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List of Publications

Electrochemical Sensors: The application of molecular recognition in analytical chemistry is a central topic in my research. We reported on several new host-guest chemistry systems and their practical application for chemical sensing. For example, a chloride-selective complexing agent developed for measurements in human blood is now commercially available, and a sulfate-selective electrode is being tested by a NASA contractor for use on a Mars lander. In the course of this application-oriented work I experienced repeatedly significant insufficiencies in the theory of electrochemical sensors. This caused my interest in the response mechanism of ion-selective electrodes and chemically modified electrodes. The goal of his theoretical work is to assist the design and development of new complexing agents by organic chemists and to provide the theory to put these complexing agents to optimum use for sensing. Several groups in the US and in Europe collaborate with me. Organic synthesists provide me with interesting compounds that we can use to confirm our theoretical models and to construct sensors for real-life applications. We help electroanalytical chemists to use the models we have developed to explain and improve the characteristics of their sensors. Over the last two years I have published papers together with five other research groups.

New Type of Electrochemical Sensor With Very Low Detection Limit: Taking advantage of my theoretical background, I am now suggesting a new type of electrochemical sensor for the highly selective ionophore-based analysis at nanomolar and lower concentrations. These new devices distinguish themselves from previous electrochemical sensors by the application of two types of complexing agents (also called ionophores). Besides low detection limits and the ease of production, the combination of two types of ionophores in a unit construction system is expected to allow the easy fine-tuning of the selectivities and sensitivities of these new electrochemical devices. Applications of this new sensor type for environmental and industrial process monitoring as well as for analyses in clinical chemistry will be investigated.

Scanning tunneling microscopy (STM) is the second area of my research interests. Since its invention in the early 1980s, STM has become one of the most powerful tools for surface observations at the molecular and atomic scale. Unfortunately, the differentiation of chemical species with conventional STM is often very difficult. We have recently shown that chemically modified STM tips can be used for the recognition of specific chemical groups. The modified STM tips chemically interact with the imaged samples. The resulting STM images reflect the chemical selectivity of the tipﾐsample interactions. This exciting new application of molecular recognition promises to become a very general approach to selective surface imaging with high resolution. Present research focuses on the evaluation of various chemical interaction types that may be used for this approach. Efforts to use hydrogen bond and coordination bond interactions are under way. Also, the possibility of distinguishing between different spatial orientations of particular functional groups is being tested. I plan to use this new STM method to observe in-situ chemical surface reactions and to demonstrate various applications in nanotechnology and biosciences.

　

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