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The number of application fields of micro systems and microelectronic components is increasing continuously. International fairs clearly show smaller and compact circuits on foil substrates. Especially, the sensoric and actuatoric sensor systems become more flexible. However, nonrigid and extremely loadable and bendable systems may only be manufactured from textiles. The galvanic and electrochemical finishing of textiles is one way to build textile-based micro systems. A concept for the production of electrically highly conductive, functionalized, and interactive yarns is proposed. The first step of the concept, the highly conducting yarns, are already transferred into an industrialized production and are commercially available. Silver-coated polyamide yarns are already on the market since the end of the 1970s. Till now, the applications have been limited on the use of their anti-electrostatic and antimicrobic properties. The drawbacks of the yarns can be overcome by an electrochemical treatment to increase the metal layer and to create multilayer systems or functional top layers by anodization and other electrochemical techniques like the electro-polymerization and electro-deposition of paint. The treated yarns can be processed by any textile technology. Especially, the metal oxide layers of valve metals and the redox polymer layers are highly interesting due to their semiconducting properties. The surface treatment can be understood as a novel kind of textile finishing. In this way, high conductivity, nano-functionalized surfaces by electro-grafting and special redox-properties for an interactive release of drugs are available. First applications (electroluminescenting fabrics, woven electronic circuits, microelectronic devices as for example textile antennas, capacitors, solar cells and even interactive textiles for the controlled release of drugs) will be demonstrated in this contribution.

Zusammenfassung In der Medizin wird eine Vielzahl funktioneller Textilien eingesetzt, da sie ein Höchstmaß an geometrischer und mechanischer Flexibilität bieten und die im Bereich der Prävention geforderte gute Patientencompliance gewährleisten. Die Integration von Sensoren und Aktuatoren in die Bekleidung selbst bietet dabei innovative Lösungen für die Prävention und Rehabilitation. Im Ergebnis zeigt sich, dass vor allem textilbasierte Präventions- und Rehabilitationssysteme dem Patienten bestmögliche Mobilität und Lebensqualität kombiniert mit höchstem Komfort bieten.

A new and versatile procedure, based on convolution analysis, for the evaluation of complex electron transfer kinetic data from cyclic voltammetnc experiments is proposed. Both the anodic and the cathodic partial reaction are analyzed independently by the use of a linearized form of the Butler-Volmer equation. It is shown that for both branches well-defined Tafel-type plots can be obtained even from quasireversible cyclic voltammograms. Processes inconsistent with Butler-Volmer kinetics can be analyzed. The approximations inherent in Tafel analysis associated with (i) concentration gradients in the solution phase and (ii) mixed anodic and cathodic processes close to the equilibrium potential can be overcome. Additionally, the sum of anodic and cathodic transfer coefficient needs not to be unity and may even change with potential. The analysis therefore provides a general tool for parametrization and for testing the validity of the Butler-Volmer expression for a given electrode process.The application of the new methodology is tested with simulated voltammograms and is demonstrated for the Fe(CN)63-/4- redox system at a metal electrode, platinum, and at a polished highly boron-doped diamond electrode. At the diamond electrode both reduction and oxidation processes give linear Tafel-type plots with α = 0.29 ± 0.02 and β = 0.42 ± 0.03.

The use of microcylindrical electrodes for the determination of the rate constant of the charge transfer from the peak separation is possible if the function between the peak separation and the rate constant can be approximated as depending on the radius. This dependence is investigated for a reversible, quasireversible and irreversible charge transfer in the present paper. As a result a function is developed which makes it possible to calculate the rate constant of the heterogeneous charge transfer if the dependence of the peak separation of the sweep rate and if α is approximately 0.5. It is shown that the last dependence of the peak separation has a minimum for microcylindrical electrodes with a radius of a few micrometer, if k < 0.06 cm/s. This permits the determination of an optimal sweep rate for analytical problems.

A strategy is presented to realize textile-based photovoltaic cells motivated by developments of textile-based electronics and their demand of grid-independent energy supply. Beyond this, a development of textile-based photovoltaics also represents an attractive pathway towards very flexible and rugged solar cells. The need for compatibility of an appropriate photovoltaic technology with the physical limitations of textiles is stressed. Electrodeposition from aqueous solutions is presented as a successful strategy to realize semiconductor structures on textiles and detailed control and influence of the deposition conditions is discussed. The role of microelectrode effects, options of forced convection, deposition under pulsed potential, alternative deposition baths and different substrate metals are emphasized. An active electrode material is presented which reaches a conversion efficiency close to the 1% limit under AM 1.5 illumination conditions and thereby opens the door for a further optimization towards devices of technical interest.

A mathematical model of the novel redox cycling sensor was developed to understand and predict its behavior and thus enable further sensor development. Because of size and the electrochemical matrix used the model could be restricted to diffusion processes in solution and membrane and charge transfer at the electrodes. Contrary to many other electrode models it incorporates electrode processes for both anode and cathode due to the nature of the electroanalytical method. The model was solved for two geometries that allowed comparison to experimental data. The model then served to derive parameters for structural optimization and calibration of manufactured sensors.

The temperature dependence of the magnetic susceptibility of polyaniline at significant different doping levels has been investigated. The samples cover the conducting as well as the insulating region. The conductivity varies from 10−4 to 5 S cm−1. A temperature independent behaviour of the spin susceptibility is found in all cases. While the interpretation of the temperature dependence was formerly done by assuming metallic properties (Pauli paramagnetism) we give an alternative explanation of the results here based on the temperature dependence of a chemical equilibrium.

The present paper presents a proceeding to prepare partially conductive textile structures as basic substrates to integrate sensors and microelectronic devices into textiles. The proceeding is based on two steps. The first is to create a textile prestructure by conventional textile technologies, such as Jacquard weaving, embroidery etc. using silver-coated polyamide threads. The second is a galvanic and/or electrochemical treatment of the textile prestructure. It will be shown that galvanic and electrochemical treatment of such structures permit a change in the conductivity of two to three orders of magnitude, modification of the surface as it is needed to get sensor properties, and insulation or encapsulation of the conducting structure.

Recently, voltammetry with carbon fibre electrodes (CFE) has been implemented for real time measurement of nitrogen monoxide (NO) indicating that it is oxidised at the potential value of nitrites, approximately +700 mV. In contrast, here we show that modified CFE can monitor NO at oxidation potentials different than that of nitrites, i.e. +550 mV. Indeed, at +550 mV a significant increase of amperometric current levels was obtained when NO but not nitrites, were added to a phosphate buffer saline solution (PBS). Differential pulse voltammetry (DPV) supports these findings as two oxidation peaks were obtained when examining air preserved NO; peak 1 at +550 mV and peak 2 at +700 mV, respectively. In contrast, only peak 2 was monitored when nitrites or a solution of NO oxidised in air was added to PBS. Biological support to these in vitro data comes from the observation that the relaxation of an adrenaline-contracted aortic ring produced via addition of NO is concomitant with peak 1 at +550 mV. The relaxation is almost completed before the appearance of peak 2 at +700 mV. Furthermore, in vivo experiments performed in the striatum of rats show that the amperometric signal monitored at +550 mV is responsive to glutamatergic stimulation or inhibition of NO synthase.

Solvated electrons in liquid ammonia at −60°C (0.03 M LiCl) can be electrogenerated in the presence of power ultrasound and are shown to be essentially inert under these conditions in the presence of 3-methylanisole (3-MA). The fast mass transport and mixing induced by power ultrasound is then used to monitor the homogeneous Birch reduction process facilitated by the addition of ethanol as a proton source. Pseudo first-order kinetics for both the reduction of 3-MA and the unwanted formation of hydrogen is observed and analysed quantitatively. The rate laws proposed by Greenfield and Schindewolf (A. Greenfield, U. Schindewolf, Ber. Bunsenges. Phys. Chem. 102 (1998) 1808) for the reduction of protons, −(d[e − ]/d t )= k H [CH 3 CH 2 OH][e − ][Li + ], and for the Birch reduction of 3-MA, −(d[e − ]/d t )= k A [CH 3 CH 2 OH][e − ][Li + ][3-MA], are confirmed by varying the concentrations [CH 3 CH 2 OH] and [3-MA]. The rate constants k H =2±0.2 M −2 s −1 and k A =700±100 M −3 s −1 at −60°C are determined and employed for the optimisation of the product yield and current efficiency. Fast mass transport and electrode depassivation induced by power ultrasound are shown to maximise the current efficiency observed for the electrochemical Birch reduction process and to allow the process to be conducted in the presence of a high ethanol concentration and therefore with high overall rate.

Room temperature ionic liquids exhibit unusual and, for electrochemical applications, promising properties such as ionic conductivity and non-volatility. Microdroplet and thin film deposits of an ionic liquid, 1-methyl-3-(2,6-(S)-dimethylocten-2-yl)-imidazolium tetrafluoroborate (MDIM+BF4-) on electrode surfaces are studied in order to assess the ability of aqueous ions to partition into the ionic liquid. Two complementary methodologies, deposition of ionic liquid onto a 4.9 mm diameter basal plane pyrolytic graphite electrode followed by voltammetric analysis and casting of an ionic liquid film onto a random array of 7 μm diameter carbon microelectrodes (RAM™ electrode) followed by chronoamperometry, are employed. The ability of hydrophilic ions to partition from the water phase into the ionic liquid phase is unexpected and is shown to depend strongly on (i) the type of ion, (ii) specific interaction of the ion with the ionic liquid, and (iii) the concentration of the supporting electrolyte. Voltammetric responses obtained for the reduction of Fe(CN)63- partitioned into microdroplet and thin film deposits of MDIM+BF4- indicate selective uptake of ferricyanide into the ionic liquid phase. Chronoamperometric experiments at RAM™ electrodes are used to quantify both the concentration of Fe(CN)63- in the ionic liquid and the diffusion coefficient. © 2000 Elsevier Science B.V.

The advantages of lithographic-galvanic (LIGA) fabricated microstructured honeycomb electrodes are demonstrated for spectroelectrochemical cells with respect to the response time (the time necessary to generate the product in a sufficient layer thickness close to the electrode to be detectable by UV-Vis-NIR spectroscopy) and to the conversion of the redox system in solution under thin-layer conditions. Transmission UV-Vis-NIR spectroscopy for several electrochemical applications can be performed in a special spectroelectrochemical cell based on the LIGA electrode and the two quartz rods, forming the walls of the cell and conducting the light beam through the cell. They are limiting the diffusion layer at the structured part of the working LIGA electrode. These microstructured LIGA-electrodes can be used as well defined models of porous electrodes at which redox processes occur under finite diffusion conditions. Such electrodes have been successfully used in the voltammetric and spectroelectrochemical study of various redox systems in both aqueous and non-aqueous solvents. The possibility to fabricate the well defined microstructures from various organic conducting polymers is demonstrated by the electrochemical deposition of polypyrrole in moulded LIGA-forms at high current densities in aqueous solutions.

The electrochemical redox process to charge and discharge polyaniline layers is studied by simultaneous Electron Spin Resonance (ESR) and UV–vis spectroscopic measurements. For this purpose, optically transparent electrodes were applied under potential-controlled conditions. The use of a calibrated manganese ESR standard ensures the calculation of the absolute numbers of free spins in the polymer layer during electrochemical doping. A general procedure is given to analyse the simultaneously recorded electrochemical and spectroscopic data. The procedure proposed following the time dependence of charge, ESR absorption and the absorbance demonstrates that the electrochemical charging/discharging mechanism of polyaniline can be described on the base of three oxidation states. In this way, the separated UV–vis spectra and the time/potential dependence of each redox state can be shown. Only little changes are observed in the shape of the separated spectra using the polaron/bipolaron model in comparison to the polaron/ σ -dimer model. A square ladder scheme of the redox mechanism is discussed, considering neutral, polaronic and bipolaronic states and the protonation equilibria. Furthermore, experimental evidence for the Faradaic nature of the “capacitive” current plateau is presented.

Sonoelectrochemical processes in liquid ammonia in a temperature range between −70 and −35°C in the presence of 20 kHz power ultrasound are studied with the aim of improving low temperature electrosynthetic procedures. The one and two electron reductions of nitrobenzene and para-chloronitrobenzene are investigated as model systems. Placing an immersed ultrasonic horn emitter ‘face-on’ to a platinum disc electrode in liquid ammonia is shown to result in extreme mass transport enhancements with a resulting diffusion layer thickness of approximately δ=2 μm. This limit of the diffusion layer thickness is shown to be essentially temperature independent and correspondingly, the highest limiting currents can be observed near the boiling point of liquid ammonia. Cavitation processes are detected even at −70°C and result in a considerable fluctuation in the observed mass transport controlled limiting current. Further, the deposition of ionic products formed in the second reduction step for both nitrobenzene and para-chloronitrobenzene reduction and the associated drop in current, can be shown to be affected by sonication. Ultrasound has been found to be beneficial by (i) causing extremely fast mass transport; (ii) enhancing the mixing and dissolution kinetics at low temperature; and (iii) affecting the formation of solid products at the electrode surface.

We present here the first studies on copolymer layers obtained from electrosynthesis of pyrrole and salen compounds. This work comes into the field of modified electrodes for sensoring applications. We investigated this electro-copolymerization because the coupling occurs by radical cation (RC) coupling for both compounds. The electrochemical behavior was studied by cyclic voltammetry, spectroelectrochemistry and in situ electron spin resonance (ESR); quantitative characterization was performed with electron dispersive spectroscopy and mass spectrometry (Maldi-Tof). In the case of the copolymer prepared with little pyrrole (versus salen) in the starting solution, the ESR data gave no typical PPy signal although cyclic voltammograms (CVs) were completely different from those of poly(salen). The composition of the layers is estimated with good approximation and this is evidently an interesting material for sensoring applications such as gas (vapor) or heavy metal sensors.

(Z)-4-Nitrophenyl tert-butylsulfide [(Z)-4-NO2−1], upon formation of its radical anion, isomerizes to the (E)-isomer at a very fast rate of 6.3 × 106 s-1, about 103 times faster than azobenzene, while the 4-fluoro tert-butylsulfide (4-F−1) cleaves without isomerization. The particular behavior of 4-NO2−1 is related to the occurrence of a cleavage recombination mechanism, different from the usual inversion rotation mechanism. The existence of a reversible cleavage for the radical anion of 4-NO2−1 bears consequences on the mechanism of SRN1 reactions of azosulfides; the attack of the nucleophile would take place on the intermediate diazenyl radical and not on the ensuing aryl radical as previously proposed.

Stable regular honeycomb structures of various polypyrroles having a stick width of 50 μm and a structure height of 110 μm were formed by the electropolymerization of pyrrole or substituted pyrrole in aqueous solutions at high current densities. The advantages of these microstructures in sensorics and spectroelectrochemistry are shown for specific applications. The high electrical conductivity and the stability of the polymer were attained using aromatic sulfonate derivatives as electrolytes. Regular honeycomb structured polymer electrodes with channels of 50 μm were prepared and used for electrochemical and spectroelectrochemical studies. The cation-exchange properties of such structures were tested by Al3+ ions. The preparation of PPy–LIGA structures with specific groups was demonstrated by copolymerization of pyrrole with pyrrole-2-carboxylic acid. The high sensitivity and specificity of ESR signal of PPy–LIGA structures to the oxygen was observed.

The electrochemical oxidation of polyaniline (PAni) films on gold electrodes is studied by simultaneous electron spin resonance (ESR) and UV−vis spectroelectrochemistry. The technique permits the separation of the superimposed UV−vis spectra of three redox states: the protonated reduced polyaniline chains, the deprotonated polaronic state, and the bipolaronic state. The separated UV−vis spectra as well as the potential dependence of each redox state concentration enables a more precise determination of the energy levels and the stability of paramagnetic species.

Nitrogen-centered radicals have been generated upon electron transfer from the corresponding (1b~, 2b~, 3b~, 4b~) stable nitrenium ions (1b`, 2b`, 3b`, 4b`) and characterized by electrochemistry and simultaneous spectro-electrochemistry. Reactivity of the radicals is strongly inNuenced by the substituents attached to the two nitrogen atoms that are directly linked to the ion nitrenium center. While and are stable on the timescale 1b~ 2b~ of the electrochemical experiment, and have half-lifetimes of 3b~ 4b~ ca. 1.2E1.25 and 0.9E1 ls, respectively, in acetonitrile, as determined with ultramicroelectrodes. Redox properties of the nitrenium ion/radical couples and relative stability of the radicals are discussed in light of both experimental results and ab initio calculations

The redox behaviour of polypyrrole layers prepared by the electrochemical oxidation of pyrrole in acetonitrile solutions was studied using insitu EPR/UV–VIS spectroelectrochemistry. Various supporting electrolytes: p-toluene sulfonic acid, tetrabutylammonium perchlorate (TBAP) and tetraethylammonium p-toluene sulfonate (TEATos), were used. Optically transparent indium tin oxide (ITO)-coated glass and gold mesh electrodes were used as electrode materials. Using the calibrated manganese EPR standard, the quantitative time dependences of the three oxidation states in the polymer layer were obtained during redox cycling. The separation of the superimposed UV–VIS spectra was carried out by a least-squares method. The different mechanisms of the polymer oxidation, the polaron/bipolaron route and polaron/dimer route, are compared.

A new kind of optically transparent electrode based on very fine galvanically deposited metal meshes (1500 wires/inch= 64wires/mm) and mechanically stabilised by insulating the edge and the connection wire by thermal laminating foil is presented for use in electrochemistry with common solvents. The new electrodes were characterised by cyclic voltammetry as well as the ESR-UV-vis spectroelectrochemical measurements. The extremely fine mesh (with the scope of the diffusion layer exceeding the range of wind distance) with the well insulated border enables us to describe the voltammetric as well as the spectroscopic behaviour with the simple model of finite planar diffusion.

The electrochemical reduction of 2,5-diphenyl-1,3,4-oxadiazole has been studied by both cyclic voltammetry and spectroelectrochemistry. The in situ spectroscopic techniques were applied to obtain structural information on the products of the follow-up reactions. Time-resolved UV-vis spectroscopy, with spectra measured on a time scale of 20ms by a diode array spectrometer, was used in cyclic voltammetry to obtain up to 60 single spectra in the forward and backward scans. The radical anion of 2,5-diphenyl-1,3,4-oxadiazole, which is formed in the electron transfer reaction at the electrode, was studied by ESR spectroscopy. Furthermore, paramagnetic products of the follow-up reactions were detected. A reaction mechanism is formulated that includes an irreversible protonation reaction and, in parallel, a reversible ion-pairing reaction with the supporting electrolyte cation for the electrochemically generated radical anion and an irreversible follow-up reaction for the dianion of 2,5-diphenyl-l,3,4-oxadiazole.

Simultaneous in situ measurements by both ESR and UV-vis spectroscopy have been carried out at the same electrode for the first time during a single electrochemical experiment in order to spectroscopically characterize the electrochemical reaction products. The experimental technique, including a special TE102 optical ESR cavity and an electrochemical cell for both ESR and UV-vis spectroscopy in transmission, is described. It is shown that the UV-vis absorbance measured in situ, as well as the ESR intensity characteristics of the electrochemical system under study, can be understood in terms of the faradaic current. The reliability of this system is proved by measuring the organic redox couple of methyl-substituted p-phenylenediamine and by comparing calculated and experimental curves.

An in situ spectroelectrochemical capillary slit cell based on honeycombed gold-LIGA structures with a response time below 100ms and a conversion time of 1.2 s is described. The construction and the advances of the LIGA-spectroelectrochemical cell are discussed in detail. This cell is applied in studies of the electrochemical oxidation of Wursters reagent and in kinetic investigations of the cathodic trithioisatoic anhydride reduction.

The advantages of a new electrochemical cell for in situ UV-visible spectroscopy are presented using lithographic-galvanic microstructured metal foils (LIGA structures) as working electrodes to study electrochemical reaction mechanisms in aqueous and organic solvents under inert conditions. The properties (sensitivity, response time, conversion time) of this new type of spectroelectrochemical cell are determined with model redox systems in organic electrolytes. Furthermore, the calculation of the charge-time curves for the use of LIGA structures as a working electrode in a capillary slit is treated. The experimental results are compared with calculated curves as well as with the response behaviour of capillary slit cells with planar electrodes. The fast response time of the LIGA cell permits the study of fast chemical follow-up reactions and mechanistic investigations of more complex electrochemical reactions.

Methods for coating cylindrical carbon fiber microelectrodes with Nafion films of different thickness have been developed. It has been shown that it is possible to form thicker Nafion layers on the microelectrodes by adding multiple coats. The charge required to oxidize methylviologen incorporated in Nafion films was used to estimate the average thickness of the Nafion films. The ion-exchange equilibrium between Nafion film and solution was established more rapidly on the microelectrodes by cylindrical diffusion in the solutions and thicker Nafion films. A procedure for the desorption of viologen and dissolution of Nafion films on microelectrodes has been developed. Their use resulted in regeneration of the microelectrodes before the application of new coatings of Nafion.

The interconnection of electronics and textile circuits is still a main challenge for the fabrication of reliable smart textiles. This paper investigates the thermoplastic adhesive bonding technology. Electronic modules are bonded to textile substrates with a thermoplastic non-conductive adhesive (NCA) film. The modules are placed onto textile circuits with an NCA-film in-between. By applying pressure and heat, the adhesive melts and contact partners touch. Subsequently cooling solidifies the NCA resulting in an electrical and mechanical contact of the electronic module and the textile circuit. This paper shows the suitability of this technology for knitted, woven, non-woven and embroidered fabrics with metal coated yarns as well as with litz-wires as conductors. Besides, it shows that the interconnection process works well with thermoplastically insulated conductors. In addition, the design of interposers has been improved in respect to contact formation and miniaturization compared to previous publications. The pitch of the contact pads is set to 1.27 mm. A textile display was realized with smart RGB-Pixels, which are controlled by an I²C-bus on a quadrupolic woven substrate. It demonstrates the applicability and the potential of this technology.

3,3-Dimethyl-1-(4-R-phenyl)- [R = (CH3)2N, C2H5O, CH3O, CH3; 3] and 3-Methyl-1-(4-R1-phenyl)-3-(4-R2-phenyl)triazenes [R1 = (CH3)2N, CH3O, NO2, R2 = CH3O, H, 4] are oxidized electrochemically and chemically to their one-electron oxidation products. Cyclic voltammograms of the triazenes are discussed, and ESR as well as UV/Vis spectra of the radical cations are presented. The stability of the triazene radical cations generated depends on the substituents on the aryl rings. 4-R-Benzenediazonium ions are identified as one of the decay products of the radical cations by means of cyclic voltammetry and UV/Vis spectroelectrochemistry.

The electrochemical reduction of isatoic anhydride and its derivatives was studied by simultaneous electrochemical and ESR-measurements. For the first time 9 new radicals were characterized by its formal redox potentials, hyperfine coupling constants, g-factors and lifetimes. The advantage of measuring the kinetic data in stagnant and renewed electrolyte combined with accumulation of the ESR-spectra is demonstrated in the case of shortlived radicals. It is shown that the electrochemical reduction of isatoic structures follows a self protonation mechanism.

We present the theoretical treatment of cyclic voltammograms at microstructured electrodes. Calculations of voltammograms permit the determination of electrochemical parameters of redox systems in a single cell in parallel with the determinations of the spectroscopic parameters. The structural parameters of the electrode can be determined using the theoretical treatment presented if the electrochemical parameters of the redox system are known. Furthermore, lithographic-galvanic (LIGA) structures can be used as a model for microporous electrodes. Regression analysis was used to compare experimental and calculated cyclic voltammograms as well as to determine the electrochemical and spectroscopic parameters. A modified Randles-Sevcik equation has been derived to described the peak current dependence of cyclic voltammograms at micro-structured electrodes for both reversible and quasi-reversible charge transfer.

Textiles are common materials for many medical applications. They are used, for example, as bandages, medical stockings, or scrubs. Developments during the last 10 years in the areas of wearable electronics, smart textiles and material research offer new possibilities to create medical textiles with a higher level of functionality and allow the development of completely new active medical textiles. This trend was made possible by the interdisciplinary cooperation of engineers and scientists from textile research, electronics, informatics, and mechanical engineering, together with medical experts.

The theoretical dependence of the peak separation and the peak current on the radius of micro-cylindrical electrodes has been determined in dimensionless form for the evaluation of the rate constant of heterogeneous charge transfer and the diffusion coefficient. The data were determined from calculated cyclic voltammograms. The calculation is based on the numerical solution of the integral equation for a simple charge transfer and diffusion to a micro-cylindrical electrode. The dependences found are described by hyperbolic functions. Replacing the dimensionless quantities in the approximation function leads to a dependence of the peak separation and the peak current on the scan rate, ΔEp(v) and Ip(v), respectively. Both functions include the following parameters: diffusion coefficient, rate constant, electrode radius, number of transferred electrons and temperature. This makes it possible to determine the diffusion coefficient and the rate constant from the experimental peak separation and peak current dependence on the scan rate by non-linear regression. The diffusion coefficient and the rate constant were determined for the reduction of potassium hexacyanoferrate(III) at carbon fibre electrodes in the way described. The parameters determined are compared with published data.

Metal-coated polyamide threads and filaments were chosen as substrate electrodes to deposit highly porous ZnO films for photovoltaic application. The films were electrodeposited at 70 degrees C from oxygen-saturated aqueous zinc salt solutions containing EosinY as a structure directing agent. The current density during deposition was increased compared with planar electrodes by enhanced diffusion at the filaments operating as cylindrical microelectrodes. Analysis by scanning electron microscopy showed an influence of geometrical constraints within the textiles and the hydrodynamic flow rate in the deposition solution on the film morphology. Photoelectrochemical characterization of sensitized films revealed the feasibility of the presented approach and indicated further steps needed for electrode optimization.

Voltammetric techniques used in electrochemistry monitor the flow of current as a function of potential, time, and mass transport. A huge variety of different experiments are possible, giving information about reaction energies, reaction intermediates, and the kinetics of a process [1-4]. However, additional data are often required and are accessible, in particular, via in situ spectroelectrochemical approaches. By coupling a spectroscopic technique such as UV/Vis/NIR spectroscopy [5, 6] to an electrochemical experiment, a wealth of complementary information as a function of the potential, time, and mass transport is available. In a recently published book dedicated to spectroelectrochemical techniques [7] the diversity of methods and new chemical information obtained is apparent. Both spectroscopic information about short-lived unstable intermediates and spectroscopic information disentangling the composition of complex mixtures of reactants can be obtained. Figure II.6.1 shows a schematic diagram for the case of a computer-controlled potentiostat system connected to a conventional electrochemical cell (working electrode WE, reference electrode RE, counter electrode CE) and simultaneously controlling the emitter and detector of a spectrometer. This kind of experimental arrangement allows the electrochemical and the spectroscopic data to be recorded simultaneously and, therefore, in contrast to the analysis of two independent data sets, direct correlation of data as a function of time and potential is possible. © Springer-Verlag Berlin Heidelberg 2010.

Vacuum-annealed highly boron-doped diamond (BDD) thin-film electrodes are shown to allow reversible voltammetric responses for the reduction of nitrobenzene, 3,5-difluoronitrobenzene, and for the generation of solvated electrons in liquid ammonia at -60°C. In liquid ammonia (0.1 M KI) a considerably extended positive potential window at BDD electrodes compared to platinum is observed. At the negative end of the potential scale facile generation of solvated electrons occurs at both platinum and BDD electrodes. After exposure to solvated electrons in liquid ammonia, the surface of the diamond becomes hydrophilic and nitrogen functionalities were detected by X-ray photoelectron spectroscopy.

A newly developed in situ electron paramagnetic resonance (EPR)/ultraviolet-visible (UV-vis) spectroelectrochemical cell equipped with a laminated indium-tin oxide (ITO) working electrode was used in the investigation of various organic substrates which are potential hole-transporting materials. The experiment demonstrated the possibility of using such a technique for examining redox behavior of conducting polymers (polypyrrole, PPy), oligomers (thiophene dimmer and quarterthiophene) and bis -anilines (N,N,N′,N′-tetraphenylbenzidine, TPB). All investigated structures formed stable paramagnetic intermediates in the first oxidation step characterised with UV-vis spectra in the region 400–600 nm. In the second oxidation step EPR-silent di-cationic structures are formed with broad vis bands in the region 600–1000 nm. The measurement of the reference UV-vis spectra direct in the EPR cavity was possible using a specially-constructed non-contacted ITO plate in the spectroelectrochemical cell in the case of polypyrrole.

Microelectrode wires heated directly in situ by an electric current generate mass as well as heat energy transport phenomena. With continuous heating, a stationary surface temperature is established as a result of thermally promoted convection. The geometry of concentration and temperature profiles under these conditions are investigated by cyclic voltammetry, potential step experiments, and finite element simulation of convection and diffusion processes. It is shown that the Nernst diffusion layer approaches a constant, temperature-independent thickness if the temperature difference between bulk and electrode surface exceeds ca. 30 K in aqueous solution. At continuously heated wire electrodes, diffusion coefficient values as well as kinetic data can be determined under well-defined temperature conditions, and in a very convenient way.

The crystalline, spinless π dimer (1.+ ⋅PF6 )2 was obtained by the oxidation of bipyrrole 1 with ferrocenium hexafluorophosphate. The diamagnetic species generated electrochemically in solution was identified as the σ dimer by NMR spectroscopy.

Oxidation of caffeic acid (3,4-dihydroxycinnamic acid) 1H3 has been studied by electrochemical methods and by pulse radiolysis in aqueous and organic solvents. The results have been compared with the behaviour of 4-coumaric acid 2H2 and ferulic acid 3H2. The first oxidative intermediates have been characterised by their UV spectra and oxidation potentials. In the case of 2H2 and 3H2, the initial radicals decay by a second order process indicating a radical-radical coupling mechanism. On the contrary, for caffeic acid the oxidation leads to the formation of the corresponding o-quinone through disproportionation of the initial semiquinone radical.

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Silver-coated polyamide filaments were used as substrates for the electrodeposition of ZnO/eosinY hybrid thin films from aqueous mixed solutions containing Zn(NO(3))(2) and eosinY. Electrodeposition under pulsed potentiostatic control turned out advantageous to control the conditions of mass flow and to suppress parasitic currents and thereby obtain homogeneous porous films of ZnO as proven by scanning electron microscopy. Crystalline films of ZnO were formed as shown by X-ray diffraction. Diffuse optical reflectance spectra revealed the successful processing of the dye content of the porous ZnO coatings on the textile substrates. Photovoltage measurements served to proof sensitization of the textile based ZnO films.