The 7th Meeting on

Electrode Reaction Mechanism and Interfacial

Structure

Königstein, 3-6 April 2003

ERMIS 7 April, 3rd to April, 6th, 2003 Königsstein, Sächsische Schweiz

Programm

The oral presentations should be 20 min leaving at least 10 min for discussion

Thursday, April, 3rd

14:00 Opening

14:15 Sabine Szunerits, David R. Walt The use of optical fiber bundles combined with electrochemistry for chemical imaging

14:45 Jörg Bonekamp, Holger Frohne, Klaus Meerholz

Conjugated Polymers - Materials with Adjustable Work Function

9:00 K. Nonomura, E. Ebel, D. Wöhrle, T. Oekermann, T. Yoshida, H. Minoura, D. Schlettwein

Photoelectrochemical Properties of Dye-modified ZnO Thin Films Prepared by One-step Electrochemical Deposition

15:45 Coffee Break

16:15 Chuan Zhao, Charles Ajith Wijayawardhana, Gunther Wittstock

Fabrication and Characterization of Galactosidase Microspot Assemblies by Scanning Electrochemical Microscopy

16:45 Jie Zhang, Patrick R. Unwin, Daniel Mandler Studying lateral charge propagation at mono and multilayers of polyaniline films by the scanning electrochemical microscope (SECM)

17:15 – 17:45 Susan Cannan, I. Douglas Macklam, Nicola Rudd, Patrick R. Unwin

Spatially-Resolved Measurements of Diffusion and Reactivity in Electrochemical Systems using Confocal Laser Scanning Microscopy

18:00 – 19:30 Dinner

19:30 Oleg Sklyar, Gunther Wittstock 3D Simulations for the Scanning Electrochemical Microscopic (SECM) Investigations of Systems with Finite Kinetics and Complex Geometries

20:00 F.-M. Boldt, M. Diez, J. Petersen, M. Börsch, J. Heinze

Real Time pH-Nanoscopy with Combined Scanning Electrochemical/Confocal Laser Fluorescence Microscope

20:30 – 21:00 Mathieu Etienne, Ingrid Fritsch, Wolfgang Schuhmann

High-resolution SECM imaging of concentration profiles in electrochemical microcavities

Friday, April, 4th

9:00 Sabine Reiter, Victoria Ryabova, Thomas Erichsen, Ina Radtke, Wolfgang Schuhmann

Combinatorial Microelectrochemistry – Automated Fabrication and Evaluation of Sensors for Nitric Oxide in the Microtiter Plate Format

9:30 Wolfgang Märkle, Bernd Speiser Electrolyses in Micro-Titer Plates

10:00 Coffee Break

10:30 Kai Ludwig, Bernd Speiser Echem++ - An open source project for computational electrochemistry

11:00 – 11:30 Manfred Rudolph Conserving the flux in digital simulations by using the box method on unequally spaced grids

11:50 Excursion

18:00 – 19:30 Dinner

19:30 Dieter Britz, Jörg Strutwolf Higher-order spatial discretisations in digital simulations on an arbitraily spaced grid

20:00 – 20:30 L. K. Bieniasz Recent extensions of the patch−adaptive strategy for electrochemical kinetic simulations

Saturday, April, 5th

9:00 Carmen Ioana Ladiu, Ionel Catalin Popescu, Lo Gorton

NADH Electrocatalytic Oxidation at Carbon Paste Electrodes Modified with Meldola Blue Adsorbed on Zirconium Phosphate

9:30 Andreas Christenson, Eva Dock, Sveltana Sapelnikova, Jan Krejci, Jenny Emneus, Tautgirdas Ruzgas

Electrochemical biosensor arrays: technology of manufacture and measurements

10:00 Stepan Shipovskov, Andreas Christenson, Andrey Levashov, Tautgirdas Ruzgas

Development of Biosensors by Spraying Enzymes in Reverse Micelles

10:30 – 11:15 Coffee Break

11:15 Steffen Kröning, Frieder W. Scheller, Fred Lisdat

Nitric oxide (NO) sensor based on myoglobin immobilized on Clay-modified electrodes

11:45 J. Posdorfer Recent applications of the conducting polymer polyaniline in smart coatings

12:15 – 14:00 Lunch

14:00 Agnieszka Kochman, Karsten Haupt, Tibor Hianik, Victor Gajdos, Pankaj Vadgama, Giosio Farace, Wlodzimierz Kutner

Piezoelectric microgravimetry study of adsorption of selected compounds of biological importance

14:30 Malgorzata Chojak, Krzysztof Miecznikowski, Pawel J. Kulesza

Inorganic monolayers as templates for two-dimensional and three-dimensional arrays of polyaniline and metal nanoparticles

15:00 Jovan Alston, Abert Fry Recent studies of substituent effects on the electrochemical reduction of benzylideneacetophenones (chalcones)

15:30 – 16:00 Coffee Break

16:00 Renata Marczak, Krzysztof Noworyta, Wlodzimierz Kutner, Gadde Suresh, Francis D’Souza

Spectroscopic and electrochemical properties of self-assembled complexes of some C60 adducts and water-soluble Zinc porphyrins in the Langmuir and Langmuir-Blodgett films

16:30 Rafal Czerwieniec, Andrzej Kapturkiewicz Syntheses, crystallographic structures, electrochemical and spectroscopic properties of rhenium(I)tris-carbonyl complexes

17:00 D. Rohde, L. Dunsch, A. Noack, H. Hartmann Electrochemical and spectroelectrochemical investigations of novel aminothiophenes

17:30 Filip Novak, Bernd Speiser The Electrochemistry of Ir-Pincer Complexes and Their Electrochemically Activated Intramolecular C-H Bond Activation

18:00 – 19:30 Dinner

Sunday, April, 6th

9:00 Sabine Gimpel, Uwe Möhring, Walther Müller-Litz, Andreas Neudeck, Wolfgang Scheibner

Textile Electrode Structures and Applications

9:30 Pawel Szrebowaty, Andrzej Kapturkiewicz Electron transfer generation and annihilation of the excited MLCT (metal-to-ligand-charge-transfer) states

10:00 Thomas Ebert, Josef Salbeck Electrochemical and spectroelectrochemical investigations on symmetrical and unsymmetrical substituted spiro-compounds

10:30 – 11:00 Coffee Break

11:00 P.C. Pandey, B.C. Upadhyay, R.A. Misra Ormosil Sandwiched Bacteriorhodopsin--A Novel Photoelectrochemical Sensor

11:30 – 12:00 Claudia Muresanu, Günther Grampp Redox Potentials Determined by Photomodulated Voltammetry and Bond Dissociation Energies of Phenoxyl Radicals

12:00 Closing remaks

The use of optical fiber bundles combined with electrochemistry for chemical imaging

Sabine Szunerits,a,b David R. Walt,a

aThe Max Tishler Laboratory for Organic Chemistry, Department of Chemistry, Tufts

University, Medford, Massachusetts, 02155

bDRFMC/SI3M, UMR 5819, CEA Grenoble, 17, avenue des Martyrs, 38054 GRENOBLE Cedex 09, France

Imaging methods are used widely as they enable processes to be visualized in situ both

at surfaces and in solution. They offer excellent spatial resolution, approaching the nanometer scale, but are limited to samples that can be brought to the microscope stage. Imaging fiber bundles, on the other hand, are highly flexible and can be brought directly to the sample. The instrumentation for imaging the sample is furthermore very simple.1

The progress made in using imaging optical fiber bundles for electrochemical-initiated chemiluminescence imaging will be presented. A novel opto-electrochemical micro-ring array has been fabricated and demonstrated for concurrent electrochemical and optical measurements to combine the advantages of microelectrode arrays with the imaging properties offered by optical fiber bundles.2,3 The resolution of this device is in the tens of micrometers range, determined by the diameter of the optical fiber (25 �m) and by the spacing between each electrically connected fiber. For the purpose of having well-behaved microelectrode characteristics, this spacing was designed to be larger than 60 �m. The array was characterized using ferrocyanide in aqueous solution as a model electroactive species to demonstrate that this microelectrode array format exhibits steady state currents at short response times. This device has potential application to be used as an optoelectronic sensor, especially for the electrolytic generation and transmission of electrochemiluminescence, and was used to demonstrate that electrochemically generated luminescent products can be detected with the fiber assembly.

[1] K. S Bronk, K. L Michael, P. Pantano, D. R. Walt, Anal. Chem. 1995, 67, 2750. [2] S.Szunerits, D. R. Walt, Anal. Chem. 2001, 74, 886. [3] S.Szunerits, D. R. Walt, ChemPhysChem 2002, 3, 101.

Conjugated Polymers - Materials with Adjustable Work Function

Jörg Bonekamp, Holger Frohne, Klaus Meerholz

Department of Physical Chemistry Department; Universität Köln Luxemburgerstr. 116, D-50939 Köln, Germany

Organic light-emitting diodes and solar cells, respectively, have been prepared using a poly(phenylene-vinylene) (PPV) based polymer as the active layer. Poly(3,4-ethylenedioxythiophene) (PEDOT) was grown potentiostatically atop indium-tin oxide to serve as the hole-injecting/collecting electrode, and its work function was pre-adjusted by electrochemically altering the doping level. If the devices are prepared in inert gas atmosphere, there is a linear correlation between between the the open-circuit voltage of the devices and the work function of the PEDOT layer. By contrast, when prepared in air no such correlation was observed. By contrast, the short-circuit current varied systematically with the work function in both cases. We discuss the implications of these findings on the performance and stability of organic semiconductor devices.

Photoelectrochemical Properties of Dye-modified ZnO Thin Films Prepared by One-step Electrochemical Deposition

K. Nonomuraa,b), E. Ebelc), D. Wöhrlec), T. Oekermannb), T. Yoshidab), H. Minourab)

and D. Schlettweina)

a)Department of Chemistry, Physical Chemistry 1, University of Oldenburg, P.O. Box 2503, D-26111 Oldenburg, Germany; Kazuteru.Nonomura@mail.uni-oldenburg.de

b)Environmental and Renewable Energy Systems Division, Graduate School of Engineering, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan

c)Department of Chemistry, Institute of Organic and Macromolecular Chemistry, University of Bremen, P.O. Box 33 04 40, D- 28334 Bremen, Germany

Solar energy is expected to be one of the most promising solutions to solve many of the current environmental problems because solar energy is limitless and very clean. Photovoltaic cells are an attractive way of direct conversion of solar radiation to electricity. Silicon solar cells are the best-known cells and are widely commercially available. Among other (thin- film) technologies, dye-sensitized solar cells present an alternative, probably more cost- efficient, environmentally safe and applicable to versatile applications. The (almost) free choice of the color of such cells (albeit dependent efficiency) represents a unique attractive point of such solar cells. Prof. Greatzel and co-workers in Lausanne succeeded to prepare dye-sensitized solar cells based on sintered TiO2, a Ru complex dye (hereafter denoted N3) and an iodine/iodide redox electrolyte which have high conversion efficiencies of about 10%.[1] A number of efforts are seen worldwide to further develop electrodes based on this concept. Electrochemical deposition from aqueous baths represents an alternative technique to prepare semiconducting oxide thin films. By adding a water-soluble dye to the deposition bath, dye-modified ZnO hybrid thin films can be prepared in a one-step process.[2] The films prepared by this method consist of highly crystalline ZnO, intensely colored by adsorbed dyes. In this study, we prepared ZnO/N3, ZnO/TSTPP(tetraphenyl porphyrines) and ZnO/TSPc(tetrasulfonated phthalocyanines) hybrid thin films. The films are characterized in their structure and morphology and are then studied in their photoelectrochemical characteristics. By changing the dye concentration, deposition voltage and the deposition time, we can control the film thickness (~3ìm), the amount of dye loaded (~1×10-7mol/cm2) the crystallinity and porosity. ZnO/N3 hybrid thin films prepared by this method work as photo electrode and 1 mA/cm2 of photo current in a 3-electrode setup is available. In (two- electrode) sandwich cells, these hybrid thin films work as "solar cells" with 0.6 mA/cm2 of short- circuit photocurrent Isc, 0.6 V of open circuit photovoltage Voc, a fill factor of 0.37 leading to 0.23% of conversion efficiency. This does not represent a cell of technical significance but it proves the feasibility of the concept. Using this deposition method, heat treatment is not necessary. Then it’s possible to use conductive plastic substrate as cheap and mechanically flexible (!) working electrode. ZnO/TSTPP and ZnO/TSPc hybrid thin films also work as photo electrode. Their photoelectrochemical properties will also be discussed in comparison and photocurrent transients as well as intensity- modulated photocurrent spectroscopy (IMPS) will be used to analyze the photoelectrochemical kinetics. [1] B.O’Regan and M.Grätzel, Nature 353, 739 (1991) [2] T.Yoshida, K.Terada, D.Schlettwein, T.Oekermann, T.Sugiura and H.Minoura, Adv,

Mater. 12, 1214

Fabrication and Characterization of Galactosidase Microspot Assemblies by Scanning Electrochemical Microscopy

Chuan Zhao*, Charles Ajith Wijayawardhana and Gunther Wittstock

Universitaet Oldenburg, FB Chemie, D-26111 Oldenburg

The suitability of scanning electrochemical microscopy (SECM) for study of biological systems, e.g. enzymes, has received particular attention since its introduction. Much attention in our laboratory have been devoted to the activity of imaging immobilized enzymes on patterned surface by SECM. Both feedback mode and generation-collection mode have been used so far [1]. Patterning of enzyme has also been explored by a variety of ways including site-directed microbead deposition [2]. Horseradish peroxidase, alkaline phosphatase and galactosidase are the most commonly used labelling enzymes because of their high activity. The former two have been studied by SECM because suitable substrates for amperometric detection are available. Galactosidase is another interesting labelling enzyme. However, with the commonly used substrate, p-nitrophenyl-$\beta$-D-galactopyranoside, it is difficult to directly detect the enzyme reaction product, 4-nitrophenol, because of its high overpotential and electrode fouling. It has been shown that p-aminophenyl-$\beta$-D-galactopyranoside (PAPG) is a suitable substrate for galactosidase with the easily detected enzyme reaction product, 4-aminophenol. In this contribution, the activity of galactosidase is characterized by SECM. The galactosidase microspots are fabricated by immobilizing galactosidase on streptavidin-coated paramagnetic beads and depositing the beads as microscopic agglomerates one by one. The enzyme activity is mapped with SECM in generation-collection mode. The procedure is expected to lead to galactosidase-labelled electrochemical immunoassays with SECM. [1] G. Wittstock, Fresenius J. Anal. Chem. 2001, 370, 303-315 [2] C.A. Wijayawardhana, G. Wittstock, H.B. Halsall, W.R. Heineman, Anal. Chem. 2000,

72, 333-338

Studying lateral charge propagation at mono and multilayers of polyaniline films by the scanning electrochemical microscope (SECM)

Jie Zhang, Patrick R. Unwin and Daniel Mandler*

Department of Inorganic and Analytical Chemistry, The Hebrew University of Jerusalem,

Jerusalem 91904, Israel Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK

Electron and charge transfer across thin films has been the subject of numerous

studies. On the other hand, lateral charge transfer in either thin films or monolayers has received less attention, mostly due to the inadequacy of experimental methods to study this process. Yet, lateral charge propagation plays a major role in biological membranes and in the operation of some electronic devices based on conducting polymer films.

We have studied the lateral charge propagation across mono and multilayers of polyaniline (PAN) at the liquid-air and the liquid-solid interface using the scanning electrochemical microscope (SECM). This SPM tool is quite unique in its ability to generate a flux of electroactive species close to the interface and measure the effect of the surface on the generated flux.

Charge propagation across a Langmuir film of PAN, which was spread at the liquid-air interface was studied by approaching the interface with a “submarine” microelectrode immersed entirely in the subphase. A clear insulator-conductor transition could be detected as a result of compressing the Langmuir film. This transition has been attributed to decreasing the chain-chain distance at the PAN monolayer, thus increasing its electronic conductivity.

On the other hand, we deposited mono and multilayers of PAN onto a solid support (glass or ITO) by the LB method. This enabled us to characterize and study these films by a variety of methods, such as XPS, AFM, UV-vis spectroscopy and electrochemistry. The films are very homogeneous and layered and exhibited very fast charge propagation across them as studied and simulated by the SECM.

Spatially-Resolved Measurements of Diffusion and Reactivity in Electrochemical Systems using Confocal Laser Scanning Microscopy

Susan Cannan, I. Douglas Macklam, Nicola Rudd and Patrick R. Unwin

Department of Chemistry University of Warwick

Coventry CV4 7AL UK

There are many instances in electrochemistry where quantitative knowledge of reactivity and diffusion at high spatial resolution is invaluable. We have recently been exploring the use of fluorescence confocal laser scanning microscopy (CLSM) to investigate proton diffusion profiles and identify reactive sites on electrode surfaces. This talk will cover some of the many possible applications of CLSM in electrochemical systems and outline future areas of application. In initial studies, CLSM has been used to image three-dimensional pH gradients associated with electrochemical reactions at microelectrode surfaces, using the reduction of benzoquinone to hydroquinone in aqueous solution as an example. The associated local pH change accompanying this process has been imaged using a trace amount of fluorescein, which has a pH-dependent fluorescent signal. Images recorded in x-y-z space, allow pH profiles to be obtained as a function of applied electrode potential. To further illustrate the capability of the method, proton diffusion profiles have been imaged at Pt microelectrode array devices, to locate small defects in the insulation of conducting tracks, and at the surface of graphite-epoxy composite electrodes, where active sites have been readily highlighted. In conjunction with scanning electrochemical microscopy (SECM) and a Langmuir trough, CLSM has been used to investigate proton transport at simple biomolecular membranes. The experiments developed have involved incorporating a pH-sensitive fluorescent molecular probe into a phospholipid monolayer, assembled on an aqueous subphase in a Langmuir trough, to allow ready control of the surface pressure. The microelectrode probe utilised in SECM was positioned close to the phospholipid/air interface and used to locally alter the pH of the subphase via the oxidation of water. CLSM was used to measure the resulting change in surface pH across the monolayer, in real time, and a spatio-temporal fluorescence map showing interfacial proton dispersion was produced. Modelling of mass transport has allowed bulk versus surface diffusion effects to be identified. This work is important in connection with bioenergetic processes, where the significance of surface versus bulk diffusion in the transport of protons, between source and sink sites in cell membranes, is a matter of considerable debate.

3D Simulations for the Scanning Electrochemical Microscopic (SECM) Investigations of Systems with Finite Kinetics and Complex Geometries

Oleg Sklyar* and Gunther Wittstock

Universität Oldenburg, FB Chemie, D-26111 Oldenburg

Numerical simulations with the dual reciprocity boundary element method (DRBEM) are used to evaluate currents generated at ultramicroelectrodes of the scanning electrochemical microscope (SECM) under the conditions of (in)finite sample kinetics. The SECM uses Faradayic currents controlled by the diffusion of oxidizable/reducible particles for investigations of the surface reactivity/topography. The numerical simulations allow to predict the SECM signal that one would obtain in every particular experiment, thus helping in understanding the experimental results or in designing new experiments. For that the geometry as well as the boundary conditions, which include possible boundary fluxes or concentration values, have to be set up to fully describe the system under investigations. As compared to other numerical techniques the DRBEM simplifies significantly simulations in the 3D space thus enabling treatment of complex geometries of real systems,[1] which arise from combinations of the SECM with such techniques as the scanning force microscopy (SFM) [2] or scanning tunnelling microscopy (STM) that work in the nano-scale region. This contribution represents our results on the DRBEM simulations for the SECM-SFM experiments. The contribution focuses on the evaluation of kinetics of heterogeneous reactions at the sample, on the complexity of system geometries, and on the conformity of the numerical simulations with the experimental measurements. 1. O.Sklyar, G.Wittstock J.Phys.Chem.B 2002, 106, 7499 2. C.Kranz, G.Friedbacher, B.Mizaikoff, A.Lugstein, J.Smoliner, E.Bertagnolli Anal.Chem. 2001, 11, 2491

Real Time pH-Nanoscopy with Combined Scanning Electrochemical/Confocal Laser Fluorescence Microscope

F.-M. Boldt, M. Diez, J. Petersen, M. Börsch, J. Heinze

Freiburg Materials Research Center (FMF) and Institute of Physical Chemistry, University of

Freiburg, Stefan-Meier-Str. 19, 79104 Freiburg, Germany One great advantage of the scanning electrochemical microscope (SECM) is its flexibility as an electrochemical tool with a currently spatial resolution of 100 nm and consequently its application not only in the fields of material research but also of biophysical chemistry and life sciences. For in situ experiments related to biochemical or bioelectrochemical research, we have integrated a SECM in a confocal laser fluorescence microscope (CLFM) with possibility to detect single molecules. The very high resolution of the CLFM is achieved by the laser induced confocal excitation volume of 1 µm³ in the solution and so it is possible to excite single molecules in solutions with nanomolar concentrations. We present the instrumental setup and real time measurements of the pH-dependent fluorescence intensity during pH shifting caused by electrochemical reactions at micro- and nanoelectrodes with diameters from 10 µm down to 70 nm. Locally defined pH-adjustments could be carried out both in solutions and on surfaces and were detected ratio metrically at two different wavelengths to receive a better fluorescence signal-to-noise ratio. On surfaces pH-measurements were performed in total internal reflection fluorescence mode to obtain a small only a few hundred-nanometer thick fluorescence excitation field on the surface. Previously the pH-sensitive fluorophores were immobilized on SAM modified slides. With a CCD camera cooled with liquid nitrogen we received high-resolution images of the local pH profiles on the surface induced by electrodes reactions at different distances.

High-resolution SECM imaging of concentration profiles in electrochemical microcavities

Mathieu Etiennea, Ingrid Fritschb, Wolfgang Schuhmanna

a Elektroanalytik & Sensorik, Ruhr-Universität Bochum, Bochum, Germany

b Depart. of chemistry and biochemistry, Univ. of Arkansas, Fayetteville, AR, USA

Scanning Electrochemical Microscopy is a very powerful technique for the electro-chemical investigation of surface phenomenona1. The spatial resolution of the technique depends on the radius of the used microelectrode and the distance between this probe and the analysed surface. Moreover, the smaller the electrode radius, the stronger is the effect of small topographic variations of the analysed surface on the electrode response. Hence, in order to perform high-resolution SECM experiments on complex surfaces, shear-force measurement has been introduced as a current-independent control permitting to keep the distance between the electrode and the surface constant 2, 3. We will present our recent results concerning the application of a SECM setup equipped with a non-optical shear-force control for visualising the concentrations profiles inside electrochemical microcavities4. The microcavities have typically a diameter of 50 µm and a depth of 8 µm. The production of Ru(NH3)6

2+ has been observed with specially designed Pt nanoelectrodes permitting a pure generation/collection mode with no feedback effect. Moreover, the low current passing through the nanoelectrodes has a negligible effect on the measured concentration profiles. Additionally, pH profiles have been measured with a potentiometric micro-pH electrode showing a diameter of only about 1 µm. For both potentiometric and amperometric measurements, the shear-force control allow us to precisely position the tip at the surface (no current feedback) and to follow the complex topography of the sample throughout scanning. Future work is aiming Current work is aiming on the application of high-resolution constant-distance mode SECM for visualising the activity of living neuronal cells and for studying the initiation and the growth of precursor sites of localised corrosion. 1 Bard A. J. and Mirkin M.V., Scanning Electrochemical Microscopy, M. Dekker, New

York, 2001. 2 Ludwig M., Kranz C, Schuhmann W, Gaub HE, Rev. Sci. Instr., 1995, 66, 2857. 3 Ballesteros Katemann B., Schulte A., Schuhmann W., Eur. J. Chem., in press. 4 Henry CS, Fritsch I, J. Eletrochem. Soc., 1999, 146, 3367.

Combinatorial Microelectrochemistry – Automated Fabrication and Evaluation of Sensors for Nitric Oxide in the Microtiter Plate Format

S. Reiter, V. Ryabova, T. Erichsen, I. Radtke, W. Schuhmann

Analytische Chemie – Elektroanalytik & Sensorik

Ruhr-Universität Bochum, D-44780 Bochum, Germany

The introduction of automation and parallelism to the field of electrochemistry facilitates the evaluation of large compound collections for various applications such as combinatorial automated electroanalysis, electrosynthesis and sensor tests. In order to enable fully automated electrochemical experiments a flexible technical platform is required which allows the application of a variety of electrochemical techniques in combination with a wide range of parameters and procedures. Therefore, a robotic system was developed that is compatible to the microtiter plate format as being widely used for biological assays and in combinatorial chemistry. In brief, precise micro-positioning devices move the microtiter plate in x- and y-direction and place specially designed electrodes into its individual wells. The system can be used with aqueous and organic solutions as well as in inert-gas atmosphere. Using an eight-channel potentiostat, measurements with up to eight individually addressable working electrodes can be done in parallel. A modular software integrates conventional electrochemical techniques such as constant-potential amperometry, cyclic voltammetry, differential pulse voltammetry and amperometry, constant potential and constant current electrolysis, and is easy adaptable to meet specific experimental needs.

As a representative example for possible applications of our system, the optimisation of electrochemical NO sensors has been studied. Nitric oxide (NO) is important in a variety of biological process like neurotransmission, blood vasodilatation, platelet inhibition, cell adhesion, enzyme regulation, penile erection and immune regulation. Among different methods for NO detection and quantification electrochemical oxidation of NO at metallo-porphyrin-modified electrodes was demonstrated to be very sensitive and fast.1 However, the influence of the central metal and the role of substituents in the phenyl ring of the porphyrins are still not well understood. For this reason, the robotic device has first been used to accomplish a combinatorial electrochemical screening of a porphyrin library consisting of 100 different porphyrins as potential electrocatalysts for the oxidation of NO. Based on the obtained results, porphyrins with good electrocatalytic characteristics have been chosen for the fabrication of NO-selective macro- and microsensors. Using an automated approach for sensor evaluation they were tested for their sensitivity, specificity, reproducibility and stability.

NO microsensors of improved quality were finally employed to monitor in vitro changes of NO concentrations occurring in the vicinity of NO-secreting cells upon suitable stimulation. Epithelial cells were plated in the individual wells of a microtiter plate and bulk NO release was measured sequentially from well to well using the robotic system for the positioning the NO microsensors and for triggering both the stimulation and the amperometric recordings of NO release at appropriate time. First results on the kinetics of the NO release of epithelial cells after cell stimulation will be presented.

1 T. Malinski, Z. Taha, Nature 358 (1992) 676.

Electrolyses in Micro-Titer Plates

Wolfgang Märkle, Bernd Speiser

Universität Tübingen, Institut für Organische Chemie Auf der Morgenstelle 18; D-72076 Tübingen; Germany

Combinatorial synthesis is a technology which provides large numbers of chemical substances in a short time[1]. Different educts are combined in parallel reaction compartments, e.g. in wells of micro-titer plates or at polymer beads. Electrosynthetic methods are still uncommon in this field[2][3]. Among others, the advantages of electrosynthesis are selective oxidation/reduction of one or more educts and the often mild reaction conditions[4]. By recording cyclic voltammograms during the electrolysis, the development of educt, product and intermediates´ concentrations can be followed. Thus, the end-point of the electrolysis can be detected by monitoring the educt current with for example steady-state voltammetry. Changes of voltammograms during an electrolysis were simulated digitally and experimentally with mixtures of ferro-/ferricyanide in different ratios. The simulations were confirmed by experiments in a conventional electrolysis cell in aqueous and non-aqueous media with model substrates like ferrocyanide, ferrocene and N,N,N’,N’-tetramethyl-p-phenylenediamine. For the rapid electrolysis of reaction solutions in the wells of a conventional micro-titer plate a miniaturized electrode bundle was constructed. The model compounds were electrolyzed in a micro-titer plate and monitored by steady-state voltammetry with our “combinatorial scanning electrochemical microscope” (Combi-SECM) which allows a sequential positioning of the electrode bundle in all the wells. Furthermore, with this arrangement, electrosyntheses of 1,3,5-trisubstituted 1,2,4-triazoles were performed by anodic oxidation of benzaldehyde phenylhydrazones in the presence of nitriles. This work was supported by the Deutsche Forschungsgemeinschaft in the co-operative project “Kombinatorische Mikroelektrochemie”. [1] N. K. Terrett, Kombinatorische Chemie, Springer Verlag Berlin Heidelberg New York,

1998. [2] T. Siu, W. Liu, A. K. Yudin, J. Comb. Chem. 2000, 2, 545-549. [3] S. H. Baeck, T. F. Jaramillo, C. Brändli, E. W. McFarland, J. Comb. Chem. 2002, 4, 563-

568. [4] E. Steckhan in P. T. Kissinger, W. R. Heineman, Laboratory Techniques in Electro-

analytical Chemistry, 2nd Edition, Marcel Dekker, Inc., New York, 1996.

���������� �������������������������! "�#��$%���#&(')���*���+������&),�&#-.���/,+01�"02���#&��#�3�#�����"-.45&#�)6

798;:�<�=2>@?A:CB2DFE3GIHKJ2>�LNMOGI:QPRGSHTUJ2:WVXGIHYPR:WZ\[8;Z^]"[=F_2:WJFBXGIJ�D2`aJ2PbZK:cZK=@ZUdY[=FHfefHKBX85JF:QPhgYiFGkj�iFGSl�:CG

m =@d�>@GSHUn�o5HKB5GSJ2PbZKGIpCpWG�qSrsUtRu;v5wxuzy"]{[=F_F:CJFB5GSJ�D)|}GSHhl8;JN~

�����@���O�����z�@�����@���O���������z���;���%���N�������I�@�����F���@�������������@�;�������%�F���������N�����F���@�#���z���������z�^�Y���;���;�%���I�O�S���;����������I�����;�N�I����z�@�z���������z���@���@���@���@���O�����z�@�)�������%�;�������}���3 ��@���;�¡�F�������9���;���¢�@�#�@���@�z�%�@�I������£����@�.�R¤��N������O�F�a¥A¦k���k�%�F�)�����F���@�����z�I�������z�I�@�����������S�����;�)���N�����F�/§F�����"���;�@�������;�¨�;�2�f�@�#�%©����z�I�����;�)���@�����N����§����N����@���@���������;§#�@���I�������@���%�����ª�«�;�N���������%©O���I�@�%�����F�/§������������������N�����F�¬�@��¤}�;�����@���������%�F�¨���N�I�����F�¬ ��z�R¤}�z�;��%©��#�z�S�����;�)���@���(�����¡�����N�����F�/�������A�����;���¬­®�@���¯�z�@�;�°���@���X±���@�����¡�z�@�( #���%�F�¢ ������;�²���¯�����¨���z�I�³I´@µ{¶#·�¸b¹F¸®º®´N»#¹N¼¾½%¼�½�³;¸®¿�´;³zÀ�½%µ�º«Á\¸®¿\ ����z�%�@�I������£F���@§��Ã�����@ ����;�Ä���F���O����£Å�;�)�������F�����;�)�¨­®Æ}Ç�È�±"�«�@���%�F�¨�������N�����F���@�^�;���;�%�����O�S���;�¨���������ª¤��@����;�%�;�)����������£@£@�;�����;�É�@�ËÊ��Ì�%�F���������z�Ã�����@£@�S�@�Í�����N�Ã���I�5�������;�Å�@���{�����¬�%�F���������N�����F���@���®�@�z�����������;����;�%�;���I�N���Ã�������F���@�¢�����N�I£@�z�"�z���@���k�@�3�����@ ����;�¨�;§��%�F�)�@�;�����;�)�����1�@���Ã�zÎ��z���;�2������ÏÃÐz��Y�*�F�����@���������F��§¾�����ª���;�@����Ñ;�N�����F�*�@�������I���@���������@�z�I���@�9�����xÒY�;�%�Å���;�¨�@������ ��@���*�����Ó�����Ó�@��@����N�@���%�;�(�%�F���������N�����F���@�A���;�S������ÔO���;���@���¯�������%�O�@���z�I�N�����F�¯ ��z�R¤}�z�;�°���z�@�z�I�@�¾���2���z���;�����;�¯£@���F�������@��;���;�%�������I���;�¨�������"�@���1�%�F���������z�����z���;�)���������z�¦k���k�����;��@���@ �Ò��;�%�U�@�I���;�)���;�¨���I�@£@�I�@�¨�¨����£����@�A ��z�;�����z�@�;���@�#�;�¨�����F���k�@�������������@�����N�I���%�F���%�z��������Ì���@�������ª�%�F�������%©����@�.�R¤��N���!�����xÒ��;�%���Å�����I����£¯�����¬���@���ÅÕNÖ×�@�;�N�I�z�ئk���Ó�����F�¨�����Ó�@���@���@ �Ò��;�%��@�I���;�)���;�����;����£F�������@�I�����z�@�9�z�@�F���x�N ��������R���@�������;�����N ��������h���@�����@�.�R¤��N���{�%�F�¨�#�F���;�2���A¤��@�^�����k���S���O����£�.�@�I�%�¢���Ã���������������%�;����Ùx�Ç������������@���z�F�������@§����z�@�z�S�@�¾�@ �Ò��;�%�¢�@�S���;�2���;�(�����@£@�I�@���¨����£1���@��£F���N£@�;�¢���5�@�� ��z�;�¯�z�@�F���@�;���Ŧ��O���;�@§ÚkÛ�Û �����F����@�����������F���9���@�������N�9�@���ä"�����;�����I�;�@���@ �ÒY�;�%�k�@�S���;�2���;�Ü�����@£@�I�@�¨������£����@��£F���N£@�;�z�f��O��£@�{�O���¢ ��z�A�@� ÚkÛ�Û  ��@���;�����I�@£@�I�@�¨�z§2�����@��������£��@���������kÝ��;�����^�@���I�z���;�2����Ý������;���;�N�I�S�����¾�;�N�@�����N �����.���F�Þ���������)���z�I���z�z§��@�«���;�ª�@�9�@���;�Ü���F���I�%�¢�����xÒ��;�%���kßN��Y�×�����������I�@���������F��§A�����ÜÈ Ú ���;� Û�Û �����xÒ��;�%�¨�����ª�I�;�@���F���N ����1����£@£@�;�������F�Ì���¯�����Ã�;���;�%�������I���;�¨���z�@��%�F�¨���������h�¯���Ó���N�@�Ã���N�����N�¢�������������@£@�I�;���z�Ü�à�.�I�@���z¤}�@���¯�«�@�������F���Å�%�F�����F���;�)���¡���;�%�;�I���N���²����.�@�I�á��£@�;���z�S�@��Æ}Ç�È��«�@�"�%�F���������N�����F���@�/�;���;�%�������I���;�����������Ã���������X�O�����;�/��"���N�����«�I�F�â�����"���@�������N�I���h�@§������ ÚkÛ�Û ���@��£F���N£@���Nã#�z�I��%�z�I���@���!���;�I�������z�@�^�%�F�������I���%����N�������@�����N����.�@�{�@�Ü���������;���;�)���N�����F�Å�@�^��Æ�Ç�È*���Ã��������z�I�¨�k�N ��5�@�@�f�K�Ü���N�������z�����N�;§�ä ½%»#½z¿Sºa³k¶�¿�´ ä ¿�¹Nµ�µ�º«» ä����9����5¤}�z���®���������;�S������ÔO���������N�����;�����;� ¸R½%µ"¶�¼�¹@¸R½%Á ���Ã�;���z���F���¡�I�z�#�;�N������£����N�����z�S����@��¤f�;���3�@�����Ã�;���������¸®ÂS¶�½�Áz¹Yå;½z¸®Â �@���ª�����z���z�.�@���@§����Å�5�@�F���¬�z�����@�������F���¢�%�����zæ@�"�K�ª�@�����������F��§������������¢�@�¾���;�����N ��������;����£F����N�����z�I���9�.�@�z���������N���;�9�����¢�����������%�����F�Å�@�^���;�����N �����%�F�����F���;�2���IçN�È Ú ���;� Û�Û ���U�%�F���%�;���@�;�Ã�@�¾�@���@���;�����F���S�%�{�����xÒ��;�%�z§O¤{�����S�¨�z�@�� ��k�N���������;�/§F�%©����;�����;��§)���������5�@�;��@���¢���;�����;���«���z�;���� O���@�)�����2���z�I�;�����;�¢�;���;�%�����O�S���;�¨�����z§N�I�����%�U�����}���F���I�%���%�����¾¤{�����N ��¾�¨�@���}�;�N�@�����N ����è �é �²���5¤¢§3���������z�@�;���@�����;�2���������%�z�;���¡�������z�������Åê����)��©¬�@���z�I�N������£Ó���������;�1�Ó¦k���������������¨¤"�����I����������;���;�)���k�������%�F�)�����F�3�@�U�%©O���z�I�����;�2���"�������F��£F�¬���#�;�z��Ý������N�I��¤}�N����¤{������������������ë3¦{ê+���O��©Ü���;�@��������Ã�%©����;�������F��ì5�Ëí"�5¤}�z�@�z�;§��«�@���@�����z���%�F�����F���;�)���¨���!���;�����S���%�����F�Ì���(�!���N�I�����z�����N���@���z�I�N������£���������;� ���9���2���;�����;�/�¦k���f�����;���;�)���N�����F��¤{�����@���;�@�2¤"�����¡�����@���}���z���@�����;�����;���%�S���������F��@�������f�����xÒY�;�%�3�����@Ý����@§X�����¾���;�I�������z�@��%�F���%�z�����}�@���������{���I�xÒY�;�%�f�@��£F�@����Ñ;�N�����F���¾îÜ�@���z�X�@�z�;§������"�����N���"�@�/���z�@�;���@�����;�2�f�@�/�@ �Ò��;�%�¾�@�I���;�)���;��@���@���������9�@���Ü���;����£F�1�@�{¤f�;���/�@�{�%�F���%���z���¡�%�O���¢�%©��@�������;�9¤{������ �������I�z�������;�/�ïbð�ñ ò�ñ5ó#ôöõY÷xôcøSùaúSû�üNýSþ�ÿ���������ý���� ��ÿ�����ý��@ÿ��������������aý������������������! #"%$&���'�����(���)���+* ��,-�����(�.��������/���02ôö÷�ó+ñ 1/ñ.243\÷65�ø�7{øI÷98

: ñ 1/ñ ;=<xô?>bõ\ûXõ�8Xô?>�3�@bùYûBA¡ý��6CD"E�(�BCD�����������aý��������FC�0HGXýI��CKJ6L�0)ò&MONP5#õ�@-QSRYøI8Xõ�T9ô�R�U�VWMcõK÷ N.TXVYN.Z�Möôöù�<xõ�@bùYû9[�\�\][^ 2�ñ`_<xõYúKúYô�û`a¡ñ9b%øSú�øc7zõ�@bô�û�d}ñ�a�øS÷�8 @bôO3IMöô�ûBeBP�`�\ÿ��!���.��ÿI� �¾ýgfEh@ýgf���þ#ÿ����E�D�Pi����`���������6ikû�VW@bõK÷P>bôORYõ�jlk3ø�MOM�ûnmcoIo mp�q]r]rIsYtguIu6vIw�x6yPz�{I|Pw�yI}6{#~��P{�r� dfñ���øS÷�8Xõ�@��]363�@�8XõAøI÷98��fñ a¡ñ9b�3\ù�N.>�>bôöùYû����E�(ü'����`�öÿ��l���� Aü����!��ý��S�`�����l�!�4 ���6��0�Q8�85ôöù�3\÷.j(;�õYù�Möõ�7zû�[�\I\I[� 1/ñn_^ø�TFTkø;û : ñ'k�õcMOT�û : ñBbI3�<x÷xù�3S÷)û�bXñB�Möôöùaùaô�8XõYùYûW��������i���,�ÿ����l�������F D�K�����F��������ýgf��K�� �hÿ]�c�����K���+�����( ��D���������l���

h@ý�f���þ�ÿ�����0nQ8.8Xôöù�3\÷ j�;�õYù�Möõ�7zû'm�o�o]�� q]r]rIsYtguIu6vIw�x6yPz�{I|Pw�yI}6{#~��P{�rPu�s6yPwI�I{ z�r vIu]{6z+qP{��.s]s� q]r]rIsYtguIu�| v��9�I���.vn~�z�wc�9u�s6y6w��Ix.z�rPvIu6w�sP{��PyIrP�6�+�6x6�

�

Conserving the flux in digital simulations by using the box method on unequally spaced grids

Manfred Rudolph

Friedrich Schiller Universität Jena

Institut für Anorganische und Analytische Chemie

It will be demonstrated that the partial difference equations describing a kinetic-diffusion problem can be discretized in such a way that the integral flux conservation property of the exact equations will be preserved by the discretized ones. That means, when executing simulations on exponentially expanding grids, the computed flux becomes virtually independent of grid expansion. It will be shown why this property will be automatically attained when discretizing the underlying partial differential equations on a transformed equally spaced grid with the aid of the box (volume element) method. It can be done with the smallest possible number of grid points even on strongly expanding grids without affecting the accuracy of the flux computation provided the grid expansion Y∆ remains smaller than 0.5 and the distance of the fist concentration point from the electrode is sufficiently small. The mathematical explanation of the flux conservation property given for a simple diffusion problem can be readily extended to more relevant systems involving an arbitrary number of chemical reactions coupled with the charge transfer processes.

Contribution: Higher-order spatial discretisations in digital simulations on an arbitrarily spaced grid.

Dieter Britz and Jörg Strutwolf

Some higher-order formulae for first and second spatial derivatives on arbitrarily spaced grids were constructed and tested. A good compromise between ease of programming and accuracy appears to be a one-sided multi-point current approximation and an asymmetric four-point, second-order approximation to the second derivative. This approximation allows the use of a convenient small extension of the Thomas algorithm. Also, a general algorithm for the generation of a first- or second derivative approximation on an arbitrarily spaced grid, using any number of points for the approximation and referring to any point within that group, is presented.

Recent extensions of the patch−−adaptive strategy for electrochemical kinetic simulations

L. K. Bieniasz

Institute of Physical Chemistry of the Polish Academy of Sciences, Molten Salts Laboratory, ul. Zagrody 13, 30-318 Cracow, Poland.

Tel. /fax.: (+48 12) 266 03 41. E-mail: nbbienia@cyf-kr.edu.pl, URL: http://www.cyf-kr.edu.pl/~nbbienia

Keywords: computational electrochemistry; adaptive grid strategies; liquid-liquid systems;

amalgam electrodes; electrochemical biosensors; pattern formation at electrodes.

The recent extensions of the finite-difference patch-adaptive strategy for electrochemical kinetic simulations [1], developed by the author [2-10], will be discussed. The strategy is a good candidate for a fully automatic simulation method, capable of a dynamic local adjustment of the spatial and temporal grids at run time, to meet the requirements of the developing solution features. This has been previously demonstrated [2-6] for a number of representative example kinetic models involving exclusively distributed unknowns, and defined over a single space interval in one-dimensional space geometry, under local boundary conditions. The extensions to be discussed [7-10] refer to models involving simultaneously distributed and localised unknowns, models defined over multiple space intervals, and models with non-local boundary conditions, still assuming one-dimensional space geometry. Localised unknowns are common in electrochemical kinetics, due to the presence of adsorption, or in the studies of electrocatalytic reactions. Multiple space intervals occur, among other things, in the models of liquid-liquid systems, amalgam electrodes, and electrochemical biosensors. Non-local boundary conditions are of interest in connection with the studies of pattern formation on electrodes. The principles of the extended strategy will be explained, and its performance will be evaluated, using simple examples of such problems. References [1] D. Britz, Digital Simulation in Electrochemistry, Springer, Berlin, 1988. [2] L. K. Bieniasz, J. Electroanal. Chem. 481 (2000) 115. [3] L. K. Bieniasz, J. Electroanal. Chem. 481 (2000) 134. [4] L. K. Bieniasz, C. Bureau, J. Electroanal. Chem. 481 (2000) 152. [5] L. K. Bieniasz, Electrochem. Commun. 3 (2001) 149. [6] L. K. Bieniasz, Electrochem. Commun. 4 (2002) 5. [7] L. K. Bieniasz, J. Electroanal. Chem. 527 (2002) 1. [8] L. K. Bieniasz, J. Electroanal. Chem. 527 (2002) 11. [9] L. K. Bieniasz, J. Electroanal. Chem. 527 (2002) 21. [10] L. K. Bieniasz, J. Electroanal. Chem. 529 (2002) 51.

NADH Electrocatalytic Oxidation at Carbon Paste Electrodes Modified

with Meldola Blue Adsorbed on Zirconium Phosphate

Carmen Ioana Ladiua, Ionel Catalin Popescua, Lo Gortonb aDepartment of Physical Chemistry, “Babes-Bolyai” University, 3400 Cluj-Napoca, Romania bDepartment of Analytical Chemistry, Lund University,P.O. Box 124,SE –22100 Lund,Sweden

Abstract Continuing our preoccupation on the NADH electrocatalytic oxidation

at different modified electrodes [1], basic electrochemistry of carbon paste electrodes modified with Meldola Blue adsorbed on zirconium phosphate (MB-ZP-CPE) as well as their ability to electrocatalytically oxidize NADH have been studied. Various types of carbon powder (glassy carbon (Sigradur K, Sigradur G) and graphite powder) were used to obtain MB-ZP-CPEs. Cyclic voltammetry measurements, performed in tris buffer solution (pH 7), showed that MB-ZP-CPEs prepared with Sigradur K exhibited the best-shaped voltammetric response.

Fig. 1. Cyclic voltammograms obtained at MB-ZP-CPEs (Sigradur K) in 0.1M tris buffer solution (pH 7): in the absence (1) and in the presence of 5 mM NADH (2).

Fig. 2. Cyclic voltammograms obtained at MB-ZP-CPEs in 0.1 M tris buffer (pH 7) containing 5 mM NADH (1); 5 mM NADH and 0.2 M Ca2+ (2), and at PEI-MB-ZP-CPEs in 0.1 M tris buffer (pH 7) containing 5 mM NADH (3)

A detailed study was also made by cyclic voltammetry on the NADH

electrooxidation at MB-ZP-CPEs in tris buffer solution (pH 7), containing different concentrations of Ca+2. As expected [2,3], it was noticed that Ca+2 ions have a significant beneficial effect on the NADH electrooxidation, and it is depending on the concentrations of Ca+2 ions. Finally, taking into account that the presence of a positive charge could improve the mediator efficiency [4], the influence of polyethyleneimine (PEI) addition into the carbon paste was investigated. As a general conclusion, it can be stated that carbon paste electrodes modified with Meldola Blue adsorbed on zirconium phosphate and incorporating PEI showed the best behaviour for NADH electrocatalytic oxidation. 1. F. D. Munteanu, L. T. Kubota, L. Gorton, J. Electroanal. Chem. 509 (2001) 2. 2. E. Katz, T. Lötzbeyer, D. D. Schlereth, W. Schuhmann, H-L. Schmidt, J. Electroanal. Chem. 373

(1994), 189. 3. N. Mano, A. Kuhn, J. Electroanal. Chem. 498 (2001) 58. 4. V. Kacaniklic, K. Johansson, G. Marko-Varga, L. Gorton, G. Jönsson-Pettersson, E. Csöregi,

Electroanalysis, 6 (1994) 381.

- 1 2 0

- 9 5

- 7 0

- 4 5

- 2 0

5

3 0

5 5

8 0

- 2 5 0 - 1 5 0 - 5 0 5 0 1 5 0 2 5 0

P o t e n t i a l , m V

Cu

rre

nt,

µA

- 2 0

- 1 0

0

1 0

2 0

- 2 5 0 - 1 5 0 - 5 0 5 0 1 5 0 2 5 0

Potent ia l , mV

Cur

rent

, µA

2

1

1 2

3

Electrochemical biosensor arrays: technology of manufacture and measurements

Andreas Christenson1, Eva Dock1, Sveltana Sapelnikova1, Jan Krejci2, Jenny Emneus1, and

Tautgirdas Ruzgas1

1Department of Analytical Chemistry, Lund University, Box 124, SE-221 00 Lund, Sweden 2BVT Technologies a.s., Hudcova 78, 612 00 Brno, Czech Republic

Compared to single electrodes, arrays have the advantage of measuring several analytes

simultaneously. Due to a possibility of higher sample throughput as well as increased selectivity of analysis electrochemical arrays have become an interesting and important research area. A recent review about electrochemical arrays has been published [1]. Application examples can be found in food, environmental or clinical analytical chemistry where arrays serve a basis for analytical devices with high discriminating power.

Our recent research is focused on screen-printed eight-electrode arrays with the intention to create biosensors for wastewater analysis. The basic array construction can be described as a circular distribution of eight electrodes, where a single electrode in array is a one mm in diameter screen-printed disk of platinum.

In this presentation several issues concerning preparation of biosensor arrays will be discussed summarising our experience in this field. First, electrochemical steady-state and flow-injection cells, enabling equal hydrodynamics at eight electrodes in array, will be presented [2]. Secondly, electrochemical characteristics and reproducibility of manufacture of carbon array electrodes by screen-printing and spraying of carbon/graphite will be compared. Finally, some characteristics of enzyme-modified arrays will be presented regarding reproducibility of their preparation and performance.

[1] R.-I. Stefan, J. F van Staden, H. Y. Aboul-Enein, Electrochemical Sensor Arrays, Crit.

Rev. Anal. Chem., 29 (1999) 133-153. [2] J. Krejci, J. Kupka, T. Ruzgas, Patent title “Cell for chemical analysis”, No: CZ PV 2002-

3611, priority date: 2002-11-01.

ACKNOWLEDGEMENT The European Commission is acknowledged for financial support (INTELLISENS, QLK3-2000-01481).

Development of Biosensors by Spraying Enzymes in Reverse Micelles

Stepan Shipovskov1,2, Andreas Christenson1, Andrey Levashov2, Tautgirdas Ruzgas1

1Department of Analytical Chemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden 2Laboratory of Micellar Enzymology, Department of Chemical Enzymology, Chemical Faculty,

Moscow State University, 119899 Moscow, Russia

tel.: +46 46 222 0103; fax: +46 46 222 4544 e-mail: shipovskov@yahoo.com, stepa@enzyme.chem.msu.ru

Redox enzymes immobilised at electrode surfaces, which catalyse chemical

transformations of the specific analytes, are of the evident interest for analytical chemistry and biotechnology. One of the problems of their application as heterogeneous catalysts is their decreasing catalytic activity when immobilised at solid supports, particularly when developing biosensors operating in non-aqueous media [1 and refs. therein], or e.g., exploiting organic-based carbon inks in screen printing. A possible solution is to entrap the enzyme in the system of reverse micelles [2, 3]. This system consists of surfactant, H2O, and non-polar organic solvent, representing itself water micro-emulsion where polar surfactant “heads” face water, and surfactant non-polar “tails” are oriented towards organic media.

In this work we will report a novel method of immobilisation of enzymes from organic-based carbon inks by spraying the solution of reverse micelles containing enzyme and graphite particles. The developed method allows one to avoid the inactivation of enzyme by the organic media. From the other hand this technique can be exploited to prepare biosensors for measurements in organic media. The characteristics of biosensor prepared by spraying enzymes in reverse micelles will be discussed. References 1. T. Ruzgas, E. Csöregi, J. Emnéus, L. Gorton, G. Marko-Varga, Anal. Chim. Acta, 330

(1996) 123. 2. N.L.Klyachko, A.V.Levashov, A.V.Kabanov, K.Martinek, In: Kinetics and Catalysis in

Microheterogeneous Systems, M.Gratzel, K.Kalianasundaram, eds, Marcel Dekker Inc. 1991, 135

3. S. Shipovskov, E. Ferapontova, T. Ruzgas, A. Levashov, BBA in press.

Nitric oxide (NO) sensor based on myoglobin immobilized on clay-modified electrodes

Steffen Kröning, Frieder W. Scheller and Fred Lisdat

Institute of Biochemistry and Biology, Department of Analytical Biochemistry, University of Potsdam; Karl-Liebknecht-Str. 24/25, 14476 Golm, Germany

e-mail: kroening@rz.uni-potsdam.de

The fast and sensitive quantification of substances capable of scavinging free radicals is of importance for fundamental research as well as for medical purposes. Nitric oxide (NO) is one of the most investigated species. It is a small molecule with free radical character, which is produced by nitric oxide synthase (NOS) from L-arginine. In the human body NO is an important bio-regulatory molecule and plays a significant role in many physiological processes. It is recognized as the endothelium-derived relaxing factor (EDRF) and is a major defense molecule of the immune system against tumor cells. Myoglobin (Mb) is a small water-soluble heme protein, which has a free accessible sixth coordination position of the heme iron so that small molecules and ligands can coordinatively bind to that position. This can be used for the analytical detection of these ligands. The electrochemistry of immobilized myoglobin has been investigated in polyelectrolytes and in surfactant films. Clay films, especially sodium montmorillonite colloid (SMC), can be used as an alternative electrode modifier. They have the advantage of being highly stable with good adsorption properties, high conductivity and penetrability due to their large surface aera. In the present work we report on the direct electrochemistry of myoglobin immobilized on SMC – modified glassy carbon electrodes. Thermodynamic and kinetic properties have been determined: The heterogenous electron transfer rate constant of the immobilized myoglobin was found to be strongly influenced by the ionic strength of the solution. The formal potential E°‘ of Mb within the clay was determined with –0.380 ± 0.010 V vs Ag/AgCl (pH 7.5). The interaction of myoglobin/clay/glassy carbon electrode (Mb/clay/GCE) with nitric oxide has been investigated. The results showed a shift of the formal potential of the redox system Mb(FeII)/Mb(FeIII) towards negative potentials with increasing NO concentrations. This is an argument that NO coordinates to the iron center of myoglobin. The effect was found to be sensitive to nanomolar (nM) NO concentrations. At micromolar (µM) NO concentrations the Mb(FeII)/Mb(FeIII) redox waves tended to decrease and a new reduction peak at –0.75 V appeared. This peak can be also used for NO analysis but at higher concentrations. The influence of oxygen was also investigated.

Recent applications of the conducting polymer polyaniline

in smart coatings

Dr. J. Posdorfer, Ormecon Chemie GmbH & Co. KG, Ammersbek This contribution describes the capabilities of the conducting polymer polyaniline (PAni) as a nano-particulate function element in smart coatings. Due to new dispersion techniques and the unique set of properties of this materials class recent developments generated various new coatings for different applications. Industrial applications are in the field of the manufacturing of printed circuit boards, in corrosion protection, and especially in other functional surface coatings like electrodes for electroluminescence (EL) or hole-injection layers (HIL) in light emitting diodes (LED). Recent results will be presented showing that PAni can be efficiently used in EL or LED devices. Intensive investigations on the influence of conductivity, morphology and the work function onto device performances have led to commercially available PAni dispersions. Using waterborne PAni dispersions for the generation of HILs the final device performance in LEDs could be significantly improved.

Piezoelectric microgravimetry study of adsorption of selected compounds of biological importance

Agnieszka Kochmana, Karsten Hauptb, Tibor Hianikc, Victor Gajdosc, Pankaj Vadgamad,

Giosio Faraced, Wlodzimierz Kutnera

aInstitute of Physical Chemistry, Kasprzaka 44/52, 01-224 Warsaw, Poland

bLund University, S-221 Lund, Sweden, cComenius University, Mlynska Dolina F1, 84248 Bratislava, Slovakia,

dQueen Mary University, Mile End Road, London E1 4NS, UK E-mail: agakoch@ichf.edu.pl

Adsorption of some biologically significant compounds, such as pirimicarb (PIR) pesticide, avidine (AV) protein, and 7-N nucleotide, at an Au chemically modified electrode of a quartz crystal piezoelectric transducer (QCPT) was investigated by using piezoelectric microgravimetry with an electrochemical quartz crystal microbalance (EQCM). This adsorption was utilized for determination of the compounds under flow injection analysis (FIA) conditions.

PIR was determined by using QCPT modified with a molecularly imprinted polymer (MIP) thin film. The MIP film was prepared by a UV light polymerization of a mixture of suitable functional and cross-linking monomers, polymerization initiator, and PIR template. Next, the template was washed out leaving molecular cavities in the MIP film of the size and shape of the template molecule. Then, PIR was determined (limit of detection 0.22 mM and linear concentration range 0.36 to 1.5 mM) by measuring the frequency change, ∆f. FIA peaks rather than steps of ∆f vs. time were formed indicating lack of chemical interactions between PIR and MIP.

AV was determined by using QCPT coated with a poly(pyrrole)-biotin film prepared by electropolymerization of pyrrole under cyclic voltammetry conditions (CV) in the presence of biotin. The growth of the biotin-modified poly(pyrrole) film was monitored by simultaneous measurement of the CV and piezoelectric microgravimetry curves with the use of an electrochemical quartz crystal microbalance (EQCM) under quiescent solution conditions. Steps rather than peaks were present in the FIA curve due to consecutive injections of the AV samples. These steps were smaller the larger was the injection number indicating that AV interacted chemically with the biotin sites of the poly(pyrrole) film and that these sites were gradually saturated.

A 7-N nucleotide was determined by virtue of hybridization with a single strand of complementary deoxyribonucleic acid (DNAss). For that purpose QCPT was modified with self-assembled monolayers (SAMs) of DNAss. Two modification procedures were adopted, i.e., (i) a direct procedure using ω-thiolated DNAss to form SAMs and (ii) an indirect procedure using ω-thiolated mercaptoundodecanoic acid (MUA) esterified with AV for SAMs; then, DNAss modified with biotin was attached to the immobilized MUA by the AV-biotin non-covalent bonds. The FIA steps and peaks were obtained for DNAss immobilized according to the (i) and (ii) procedure, respectively, after injecting samples of 7-N nucleotide.

Inorganic monolayers as templates for two-dimensional and three-dimensional arrays of polyaniline and metal nanoparticles

Malgorzata Chojak, Krzysztof Miecznikowski, Pawel J. Kulesza

Department of Chemistry, University of Warsaw, Pasteura 1, PL-02-093 Warsaw, Poland

The ability of a polyoxometallate (dodecamolybdophosphate) to form negatively charged monolayers on solid electrode surfaces is explored here to perform immobilization of monomeric (anilinium) units followed by electropolymerization within the monolayer. Consequently, hybrid films containing ultrathin conducting polymer (polyaniline, PANI) layers can be formed. By repeated and alternate treatments in solutions of dodecamolybdophosphate anions and anilinium cations, the amount of the material can be increased systematically in a controlled fashion leading to stable three-dimensional multilayer hybrid assemblies. The fact, that formal potentials of the dodecamolybdophosphate redox processes appear in the potential range where PANI is conductive, allows the system to operate reversibly and reproducibly in acid electrolyte. We have also extended this concept to the formation of inorganic templates from metal (nickel or cobalt) hexacyanoferrates. In the latter case, an organic precursor monolayer is initially formed.

Although we have not addressed lateral conductivity of PANI layers, this work has much in common with recent concepts of preparation of “two-dimensional” conducting polymer layers. Our approach is based on the electrochemical polymerization of surface-confined anilinium (monomer) ions that are electrostatically attached and chemically attracted to a negatively charged self-assembled polyoxometallate or cynaometallate monolayer. This inorganic template is demonstrated to influence the formation of the organic component. The layer-by-layer self-assembly scheme has also been extended to the formation of multilayer films composed of alternately deposited inorganic and PANI monolayers. An important feature of our multilayer system is that the PANI interlayers are electronically/ionically conducting in the potential range where the inorganic layers are electroactive. This observation implies good electrical contact in the vertical dimension. Fabrication of fairly thick hybrid films characterized by fast dynamics of charge transport and capable of effective mediation of redox reactions in solution is feasible. Further, we have also found that polyoxometallate can also form a protective monolayer on a metal (Pt) nanoparticle. Consequently, three-dimensional arrays of metal nanoparticles, conducting polymer and polyoxometallate interlayers can be produced on common electrode substrates. Our ultimate goal is to produce not only durable conducting polymer monolayers having desired functions (e.g. reactivity or charge injection capabilities) but also dense robust films of controlled architecture and hierarchical organization in which concentration of functional redox centers (e.g. catalytic metal nanoparticles) is high. This research is of importance to the development of catalysts, sensors, luminescent devices, light emitting diodes and organic-inorganic electronics.

Recent studies of substituent effects on the electrochemical reduction of

benzylideneacetophenones (Chalcones)

Jovan Alston, Albert Fry

A large number of corrrelations between cathodic reduction potentials and Hammett substituent constants have been reported in the literature, largely by Zuman and coworkers. Typically one measures the voltammetric reduction potentials of a series of five to ten aromatic compounds of a given structural type bearing different substituents in the aromatic ring; one then plots the reduction potentials against the Hammett sigma values of the substituents. Where a linear correlation is found, the slope of the line can provide mechanistic information on the nature of the electrode process. We have synthesized more than thirty benzylideneacetophenones (chalcones) bearing one or more substituents in one or both aromatic rings. We find a good linear correlation with Hammett values, except for the 4-dimethylamino group, which lies distinctly away from the line. Zuman observed similar behavior and proposed use of a so-called "electrochemical sigma value" for the dimethylamino group to bring it in alignment with the correlation line. We find, however, that use of the "pure-inductive" set of substituent constants developed by van Bekkum, Verkade, and Wepster, instead of the Hammett constants, not only provides a distinctly better correlation but also eliminates need to treat the dimethylamino group as a special case. We are also exploring computational alternatives to the traditional substituent constant-based approach to such correlations. We hope that quantum mechanical calculations can be used eventually to replace substituent constants in this type of study. If so, we may ultimately be able to develop a single line to include a wide variety of types of compound, rather than having to develop a different line for every class of compound as is presently the case. It is not clear what level of sophistication will be required in the quantum mechanical calculations in order to achieve any arbitrary degree of accuracy. The presentation will report our progress in this area.

Spectroscopic and electrochemical properties of self-assembled complexes of some C60 adducts and water-soluble Zinc porphyrins in the Langmuir and Langmuir-Blodgett films

Renata Marczak,a Krzysztof Noworyta,a Wlodzimierz Kutner,a Gadde Suresh,b and Francis D’Souza b,*

a Institute of Physical Chemistry, Kasprzaka 44/52, 01-224 Warsaw, Poland

b Department of Chemistry, Wichita State University, Wichita KS 67260-0051, USA

The C60-pyridine, C60py, and C60-imidazole, C60im, adducts formed self-assembled Langmuir films on aqueous solutions of zinc tetrakis (N-methylpyridinium)porphyrin cation, Zn(TMPyP), or zinc tetrakis (4-sulfonatophenyl)porphyrin anion, Zn(TPPS). The C60 adducts (acceptors) were axially ligated by Zn porphyrins (donors) forming relatively stable donor-acceptor dyads. The Langmuir films were characterized by isotherms of surface pressure and surface potential vs. area per molecule as well as by the Brewster angle microscopy imaging. All systems formed aggregated Langmuir films of the "expanded liquid" type. Extensive compression of the films resulted in two-dimensional phase transitions. The area per molecule at infinite dilution of the adducts in films increased for water < Zn(TPPS) < Zn(TPMyP) solution. Values of the determined and calculated area per molecule were conclusive with respect to orientation of the complexes in the films. The Langmuir films were transferred, by using the Langmuir-Blodgett technique, onto both uncoated and ITO electrode coated quartz slides for the UV-vis spectroscopic and voltammetric studies, respectively. The former revealed that Zn porphyrins were transferred together with the adducts in films and that the transfer efficiency increased in the order: C60py-Zn(TPPS) < C60py-Zn(TMPyP) < C60im-Zn(TPPS) < C60im-Zn(TMPyP), in accord with the increase of stability of the respective complexes in solutions.

Syntheses, crystallographic structures, electrochemical and spectroscopic properties of rhenium(I)tris-carbonyl complexes.

Rafal Czerwieniec and Andrzej Kapturkiewicz

Institute of Physical Chemistry Polish Academy of Sciences; 01224; Warsaw; Kasprzaka 44/52; Poland

The reactions of Re(CO)5Cl with the chelating ligands L = 2-(2-pyridyl)-N-methylbenzimidazole, 2-[2]pyridyl-benzoksazole and 2-[2]pyridyl-benzothiazole afforded

neutral fac�Re(CO)3(L)Cl and ionic fac�Re(CO)3(L)(acetonitrile)�PF6� complexes with structures

confirmed by means of the X-ray measurements. UV-VIS absorption and emission properties have been studied at room and 77K temperatures in order to determine the nature of the lowest electronically excited states. Electrochemical behaviour of the investigated

fac�Re(CO)3(L)Cl and Re(CO)3(L)(acetonitrile)�PF6� complexes have been studied using cyclic

voltammetry and square-wave polarography. Possible applications of the studied complexes in electroliuminescent or electrochemiluminescent devices will be briefly discussed.

Electrochemical and spectroelectrochemical investigations of novel aminothiophenes

D. Rohde, L. Dunsch, A. Noacka, H. Hartmanna IFW-Dresden, D-01069 Dresden, Germany; a FH-Merseburg, D-06217 Merseburg, Germany

Aminothiophenes are among the most interesting structures in dye chemistry and material science in the last few years.1 These new materials exhibit a strongh tendency to form stable radical cations. Furthermore N,N-diaryl-substituted 2-aminothiophenes form amorphous glasses as well in which the radical cations possess strong mobility. These materials can be used for constructing optical and/or electronic devices, such as organic luminescence diodes 2 or organic field-effect transistors 3. At tetrathienylethylene (R = mercapto) it has been shown by X-ray structure analysis that the neutral form B has a planar structure, while for the cationic from A gives a twisted arrangement of the molecule parts around 90°.4

SS“

SS“

SS“

SS

RR“

R1n

SS SS SS SS

RR

R1n

SS SS SS SS

RR

R1n

““•

•

- n e-+ n e-

R = morpholin; dimethylamin; diphenylamin

R1 = ethylen; p-phenylen; o-phenylen; biphenylen; naphthylen; thiophen; phenyl; 1,3,5-phenylen

n = 1; 2; 3

AB C

We investigated the cationic aminothiophenes A (Fig. 1). For this type of polymethines, we observed a long-wave absorption in UV-VIS. The charge transfer in solution at anodic and cathodic potentials has shown that one electron is transferred for each chromophore unit simultaneous. In the case of n = 2 or 3 the ESR-signal was not found for B, while for n = 1 a radical structure was detected. But for C we find a signal in each case (n = 1; 2; 3). The results give a strong reference for the twisted arrangement of the molecule parts. 1 Wuerthner, F., Thalacker,C., Matschiner, R., Kukazuk, K. and Wortmann, R., Chem.

Commun. 1739 (1998) 2 Rothberg, L. J. and Lovinger, A. J., J. Mat. Res. 11, 3174 (1996) 3 Brown, A. R., Jarratt, C. P., deLeeuw, D. M. and Matters, M., Synth. Met. 88, 37 (1997) 4 Suzuki, T., Shiohara, H., Sakimura, T., Tanaka, S., Yamashita, Y. and Miyashi T.,

Angew. Chem. 104, 454-456 (1992)

The Electrochemistry of Ir-Pincer Complexes and Their Electrochemically Activated Intramolecular C-H Bond Activation

F. Novak1, B. Speiser1, H.A.Y. Mohammad2, H.A. Mayer2, G.M. Quintanilla3

1Institut für Organische Chemie, Universität Tübingen; Auf der Morgenstelle 18, D-72076 Tübingen Germany; 2Istitut für Anorganische Chemie, Universität Tübingen; Auf der Morgenstelle 18, D-72076

Tübingen Germany; 3Dpto de Química Orgánica, Universdad de Alcála, Spain

An electrochemical investigation of the novel Ir(III) complexes 1, 2 and 3 has been done using cyclic voltammetry. The complexes are in the center of our interest because of their catalytic activity for dehydrogenation reactions e.g. con-version of cylkoalkenes to arenes[1]. The aim of the work was (i) to prove the existence of the complex 1 as a new species and (ii) to gain the parameters of the redox processes of the complexes.

PtBu2

PtBu

IrMeO Cl

H

PtBu2

PtBu2

IrMeO Cl

H

PtBu2

PtBu2

Ir Cl

1 2 3 Despite quite similar structure, the redox properties of the species are very different [2]. 1 undergoes one-electron oxidation with slow follow-up reaction. On the other hand, the voltammetric observation of 2 reveals electrochemically induced intramolecular C-H activation after one-electron oxidation forming 1+ and a “square-scheme” mechanism is proposed for this process (Fig.1). We also tried to replace intra- by intermolecular C-H activation and we followed the system 2 + cyclooctane with cyclic voltammetry. We observed the formation of a new species with a formal potential close to 1.

2

1

-e

-e

1+

2+

K2/1 K2+/1+

X

Kx

+ H2 + H2

Fig. 1

Complex 3 exhibits even more complicated voltammetric behaviour with a further oxidation step where an Ir (V) species is produced. From computer simulations of the cyclic voltammograms, we have also obtained some electrochemical, thermodynamical and kinetic data for the redox processes of these compounds and these will be discussed. This work was supported by the Deutsche Forschunggemeinschaft within the Graduiertenkolleg “ Chemie in Interphasen” References: [1] M. Gupta, Ch. Hagen, W. C. Kaska, R.E. Cramer, C. M. Jensen; J. Am. Chem. Soc., 1997, 119, 840-841 [2] Mohammad, H. A. Y.; Grimm, J. C.; Eichele, K.; Mack, H.-G.; Speiser, B.; Novak, F.; Quintanilla, M. G.;

Kaska, W. C.; Mayer, H. A.; Organometallics; 2002; 21; 5775-5784

Textile Electrode Structures and Applications

Sabine Gimpel, Uwe Möhring, Walther Müller-Litz, Andreas Neudeck, and Wolfgang Scheibner

Textilforschungsinstitut Thüringen-Vogtland e.V., Greiz

The integration of microelectronic devices in textiles /1/ can be very useful for communication and controlling aims, especially for occupational clothes and medical applications. Unfortunately microelectronic devices are not really integrated into textile structures: in most cases, they are “stitched” on the fabric or hidden in the textile structure /2/. Textiles are inherent microstructures with fantastic properties: They are flexible and much more mechanically stable than foils. However till now we do not have the right materials or we apply the wrong materials to use textile structures as electrodes, sensors and even as parts of a microelectronic structure. The aim of this proposal give an overview about promising materials and composite structures as well as techniques to prepare them on textile substrates. Electrochemical or galvanic deposition processes are the cheapest way to coat or to modify a precursor structure. Metallized threads with a low conductivity are already on the market. They are used to produce textiles to shield electromagnetic waves. The metal layers are thin enough to be undamaged in the textile processing to form the final product, but they are too thin to achieve the conductivity necessary for the applications mentioned above. Further more conducting inks are available to form a pre-cursor structure on textile substrates. The conductivity of such pre-cursor structures are insufficient for electrodes, sensor structures and to build electronic devices but sufficient for a further galvanic metal deposition, by using special coating procedures and galvanic baths. The precursor structure can be electrochemically modified by metals and even noble metals, as well as by electro-polymerisation /3/ and electrodeposition of paint. The metals can be electrochemically oxidized to form oxide structures with semiconducting properties. The textile precursor structure permits to coat various zones by various metals, metal oxides and even new materials. First applications of textile substrates structured in this way will be presented. REFERENCES : /1/ See for example: W.D. Hartmann, K. Steilmann, A. Ullsperger, high-tech-fashion, Heimdall Verlag, Witten, 2000 ; B.

Lancaze, Funktionelle Textilien, mitttex, 1 (2000) 14 ; Rainer Klose, Denkende Kleider - automatisch wärmen oder kühlen: Ein neues Material revolutioniert die Kleiderwelt, Facts Interactiv. ; B. Müller, “Kraft aus Kunststoff”, Bild der Wissenschaft, 10 (2000) ; G. Wallace, “Smart bra heralds age of intelligent fabrics”, Technical Textiles International, 07/08 (2000) 32.

/2/ See for example: Klaus Rönnebeck, Patent, Notrufsystem in Kinder- und Jugendbekleidung, DP 198 43 237 2 ; Symposium of

Wearable Computer (1. Meeting 1997 by Georia Tech and IEEE; 2. Meeting 1998 Pittsburg, 3. Meeting 1999 San Francisco, 4. Meeting 2000 Atlanta) ; International Meeting of Wearable Computing 2000 Washington sponsored by Xypernaut (McLean).P. Lukowitz, G. Tröster, “Wearable Computing”, Bulletin ASE/VSE, 9 (2000) 15 ; Electro Textiles Company Ltd., www.electrotextiles.co, Peratech, www.peratech.co.uk/profile/

/3/ See for example: M. Maumy, P. Capdevielle, P.H. Aubert, M. Roche, P. Audebert, A. Neudeck and L. Dunsch, J. Electroanal.

Chem. 470, (1999) 77 ; A. Neudeck, L. Guyard, P. Audebert, L. Dunsch, P. Guiriec and P. Hapiot, Acta Chem. Scand., 53 (1999) 867.

Electron transfer generation and annihilation of the excited MLCT (metal-to-ligand-charge-transfer) states

Pawel Szrebowaty and Andrzej Kapturkiewicz

Institute of Physical Chemistry Polish Academy of Sciences; 01224; Warsaw;

Kasprzaka 44/52; Poland

Tris(4,7-diphenylo-1,10-phenanthroline)ruthenium(II) Ru(baph)32+ and tris(2,2'-bipyridine)-

ruthenium(II) Ru(bipy)32+ complexes with four series organic co-reactants Q in 0.1 M

(C2H5)4NPF6 acetonitrile solutions were employed as systems in the electrochemically generated chemiluminescence (ECL) and electron transfer quenching studies. The MLCT (metal-to-ligand charge-transfer) excited states of *RuL3

2+ are formed in electron transfer reactions (ET) with electron donors (nitroaromatic or quinone radical anions and N-methylpyridinium radicals) as well as with electron donors (aromatic amine radical cations). The yields for the excited state formation were estimated by means of the triple-potential-step technique. On the other hand quenching of the excited states *Ru(bipy)3

2+ and *Ru(baph)32+

with the same organic co-reactants have been studied. using steady-state Stern-Volmer approach. The main purpose of the performed studies was the quantitative analysis of both, complementary electron transfer reactions with the same set of the kinetic parameters. Special attention have been paid on the role of spin conversion between two spin forms of an activated complex in the proposed reaction's mechanism kinetic schemes.

Electrochemical and spectroelectrochemical investigations on symmetrical and unsymmetrical substituted spiro-compounds

Thomas Ebert, Josef Salbeck

University of Kassel Macromolecular Chemistry and Molecular Materials, FB 18, Physics

Heinrich- Plett- Str. 40, 34132 Kassel (Germany) Fax: +49 561/804-4555, E- Mail: t.ebert@uni-kassel.de

p-Oligophenyles are well known as compounds with interesting electronic properties. The basic problem is their very poor solubility. Instead of substituting the p-Oligophenyles with aliphatic ligands to increase their solubility which is a very common method, but disturbs the conjugated ð- system, the problem was solved by spiro- linkage of two p-Oligophenyles to yield Spiro- p-oligophenyl- compounds with a much better solubility combined with nearly unchanged electronic properties. As a result it is now possible to study the redox behavior of the undisturbed oligophenyl- ð- system in solution. Through substitution of Spirobifluorenes, the central moiety of Spiro- p-oligophenyles, with appropriate electron donating and electron accepting groups it is possible to fine tune the electronic and spectroscopic properties of the resulting compounds. These properties make the compounds favorable for the application in organic light emitting devices (OLEDs) or organic solar cells. I want to present some recent results in the characterisation and interpretation of the electrochemical and spectroelectrochemical properties of these materials. Keywords electrochemistry, spectroelectrochemistry, Spiro- p-oligophenyles,

Spirobifluorene, OLED, solar cell

Ormosil Sandwiched Bacteriorhodopsin--A Novel Photoelectrochemical Sensor

P.C. Pandey, B.C. Upadhyay and R.A. Misra Department of Chemistry, Faculty of Science

Banaras Hindu University,Varanasi-221005,India

The photo-electrochemistry of D 96N bacteriorhodopsin (BR) is reported based on chronoamperometry using ormosil sandwiched BR on antimony-tin oxide(ATO) electrode.The absorption spectra of ormosil sandwiched BR on ATO electrode shows broader absorption peak between 550 nm suggesting the stability of immobilized BR on ATO.The effect of light intensity and immobilization protocol on photo-electrochemistry are studied.It has been found that photo-electrochemical behaviour of ormosil encapsulated BR has remarkable dependence on immobilization technique.The result on three immobilization techniques are reported.The photo-electrochemistry oformosil sandwiched BR on ATO electrode is studied using a one compartment home made electro- chemical cell having an arrangement of device for external light source. A good correlation between peak current and the concentration of amine and ammonium compound is recorded. The calibration curves for the analysis of ammonium ion and amines based on the measurement of photo-current are reported.

Redox potentials determined by photomodulated voltammetry and bond dissociation

energies of phenoxyl radicals

Claudia Mureºanu and Günter Grampp

Institute of Physical and Theoretical Chemistry, Graz University of Technology, Technikerstraße 4/I, A – 8010 Graz, Austia

Reduction half – wave potentials of several phenoxyl radicals have been measured by

photomodulated voltammetry in acetonitrile. Two of the investigated radicals exhibit a reversible behavior, but for the others a rather irreversible or quasi – reversible nature of the heterogeneous electron transfer has to be considered. The measured reduction half – wave potentials are within 70 mV of reported values for formal one – electron potential of the phenolate/phenoxyl couple. That is why one can assume that the half – wave reduction potentials values are close to the standard potentials of the electron transfer reactions. Differences of the BDE(O-H) for the substituted phenols relative to the BDE (O-H) of the phenol were calculated and compared with corresponding data in the gas – phase.

Name Address Email

Baltes, Norman Abt. J. Heinze, Elektrochemie d. Uni Freiburg, Stefan-Maier-Str. 21, 79104 Freiburg

Norman.Baltes@physchem.uni-freiburg.de

Bieniasz, L. K. Inst. of Phys. Chemistry; Polish Academy of Sciences; Molten Salts Laboratory, ul. Zagrody 13, 30-318 Cracow, Poland

nbbienia@cyf-kr.edu.pl

Boldt, Frank-Mario Freiburg Materials Research Center (FMF) and Institute of Physical Chemistry, University of Freiburg, Stefan-Meier-Str. 19, 79104 Freiburg

frank-mario.boldt@ physchem.uni-freiburg.de

Bonekamp Jörg Universität zu Köln, Luxemburger Str. 116, 50939 Köln jb.bonekamp@uni-koeln.de

Britz, Dieter Dept. of Chemistry, University of Aarhus, Langelandsgade 140, 8000 Aarhus C

db@chem.au.dk

Christenson, Andreas Department of Analytical Chemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden

Andreas.Christenson@analykem.lu.se

Czerwieniec, Rafal Institute of Phys. Chemistry; Polish Academy of Sciences; 01-224 Warsaw, Kasprzaka 44/52 Poland

rafczerw@ichf.edu.pl

Ebert ,Thomas University of Kassel; Macromolecular Chemistry and Molecular Materials, FB 18, Physics; Heinrich- Plett- Str. 40, 34132 Kassel (Germany)

t.ebert@uni-kassel.de

Etienne, Mathieu Anal. Chem. – Elektroanalytik & Sensorik; Ruhr-Universität Bochum; Universitätsstr. 150; D-44780 Bochum, Germany

mathieu.etienne@rub.de

Fischer, Bert Fraunhofer IAP, Geiselbergstr. 69, 14476 Golm fischer@iap.fhg.de

Fry, Albert J. Wesleyan University, Chemistry Department, Middletown, CT 06457 USA afry@wesleyan.edu

Janietz, Silvia Fraunhofer IAP, Geiselbergstr. 69, 14476 Golm janietz@iap.fhg.de

Kalisz, Ewa Maria Inst. f. Phys. u. Theor. Chemie, Techn. Universität Graz, Technikerstr. 4/I, A-8010 Graz

kalisz@ptc.tugraz.at

Kapturkiewicz, Andrzej Institute of Physical Chemistry Polish Academy of Sciences; 01224; Warsaw; Kasprzaka 44/52; Poland

akaptur@ichf.edu.pl

Kochmann, Agnieszka Inst. of Phys. Chemistry; Polish Academy of Sciences; Ul. Kasprzaka 44/52; 01-224 Warszawa, Poland

agakoch@ichf.edu.pl

Kröning, Steffen Institute of Biochemistry and Biology, Analytical Biochemistry, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Golm, Germany

kroening@rz.uni-potsdam.de

Kulesza, Pawel J. University of Warsaw; Department of Chemistry; Pasteura 1; PL-02-093 Warsaw, Poland

pkulesza@alfa.chem.uw.edu.pl

Kutner, Wlodzimierz Inst. of Phys. Chemistry; Polish Academy of Sciences; Kasprzaka 44; 01-224 Warszawa, Poland

wkutner@ichf.edu.pl

Ladiu, Carmen-Ioana Dept. Anal. Chem., Lund University, PO Box 124, SE-22100 Lund, Sweden Ioana.Ladiu@analykem.lu.se

Ludwig, Kai Institut f. Org. Chemie Universität Tübingen; Auf der Morgenstelle 18; 72076 Tübingen

kai.ludwig@uni-tuebingen.de

Mandler, Daniel Dept. Inorg. Anal. Chem., The Hebrew University Jerusalem 91904 Israel mandler@vms.huji.ac.il

Marczak, Renata Inst. of Phys. Chemistry; Polish Academy of Sciences; Ul. Kasprzaka 44/52; 01-224 Warszawa, Poland

rmarczak@ichf.edu.pl

Märkle, Wolfgang Institut f. Org. Chemie Universität Tübingen; Auf der Morgenstelle 18; 72076 Tübingen

wolfgang.maerkle@uni-tuebingen.de

Meerholz, Klaus Universität zu Köln, Luxemburger Str. 116, 50939 Köln klaus.meerholz@uni-koeln.de

Miecznikowski, Krzysztof

University of Warsaw; Department of Chemistry; Pasteura 1; PL-02-093 Warsaw, Poland

kmiecz@alfa.chem.uw.edu.pl

Misra, R.A. Chemistry Department, Banaras Hindu University, Varanasi, India; B31/46AH, Bhogabir, Lanka, Varanasi-221005, India

ramisra@banaras.ernet.in

Murasanu, Claudia Inst. f. Theor. u. Phys. Chemie, TU-Graz, Technikerstr. 4/1, A-8010 Graz muresanu@ptc.tugraz.at

Neudeck, Andreas Textilforschungsinstitut Thüringen-Vogtland, Zeulenrodaer Str. 42, 07973 Greiz

andreas.neudeck@t-online.de

Nonomura, Kazuteru Dept. of Chem., Phys. Chem. 1, Uni. Oldenburg, PO Box 2503, 26111 Oldenburg

Kazuteru.Nonomura@mail.uni-oldenburg.de

Novak, Filip Institut f. Org. Chemie Universität Tübingen; Auf der Morgenstelle 18; 72076 Tübingen

filip.novak@uni-tuebingen.de

Posdorfer, Jörg Ormecon Chemie GmbH & Co KG; Ferdinand- Harten-Str. 7; 22949 Ammersbek

mailbox@ormecon.de

Ammersbek

Reiter, Sabine Anal. Chem. – Elektroanalytik & Sensorik; Ruhr-Universität Bochum; Universitätsstr. 150 ; D-44780 Bochum, Germany

sabine.reiter@rub.de

Rohde, D. IFW-Dresden, D-01069 Dresden, Germany; a FH-Merseburg, D-06217 Merseburg, Germany

D.Rohde@ifw-dresden.de

Rudolph, Manfred Friedrich Schiller Universität Jena; Institut für Anorganische und Analytische Chemie

cfr@uni-jena.de

Ryabova, Victorya Anal. Chem. – Elektroanalytik & Sensorik; Ruhr-Universität Bochum; Universitätsstr. 150 ; D-44780 Bochum, Germany

victorija.rjabova@rub.de

Schäfer, Dominik Anal. Chem. – Elektroanalytik & Sensorik; Ruhr-Universität Bochum; Universitätsstr. 150; D-44780 Bochum, Germany

dominik.schaefer@rub.de

Schuhmann, Wolfgang Anal. Chem. – Elektroanalytik & Sensorik; Ruhr-Universität Bochum; Universitätsstr. 150; D-44780 Bochum, Germany

Wolfgang.schuhmann@rub.de

Shipovskov, Stepan Department of Analytical Chemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden

shipovskov@yahoo.com

Sklyar, Oleg Deparment of Chemistry, University of Oldenburg, Germany Oleg.Sklyar@uni-oldenburg.de

Speiser, Bernd Inst. f. Org. Chemie, Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen

bernd.speiser@uni-tuebingen.de

Szrebowaty, Pawel Institute of Phys. Chemistry; Polish Academy of Sciences; 01-224 Warsaw, Kasprzaka 44/52 Poland

pas@ichf.edu.pl

Szunerits, Sabine CEA Grenoble; UMR SPrAM 5819; 17, avenue des Martyrs; 38054 GRENOBLE Cedex09, France

szunerit@drfmc.ceng.cea.fr

Tittel, Carsten Institut f. Org. Chemie Universität Tübingen; Auf der Morgenstelle 18; 72076 Tübingen

carsten.tittel@uni-tuebingen.de

Unwin, Patrick R. Department of Chemistry; University of Warwick; Coventry CV4 7AL; UK p.r.unwin@warwick.ac.uk

Zhao, Chuan Department of Chemistry (FB9) Carl von Ossietzky University Oldenburg Ammerlaender-Heerstr. 114-118; (AVZ-A1) D-26129 Oldenburg

chuan.zhao@uni-oldenburg.de

Travel information By train: From the main railway station in Dresden (Dresden Hauptbahnhof) catch a local train (called S-Bahn), specifically S1 with the direction Schöna. The S1 is departing every 30 minutes (for example 12:35; 13:05) and it will need 46 min to reach Königstein. To arrive at the Naturfreundehaus, the river Elbe has to be crossed. This can be done by a ferry, and from the ferry there are about 800 m to the conference site. By plane: From Dresden airport catch a bus to the main railway station. From there follow the suggestions listed above. By car: From Dresden one has to drive on the street +172 (direction Pirna). Stay on this street until you will reach Bad Schandau. Although the street 172 leads to Königstein, following this street will end at the wrong side of the river Elbe and no car ferry is crossing the river in Königstein. Thus, one should drive until Bas Schandau where one may cross the river Elbe on a bridge. From here turn to the left following the direction Possen. From Possen there is a very small street close to the river Elbe which leads back towards Königstein (to a part of Königstein named Halbestadt). The “Naturfreundehaus” is located on the left hand side of the street named Halbestadt 13.

Suggested excursions

Easy: Visiting the famous “Festung Königstein” (a way of appr. 2 km has to be taken to the fortress) The “Festung Königstein” was built at the end of the 16th century and it was not changed yet. 1241 the fortress was mentioned for the first time as a border guarding from Bohemia.

Medium Tour 1 Pfaffenstein; WALKINGTIME: ca. 3 hours TRAIL: Königstein - Cunnersdorfer Str.- Charlottenburg - Quirl - Diebskeller

- Pfaffendorf/ parking place - Pfaffenstein - Nadelöhr - Pfaffendorf – Königstein

WORTH SEEING: Diebskeller, Felsnadel der Barbarine CHARACTER: very nice hiking trail but many steps up to the Pfaffenstein REST: Pfaffendorf; snack bar on top of the Pfaffenstein

Demanding Tour 2 Schrammsteinaussicht; WALKINGTIME: 4.5 hours TRAIL: Bad Schandau - elevator - Ostrau - Schrammsteinbaude - Lattengrund

- Schrammtor - Jägersteig - Schrammsteinaussicht - Zurückesteig - Reitsteig - Großer Winterberg - Bergsteig – Schmilka

WORTH SEEING Bad Schandaus elevator, Schrammsteinaussicht (look out) and the

Kipphornaussicht (look out) CHARACTER the trail keeps on going up and down RESTS Großer Winterberg, Bad Schandau