sensor is proposed in blind analysis of red wines, for classificationand calibration purposes. The data obtained from voltammetric measurements have been treated using partial least squares analysis. A calibration procedure has been performed to correlate results from analyses of wines, executed with traditional analytical methods, with the corresponding voltammetricresponses. Moreover, classification models of the wine samples, based on quantitative parameters and qualitative information about origin and variety, have been built. The developed electrochemical sensor also allows the fast identification of samples exceeding threshold limits of meaningful parameters forquality control in the wine industry, such as SO2, colour intensity and total polyphenols. The application of the system within a sensor array (electronic tongue) to fast pre-screening routine control procedure is proposed.

Fabio Terzi; Barbara Zanfrognini; Chiara Zanardi; Laura Pigani; Renato Seeber ( 2011 ) - Poly(3,4-ethylenedioxythiophene)/Au-nanoparticles composite as electrode coating suitable for electrocatalytic oxidation - ELECTROCHIMICA ACTA - n. volume 56 - pp. da 3575 a 3579 ISSN: 0013-4686 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Composite materials consisting of poly(3,4-ethylenedioxythiophene) including Au nanoparticles, encapsulated by citrate anions, have been firmly deposited on an electrode surface through a simple method, taking advantage of the interaction between Au metal and thiophene polymeric backbone. A series of similar electrode coatings, also including different amounts of nanoparticles inside, has been characterised in terms of thickness and surface morphology, through different microscopic techniques. The electrocatalytic properties have been studied with respect to the oxidation of glucose in alkaline media,which is prevented from occurring on the pure organic material.

Zanardi, Chiara; Terzi, Fabio; Zanfrognini, Barbara; Pigani, Laura; Seeber, Renato; J., Lukkari; T., Ääritalo ( 2010 ) - Effective catalytic electrode system based on polyviologen and Au nanoparticles multilayer - SENSORS AND ACTUATORS. B, CHEMICAL - n. volume 144 - pp. da 92 a 96 ISSN: 0925-4005 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Au nanoparticles encapsulated by very labile chloride ions are synthesised and characterised. Through layer-by-layer deposition technique they are stably anchored to an electrode surface, using a polyviologen derivative as the polycationic organic component. The structure and morphology of the multilayer is exhaustively studied by UV–vis spectroscopy, X-ray diffraction, scanning and transmission electron microscopy. The nanocomposite material shows very interesting electrocatalytic properties with respect to the reduction of H2O2, which occurs at particularly less negative potentials. Furthermore, the presence of Au nanoparticles inside the electrode coating greatly improves the sensitivity of the electrochemical system. The system results to be a well suitable sensor for H2O2 quantification, with high sensitivity and low detection limit.

Pasquini, I.; Foresti, M. L.; Innocenti, M.; Fort, A.; Mugnaini, M.; Pigani, L.; Vignoli, V.; Rocchi, S.; Loglio, F. ( 2010 ) - Preparation of Poly(3,4-ethylenedioxythiophene) Films on Piezoelectric Quartz Crystal and Their Gas Sensitivities - ECS TRANSACTIONS - n. volume 25 - pp. da 125 a 131 ISSN: 1938-5862 [Articolo in rivista (262) - Articolo su rivista]
Abstract

This paper describes the development and the results of a Quartz Crystal Microbalance (QCM) sensor for NO2 detection with the sensitive layer made of a thin film of poly (3,4-ethylenedioxythiophene) PEDOT. The PEDOT was obtained by electropolymerization on one of the gold electrodes of a 10 MHz AT-cut commercial quartz crystal. The sensor performance in terms of sensitivity and selectivity were assessed exploiting an ad hoc chemical sampling unit, and a low noise conditioning and processing electronic system. The preliminary obtained results show a NO2 resolution and sensitivity of the order of 1 ppm, and 2.6 Hz/ppm, respectively, at 35°C constant room temperature and 0% relative humidity, and show that a satisfactory repeatability can be achieved with recovery cycles in N2 at room temperature.

Pigani, Laura; Foca, Giorgia; Ulrici, Alessandro; K., Ionescu; V., Martina; Terzi, Fabio; M., Vignali; Zanardi, Chiara; Seeber, Renato ( 2009 ) - Classification of Red Wines by Chemometric Analysis of Voltammetric Signals from Pedot-Modified Electrodes. - ANALYTICA CHIMICA ACTA - n. volume 643 - pp. da 67 a 73 ISSN: 0003-2670 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Nine different types of Italian red wines of four different varieties were analysed, without any samplepre-treatments, by voltammetric techniques using a poly(3,4-ethylenedioxythiophene)-modified electrode.The data matrices consisting of the currents measured at different potentials, by repeated CyclicVoltammetry or Differential Pulse Voltammetry, are submitted to chemometric analysis. After explorativetests based on Principal Component Analysis, Partial Least Squares-Discriminant Analysis classificationmodels are built both for the training and for the test sets. To this aim, different classification strategiesare adopted, considering the responses from the two techniques either separately or joined together toform a data matrix including the whole voltammetric information.

Chiara Zanardi; Fabio Terzi; Laura Pigani; Renato Seeber ( 2009 ) - Electrode coatings consisting of polythiophene-based composites containing metal centres. - Encyclopedia of Polymer Composites: Properties, Performance and Applications - Nova Publishers New York USA) - pp. da 1 a 74 ISBN: 9781607417170 ISSN: - [Contributo in volume (Capitolo o Saggio) (268) - Capitolo/Saggio]
Abstract

Polythiophene derivatives constitute nowadays the most extensively studied class of conducting polymers, thanks to their mechanical and thermal stability, as well as to their physical and chemical properties, such as electronic conductivity, electrochromism, solvatochromism, thermochromism and luminescence. These materials have been proposed for use in a wide range of applications, including chemical sensors, light emitting diodes, thin film transistors, different electrocatalytic systems, batteries, smart windows, and even artificial muscles.Peculiar systems are realised by anchoring similar materials on substrates. In particular, conductive substrates suitably coated by polythiophene derivatives constitute particularly interesting electrode systems that can be exploited in numerous electrochemical-electroanalytical applications. However, a notable part of the research activity in these fields is today evolving toward the insertion of metals into the polythiophenes matrix, in order to further improve the performances of the pure organic material. The driving force to these studies lies in the possibility to combine the properties of the organic and inorganic entities, taking advantage of their synergic interaction. Basically, two different approaches, resulting in hybrids/composites of quite different nature, have been followed: i) link of metal complexes to the polymeric backbone; ii) inclusion of metal ions and complexes, of clusters, oxides or nanoparticles into the polymer. In similar systems, the presence of the metal is supposed to deeply affect the electronic and electrochemical properties of the resulting hybrid/composite material.The aim of the present contribution is to give a picture of the variety of polythiophene-based hybrid/composite materials developed, with reference to the systems in which the polymer is supported on a conductive substrate, to constitute an electrode system. The different physico-chemical characterisations are treated, mainly devoted to clarify the interactions between the polymer and the metal centres, as well as the nature of the interface between the ambient and the composite as a whole. Description is given of some applications in electrochemical environments.

Terzi, Fabio; Zanardi, Chiara; Zanfrognini, Barbara; Pigani, Laura; Seeber, Renato; J., Lukkari; T., Aaritalo; J., Kankare ( 2009 ) - Preparation and Characterization of a RedoxMultilayer Film Containing Au Nanoparticles - JOURNAL OF PHYSICAL CHEMISTRY. C - n. volume 113 - pp. da 4868 a 4874 ISSN: 1932-7447 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Gold nanoparticles encapsulated by negatively charged molecules have been stably anchored at a Au substratethrough layer-by-layer deposition technique, employing a redox polyviologen derivative as the cationiccounterpart. UV-vis spectroscopy, quartz crystal microbalance, transmission electron microscopy, scanningelectron microscopy, atomic force microscopy, and voltammetric measurements have been performed in orderto characterize the systems and to give a rationale to the effect of the deposition conditions on the propertiesof the resulting multilayers. The behavior of two benchmark electroactive species ([Fe(CN)6]4- and[Ru(NH3)6]3+) has been studied on nanoparticle-terminated multilayers. The nanoparticles provide chargepercolation through the multilayer and charge transfer with redox species in solution. The results imply thatthe electrochemical behavior of nanoparticle-containing films is partly dependent on the charge compensationmode within polyelectrolyte multilayers.

R.Seeber; L.Pigani; C.Zanardi; F.Terzi; B.Zanfrognini ( 2009 ) - Sensori Amperometrici. Nuoivi materiali elettrodici - LA CHIMICA E L'INDUSTRIA - n. volume 2009 - pp. da 82 a 84 ISSN: 0009-4315 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The article concerns the development of new materials for electrode systems. A complete characterisation of the materials and of the electrochemical systems is obtained by combiningthe results from different spectroscopic and electrochemical techniques. The resulting modified electrodes are tested as amperometric sensors. A particularly attractive applicationof these devices, even using (ultra)microelectrodes, is in the field of “blind analysis”, as elements of electronic tongues for the classification of real matrices.

L. PIGANI; G. FOCA; K. IONESCU; V. MARTINA; A. ULRICI; F. TERZI; M. VIGNALI; C. ZANARDI; R. SEEBER ( 2008 ) - Amperometric sensors based on poly(3,4-ethylenedioxythiophene)-modified electrodes: Discrimination of white wines - ANALYTICA CHIMICA ACTA - n. volume 614 - pp. da 213 a 222 ISSN: 0003-2670 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The voltammetric responses on selected white wines of different vintages and origins havebeen systematically collected by three different modified electrodes, in order to check theireffectiveness in performing blind analysis of similar matrices. The electrode modifiers consistof a conducting polymer, namely poly(3,4-ethylenedioxythiophene) (PEDOT) and of compositematerials of Au and Pt nanoparticles embedded in a PEDOT layer. Wine samples havebeen tested, without any prior treatments, with differential pulse voltammetry technique.The subsequent chemometric analysis has been carried out both separately on the signals ofeach sensor, and on the signals of two or even three sensors as a unique set of data, in order tocheck the possible complementarity of the information brought by the different electrodes.After a preliminary inspection by principal component analysis, classification models havebeen built and validated by partial least squares-discriminant analysis. The discriminantcapability has been evaluated in terms of sensitivity and specificity of classification; in allcases quite good results have been obtained.

Zanardi, Chiara; Terzi, Fabio; Pigani, Laura; A., Heras; A., Colina; J., LOPEZ PALACIOS; Seeber, Renato ( 2008 ) - Development and characterisation of a novel composite electrode material consisting of poly(3,4-ethylenedioxythiophene) including Au nanoparticles - ELECTROCHIMICA ACTA - n. volume 53 - pp. da 3916 a 3923 ISSN: 0013-4686 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Composite materials consisting of poly(3,4-ethylenedioxithiophene) including Au nanoparticles encapsulatedby bulky anionic species have been electrogenerated and characterised through spectroscopic andmicroscopic techniques. The properties of electrodes modified by similar materials have been studiedwith respect to the oxidation of different benchmark electroactive species, such as negatively chargedascorbic and uric acids, and positively charged dopamine. The responses obtained evidence the dependenceof sensitivity and selectivity of the electrochemical responses on the presence and density of thenanoparticles and on the nature of the relevant encapsulating agent. In particular, the insertion of negativelycharged NPs activates a sort of electrostatic shield toward negatively charged molecules; however,also positively charged species result to be conditioned in accessing the redox active centres, locatedeither on the nanoparticle’s surface or on the conducting polymer’s molecules.

Terzi, Fabio; Zanardi, Chiara; V., Martina; Pigani, Laura; Seeber, Renato ( 2008 ) - Electrochemical, Spectroscopic and Microscopic Characterisation of Novel Poly(3,4-ethylenedioxythiophene)/Gold Nanoparticles Composite Materials. - JOURNAL OF ELECTROANALYTICAL CHEMISTRY - n. volume 619-620 - pp. da 75 a 82 ISSN: 1572-6657 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Composite materials consisting of poly(3,4-ethylenedioxithiophene) including Au nanoparticles encapsulatedby bulky anionic species have been electrogenerated and characterised through spectroscopic andmicroscopic techniques. The properties of electrodes modified by similar materials have been studiedwith respect to the oxidation of different benchmark electroactive species, such as negatively chargedascorbic and uric acids, and positively charged dopamine. The responses obtained evidence the dependenceof sensitivity and selectivity of the electrochemical responses on the presence and density of thenanoparticles and on the nature of the relevant encapsulating agent. In particular, the insertion of negativelycharged NPs activates a sort of electrostatic shield toward negatively charged molecules; however,also positively charged species result to be conditioned in accessing the redox active centres, locatedeither on the nanoparticle’s surface or on the conducting polymer’s molecules.

V., Martina; K., Ionescu; Pigani, Laura; Terzi, Fabio; Ulrici, Alessandro; Zanardi, Chiara; Seeber, Renato ( 2007 ) - Development of an electronic tongue based on a PEDOT-modified voltammetric sensor - ANALYTICAL AND BIOANALYTICAL CHEMISTRY - n. volume 387 (6) - pp. da 2101 a 2110 ISSN: 1618-2642 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Three different electrodes were tested for use as nonspecific amperometric sensors for blind analysis on real matrices, namely different fruit juices from different fruits or different brands. The first two electrodes were traditional Pt and Au electrodes, while the third one was modified with poly(3,4-ethylenedioxythiophene) conducting polymer. The sensors were tested separately, tested coupled to each other, and also tested together. The responses of the electrode system(s) were first screened via PCA and then their discriminant capabilities were quantified in terms of the sensitivities and specificities of their corresponding PLS-DA multivariate classification models. Particular attention was paid to analyzing the evolution of the response over subsequent potential sweeps. The modified electrode demonstrated the most discriminating ability, and it was the only system capable of satisfactorily performing the most complex task attempted during the analysis: discriminating between juices from the same fruit but from different brands. Moreover, the electrode cleaning procedure required between two subsequent potential sweeps was much simpler for the modified electrode than for the others. This electrode system was therefore shown to be a good candidate for use as an informative element in an electronic tongue applied to the analysis of other food matrices.

Pigani, Laura; M., Musiani; C., Pirvu; Terzi, Fabio; Zanardi, Chiara; Seeber, Renato ( 2007 ) - Electro-oxidation of chlorophenols on poly (3,4-ethylenedioxythiophene)-poly(styrene sulphonate) composite electrode - ELECTROCHIMICA ACTA - n. volume 52 - pp. da 1910 a 1918 ISSN: 0013-4686 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The electrochemical behaviour of chlorinated phenols on Pt/poly(3,4-ethylenedioxy)thiophene, LiClO4 and on Pt/poly(3,4-ethylenedioxy) thiophene,poly(sodium-4-styrenesulphonate) electrodes has been investigated in phosphate buffer solution. Poly(sodium-4-styrenesulphonate) exerts remarkable effect against the electrode fouling induced by oxidation of chlorophenols, allowing us to record the relevant anodic response even after repeated potential cycles. Hypotheses about the role exerted by poly(sodium 4-styrenesulphonate) are made, on the basis of evidences provided by several techniques, such as cyclic voltammetry, electrochemical impedance spectroscopy, electrochemical microgravimetry and atomic force microscopy. Thanks to the fact that different chlorophenols show differences in the voltammetric responses, depending on number and position of the chloro substituents on the aromatic ring, applications of the modified electrode in the analysis of mixtures of chlorinated phenols are possible. (c) 2006 Elsevier Ltd. All rights reserved.

L. PASQUALI; F. TERZI; C. ZANARDI; L. PIGANI; R. SEEBER; G. PAOLICELLI; SM SUTURIN; N. MAHNE; S. NANNARONE ( 2007 ) - Structure and properties of 1,4-benzenedimethanethiol films grown from solution on Au(111): An XPS and NEXAFS study - SURFACE SCIENCE - n. volume 601 - pp. da 1419 a 1427 ISSN: 0039-6028 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Core level photoemission and X-ray absorption at the carbon C 1s edge are applied to the study of chemisorption of 1,4-benzenedimethanethiol molecules oil Au(111) and to investigate the effect of the solvent used to prepare the organic films. 1,4-Benzeiledimethanethiol films were prepared in polar and non-polar solvents, i.e. ethanol, methanol and n-hexane. 1,4-Benzenedimethanethiol molecules are anchored to the substrate through a single S-Au bond; the molecules in the films tend to assume an upright orientation, the aromatic ring resulting tilted towards the direction perpendicular to the substrate plane. The films present an effective thickness corresponding to more than a single layer. Only small differences are observed among behaviours in different solvents. It is concluded that the filial properties and conformation of the 1,4-belizenedimethanethiol films are largely determined by the reciprocal interactions between the molecules and with the substrate. (c) 2007 Elsevier B.V. All rights reserved.

C. Zanardi; R. Scanu; L. Pigani; MI Pilo; G. Sanna; R. Seeber; N. Spano; F. Terzi; A. Zucca ( 2006 ) - Electrochemical and spectroelectrochemical characterisation of poly(3 '-hydroxymethyl-2,2 ': 5 ',2 ''-terthiophene) - SYNTHETIC METALS - n. volume 156 - pp. da 984 a 989 ISSN: 0379-6779 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The electrochemical polymerisation of 3'-hydroxymethyl-2,2':5',2-terthiophene, afforded a new conducting polymer bearing the nucleophilic-CH2OH substituent in beta-position. The characteristics of the system obtained have been defined through electrochemical and spectroelectrochemical techniques, as a function of the nature of the solvent in which polymerisation has been carried out and in which polymer doping is electrochemically induced. Two different morphological and/or structural fractions are obtained when the polymer is electrogenerated in CH3CN solvent, while a more homogeneous deposit, consisting of molecules with shorter conjugation system, forms in CH2Cl2. Marked differences are also evidenced when the polymer is p-doped in the two different solvents.

Pigani, Laura; Seeber, Renato; Terzi, Fabio; O., Cerri; M., Innocenti; R., Udisti; G., Sanna ( 2006 ) - Relaxation phenomena and structural modifications of substituted polythiophenes during the p-doping processes. An electrochemical and morphological study - ELECTROCHIMICA ACTA - n. volume 51 - pp. da 2698 a 2705 ISSN: 0013-4686 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Electrodes modified by polythiophenes bearing different substituents have been prepared and the behaviour of the conducting polymers has been studied with respect to the structural phenomena occurring in the correspondence to the doping and the relevant undoping processes. The effects of experimental parameters, such as undoping potential and time, have been investigated. The steric hindrance of the substituents on the polymer chain is demonstrated to play a fundamental role in determining the extent of compactness of the film, as induced by polarisation of the electrode at potentials at which the previously charged polymer is neutralised. Such a conclusion is in accordance with prediction of the electrochemical stimulated conformational relaxation model. Electrochemical AFM measurements have been performed in order to acquire a direct view of the morphological modifications of the polymer coatings during the reduction.

C. Zanardi; R. Scanu; L. Pigani; M.I. Pilo; G. Sanna; R. Seeber; N. Spano; F. Terzi; A. Zucca ( 2006 ) - Synthesis and electrochemical polymerisation of 3 '-functionalised terthiophenes - Electrochemical and spectroelectrochemical characterisation - ELECTROCHIMICA ACTA - n. volume 51 - pp. da 4859 a 4864 ISSN: 0013-4686 [Articolo in rivista (262) - Articolo su rivista]
Abstract

A new terthienyl derivative, 4-[(2,2:5´,2-terthien-3´-yl)methoxyl-2,2´:6´,2-terpyridine, was synthesised in order to clectrogenerate a new conducting polymer as an electrode coating suitable to complex metal ions. The characteristics of the system obtained have been defined through electrochemical and spectroelectrochernical techniques. The physical and chemical properties of 4´-[(2,2´:5´.2-terthien-3´-yl)methoxy]2,2´: 6´,2-terpyfi dine are compared with those of 3´-hydroxymethyl-2,2´:5´,2-terthiophene, i.e. the corresponding trimer not bearing the terpyridine ligand. Under the same conditions for both monomers, both electrochemical and spectroelectrochentical tests show that 4´-[(2,2´:5´,2-terthien-3´yl)methoxyl-2,2´:6´,2-terpyfidine leads to the formation of a narrower molecular weight distribution, with shorter-conjugated polymer chains.

Ma, Heras; S., Lupu; Pigani, Laura; C., Pirvu; Seeber, Renato; Terzi, Fabio; Zanardi, Chiara ( 2005 ) - A poly(3,4-ethylenedioxythiophene)-poly(styrene sulphonate) composite electrode coating in the electrooxidation of phenol - ELECTROCHIMICA ACTA - n. volume 50 - pp. da 1685 a 1691 ISSN: 0013-4686 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The effectiveness of using conducting polymers as electrode coating material in order to prevent electrode fouling caused by electrochemical oxidation of phenol is investigated. In particular, the use of poly(3,4-ethylenedioxythiophene) (PEDOT) has been tested. Electrode passivation is dramatically reduced while incorporating surfactants containing hydrophilic groups into the polymeric structure. A significant improvement in performance is obtained using poly(sodium 4-styrenesulfonate); its presence in the solution during electropolymerisation leads to successful formation of the composite material. The influence of polymer thickness and of surfactant nature on phenol oxidation is studied in order to obtain repeatable responses for phenol oxidation.

M., Innocenti; F., Loglio; Pigani, Laura; Seeber, Renato; Terzi, Fabio; R., Udisti ( 2005 ) - In situ atomic force microscopy in the study of electrogeneration of polybithiophene on Pt electrode - ELECTROCHIMICA ACTA - n. volume 50 - pp. da 1497 a 1503 ISSN: 0013-4686 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Electrochemical AFM technique has been used for the in situ study of the electrogeneration-deposition process of polybithiophene at varying the polymerisation conditions, such as supporting electrolyte, i.e., LiClO4 or tetrabutylammonium hexafluorophosphate, and polymerisation procedure, i.e., either potentiostatic or potentiodynamic method. In order to better follow the evolution of the morphology of the deposit, particularly during the early stages of the polymer film growth, a suitable home-made electrochemical cell has been used.

L. ANTOLINI; G. MINGHETTI; A. MUCCI; F. PARENTI; L. PIGANI; G. SANNA; R. SEEBER; C. ZANARDI ( 2005 ) - Palladium(II) derivatives of alkylsulfanyl substituted thiophenes as precursors of inorganic polymers: Spectroscopic, electrochemical investigations and X-ray crystal structure of trans-PdCl2[3-(butylsulfanyl)thiophene](2) - INORGANICA CHIMICA ACTA - n. volume 358 - pp. da 3033 a 3040 ISSN: 0020-1693 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Palladium(II) complexes with two thiophene derivatives bearing alkylsulfanyl chains, i.e., 3-(n-butylsulfanyl)thiophene and 4,4´-bis(n-butylsulfanyl)-2,2´-bithiophene, are synthesised and spectroscopically and electrochemically characterised. The molecular structure of PdCl2[3-(n-butylsulfanyl)thiophene]2 was determined by X-ray analysis. The properties of the complexes have been compared with those of PdCl2[3,3´-bis(n-butylsulfanyl)-2,2´-bithiophene] and of a conductive polymer partially coordinated with Pd(II), previously synthesised by us. We found that Pd(11) ions can coordinate sulfanyl sulfur atoms both in cis and trans configuration, leading to a reticulate material, where some kind of interchain bridging may be reasonably supposed to enhance the bulk conductivity.

S., Lupu; Pigani, Laura; Seeber, Renato; Terzi, Fabio; Zanardi, Chiara ( 2005 ) - Study of ultrathin Prussian Blue films using in situ electrochemical surface plasmon resonance - COLLECTION OF CZECHOSLOVAK CHEMICAL COMMUNICATIONS - n. volume 70 - pp. da 154 a 167 ISSN: 0010-0765 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Characterisation of ultrathin Prussian Blue films has been performed using in situ electrochemical surface plasmon resonance technique. Prussian Blue films have been prepared by potentiostatic method on a gold-coated glass surface plasmon resonance sensor. The electrochemical reduction of Prussian Blue to Prussian White and oxidation to Berlin Green are accompanied by a change of the refractive index; the system shows repeating voltammetric responses over subsequent potential cycles. The surface plasmon resonance signal is capable of evidencing minute electrochemically induced changes in the inorganic film coating the electrode.

F. TERZI; R. SEEBER; L. PIGANI; C. ZANARDI; L. PASQUALI; S. NANNARONE; M. FABRIZIO; S. DAOLIO ( 2005 ) - 3-methylthiophene Self Assembled Monolayers on planar and nanoparticle Au surfaces - JOURNAL OF PHYSICAL CHEMISTRY. B, CONDENSED MATTER, MATERIALS, SURFACES, INTERFACES & BIOPHYSICAL - n. volume 109 - pp. da 19397 a 19402 ISSN: 1520-6106 [Articolo in rivista (262) - Articolo su rivista]
Abstract

In this article the adsorption of 3-methylthiophene on planar and nanoparticle Au surfaces is investigated. The resulting systems are compared with a benchmark system based on 1-decanethiol. The characterization data collected evidence the formation of a packed 3-methylthiophene SAM on the planar surface. In particular, spectroscopic investigations suggest that 3-methylthiophene aromatic system is not adsorbed on the surface through the pi-electron system but rather through the S atom alone. On the other hand, the behavior of 3-methylthiophene on nanoparticle surfaces is notably different from that of the alkanethiol. Only a limited fraction of the surface of Au nanoparticles results to be actually coated after purification; this notwithstanding, the nanoparticle growth seems to be strongly influenced by the presence of such a labile encapsulating agent.

M. COCCHI; G.C. FRANCHINI; A. MARCHETTI; L. PIGANI; R. SEEBER; L. TASSI; A. ULRICI; C. ZANARDI; P. ZANNINI ( 2004 ) - A study of the dielectric behavior and the liquid structure of a ternary solvent system - ANNALI DI CHIMICA - n. volume 94 - pp. da 165 a 176 ISSN: 0003-4592 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The static dielectric constant of the {DMF(1) + ME(2) + DME(3)} ternary mixtures was measured as a function of temperature (25 less than or equal to t/degreesC less than or equal to 80) and composition, over the whole mole fraction range 0 less than or equal to x(1),x(2),x(3) less than or equal to 1. The experimental values were processed by an empirical equation accounting for the dependence epsilon = epsilon(T, phi(i)), where phi(i) is the volume fraction of the components. A comparison between calculated and experimental data shows that this fitting relationship can be effectively employed to predict epsilon values in correspondence to experimental data gaps. Starting from the experimental measurements, some derived quantities such as molar polarisation (P), and excess counterpart (P-E) were obtained. Both the excess properties, epsilon(E) and P-E, take values partly positive and partly negative under all experimental conditions. The values of the excess quantities are indicative of the presence of specific interactions among different components in the mixtures.

G. FOCA; M. MANFREDINI; D. MANZINI; A. MARCHETTI; L. PIGANI; S. SIGHINOLFI; L. TASSI; A. ULRICI ( 2004 ) - Dielectric properties in ternary mixtures of ethane-1,2-diol+1,2-dimethoxyethane + water - INTERNATIONAL JOURNAL OF THERMOPHYSICS - n. volume 25(3) - pp. da 839 a 855 ISSN: 0195-928X [Articolo in rivista (262) - Articolo su rivista]
Abstract

The static dielectric constant (epsilon) of ethane-1,2-diol + 1,2-dimethoxyethane + water ternary mixtures was measured as a function of temperature (263.15 less than or equal to T (K) less than or equal to 353.15) and composition, over the complete mole fraction range 0 less than or equal to x(1), x(2), x(3) less than or equal to 1. The experimental values were analyzed by empirical relationships that accounted for the dependence epsilon = epsilon(T) and Y = Y(x(i)). A comparison between calculated and experimental data shows that these fitting relationships can be reliably used to predict epsilon values, along with other related properties, in areas of experimental data gaps. Starting from the experimental measurements, some derived quantities such as molar orientational polarization (P), dipolar interaction free energy (Fmu) and the relevant thermodynamic excess mixing properties (F-mu(E), (F) over bar (E)(mu,i)), were obtained. The values of the excess quantities are indicative of the presence of specific interactions between different components in the mixtures. A discussion of data in terms of the Kirkwood theory also provides information on the short-range intermolecular interactions, suggesting the formation of stable two-component adducts rather than of more complex moieties involving all three molecular species.

Pigani, Laura; A., Heras; Á., Colina; Seeber, Renato; J., López Palacios ( 2004 ) - Electropolymerisation of 3,4-ethylenedioxythiophene in aqueous solutions - ELECTROCHEMISTRY COMMUNICATIONS - n. volume 50 - pp. da 1192 a 1198 ISSN: 1388-2481 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The potentiostatic electrosynthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) in aqueous media without addition to the solution of any kind of surfactant has been studied by electrochemical quartz crystal microbalance (EQCM) and by spectroelectrochemistry. These tandem techniques have given valuable new information about the electropolymerisation process, allowing us to relate absorbance-charge and frequency-charge relationships to: (i) oligomers generation and chain propagation, as far as the length leading to precipitation is reached; (ii) growing of the polymer deposit and concomitant p-doping, and even (iii) overoxidation of the polymer film. An analysis of the whole of the data, in fact, shows that the charge spent is not necessarily totally involved in thepolymer deposit formation, growth, and p-doping, so that it is necessary to be particularly careful in the fitting of the experimental data to linear models.

Pigani, Laura; Seeber, Renato; Terzi, Fabio; Zanardi, Chiara ( 2004 ) - EQCM study of the p- and n-doping processes of a poly[4,4’-bis(alkylsulphanyl)-2,2’-bithiophene] - JOURNAL OF ELECTROANALYTICAL CHEMISTRY - n. volume 570 - pp. da 235 a 242 ISSN: 1572-6657 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Electrogenerated deposits of poly[4,40-bis(butylsulphanyl)-2,20-bithiophene] have been characterised in the presence of differentsupporting electrolytes, by coupling current (charge) to microgravimetric measurements from the electrochemical quartz crystal microbalance (EQCM). The simultaneous collection of voltammetric measurements and of data relative to mass changes shows the influence exerted by the nature of the supporting electrolyte on the charge-discharge steps of both p- and n-doping processes. Interestingly, the microgravimetric data collected corresponding to the pre-peaks of both doping processes suggest the occurrence of two opposite motions of ions (ingress into and exit out from the polymer) in the relevant potential region, giving a contribution to the study of the ‘residual charge’ phenomenon.

Pigani, Laura; Seeber, Renato; Terzi, Fabio; Zanardi, Chiara ( 2004 ) - Influence of the nature of the supporting electrolyte on the formation of poly[4,4'-bis(butylsulphanyl)-2,2'-bithiophene] films. A role for both counter-ion and co-ion in the polymer growth and p-doping processes - JOURNAL OF ELECTROANALYTICAL CHEMISTRY - n. volume 562 - pp. da 231 a 239 ISSN: 1572-6657 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Electrode deposits of a polythiophene with particularly interesting characteristics, i.e., poly[4,40-bis(butylsulphanyl)-2,20-bithiophene],have been generated in the presence of different supporting electrolytes. The formation of the coatings has been studied bycoupling conventional electrochemical techniques with quartz crystal microbalance measurements. The results of simultaneousvoltammetric or chronoamperometric and microgravimetric experiments allow us to show the influence exerted by the nature of thesupporting electrolyte on the polymerisation and concomitant charging–discharging processes of the conducting polymer.

S., Lupu; Parenti, Francesca; Pigani, Laura; Seeber, Renato; Zanardi, Chiara ( 2003 ) - Differential pulse techniques on modified conventional-size and microelectrodes. Electroactivity of poly[4,4'-bis(butylsulfanyl)-2,2'-bithiophene] coating towards dopamine and ascorbic acid oxidation. - ELECTROANALYSIS - n. volume 15 - pp. da 715 a 725 ISSN: 1040-0397 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Poly[4,4'-bis(butylsulfanyl)-2,2'-bithiophene] modified conventional-size and (ultra)microelectrodes are first investigated in acetonitrile and quasi-neutral aqueous solution with respect to the repeatability of the responses obtained both in cyclic voltammetry and in differential pulse voltammetry. The reactivity towards ferrocene and hydroquinone, chosen as benchmark oxidizable substances in the two media, respectively, is considered. Comparison is made with the behavior of poly(3-methylthiophene) as electrode coating, which is one of the most commonly used redox mediators in amperometric sensors based on coatings consisting of conducting polymers. The results confirm the appealing properties of poly[4,4'-bis(butylsulfanyl)-2,2'-bithiophene], previously evidenced by us in different electrochemical studies: it exhibits particularly high stability and the characteristics of the current/potential curves obtained make it particularly suitable for analytical purposes. After performing these tests, the quantitative determination of dopamine by modified microelectrode is examined and the simultaneous voltammetric determination of ascorbic acid and dopamine is considered. The possibility of working profitably with a microelectrode at very low buffer-supporting electrolyte concentration is ascertained.

A. Mucci; F. Parenti; L. Pigani; R. Seeber; C. Zanardi; M. I. Pilo; N. Spano; M. Manassero ( 2003 ) - The effect of Pd(II) coordination on the properties of an alkylsulfanyl substituted polythiophene. Comparison with the corresponding monomer - JOURNAL OF MATERIALS CHEMISTRY - n. volume 13 - pp. da 1287 a 1292 ISSN: 0959-9428 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The synthesis of a conducting polymer partially coordinated with Pd(II) ions is reported. The aim is to study the influence of the metal on the properties of the material as a whole, which is very appealing for possible applications in the field of amperometric sensors. An alkylsulfanyl substituted polythiophene is used in this first approach, due to the well known affinity of the sulfur atom for soft metals. The interaction between the organic and inorganic moieties results in the easy formation of partially coordinated polymer. The presence of the metal ions is found to affect the chemical, physical, and electrochemical properties of the organicmacromolecules, owing to interactions between the polymer p-conjugation system and the metal d orbitals.Synthesis and characterisation of the relevant monomer complex helps to better understand the behaviour of the complex polymer-metal system.

M. Cocchi; G. Franchini; M. Manfredini; A. Marchetti; L. Pigani; R. Seeber; L. Tassi; A. Ulrici; M. Vignali; C. Zanardi; P. Zannini ( 2002 ) - Beta-functionalised polythiophenes as microelectrode modifiers in low conductive media - ANNALI DI CHIMICA - n. volume 92 - pp. da 177 a 185 ISSN: 0003-4592 [Articolo in rivista (262) - Articolo su rivista]
Abstract

A study on polythiophene coated microelectrodes is reported, the goal being that of checking the capability of these electrochemical systems to work in low conductive media. The possibility of electrochemically p-doping the polymer in the presence of very low concentrations or even in the absence of supporting electrolyte in the solution is ascertained, opening the way to the use of similar systems in pure solvent media. This result is obtained in such conditions that the presence of residual charges - and corresponding counterions - trapped inside the film coating can be reasonably hypothesised.

S., Lupu; C., Mihailciuc; Pigani, Laura; Seeber, Renato; N., Totir; Zanardi, Chiara ( 2002 ) - Electrochemical preparation and characterisation of bilayer films composed by Prussian Blue and conducting polymer - ELECTROCHEMISTRY COMMUNICATIONS - n. volume 4 - pp. da 753 a 758 ISSN: 1388-2481 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Preparation and electrochemical behaviour of bilayer films consisting of iron(Ill) hexacyanoferrate, well known as Prussian Blue, and of poly[4,4´-bis(butylsulphanyl)-2,2´-bithiophene], on a platinum electrode, are reported. The electrochemical features of the Prussian Blue/conducting polymer bilayer system are examined in aqueous and acetonitrile solutions. Cyclic voltammetric studies show that, in acetonitrile solvent, the inner layer Prussian Blue is electroactive to some extent, though the electrochemical response of the system is mainly accounted for by poly[4,4´-bis(butylsulphanyl)-2,2´-bithiophene] outer layer. On the other hand, in aqueous solution Prussian Blue exhibits good electroactivity. Under specific experimental conditions, the individual redox behaviour of each constituent of the bilayer is evidenced in the two solvents separately, i.e., that of PB and that of poly[4,4´-bis(butylsulphanyl)-2,2´bithiophene] in aqueous and in organic solvent, respectively. However, interesting reciprocal influences are evident in the current/potential curves recorded under conditions which are discussed.

A. Mucci; F. Parenti; L. Pigani; M.I.Pilo; P. Piu; G. Sanna; L. Schenetti; R. Seeber; N. Spano; C. Zanardi ( 2002 ) - Polimeri conduttori coordinati con ioni metallici come nuovi materiali per sensori elettrocatalitici - Atti Del XVII Congresso Nazionale di Chimica Analitica - . . ITA) - n. volume . [Abstract in Atti di convegno (274) - Abstract in Atti di Convegno]
Abstract

v. allegato

S. LUPU; A. MUCCI; L. PIGANI; R. SEEBER; C. ZANARDI ( 2002 ) - Polythiophene derivative conducting polymer modified electrodes and microelectrodes for determination of ascorbic acid. Effect of possible interferents - ELECTROANALYSIS - n. volume 14 - pp. da 519 a 525 ISSN: 1040-0397 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Conventional-size electrodes and microelectrodes coated by electrogenerated poly[4,4'-bis(butylsulfanyl)-2,2'-bithiophene] have been tested with respect to the electrocatalytic oxidation of a particularly interesting analyte, i.e., ascorbic acid, in different concentrations of phosphate buffer, aqueous solution. Linear sweep and cyclic voltammetry have been used and the quantities related to the analyte concentration were the peak current and the diffusion (t(-1/2)) deconvoluted peak current in the case of conventional-size and of microelectrode, respectively. Fairly good linear correlation could be found; a particularly wide linearity range was obtained by working with the microelectrode. It showed to give good results also at a very low (10(-4) M) phosphate buffer-supporting electrolyte concentration. The actual interference on the analysis of compounds often coupled with ascorbic acid in natural or pharmaceutical products has been studied.

M. Cocchi; M. Manfredini; A. Marchetti; L. Pigani; R. Seeber; L. Tassi; A. Ulrici; M. Vignali; C. Zanardi; P. Zannini ( 2002 ) - Temperature and composition dependence of the refractive indices of the 2-chloroethanol + 2-methoxyethanol binary mixtures - ANNALI DI CHIMICA - n. volume 92 (3) - pp. da 187 a 201 ISSN: 0003-4592 [Articolo in rivista (262) - Articolo su rivista]
Abstract

AbstractMeasurements of the refractive index n for the binary mixtures 2-chloroethanol + 2-methoxyethanol in the 0 ≤ T/°C ≤ 70 temperature range have been carried out with the purpose of checking the capability of empirical models to express physical quantity as a function of temperature and volume fraction, both separately and together, i.e., in a two independent variables expression. Furthermore, the experimental data have been used to calculate excess properties such as the excess refractive index, the excess molar refraction, and the excess Kirkwood parameter Ag over the whole composition range. The quantities obtained have been discussed and interpreted in terms of the type and nature of the specific intermolecular interactions between the components.

Cocchi, Marina; M., Manfredini; Marchetti, Andrea; Pigani, Laura; Seeber, Renato; Tassi, Lorenzo; Ulrici, Alessandro; Zanardi, Chiara ( 2002 ) - Viscosity of (ethane-1,2-diol+1,2-dimethoxyethane + water) at temperatures from 263.15 K to 353.15 K - JOURNAL OF CHEMICAL THERMODYNAMICS - n. volume 34 (5) - pp. da 593 a 611 ISSN: 0021-9614 [Articolo in rivista (262) - Articolo su rivista]
Abstract

AbstractThe kinematic viscosity ν for (ethane-1,2-diol + 1,2-dimethoxyethane + water) was measured at 14 different ternary compositions covering the whole miscibility field, and at 19 temperatures in the range 263.15 T / K 353.15. The experimental values were fitted using empirical equations of the type ν = ν (T) and ν = ν (xi), respectively, in order to provide reliable models to account for the behaviour of the system. The excess kinematic viscosity νEhas been determined and interpreted in terms of the type and nature of the interactions among the components of the mixture. Using the experimental ν data, the thermodynamic properties ( ΔG * , ΔH * ,ΔS * ) of the viscous flow have been obtained from the Eyring’s approach and standard thermodynamic equations. Furthermore, excess mixing functions, such asΔG * E , have been determined, and found to evidence the existence of quite strong specific interactions among the components, probably due to the formation of hydrogen bonds and dipolar networks. However, all the calculated excess mixing properties suggest the absence of stable three-component adducts.

Cocchi, Marina; Marchetti, Andrea; Pigani, Laura; Tassi, Lorenzo; Ulrici, Alessandro; G., Vaccari; Zanardi, Chiara ( 2001 ) - Density and volume properties of the 2-methoxyethanol+1,2-dimethoxyethane + water ternary solvent system at various temperatures - PHYSICS AND CHEMISTRY OF LIQUIDS - n. volume 39 - pp. da 151 a 168 ISSN: 0031-9104 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Densities (rho) of the ternary mixtures 2-methoxyethanol + 1,2-dimethoxyethane + water have been measured at 19 temperatures in the range -263.15 less than or equal toT/K less than or equal to 353.15. The experimental data were processed by empirical relations accounting for the dependence of rho on temperature and ternary composition expressed as mole fraction of the components (0 less than or equal to x(i) less than or equal to 1). All checked equations seem to be suitable for correlation purposes, in order to obtain interpolated values in correspondence to experimental data gaps. Furthermore, the excess molar volume (V-E) has been investigated to make evident the possibility of forming stable solvent-cosolvent adducts. The excess property has been interpreted on the basis of specific intermolecular interactions between the components.

B. BALLARIN; F. COSTANZO; F. MORI; A. MUCCI; L. PIGANI; L. SCHENETTI; R. SEEBER; D. TONELLI; C. ZANARDI ( 2001 ) - Electropolymerisation and characterisation of poly[4,4 '-bis(butylsulphanyl)-2,2 '-bithiophene] - ELECTROCHIMICA ACTA - n. volume 46 - pp. da 881 a 889 ISSN: 0013-4686 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Electrochemical properties of electrogenerated poly[4,4'-bis(butylsulphanyl)-2.3'-bithiophene] have been studied. with particular attention to the charge-discharge processes. The possibility of both p- and n-doping is indicated. Doping and relevant de-doping processes of the specific polymer have also been considered in the context of the more general, still un-solved problem of the analysis of the mechanisms that al-e operative in the case of simple polythiophenes. In situ spectroelectrochemical measurements have been used to support the electrochemical results and both in situ UV-visible NIR spectroscopy on neutral, p- and n-doped forms of the polymer, and ex situ IR measurements have been performed. (C) 2001 Elsevier Science Ltd. All rights reserved.

H., Ding; Z., Pan; Pigani, Laura; Seeber, Renato; Zanardi, Chiara ( 2001 ) - P- and n-doping processes in polythiophene with reduced bandgap. An electrochemical impedance spectroscopy study - ELECTROCHIMICA ACTA - n. volume 46 - pp. da 2721 a 2732 ISSN: 0013-4686 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Electrochemical impedance spectroscopy has been used for the characterisation of electrodes modified with different polythiophenes, namely poly[4,4 ' -bis(butylsulfanyl)-2,2 ' -bithiophene], poly[4,4 ' -bis(methylsulfanyl)-2,2 ' -bithiophene] and poly( 3-methylthiophene), at different applied potentials, using different supporting electrolytes. By comparison of the results obtained under experimental conditions in which n-doping is prevented and those obtained from tests where it does occur, some general features have been deduced. all of them being coherently described by a recently proposed 'generalised transmission line circuit' model: impedance plots at different applied potentials exhibit progressive changes which are well accounted for by the 'evolving' model. The results obtained on the n-doping process of S-alkyl substituted polymers suggest a behaviour interestingly similar to that exhibited in the p-doping: this supports a symmetry that was also found by us in a previous work, with respect to the incorporation and release of counterions during the n- and p-charge-discharge processes.

Cocchi, Marina; Marchetti, Andrea; Pigani, Laura; G., Sanna; Tassi, Lorenzo; Ulrici, Alessandro; G., Vaccari; Zanardi, Chiara ( 2000 ) - Density and volumetric properties of ethane-1,2-diol plus di-ethylen-glycol mixtures at different temperatures - FLUID PHASE EQUILIBRIA - n. volume 172 - pp. da 93 a 104 ISSN: 0378-3812 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The density of the ethane-1,2-diol (ED) + di-ethylen-glycol (DEG) binary mixtures has been measured at different temperatures over the complete composition range. The experimental measurements have been used to check the validity of relationships accounting for the dependence of the density on temperature and composition, useful to obtain interpolated values in the correspondence of the experimented data gaps. Starting from the primary data, some derived quantities, such as partial molar volumes, excess and partial excess molar volumes, have been obtained. In these mixtures, V-E presents an S-shaped dependence on composition at each temperature, showing negative values in the ED rich-region and positive values at the opposite extreme. The results are compared and discussed to get light to the: changes in molecular association and structural effects in this solvent system. (C) 2000 Elsevier Science B.V. All rights reserved.

H. DING; L. PIGANI; R. SEEBER; C. ZANARDI ( 2000 ) - P- and n-doping of electrochemically formed poly(4,4 '-bisbutylsulfanyl-2,2 '-bithiophene). A novel material with reduced bandgap - JOURNAL OF NEW MATERIALS FOR ELECTROCHEMICAL SYSTEMS - n. volume 3 - pp. da 337 a 341 ISSN: 1480-2422 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Electrodes covered by stable electron conducting polymer films which exhibit easy p- and relatively easy n-doping have been successfully prepared by electrochemical polymerisation of symmetrical 4,4'-bisbutylsulfanyl-2,2'-bithiophene. The whole of the cyclic voltammetric behaviour has been explained based on the concept of 'electrostatically stabilised polarons'.