Studies of the Dynamics and Mechanisms of Charge Transport and Charge Mediation in Electroactive Thin Films

The aims of these investigations are to relate the electrical and electrochemical properties of organic, organometallic and inorganic thin films with the individual and collective structures of their constituent molecules. Film-preparation techniques include Langmuir-Blodgett and self-assembly procedures, for structurally defined monolayers, and spin coating or electrosynthesis, for the production of redox- and electronically conducting polymers. Experimental methods include voltammetry, potentiostatic/coulostatic pulse, impedance spectroscopy, ellipsometry, and quartz crystal microbalance gravimetry. Particular attention is being given to simultaneous measurements of electrochemical parameters and accompanying charges in mass in order to obtain a wider basis for the quantitative interpretation of electrical behaviour in terms of the contributing mass-transport and electron-hopping processes.

Pulse Voltammetry at Ultramicroelectrodes. Fundamental Studies and Analytical Applications

This is a recently initiated project, the objectives of which are to examine the advantages to be gained employing ultramicroelectrodes, in combination with pulse voltammetric techniques, for both fundamental studies of electrode kinetics and for electroanalysis. Particular areas for study include:

• Determinations of metals and organics in natural waters.
• Determinations of complexed metals in organic solvents.
• Examination of electroactivity and heterogeneous electron-transfer in novel solvent systems.
• Analysis of metals in natural oils.

Fundamental Studies of Pulse-Voltammetry in the Presence of Charging Currents and iR Drop

The goal of the ongoing work is to present mathematical models that fully account for the effects of double-layer capacitance and uncompensated solution resistance. With the theory in hand, the achievable limits are extended:

• For measurements in electrolytes with low conductivity, and
• For the determination of large reaction rate constants.

The exploitation of microelectrodes in two-electrode systems, which permits the use of very rapid instrumentation, provide exacting tests of the practical applications of these models.

Development of Membrane-Based Biosensors

The ultimate aim of this project is to develop a deeper understanding of molecular mechanisms for signal transduction in biological systems. Artificial cell membranes are created with Langmuir-Blodgett techniques or liposome fusion on electrode surfaces. In addition to electrochemical impedance spectroscopy studies, these molecular aggregates are being investigated with atomic force microscopy and ellipsometry. Substances of particular interest in connection with membrane formation include phospholipids, sterols, self-assembling alkanethiols, and anionic and cationic polyelectrolytes. Incorporation of membrane proteins is planned.

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