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Recently a Markov chain model has been proposed to predict the composition of alloys as a function of the electrolyte composition. The essential parameters of this model are selectivity constants, describing the selectivity of the growth centers, the kink site positions, for the ions of the metal components in the electrolyte. In this paper application of the simple model to deposition of intermetallic compounds will be discussed. The Markov chain model can be successfully applied to the formation of the intermetallic compound NiSn. Whereas the model can describe well the deposition of Ni rich Zn-Ni alloys at low current densities, it fails at high current densities with anomalous alloy composition.

The search for effective additives is important for the development of new metal deposition processes. The hard/soft concept is a possible way for the selection of suitable substances. Hardness or softness are connected with molecular properties like electronegativity or the chemical potential of electrons. The density functional theory (DFT) provides methods for calculating the respective values. Corresponding function of the side of the electrode is the Fermi energy, the upper level of occupied electron energy levels. Hardness and softness of the electrode depend on the electrode potential. This dependence will be discussed.

Deposition of amorphous chromium-carbon layers is possible from a trivalent chromium electrolyte containing 0.6 mol/l formic acid. The formation of chromium/formic acid complexes inhibits the aging of the electrolyte and the oligomerization. Deposition of a 15–20 μm thick chromium film is possible with DC condition. Thicker films can be deposited with pulse plating using reversed pulse sequences and pulse lengths in the millisecond region. The optimized conditions concerning pulse current densities and pulse times were determined and the composition and morphology of the films investigated.

The influences of the preparation conditions on the properties of anodic aluminium oxide films were studied by electrochemical impedance spectroscopy. A two-layer model of the film, consisting of barrier and porous layers was used to analyze the impedance data. The thickness of the barrier layer was calculated from the capacitance values. The total thickness of the aluminium oxide film was determined by cross-section SEM micrographs. Thus, anodic aluminium oxide films were prepared showing dielectric properties comparable to that of silicon dioxide films. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The residence time τ of an atom in a kink site position is a characteristic property of a growing phase. For alloys kink site positions and associated residence times must be defined for the different alloy components. For instance, for an alloy AB kink site positions A * and B * must be distinguished. Each kink site atom can react either with ions of type A or B to form new kink site positions AA * , AB * , BA * or BB * . The selectivity of the kink site positions for either A or B can be expressed by residence times τ AA , τ AB , τ BA and τ BB . Another characterization of the selectivity is possible by the application of the finite Markov chain theory. Then selectivity constants g A and g B can be defined. Assuming equilibrium between the atoms in kink site positions and the respective ions in the electrolyte, the selectivity constants represent the ratios of the respective equilibrium constants between kink site positions and electrolyte concentrations g A = K AA / K AB and g B = K BB / K BA . If the process is rate-controlled, the selectivity constants represent the ratios of the respective rate constants of deposition. The model is applied to CoNi and SnNi alloys and to bismuth telluride. A relation is derived between selectivity constants and residence times.

The copper electrodeposition from a sulfuric acid solution was investigated in a magnetic field (0–5 T). Linear sweep voltammetry showed that both the limiting current density and the hydrogen evolution were remarkably modified in a magnetic field. Depending on the cathode overpotential, the surface morphology was divided into two groups: faceted structure and columnar dendrite. The faceted structure appeared in the electrochemical activation region and it changed into the finer grain size in a magnetic field. Furthermore, the pole figure measurement suggested that the texture evolution pattern slightly shifted from two-dimensional to three-dimensional crystal growth in a magnetic field (≥3 T). No essential microstructural variation due to the magnetic effect was observed in spite of considerable morphological variations in the region purely controlled by the mass transfer.

The electrodeposition of nickel–iron alloys is studied under the influence of a superimposed external static magnetic field. It is shown that the direction of the magnetic field with regard to the electric field affects the electrodeposition process (current efficiency, composition and morphology of the layers). Furthermore, the influence of the simultaneous action of natural and magnetically driven convection is discussed in function of the orientation of the working electrode. The electrochemical quartz crystal microbalance (EQCM) technique is used to determine the partial current due to the hydrogen evolution reaction (HER). It is observed that the magnetic field applied perpendicular to the electric field lines increases the rate of the HER, while no significant variation is observed in a magnetic field parallel to the electric field.

Raman spectra of cubic nanocrystalline insertion hosts in Li-Ti-O system were measured for Li1.1Ti1.9O4-δspinels and the corresponding delithiated titanium dioxide material. To interpret the measured data optimized geometries of cubic TiyOzand LixTiyOzwere calculated using the DFT cluster approach for clusters containing up to 23 atoms. The calculated geometries were used to predict the density-of-states (DOS) diagrams and vibrational spectra of the corresponding structures upon harmonic approximation. While the DFT approach reproduces satisfactorily the main structural characteristics of TiyOzclusters, the agreement in the case of LixTiyOzclusters between calculated and real structures is less satisfactory due to the small cluster size. The band gap energies obtained from DOS diagrams represent overestimates of the actual experimental band gap energies measured on cubic Li-Ti-O oxides. The agreement between calculated and measured band gap energy improves with increasing cluster size. Raman spectra calculated under harmonic approximation from the optimized geometries reproduce all important features of the experimental Raman spectra. The agreement of DFT-calculated and experimental Raman spectra improves with increasing size of the cluster.

Alkaline solution, especially diphosphate solutions, can be used as electrolytes for the galvanic deposition of p-type semiconductors. A ternary Bi–Sb–Te alloy semiconductor was deposited at a Ni-covered cathode surface at potentials lower than −0.6 V (Ag/AgCl), under potentiostatic condition in well-stirred solutions. Additionally, it was possible to deposit antimony telluride, a binary p-semiconductor, from the ternary electrolyte. The kinetics of the process was investigated by cyclic voltammetric measurements. The influence of the electrolyte convection on the electrocrystallization was analysed with the help of rotating disc electrode. The semiconductor layers were characterized by electrochemical impedance spectroscopy.

The electrodeposition process of Co films in a sulfuric acid solution was examined in a magnetic field (0–5 T). The surface morphology of Co films electrodeposited without a magnetic field was drastically modified with the variation of hydrogen gas evolution rate. Crystalline α-Co was formed in the range of pH = 1.5–6.0, while β-Co was not observed. When the magnetic field was superimposed perpendicular to the electric field in the acidic solution (pH = 1.5), the hydrogen evolution rate was promoted by MHD convection, which enhanced the ionic mass transfer (H+ and Co2+) near the electrode surface. Moreover, crystalline β-Co was formed simultaneously with the appearance of the elongated ridge-shape precipitates under a higher magnetic field (≥3 T).

Scanning Kelvin probe and electrochemical impedance spectroscopy were used to study the release behaviour of inhibitor anions doped in polypyrrole film (e.g. molybdate, 3-nitro salicylate). The polypyrrole coatings were formed on mild steel and zinc substrates in aqueous solution. It was shown that the release behaviour of the molybdate and 3-nitro salicylate anions depends on the size of cations in the electrolyte. The delamination is determined with the migration and incorporation of small cations.

The understanding of the redox behavior of conducting polymers is essential for a successful application of these so-called synthetic metals as functional coatings. The redox process involves the exchange of ions and solvent molecules. This so called doping/dedoping process involves changes of the mechanical and the electronic structure of the polymer. This paper discusses investigations at poly(3,4-ethylenedioxythiophene (PEDOT) and poly(pyrrole) (Ppy) by the electrochemical quartz crystal microbalance (EQCM) technique and electrochemical impedance spectroscopy (EIS). In the case of PEDOT a determination of the anion and the solvent fluxes was possible, and it was found that most anions replace solvent molecules upon their incorporation. The doping/dedoping mechanism of Ppy is more complicated. Here, the first redox cycles are characterized by a complex interplay of cation, anion and solvent fluxes with irreversible changes of the polymer structure. However, in combination with EIS new insights of the ion and solvent exchange and its influence on the electronic properties can be achieved.

Iron thin films were electrodeposited on a copper substrate in FeSO 4 aqueous solution under a magnetic field (0–5 T) at 298 K. The surface morphology was observed by the atomic force microscopy (AFM). It was drastically changed from an angular to a wavy shape by superimposing the magnetic field. Moreover, rectangular shaped precipitates were aligned along the magnetic field. The grain size decreased with increasing in magnetic field intensity, B . The AFM image was characterized by the anomalous scaling method in order to quantitatively analyze the magnetic field effect on surface roughness. The roughness exponent, α , and the growth exponent, β , decreased as B increased. The variation of scaling parameters with B may be utilized to improve the surface morphology evolution and the transition of the crystal growth induced by the magnetohydrodynamic convection can be phenomenologically discussed.

Electrochemical formation of anodic oxide films on niobium (Nb) surfaces in 1 M H2SO4 solutions was studied using ellipsometry and Raman spectroscopy. By in situ ellipsometric measurements, the coefficient of film thickness growth and the complex index of refraction of anodic oxide films in the voltage range between 0 and 100 V were determined. The Raman spectra reveal that the thin passive films are amorphous. In the beginning of crystallization, the anodic oxide films consist of mixtures of NbO2 and Nb2O5, while NbO2 is completely transformed to Nb2O5 for thicker and well-crystallized films.

The interest in single molecule spectroscopy by means of surface enhanced Raman scattering (SERS) has grown enormously in the last five years. Unfortunately, the basic mechanisms leading to the giant enhancement of the Raman signals are still not understood. Almost every group working in the field of single molecule SERS uses silver or gold colloids prepared by a chemical reduction method, to which a highly diluted solution of the target molecules is added. After that, the colloids, are deposited gravitationally onto a glass cover slide. This leads to clusters of several nanoparticles with a large distribution regarding size and shape as well as the Raman efficiency, and the systematic investigation of sm-SERS suffers from this. Our aim was to develop a method to deposit silver clusters showing a high enhancement factor in a controlled way. For this purpose we used an electrochemical double-pulse method, which allows to control the particle size and density by systematic variation of the pulse parameters. We also compared measurements obtained with these surfaces to measurements made with colloids at the single molecule level.

Localized silver and gold nanoparticles, electrochemically prepared by means of the double-pulse technique, were investigated with respect to their optical and spectroscopic properties by scanning confocal microscopy combined with surface enhanced Raman spectroscopy (SERS) and subsequent comparison with the local image of scanning electron microscopy (SEM). Analogous to the silver cluster preparation technique, controlled electrodeposition of gold nanoparticles was demonstrated, varying size from 10 to 500 nm and particle density. The maximum SERS enhancement factors found in the measurements were: (i) 10 10 for silver particles and (ii) 10 8 for gold particles. The optical and spectroscopic data of the local nanoparticle structures investigated showed that SERS is a local phenomenon, because (i) only few particles are Raman active particles, (ii) strongest enhancements in SERS are obtained from particle agglomerates, (iii) typically the Raman radiation is emitted from irregular structures like the necks between two or more particles agglomerated. In the investigated range from 10 to 500 nm no significant influence of the particle size was observed.

Electropolymerization of pyrrole on mild steel was carried out in 0.01 m sodium molybdate and 0.1 m pyrrole solution at constant current 1.5 mA cm−2. The film is homogenous and adherent. The corrosion protection of polypyrrole films containing inhibitor anion molybdate as dopant anion was investigated with open circuit potential (OCP) in 0.1 m NaCl. The passivating effect of molybdate was demonstrated. The mobility of anion was investigated by cyclic voltammetry (CV), electrochemical quartz microbalance (EQCM) and electrochemical impedance spectroscopy (EIS) measurements.

A new model of the electrochemical alloy deposition has been developed. It is based on the application of the finite Markov chain theory and is called the Markov chain model. The first analytical relationship between the alloy composition (ratio of mol fractions x A /x B and the metal ion concentrations in the electrolyte (mol fraction X A and X B can be deduced from the model. formula math The general parameters of this equation are the ratios g i = K ii /K ij of the equilibrium constants between the electrolyte ions and the different kink site positions on the surface (i,j representing the different components of the alloy). It is shown that the g, values can be evaluated by the linearization of the deduced equation. The model was tested according to the literature [K.C. Belt, J.A. Crosley, R.J. Kendrick, Proceedings of 7th International Metal Finishing Conference, Hanover 1968 (data cited in Ref. [17])] by comparison of the calculated and the experimentally determined Co-Ni alloy composition and its dependence on the ion concentration in the electrolyte. The g i values are of primary importance for the quantitative analysis of the mechanism of electrochemical alloy deposition and for the control and prediction of the alloy composition.

An electrophoretic deposition (EPD) procedure was adopted for the cathodic preparation of thin films of conducting polymer/metal oxide nanocomposites with a core-shell structure. The deposition process was investigated at different potentials and in various solvents. The mechanism and kinetics of the electrophoretic deposition were studied via quartz crystal microbalance (QCM) and zeta-potential measurements. The properties of the composite layers were studied by electrochemical methods (cyclic voltammetry, impedance spectroscopy) and photocurrent measurements. The reversible redox potential of polythiophene films was about 0.75 V SCE . The p-type semiconducting behaviour of the reduced polythiophene was studied by photocurrent measurements. In the case of using TiO 2 (n-type semiconductor) as a core material, an n/p heterojunction was observed. In the photocurrent spectra the maximum of the cathodic peak of polythiophene was found around λ = 500 nm (2.5 eV), depending on the applied potential. It is in agreement with the results of UV–vis optical spectra of deposited layers and of pressed pellets. The flatband potential of polythiophene in the heterojunction with TiO 2 , obtained from photocurrent measurements, was 0.53 V SCE .

A composite of polythiophene (PTh) and nanoscopic titanium dioxide (TiO 2 ), possessing core-shell structure, was prepared via oxidative polymerization of thiophene by iron (III) chloride in the presence of TiO 2 particles. The morphology of the obtained composite particles was studied by transmission electron microscopy (TEM), proving the core-shell structure of the prepared nanocomposite. The chemical structure of the composites was investigated by Raman spectroscopy. The electrophoretic deposition (EPD) technique was used as a method to prepare composite layers on various conducting substrates (platinum and ITO plate). The characteristics of the composite layer after EPD were studied by electrochemical methods. The photoelectrical properties of PTh and TiO 2 in the nanocomposites were studied as well. In the photoelectrochemical spectra (depending on the applied potential), the characteristic anodic peak of TiO 2 at λ = 340 nm and cathodic peak of PTh around λ = 530 nm were observed. A bandgap energy, E g = 1.95 eV and a direct electron transition of PTh were found. A cathodic peak in the photocurrent spectra was detected unexpectably also around 340 nm, and ascribed to the photoelectrical activity of the TiO 2 core. The redox processes in PTh were investigated via cyclic voltammetry (CV) and electrochemical impedance microscopy (EIS).

Adhesive ultrathin polypyrrole films were deposited on Si/SiO2 substrates modified with the new adhesion promoter 11-(Pyrrol-1-yl Undecyl) TrichloroSilane (PUTS). The oxidation potential of PUTS in solution was determined electrochemically by cyclic voltammetry. Self-assembled monolayers of PUTS were investigated by cyclic voltammetry, contact angle measurements, ellipsometry, and X-ray photoelectron spectroscopy. Several oxidants for the deposition of pyrrole on adhesion promoter modified substrates were tested and a strong dependence on the obtained film morphology was found. It was possible to deposit chemically ultrathin polypyrrole films on insulating substrates.

Two different methods were used to immobilise gold nanoparticles on ultrathin films of polythiophene and polythiophene derivatives. The first method utilised ultrathin films of polythiophene to prepare gold nanoparticles by direct reduction of HAuCl4. A uniform coverage of the polythiophene films with randomly distributed gold nanopraticles possesing a polydisperse size distribution was obtained. Size and size distribution of the gold nanoparticles could be controlled by time, concentration of Au3+, and the addition of a cosolvent. With the second method, ultrathin films of polythiophene derivatives were esterified with thioctic acid, using either Steglich or Yamaguchi conditions. The dithiolane moiety of the thioctic acid was utilised to immobilise gold nanoparticles from a monodisperse gold sol. The gold nanoparticles were adhesive on the polymer films and were not removed by scotch tape tests. The samples with the obtained gold nanoparticles of both methods were analysed by scanning electron microscopy (SEM). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

The Markov chain model of alloy deposition was applied to cobalt–nickel. The characteristic parameters of the model are the gi values describing the selectivity of the deposition process for its components. The values recently determined for Co and Ni (gCo and gNi) depend on the current density. This could be quantitatively described by the mass transport limitation for Co. The model was also applied to the nickel–molybdenum system, an example for induced co-deposition. Data published by Podlaha and Landolt [4, 5] could be described by the equation $$\frac{{x_{\rm Ni}}}{{x_{\rm Mo}}} = \frac{{g_{\rm Ni}\,\frac{{c_{\rm Ni}}}{{c_{\rm Mo}}} + c_{\rm Ci}^n}}{{c_{\rm Ci}^n}},$$ where xNi and xMo are the mole fractions in the alloy, cNi and cMo the concentrations (in mol dm−3) in the electrolyte, and cCi is the concentration of citrate used as catalyst in the system. The gNi factor was determined and the dependence on current density and electrolyte convection could be quantitatively described.

The paper considers the influence of an adhesion promoter on the electrochemical behaviour and on the glass transition in adhesive joints of an epoxy coat on aluminium AlMg 3 as a function of the surface pre-treatment. The adsorption of phosphoric acid mono alkyl ester as adhesion promoter (AP) on aluminium samples and the influence of the AP on the polymer network in the epoxy/aluminium interphase has been studied by means of electrochemical impedance spectroscopy (EIS). The results reveal that the coupling layer has been well formed and it has promoted formation of a durable interphase, such as the higher cross-linking density in the epoxy network, indicated by the increased glass transition temperature and the increased corrosion performance of the coated aluminium sample, indicated by the result from the corrosion test. The combination of phosphoric acid anodic oxidation (PAA) and application of AP could be proposed as alternatives to chromium-based pre-treatments for aluminium.

Particles of silicate and mica were co-deposited with zinc from a weakly acid zinc electrolyte. The co-deposition became possible after 3 h of milling of the particles. A pH of 4.5, a rotation speed of 600 rpm and a particle concentration of 50 g/l were the optimal conditions. A change of the zeta potential to positive values was observed, caused by adsorption of zinc ions on the particle surface. Under these conditions the particle concentration in the zinc matrix was up to 20 mass per cent. The compound layers showed increased hardness and considerably improved corrosion resistance.

Copolymers of ethyl-3-thiophene acetate (ETA) and 3-methylthiophene (MT) were synthesized electrochemically. Electrospray ionization mass spectra of the electrolyte containing 2×10−3 M MT + 3×10−2 M ETA after copolymerization showed cooligomers with different combination of ETA and MT units. Just one value of the glass transition temperature was observed by differential scanning calorimetry of the formation of homogeneous copolymers. Change of the copolymer composition led to change of thermal stability characterized by thermogravimetric analysis. The morphology of the copolymer film was studied by scanning electron microscopy, indicating a homogeneous and compact film. The electroactivity of the homopolymer/copolymer films was studied. Cyclic voltammograms of the polymer films revealed that poly(ethyl-3-thiophene acetate) possesses high electroactivity in non-aqueous solution, but its electroactivity was lost entirely after 50 cycles in 0.1 M N(Bu)4PF6/acetonitrile solution having 5 volume percentage of water; however, the copolymer of ETA and MT maintains its high electroactivity even in the aqueous solution. Similar results were also derived from impedance and photoelectrochemical measurements. Additionally, it was found that a bilayer of poly(3-methylthiophene) and copolymer was formed.

A flexible organic field effect transistor was developed based on 2,5-dihexylsexithiophene (DH6T), a recently synthesized thiophene oligomer with high regioregularity. The oligomer was tested on highly doped silicon as gate electrode and SiO 2 as gate insulator film. For experiments on flexible substrates, aluminium was used as gate electrode. Several materials were tested as gate insulators with the best dielectric properties obtained for anodically formed aluminium oxide. In combination with the oligomer, this gate insulator is definitely suitable for further developments.

A procedure is presented to determine bond energies between the metal (Me) and substrate (S) components of binary alloys from characteristic underpotential deposition (UPD) potentials. The bond energy between Me and S atoms is one of the factors governing the deposition kinetics and structure of Me-S alloy deposits. The proposed procedure is based on the determination of the UPD potential for formation of a condensed two-dimensional (2D) phase of the less noble metal Me (the UPD metal) on the more noble metal S (the substrate). Making reasonable approximations, the sublimation enthalpy of the condensed 2D Me phase is obtained from the corresponding formation underpotential. From this sublimation enthalpy the bond energy of an atom of the UPD metal in a kink site position of the 2D Me phase is calculated. This value is used to calculate the bond energy (φMe-S) between an Me atom and an S atom. The method is demonstrated using experimental data obtained in selected electrochemical UPD systems.

The concept of the residence time of an atom in a kink position was introduced to predict the structure of electrochemically deposited surface coatings. The residence time is obtained from the reciprocal value of the rate constant for separation from the kink position. Residence times and deposition rates determine the density of kink positions [ksp] on the growing metal film. For equilibrium conditions (Nernst potential), the density of kink positions [ksp]0 depends on the exchange current density i 0 and on the residence time τ by the equation: % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX!

We adopted an electrophoretic deposition method for the preparation of thin layers of insoluble composite nanoparticles composed of TiO 2 core and about 2 nm thick shell of polythiophene, prepared by oxidative polymerization of thiophene. The reduced form of TiO 2 -polythiophene composite material was deposited on the conductive surface from an ultrasonically generated microdispersion. Varying the dispersion media, applied voltage and the electrode arrangement made it possible to control the quality and morphology of the films. Compact semitransparent films deposited on ITO electrodes, suitable for photoelectrical measurements, were obtained within short deposition times.

The role of electrical charges in the double layers of the electrode and in particles during the electrochemical preparation of dispersion coatings was studied for the systems Au/diamond and Au/Al2O3. The surface charge of the electrode under the conditions of electroplating will depend on the potential of zero charge (p.z.c.). For the nanoscaled particles the sign of the surface charge was estimated from the zeta potential in dilute solutions. Successful inclusion of Al2O3 and diamond nanoparticles was observed when the particles and the electrode were oppositely charged. The Vickers hardness of the layers was increased by the codeposition of Al2O3, whereas it decreased in the case of nanodiamond.

The influence of an external magnetic field B on the electrochemical behaviour of the systems Cu 2+ /Cu, Ni 2+ /Ni, and [IrCl 6 ] 2− /[IrCl 6 ] 3− has been studied. In the case of Cu depositions in an electrochemical cell with a large ratio of the electrode area and the cell volume the increase of the limiting current density with B can be explained with the interplay of natural convection and the Lorentz force acting on the resulting flow profile (magneto hydrodynamic or MHD effect). Ni depositions also show an MHD effect as well as a tendency to form more fine grained material in the presence of a magnetic field. The results on the homogeneous redox system [IrCl 6 ] 2− /[IrCl 6 ] 3− at 50 μm diameter micro electrodes are in qualitative agreement with recently proposed relationships to describe the influence of a B field on the limiting current density.

Two new thiophene derivatives bearing redox active p-nitrophenyl units were synthesized and electropolymerized to conducting polymers. It is found that not only the structure of monomer, but also the employed polymerization conditions have considerable effect on the electroactivity of the bonded redox groups of resulting polymer films. Depending on used conditions such as polymerization time, the polymerization of the same monomer could result in a polymer with well-defined redox transition of the nitrophenyl group or a polymer, in which the redox group is completely electrochemical inaccessible. Using designed experiments, we explained this phenomenon. These investigations provide further knowledge about the behaviors of redox group attached to electrode surface.

The electrolyses of solutions of bismuth oxide and tellurium oxide in nitric acid with molar ratios of Bi:Te=3:3–4:3 lead to cathodic deposits of films of bismuth telluride (Bi2Te3), an n-type semiconductor. Current densities of 2–5 mA/cm2 were applied. Voltammetric investigations showed that Bi2Te3 deposition occurred at potentials more negative than −0.125 V (Ag/AgCl, 3 M KCl). The deposit was identified as bismuth telluride (γ-phase) by X-ray analysis. Hall-effect measurements verified the n-type semiconducting behaviour. The films can be deposited in microstructures for thermoelectric microdevices like thermoelectric batteries or thermoelectric sensors.

The protection mechanism of intrinsically conducting polymers (ICPs) is still under discussion. Most of the discussions concentrate on the effect of the redox behavior and electroactivity of ICPs on the corrosion protection. In the present paper it is shown that polymethylthiophene (PMT) films electropolymerized on mild steel, with 2-(3-thienyl)ethylphosphonic acid used as adhesion promoter, show the desired redox activity. The interaction between the PMT film and some conventional coatings, and the influence of the pH of electrolyte, were investigated. It was shown that the electroactivity of PMT film is lost by the interaction with coatings of high nucleophilicity and is markedly decreased by immersion in an aqueous solution of pH 11.

A simple method for covering titanium dioxide particles with a polythiophene film by chemical preparation was developed. The resulting nanocomposites consisted of a titanium dioxide core with a grain size of 25–250 nm and a polythiophene shell between 1 and 2 nm thickness. The composites were characterized by scanning electron microscopy, thermogravimetry, X-ray photoelectron spectroscopy, cyclovoltammetry, impedance spectroscopy and photocurrent spectroscopy. The content of polythiophene in the composite (determined by thermogravimetry), was between 2% and 5%. Disk-like electrodes were prepared by pressing and then characterized by various electrochemical methods. A reversible redox potential of the polythiophene of +1.0 V (NHE) was determined by cyclic voltammetry. The reduced form of polythiophene behaved as a p-type semiconductor so that the composite with n-type TiO 2 contained the properties of a p/n-junction. In the photocurrent spectra (depending on the applied potential), the characteristic anodic peaks of the TiO 2 at λ =320 nm and cathodic peaks of the polythiophene around λ =500 nm were found. A new cathodic peak observed at 370 nm was explained as a new feature of the pn interface.

A new experimental model based on the electrochemical impedance spectroscopy for investigating the reactions taking place in a film of intrinsically conducting polymers formed on iron or steel substrate is developed, in which the reaction at the injured surface area of the coated iron and reaction of polymer could be studied separately. It is evident that a combination of adhesion promoting self assembling monolayer and a film of conducting polymer gives the protection against the delamination, but the catalytic action of the conducting polymer for the oxygen reduction and for the metal passivation is not found.

The influence of a variety of substances on technically relevant parameters of a nickel electroplating electrolyte (Watts bath) has been investigated. Special attention has been paid to the throwing power (TP), as well as visual appearance, current efficiency and codeposition of foreign atoms. Systems reported in the literature (e.g., inorganic salts to increase conductivity or complexing agents to increase polarization) were compared with typical reducing agents normally used in electroless Ni deposition. The mechanism of TP improvement in the case of sodium hypophosphite and dimethylamine-borane has been examined with the electrochemical quartz crystal microbalance (EQCM). Using the EQCM it was shown that there is a synergistic effect between the electrochemical and electroless deposition process. In addition, the activation energy of the latter was determined from temperature dependent measurements.

Various structures of silver nanoparticles were generated by means of the double-pulse technique. The interaction of the pulse parameters was modeled to demonstrate that the electrodeposition of nanoparticles can be variably controlled. The results derived showed how to create nanoparticle structures with respect to size, density and monodispersity according to the application goal.

Several random cooligomers based on thiophene and β-substituted alkyl derivatives, i.e. 3-methyl- and 3-octylthiophene, have been chemically synthesized by an oxidative coupling reaction in the presence of iron(III) chloride. The powdered samples were characterized by TGA, FTIR, UV and cyclic voltammetry measurements. The influence of the alkyl substituent on the homo/cooligomer stability, conjugation length, degree of polymerization and presence of defects is discussed.

The method of electrochemical impedance spectroscopy (EIS) was applied to investigate the behaviour of a thin intrinsically conducting polymer film (ICP) deposited on a metal substrate. Especially the conductivity, the redox properties, the anion release properties, and the corrosion protection of a coating with and without ICP film on an iron or steel substrate were studied. Combined with other electrochemical methods, the reactions taking place at an injured surface area of the coated iron were studied. The corrosion protection mechanism of polythiophene could be explained.

Ein gravierendes Problem beim Einsatz von Leichtmetallen in der Automobilindustrie ist der Kontaktkorrosionsschutz. Einen Ansatz zur Losung dieses Problems liefern Zink-Mangan-Systeme.

The integration of thin conducting polymer films as an on-chip gas sensitive medium offers the possibility of new applications in microsystems technology. Due to the material properties of polythiophene (PTh) such as adjustable conducting capability, chemical stability and mechanical properties, this heterocyclic polymer attracts attention as a promising candidate for gas sensitive layers. PTh is considered to be stable in air and moisture especially in the undoped state. However, when considering the gas adsorption behaviour of PTh films in ambient conditions the O 3 load cannot be neglected as additional chemical states are created. These changes in the surface chemistry of PTh as a result of the O 3 load were investigated by X-ray photoelectron spectroscopy (XPS). The carbon C 1s and sulphur S 2p spectra show an increasing amount of oxidised species depending on the O 3 concentration used in the experiments. The chemical shifts of these peaks suggest the occurrence of carboxyl and SO 2 groups for all O 3 -loaded samples. The relative intensity of these peaks reaches saturated values at samples loaded between 200 and 600 ppb for 1 h. In order to find a correlation to the electrical conductivity versus various ozone loads, carbon shake-up states and angle resolved valence bands were evaluated and considered in one context.

The electrodeposition of polymethylthiophene films on mild steel from organic solution is reported. It is shown that homogeneous and very adherent polymethylthiophene films are formed after a special pretreatment with 2(3-thienyl)ethylphosphono acid. Polymethylthiophene films reduce the corrosion rate of mild steel but they cannot passivate the metal surface. A model is proposed which can explain the excellent adhesion properties of polymethylthiophene films, necessary for corrosion protection of mild steel.

Extremely adhesive polybithiophene (PBT) films were grown on TiO2 in a new, two-step procedure using a silyl substituted thiophene derivative as a surface coupling agent and a subsequent chemical polymerization process. Electrochemical impedance and photocurrent measurements were carried out in order to achieve information on the semiconducting properties of both materials. When a PBT film deposited onto TiO2 is reduced it can be described as a p-type semiconductor with a flatband potential of about 0.65 V (vs. SCE), whereas the n-type semiconductor TiO2 gives a flatband potential of about −0.4 V (vs. SCE). The photocurrent measurements show an anodic photocurrent at wavelength of between 300 and 400 nm and a cathodic photocurrent of between 400 and 600–700 nm, confirming the impedance measurements. The results of the impedance and photocurrent measurements are summarized in a band structure model which explains the behaviour of the semiconductor electrode Ti/n-TiO2/p-PBT.

Polythiophene films containing ester groups on the surface of electrodes are interesting potential carrier materials for reagents. Methyl thiophene-3-acetate (3) can be copolymerized with 3-methylthiophene (1) and 3-butylthiophene (2) by means of cyclic voltammetry (CV) at potentials of 0–2.2 V. Higher potentials (0–2.4 V) lead to overoxidation of the copolymers. The ester groups were confirmed by FTIR spectra. Electrochemical investigations of 2,2′-bithiophene (6) and 3 at equimolar ratios showed no successful copolymerization at potentials of 0–1.3 V. If the copolymerization experiments of 6 with 1 or 3 were carried out at molar ratios of 1:50 at 1.3 V, 6 with its low oxidation potential was polymerized without copolymerization of the other monomers. However, if the oxidation potential was increased stepwise from 1.3 V, the oxidation of 1 or 3 occurred, forming copolymers containing both monomer components. HPLC investigations of solutions containing mixtures of 6 and 3 and also 6 and 1 in acetonitrile/TEABF4 showed, after exhaustive oxidation at a potential of 1.3 V, the complete absence of 6; 1 and the ester 3 were not oxidized and copolymerized at these potentials. From the results of the copolymerization experiments, as well as the HPLC investigations, it can be concluded that the dominant mechanism of the electrochemical polymerization is radical cation dimerization.

Polythiophene layers have been grafted onto silicon, iron, platinum and titanium for applications as organic semi-conducting films on solid surfaces. In general, the adhesion between the polymer films and substrates is insufficient for technical and microelectronic applications. The use of adhesion promoters between substrate and polymer and enables the formation of a strongly bonded composite. The polymers were synthesized by chemical or electrochemical surface polymerization.

The redox and optical properties of various well defined polymer and copolymer films containing pyrrole or thiophene units were studied. The in situ ESR/UV-Vis-NIR spectroelectrochemistry was applied to investigate polymers and copolymers deposited both electrochemically or by a special chemical procedure using adhesion promoter onto the optically transparent indium-tin-oxide (ITO) electrodes. The spectroelectrochemical responses of chemically and electrochemically prepared polythiophenes on ITO were compared and the electronic structures of both polymers found to be similar. In situ ESR/UV-Vis-NIR voltammetric studies on electrochemically prepared copolymers containing pyrrole units and various N,N'-ethylene-bis(salicylidenimine) (salen) transition metal complexes indicate the presence of both polysalen and polypyrrole redox active centers in the copolymer.

The influence of pulse parameters of a potentiostatic double-pulse on the size distribution of silver clusters was investigated. The silver clusters were deposited from a cyanide-containing electrolyte onto indium–tin oxide electrodes. Clusters with particle diameters of 100–300 nm can be prepared on a time scale of minutes. A model is presented, which is able to explain the experimental results.

Self-assembled monolayers (SAMs) of thienyl-functionalized n -alkyltrichlorosilane (11-(3-thienyl)undecyltrichlorosilane [TUTS]) have been prepared by adsorption from solution and characterized by using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact angle measurements, ellipsometry, and scanning electron microscopy (SEM). Using contact angle and SEM measurements, the film preparation protocol was optimized, resulting in reproducible SAM formation with no adverse deposition of polysiloxane particles. XPS and ellipsometry studies confirmed the existence of SAM formation. AFM results show a smooth and homogeneous SAM, with surface roughness of R a≤0.2 nm, which is slightly higher than the corresponding values for octadecyltrichlorosilane (OTS) SAMs. Such thiophene-based SAM surfaces can be used for surface-initiated polymerization of thiophene. The resulting formed polythiophene layers at non-compatible surfaces offer some practical applications in manufacturing [W. Plieth, A. Fikus, D. Appelhans, H.-J. Adler, German Patent Application No. 2661977 (1998); D. Appelhans, D. Ferse, H.-J. Adler, A. Fikus, W. Plieth, B. Aldolphi et al., J. Electrochem. Soc. (accepted)].