Development of a High-Throughput Impedance Spectroscopy Screening System (HT-IS) for Characterisation of Novel Nanoscale
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Development of a High-Throughput Impedance Spectroscopy Screening System (HT-IS) for Characterisation of Novel Nanoscaled Gas Sensing Materials Daniel Sanders, Maike Siemons, Tobias Koplin, Ulrich Simon RWTH Aachen University, Institute of Inorganic Chemistry, 52056 Aachen, Germany ABSTRACT A high-throughput work flow for rapid synthesis and testing of metal oxide nanoparticles for the discovery of new gas sensors of improved sensitivity and selectivity has been developed. The material libraries consist of nanoscaled metal oxide particles which are obtained either from pyrolysis of appropriate precursors or from polyol mediated synthesis. The design of a multielectrode array with 8x8 interdigital electrodes allows efficient and automated pipetting robot assisted sample preparation and material deposition. For characterisation of the sensor arrays high throughput impedance spectroscopy has been used. Test gas sequences and sensor temperatures can be varied. As an example, the properties of an In2O3-based library are introduced.
INTRODUCTION Gas monitoring represents a growing demand resulting from strategies for intelligent process management, environmental protection and medicinal diagnostics as well as from the domestic and automobile sector. The development of fast responding, sensitive and especially highly selective gas sensor materials therefore is of tremendous interest. However, the majority of the research activities is restricted to simple modification and improvement of known systems and is not directed towards the search for alternative sensor materials. Therefore nowadays commercial gas sensors are either based on few materials, like e.g. SnO2, ZnO or TiO2, or, for more demanding applications, are based on sensor arrays of these materials enhancing selectivity with appropriate complex signal analysis. The use of high-throughput experimentation (HTE) techniques accelerates material synthesis and characterisation, enabling to investigate a multiplicity of materials compared to 'one at a time' strategy. Besides, HTE allows the application of combinatorial strategies, which typically is based on evolutionary optimising of selected material properties. However, up to now HTE and combinatorial strategies are limited to a few fields in material sciences. In 1999, the automated electrochemical analysis of library plates of an array of 64 electrodes on a silicon wafer was published [1]. A comparable technology for the electrochemical deposition and characterisation of samples of similarly designed library plates has already been reported by Symyx Technologies in a patent application [2]. The preparation of gradient libraries has been used for the discovery of transparent transistors based on ZnO[3] as well as for the discovery of transparent ferromagnetic mixed oxides (Co-doped TiO2) [4]. Procedures for the discovery of new microwave dielectrics have also been reported [5]. It is striking, that in all these applications the library preparation has been carried out exclusively with the help of PVD and CVD
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