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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of applied electrochemistry 24 (1994), S. 1059-1065 
    ISSN: 1572-8838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract The effect of Cs+ ions added to the electrolyte for polyaniline films electrosynthesized in 0.1 m aniline/0.5m H2SO4 was investigated. Some properties of PANI films, such as the capacitance, the ohmic resistance and the charge-transfer resistance were obtained using electrochemical impedance spectroscopy. It was found that Cs+ ions used during PANI synthesis change its morphology, with a consequent increase in capacitance and conductivity, and a decrease in charge-transfer resistance.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of applied electrochemistry 22 (1992), S. 558-562 
    ISSN: 1572-8838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract The electrodeposition of tin in the presence of polyethoxylated additive TX-102 has been investigated in acid medium. The additive causes a substantial increase in the overpotential for the discharge of Sn2+ ions. Below 0.12 g dm−3 the additive has little effect on the quality of the tin deposits. Periodic oscillations in the voltage of the cell are observed, which are associated with the initial growth of whiskers. For higher concentrations of additive, the deposits are smooth and homogeneous, and no growth of whiskers and no voltage oscillations are observed. The effect of TX-102 for concentrations below the CMC has been interpreted in terms of blockage of high energy sites of preferential growth on the tin surface. For additive concentrations above the CMC, micelles are formed. These high molecular weight aggregates also block the surface, hindering the mass transport of Sn2+ through a membrane-like layer that forms on the tin.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of applied electrochemistry 26 (1996), S. 95-101 
    ISSN: 1572-8838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract The incorporation of EDTA and Fe([scii/iii])EDTA into polyaniline films has been achieved by electropolymerization of aniline in acid solutions at constant potential. The stability and electrical properties of these films have been studied by cyclic voltammetry and electrochemical impedance spectroscopy. The presence of FeEDTA species inhibits the second redox process in the polymer film corresponding to the emeraldine/pernigraniline transition and decreases degradation of these films upon cycling to positive potentials. EDTA increases the degree of cross-linking reactions within the film and leads to less conducting and thinner films compared to those obtained with FeEDTA in the electrolyte.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Journal of applied electrochemistry 25 (1995), S. 247-251 
    ISSN: 1572-8838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract Titanium oxide films, TiO2, were prepared on metallic titanium substrates employing a thermal treatment at 400° C under normal air atmosphere, with various annealing times (15, 25 and 45 min). Cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to study the electrochemical and electrical characteristics of these films. The potential range for the voltammetric measurements was −0.80 to 8.00 V vs MSE (mercurous sulfate reference electrode). An analysis of the capacitance values of these semiconducting oxide films gave information about their electronic characteristics. From Mott-Schottky plots the donor concentration (N D) and the flat band potential (E fb) were obtained. N D values ranged from 14 × 1022 cm−3 to 3.3 × 1022 cm−3, while E fb values ranged from −0.40 to −0.98 V vs MSE, depending on the heating times for the oxide growth. The thickness of the space charge region, calculated from the minimum value of the capacitance at high band bending, varied between 1.45 and 2.13 rim.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1572-9001
    Schlagwort(e): Oligoaniline band gap ; AMI ; chloride counterion ; asymmetric structures ; charge distribution ; energy levels
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract We present some semiempirical quantum chemistry calculations, geometric structures, charge distribution, gap energy, and enthalpy of formation (δH f ) for aniline oligomers in the different oxidation states using the AM1 method. A linear relationship between calculated optical transition values and the experimental reported ones was found. The effect of the interaction between the chloride counterion and these molecules was analyzed and indicates a decrease both in δH f of the aniline oligomers in the radical cation state and in δE(SOMO-LUMO). The withdrawal of one electron from the reduced aniline tetramer to form a radical cation in the presence of chloride (Cl−) yields to the radical cation band, similar to the polaron band in the polyaniline case. Contrary to the expected results, our calculations show that Cl− was able to transfer about 80% of its charge to the oligomers.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1572-9001
    Schlagwort(e): Oligoaniline ; polyaniline ; anions ; charge transfer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract We present semiempirical quantum chemical calculations of geometric structures, charge distributions, energy levels, ionization potentials, and enthalpies of formation for aniline tetramers in different oxidation states using the semiempirical AM1 method. For tetraaniline radical cation the effect of these three counterions on the above-mentioned physicochemical parameters was analyzed. The ions studied included Cl−, HSQ4 −, and CH3COO−. Chloride counterion showed a large charge transfer to the chain, as was shown in a preceding work [4]. HSO4 − showed a strong charge stabilization without transfer. CH3COO− exhibits hydrogen bond formation and also displays a strong charge stabilization in a fragment of the chain, but does not transfer any charge. Also, Cl− was able to form a hydrogen bond, depending on the initial position that it occupies in relation to the tetrameric chain, which is then optimized. Charge transfer is present for the Cl− cases. For dication structures the effect of SO 4 2− was analyzed. Our calculations showed that the distribution of the energy levels of tetraaniline radical cation can be comparable to the polyaniline ones by adding a counterion to the tetramer.
    Materialart: Digitale Medien
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