Sandro Zecchin

Università degli studi di Parma, Parma, Emilia-Romagna, Italy

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Publications (105)462.23 Total impact

  • MRS Online Proceeding Library 01/2011; 413. DOI:10.1557/PROC-413-627
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    ABSTRACT: Electrodeposition of amorphous Fe2O3 films of nanometer size was performed by reduction of Fe(ClO4)(3) or Fe(ClO4)(2) in oxygenated acetonitrile. Cyclic voltammetry has shown that the oxide-film formation occurs via oxidation of electrodeposited metal by dissolved oxygen. The oxide films were characterized by cyclic voltammetry, electrochemical quartz crystal microbalance, X-ray diffraction, and UV-visible spectroscopy. The films are reversibly reduced in acetonitrile + LiClO4 in two redox processes to the Fe3O4 and FeO oxides via lithium intercalation. The UV-visible (UV-vis) spectrum displays absorption with an optical gap (1.75 eV) characteristic of amorphous Fe2O3. Spectroelectrochemistry has shown that reduction causes bleaching of the yellowish films (electrochromic efficiency congruent to 30 C-1 cm(2) at 400 nm). Heating the films at 500 degrees C converts them to the crystalline alpha-Fe2O3 form with loss of electroactivity.
    ChemInform 05/2010; 29(19). DOI:10.1002/chin.199819019
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    ABSTRACT: In a quest for thermoelectric polymeric materials novel polycarbazole and polyindolocarbazole derivatives were synthesized. Alkyl side chains on the carbazole cycle and different side chains (alkyl or benzoyl) on the nitrogen atom of the backbone unit were introduced. Optical, electrochemical, electrical, and thermoelectric properties were investigated on these polymers and on two poly(diindolocarbazole)s. Band structure calculations were used to predict which polymers might be promising as thermoelectric materials. The best combination of Seebeck coefficient and conductivity (power factor) was around 10-7 W m-1 K-2 with copolymers comprising thiophene units alternating with carbazole or indolocarbazole. This family of polymers possesses good Seebeck coefficients, but there is still a need to improve the electrical conductivity, to produce useful thermoelectric materials.
    Chemistry of Materials 03/2007; 19(8). DOI:10.1021/cm070063h · 8.54 Impact Factor
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    ABSTRACT: Thin films of tetrahexylsexithiophenes, fluorenonyl- and fluorenyl-protected at the terminal alpha,omega-positions, were investigated by cyclic voltammetry, electrochemical quartz crystal microbalance analysis, in situ ESR, and in situ conductivity. Reversible oxidation is composed of three separate steps, two one-electron processes and a further multielectron process. ESR indicates strong magnetic dimerization for the one-electron-oxidized species. Conductivity is redox type at the cation-dication (polaron-bipolaron) state and metal-like at doping levels higher than the bipolaron with a 20-fold increase at full oxidation. Hexyl-substituted alpha,omega-capped octathiophene, decathiophene, and dodecathiophene films have been similarly investigated to compare the effects of fluorenonyl and fluorenyl extension of sexithiophene with those given by additional thiophene rings. The conductivity, which increases progressively ( by 3 orders of magnitude) with the oligothiophene chain length, is metal-like. In dodecathiophene the doping charge increases markedly, approaching four electrons per molecule, and the conductivity, maximized at the two-electron level, decreases linearly, approaching zero at the four-electron level. A bipolaron model of conductivity accounts for conductivity in oligothiophenes.
    Chemistry of Materials 05/2006; 18(13-13):3151-3161. DOI:10.1021/cm060671h · 8.54 Impact Factor
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    ABSTRACT: The magnetic and conductive properties of a series of quinoidal oligothiophenes, that is, bis-(dicyanomethylene)oligothiophenes (TnCN4, n) 2-4), have been investigated in the solid state and (for magnetic analysis) in solution, and the results have been compared with those from density functional theory (DFT) calculations. Solution electron spin resonance (ESR) spectra of radical cations and anions are characterized by hyperfine structures due to coupling with nitrogen and thiophene hydrogen atoms. Neutral solutions are ESR active, indicating a significant presence of diradical species with no hyperfine structure. ESR spectra of powder samples at room temperature give a concentration of radical species up to 1 mol % (T3CN4), that is, 0.5% of the compound exists in a diradical state. The percentage decreases dramatically from T3CN4 to T2CN4, as a result of the decreased number of aromatic rings. The diradical concentration increases with temperature according to activation energies which are higher for the shorter members and in very good agreement with DFT calculations. Tetrahexyl-substituted T4CN4 is redox conducting at the neutral-polaron mixed oxidation level with a maximum conductivity of 0.03 S cm -1 , about two orders of magnitude higher in comparison with an aromatic tetrahexyl-substituted octathiophene.
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    ABSTRACT: New alternating copolymers based on indolocarbazole (IC), both two-and three-coupled, and bithiophene (BT) or bis(3,4-ethylenedioxythiophene) (BiEDOT), were obtained using Stille or Suzuki coupling reactions. Those copolymers have been investigated by cyclic voltammetry, electrochemical quartz crystal microbalance, in situ electron spin resonance, in situ conductivity, and UV-Vis-NIR spectro-electrochemistry techniques. All polymer films undergo reversible oxidation processes. One to three isoelectronic oxidation processes, involving one electron per repeat unit, produce radical cations, dications, and radical trications. The oxidative charge is localized in the IC moiety for BT copolymers or over the whole polyconjugated backbone for BiEDOT copolymers. Redox neutral-polaron conductivities are in the ran-e of 0.02-0.1 S.cm(-1) and polaron-bipolaron conductivities in the range of 0.1-0.7 S.cm(-1).
    Macromolecular Chemistry and Physics 01/2006; 207(2):175 - 182. DOI:10.1002/macp.200500429 · 2.45 Impact Factor
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    ABSTRACT: New polyindolocarbazoles (PIC) and polydiindolocarbazoles (PDIC) have been synthesized using Yamamoto polymerization reaction. These polymers have been investigated by cyclic voltammetry, UV-Vis-NIR spectro-electrochemistry, electrochemical quartz crystal microbalance, in situ electron spin resonance, and in situ conductivity techniques. Two redox oxidation processes, each involving one electron per repeat unit, produce radical cations (free or pi-dimerized) and dications. Each one-electron redox process is generally split into two due to the stabilization of mixed-valence states. The oxidative charge is delocalized over the polyconjugated backbone with neutral-polaron conductivities in the range 0.002-0.04 S.cm(-1) and polaron-bipolaron conductivities in the range 0.04-0.5 S.cm(-1). Conductivities are higher when nitrogen atoms are involved in the conjugation pathway.
    Macromolecular Chemistry and Physics 01/2006; 207(2):166 - 174. DOI:10.1002/macp.200500423 · 2.45 Impact Factor
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    Advanced Functional Materials 01/2006; 16(4):531 - 536. DOI:10.1002/adfm.200500404 · 10.44 Impact Factor
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    ABSTRACT: doi: 10.1021/cm051798u
    Chemistry of Materials 11/2005; 17(25):6492-6502. DOI:10.1021/cm051798u · 8.54 Impact Factor
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    ABSTRACT: Self-assembly (SA) of polyviologens with linear alkyl spacers PVn (n=3–10) on sulfonate-primed gold and ITO electrode surfaces has been investigated by CV, QCM, XPS and AFM. The polymers form stable and relatively dense monolayers even from 10−4M PVn concentration. The viologen surface density is decreased as n is increased but for n=10 and on alkylsulfonate-primed surfaces a strong adsorption takes place, with decreased redox potential and very narrow cyclic voltammogram of the absorbed layer due to organized structures on the surface.Stable and regular electrostatically self-assembled (ESA) multilayers are built on sulfonate-primed surfaces with PV3 and polysulfonates. From XPS analysis, the composition of the PVn/polysulfonate multilayers corresponds to a 1:1 ratio of polyanion and polycation charges, i.e., no extra non-polymeric ion is present, independently from the alkane chain length. The rate of electron transfer within the multilayers (diffusion coefficient=ca. 10−9cm2s−1) is higher than for analogous bulk materials.
    Journal of electroanalytical chemistry 07/2005; 580(2):330-339. DOI:10.1016/j.jelechem.2005.04.003 · 2.87 Impact Factor
  • Gianni Zotti, Sandro Zecchin, Barbara Vercelli
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    ABSTRACT: Thin polyterthiophene films and oligothiophene-based self-assembled monolayers (SAMs) on indium tin oxide (ITO) and gold electrodes have been coupled with different pyrrole- and thiophene-based monomers (heterocoupling). Since the corresponding homopolymers are soluble in the electrochemical medium, only the surface-coupled polymer remains on the electrode and is detected. The method when applied to monolayers allows the formation of nanometer-size layers of polyconjugated polymers with nominally normal orientation of the chain to the surface. Thin films and SAMs were characterized before and after coupling by cyclic voltammetry, UV−vis and IR reflection absorption spectroscopy, and X-ray photoelectron spectroscopy. Microcontact printing on gold and ITO surfaces resulted in patterns for which atomic force microscopy evidenced strong height enhancement after heterocoupling.
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    ABSTRACT: Polythiophene regular copolymers bearing amino or nitro moieties directly linked to the conjugated backbone are produced by anodic coupling of 3′,4′-diamino- or 3′,4′-dinitro-terthiophenes. The polymers are characterized by cyclic voltammetry, FTIR reflection–absorption and UV–vis spectroscopy and in situ conductivity. Post-polymerization functionalization of polymer films leads to the quantitative transformation of the diamine to pyrazine and of the dinitro to diamine and subsequently pyrazine moieties. Conjugation of starting and ending functionalizations with the polythiophene backbone produces dramatic changes in electronic (electrochemical and optical) properties.
    Electrochimica Acta 02/2005; 50(s 7–8):1469–1474. DOI:10.1016/j.electacta.2004.10.037 · 4.09 Impact Factor
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    ABSTRACT: The electrochemical oxidative polymerization of 3-methylthiophene (3MT) on platinum electrodes is favoured by the presence of previously deposited polyterthiophene (PTT) films. Cyclic voltammetry CV and single sweep voltammetry SSV were used to investigate the electrocatalytic process. The CV rate of polymer growth and the SSV electrocatalytic current increase linearly with the amount of predeposited PTT. The results rule out the previously invoked electrocatalytic promotion of 3MT polymerization by terthiophene radical cations in solution. SSV analysis with other thiophene-based polymer films (e.g. 3- and 3,4-alkylsubstituted polythiophenes) and with other thiophene-based monomers (e.g. 3,4-ethylenedioxythiophene) has shown that the electrocatalytic effect is of a general nature. The formation of a charge transfer complex between the thiophene-based monomer and the oxidized thiophene-based polymer is invoked to account for the catalytic action. The results account for the previous large and unexplained body of experimental evidence of electrocatalytic effects in the electro oxidative synthesis of conducting polymers.
    Journal of electroanalytical chemistry 02/2005; 575(2):169-175. DOI:10.1016/j.jelechem.2004.09.008 · 2.87 Impact Factor
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    ABSTRACT: N-Hexyl-cyclopenta[c]pyrrole was synthesized and electrochemically and chemically polymerized to a novel 1,3,4- alkyl- substituted polypyrrole. The polymer was characterized in solution and as thin solid film by cyclic voltammetry, UV-vis, FTIR and NMR spectroscopy, MALDI mass spectroscopy, GPC analysis, electrochemical quartz crystal microbalance, ESR spectroscopy and in situ conductivity. The polymer, with a defect-free structure and an average degree of polymerization of 13 (electrochemically prepared) and 24 (chemically prepared), is soluble (>1%) in acetone, acetonitrile and chlorinated solvents. Its in situ conductivity as a function of potential and doping charge has the typical features of redox conductivity with a maximum value of ca 1 x 10(-3) S. CM-1.
    Macromolecular Chemistry and Physics 10/2004; 205(15):2026 - 2031. DOI:10.1002/macp.200400151 · 2.45 Impact Factor
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    ABSTRACT: Some C2v symmetric cyclopenta[2,1-b;3,4-b′]bithiophenes differently substituted at the 4 position with a calix[4]arene group were synthesized and electrochemically polymerized by anodic coupling. The polymers were characterized by cyclic voltammetry, UV-vis and FTIR spectroscopy. Quartz crystal microbalance analysis showed strong affinity and selectivity of the polymers for toluene and acetone from the gas phase. The absorption process associated with the calix unit was satisfactorily described through a Langmuir isotherm, while a very small linear contribution was given by the polythiophene backbone. The absorption capacity of these materials was found to be higher by a magnitude of three orders than those displayed by cyclopentabithiophene-based polymers devoid of the calix unit, thus supplying strong, though indirect, proof of the role played by the calix units in the absorption process.
    Journal of Materials Chemistry 06/2004; 14(12):1804-1811. DOI:10.1039/B314345G · 6.63 Impact Factor
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    ABSTRACT: Anodic coupling of 4,4-bis-butanesulfonate cyclopentadithiophene occurs in acetonitrile after the addition of 1:1 HClO4 to yield water-soluble polyanionic poly(1). 4,4-Bis-hexyltrimethylammonium cyclopentadithiophene is polymerized in acetonitrile to acetonitrile-soluble polycationic poly(2) which is converted to the water-soluble hydroxide form by anion exchange. These novel water-soluble polythiophenes, characterized by a rigid-rod symmetrical shape of the chain, display a high conjugation length (λmax = 560−575 nm) and a good solubility in water (>10 gL-1). MALDI and UV−vis spectroscopy assign these polymers a degree of polymerization of 5−6. The polymers form stable monolayers (storing a redox charge of 10 μC cm-2) on ITO/glass and gold electrodes. Subsequent electrostatic self-assembly (ESA) of poly(1) and poly(2), both between them and each with a non-electroactive polycation or polyanion, proceeds with a linear growth rate monitored by cyclic voltammetry (10 μC cm-2 bilayer-1) and UV−vis spectroscopy. No effect of ionic strength was observed in contrast with ESA of conventional polyionic polymers. IRRAS and XRD analysis of the multilayers agree with a regular disposition of the polythiophene chains in the layers.
    Chemistry of Materials 05/2004; 16(11). DOI:10.1021/cm0351644 · 8.54 Impact Factor
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    ABSTRACT: The in situ conductivity vs p-doping charge of low-defect polypyrroles, N-substituted polypyrroles, and polythiophenes has been investigated in acetonitrile in the presence of the weakly coordinating perchlorate ion as supporting electrolyte. In-situ ESR and EQCM measurements have given supporting information on polymer structure and conduction carriers. The structures of the polymers cover a wide range of conjugative, geometrical, and solvation conditions, but the conductive pattern follows simply the polymer ring type (pyrrole, N-substituted pyrrole, or thiophene). In polythiophenes an initial region of low conductivity, due to strongly spin-dimerized polarons, is followed by an increase of conduction to a plateau of high conductivity. N-substituted polypyrroles display a linear increase of conductivity with charge followed by a plateau of conductivity. Polypyrroles without N-substitution show an increase of conductivity to a maximum followed by a symmetrical decrease to zero at a charge corresponding to one bipolaron per tetrapyrrole unit. A redox-type bipolaron model of conduction, based on stabilization of the bipolaron positive charge by H-bonding with the counteranion, is suggested. The parent polypyrrole shows the uncomplicated conductivity pattern (increase of conductivity to a plateau) due to a uniquely strong stabilization of the π-stacked polymer chains.
    Chemistry of Materials 10/2003; 15(24). DOI:10.1021/cm030336i · 8.54 Impact Factor
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    ABSTRACT: Hexylferrocene phosphonic acid was adsorbed on indium−tin oxide (ITO) and amino-primed ITO electrodes from ethanol. The obtained monolayers are stable in acetonitrile where cyclic voltammetry shows the formation of domains of self-interacting and free ferrocene molecules. Distinct phases are observed on bare ITO, whereas a single Frumkin isotherm is obtained on amino-primed ITO. Dilution experiments with alkylphosphonic acids CnH2n+1PO(OH)2 (n = 3, 6, and 12) have shown that only the dodecyl chain may compete with the hexylferrocene chain, which remains 50 times more strongly bound to the surface. The free energy of self-interaction of the ferrocene moieties in the layers is ca. 40 kJ mol-1; that is, it is equivalent to that of a 15 carbon atom alkyl chain. Lateral interactions among hexylferrocene and dodecyl chains form isolated domains of the components, ruling out a real dilution of ferrocenes to single isolated molecules.
    Langmuir 09/2003; 19(22). DOI:10.1021/la030150y · 4.38 Impact Factor
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    ABSTRACT: Electrochemically prepared poly(3,4-ethylenedioxythiophene) (PEDT) poly(styrenesulfonate) (PSS), produced from acidic (PSSH) and basic (PSSNa) PSS, was characterized by cyclic voltammetry CV, UV−vis spectroscopy, in situ conductivity, and XPS spectroscopy and was compared with electrochemically prepared PEDT/tosylate and chemically prepared PEDT/PSS. CV analysis shows that the polymer synthesis is strongly affected by the nucleophilic character of the counteranion. Although CV and UV−vis spectroscopy show that the structure and degree of polymerization (oligomeric, ca. 10 EDT units) of the PEDT backbone is the same for all polymers, XPS is able to explain the different conductivity values for these materials (ranging from 1 S cm-1 for PEDT/PSSNa to 400−450 S cm-1 for PEDT/tosylate) based on doping level and composition. In particular, critical results are observed to be the ratios between sulfonate and thiophene units in the polymers: the higher the PEDT concentration, the higher the conductivity. XPS also explains by solvent-induced nanometer-scale segregation between PEDT/PSS and excess PSS particles the often reported conductivity enhancement of chemically prepared PEDT/PSS upon treatment with polar solvents.
    Macromolecules 05/2003; 36(9):3337-3344. DOI:10.1021/ma021715k · 5.93 Impact Factor
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    ABSTRACT: Dichloromethane-soluble poly(3,4-ethylenedioxythiophene)s modified with oligoethylene oxide chains of different lengths (PEDT−EO and PEDT−PEO) were produced by anodic coupling. PEDT−EO solutions were used to produce mono- and multilayer films on ITO−glass electrodes and float glass sheets. Layer-by-layer alternation of doped PEDT−EO with poly(p-styrene sulfonate) (PSS) or doped poly(3,4-ethylenedioxythiophene) sulfonate produced electroactive and robust multilayered surfaces with low surface resistivity (5 × 105 Ω/□ for a PEDT−EO/PSS 10-bilayer). Analogous multilayers could be built from doped PEDT−EO and polyammonium polycations. Doped PEDT−EO forms with PSS the first reported electrostatically bound polyionic multilayers in which the positive charge is delocalized over a polythiophene backbone.
    Chemistry of Materials 04/2003; 15(11). DOI:10.1021/cm030151b · 8.54 Impact Factor

Publication Stats

2k Citations
462.23 Total Impact Points

Institutions

  • 2002
    • Università degli studi di Parma
      • Department of Chemistry
      Parma, Emilia-Romagna, Italy
  • 1973–2002
    • University of Padova
      • Department of Chemical Sciences
      Padua, Veneto, Italy
  • 1999–2001
    • INO - Istituto Nazionale di Ottica
      Florens, Tuscany, Italy
  • 1975–2001
    • National Research Council
      • Institute for Organic Syntheses and Photoreactivity ISOF
      Bari, Apulia, Italy