How nanoparticles give electrons away


Whether it is in catalytic processes in the chemical industry, environmental catalysis, new types of solar cells or new electronic components, nanoparticles are everywhere in modern production and environmental technologies, in which their unique properties ensure efficiency and save resources. The special properties of nanoparticles often arise from a chemical interaction with the support material on which they are placed. Such interactions often change the electronic structure of the nanoparticle because an electrical charge is exchanged between the particle and the support. Working groups led by Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and the University of Barcelona (UBCN) have now succeeded in counting the number of elementary charges that are lost by a platinum nanoparticle when it is placed onto a typical oxide support. Their work, realized thanks to access obtained through CERIC-ERIC and as part of the FP7 project chipCAT coordinated by the Director of the Czech CERIC-ERIC Partner Facility, Prof. Vladimir Matolin, brings the possibility of developing tailor-made nanoparticles a step closer.

Authors of graphics: Sergey Kozlov and Oriol Lamiel

Nanoscience has long investigated how nanoparticles interact with the support on which they are placed. It is now clear that various physical and chemical factors, such as the electronic structure, the nanostructure and – crucially – their interaction with the support, control the properties of nanoparticles. However, previous studies have not investigated how much charge is transferred and whether there is a relationship between the transfer and the size of the nanoparticle.

In order to measure the electrical charge that is exchanged,an international team of researchers from Germany, Spain, Italy and the Czech Republic, led by Prof. Dr. Jörg Libuda and Prof. Dr. Konstantin Neyman, prepared an extremely clean and atomically well-defined oxide surface, onto which they placed platinum nanoparticles. Using a highly sensitive detection method at the Czech Materials Science Beamline (MSB) in Elettra Sincrotrone Trieste, accessed through CERIC-ERIC call 1, the CERIC user Yaroslava Lykhach was able to quantify the effect for the first time. Looking at particles with various numbers of atoms, they counted the electrons transferred and showed that the effect is most pronounced for small nanoparticles with around 50 atoms. The magnitude of the effect is surprisingly large: approximately every tenth metal atom loses an electron when the particle is in contact with the oxide. The work involved a combination of multiple experimental techniques including CERIC-ERIC access time at microscopy and spectroscopy instruments of the Surface Physics Laboratory in Prague. The researchers were also able to use theoretical methods to show how the effect can be controlled, allowing the chemical properties to be adapted better to suit their intended application. This would allow valuable raw materials and energy to be used more efficiently in catalytic processes.

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