Ligand-Linked Platinum Nanoparticles: A new Material for gas sensors with high potential

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In cooperation of the Institutes IMSAS and IAPC from the University of Bremen, a novel concept for catalytic micro gas sensors has been developed. The concept is based on platinum nanoparticles, which are stabilized by ligands. The high potential of the new catalytic material for hydrogen sensors was shown. A significant improvement of response time and of stability can be achieved. The sensitivity of the sensor based on the concept is very high, whereat low quantities of catalytic material are used. The materials consist of catalytically active platinum nanoparticles which are cross linked by bifunctional organic ligands to form a porous network. As a sensor chip, a membrane sensor with high thermal isolation is used, which contains thermopiles with a high Seebeck coefficient. The principle of the gas sensor is based on detection of heat of reaction. The results of this preliminary work have shown that the ligands ensure that the particles are kept at distance. The ligands act as a carrier, compared to a conventional catalyst. However, higher particle densities compared to non-organic carrier materials can be achieved. A further advantage is the small part of the total mass compared to conventional catalysts. The foundation of a new type of catalytic gas sensor concept has been developed by combining the micro-sensor approach with ligand-linked nanoparticle networks. Significant advantages compared to ceramic carriers for nanoparticles could be shown. The initial success that could be achieved with ligand-linked networks of catalytic nanoparticles is high. However, the chemical and physical properties are still completely unknown. The reasons are that up to now, only a small quantity of bifunctional ligands was examined, as well as only one size of nanoparticles. Furthermore, the current sensor design does not offer a post characterization or an insitu characterization of the materials. Therefore, the full potential of ligand-linked catalytic nanoparticles is still completely unknown. The assembling of special materials for gas sensors is not possible. Within this research project, a fundamental knowledge of ligand-linked nanoparticle networks and their application will be developed, especially for catalytic gas sensors. The selectivity and stability of ligand-linked nanoparticle networks for catalytic hydrogen sensors will be investigated systematically. To achieve this intention, new materials will be developed and an adiabatic reactor will be built. This reactor will allow insitu spectroscopic studies and can be used as a thermoelectric microsensor. The basic mechanisms of the new catalytic material will be explored during catalysis, in order to specifically improve the named properties through the obtained knowledge.