Assessment of an ultramicroelectrode array (UMEA) sensor for the determination of trace concentrations of heavy metals in water Zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften an der Fakultät für Bauingenieur-, Geo- und Umweltwissenschaften der Universität Karlsruhe genehmigte DISSERTATION von Xudong Xie aus VR China 2004 Tag der mündlichen Prüfung: 02.06.2004 Referentin: Prof. Dr. Doris Stüben Korreferent: Prof. Dr. Rolf-Dieter Wilken Abstract
Abstract
Rapid development in silicon technology and microelectronics has nowadays enabled the mass fabrication of microelectrode arrays with well-defined and reproducible geometries on micron scales by using thin-film technology. Compared to conventional macroelectrodes, microelectrodes possess several attractive features, such as high mass transport, reduced charging current, immunity to ohmic drop, high signal-to-noise ratio, etc., which are very advantageous for developing decentralised analytical equipments in trace metal analysis. A novel iridium-based ultramicroelectrode array chip (Ir-UMEAs) was recently designed and fabricated by means of microlithographic techniques by one of the partners (Fraunhofer Institute of Silicon Technology, ISIT, Germany) of this joint research project. The Ir-UMEA chip is made up of 4048 individual ultramicroelectrodes (working electrodes) arranged in four separate arrays. Each array consists of 46 x 22 = 1012 disc shaped microelectrodes with a diameter of 1.8 µm each, giving a total electrode