Structure and activity of single enzymes and metal clusters on a molecular scale

Nano structured noble metal materials can show a largely increased activity as compared to extended surfaces of the same material. The detailed morphology and structure of such materials on an atomic scale are decisive for a better understanding of the structure-reactivity relationship and an important factor to develop high activity catalysts for interfacial reactions. One factor that determines such enhanced activity is the modification of solid state properties considering the nanometer size of particles on given substrates, such as strain effects, modified electronic properties at interfaces etc., although a complete understanding is still missing. Potential applications of these effects can be in the area of sensors, batteries, fuel cells but also for the stability of nanostructures in electronic devices.
Nature provides a large number of catalysts with enzymes which are highly specific and often of high activity catalyzing reactions of a wide range of reactants. Enzymes can be electrically contacted through linker molecules to metal surfaces allowing a direct conversion of biochemical energy into electricity. This can be the basis for biosensors and bioelectrochemical fuel cells. The latter could provide implantable power sources for sensor applications or power sources for isolated monitoring devices.
The current focus of our research is to study the influence of microstructure and morphology of such nano sized particles on the activity of interfacial reactions. The mechanism of charge transfer from enzymes to electrodes requires a significantly better understanding in order to tailor the performance of enzymes depending on reaction and substrate used. Single metal clusters, single enzymes, as well as the charge transfer via linker molecules on nanostructured surfaces are investigated using laterally resolved in-situ scanning probe techniques at solid/liquid interfaces. These techniques are best suited for a characterization of morphology and structure, on the one hand, and the activity, on the other hand, at the same particle or molecule, thus allowing for a reliable correlation of both.

Relevant Publications:

1. J. Meier, K.A. Friedrich, U. Stimming (2002). Faraday Discussions 121, 365-372.
2. M. Del Popolo, E. Leiva H. Kleine, J. Meier, U. Stimming, M. Mariscal, W. Schmickler (2002). Applied Physics Letters 81, 2635-2637.
3. J. Meier, J. Schiøtz, P. Liu, J.K. Nørskov, U. Stimming (2004). Chemical Physics Letters 390, 440-444.