Synthesis of tailored nanoparticles - the example of a silver-zinkoxide core-shell cluster

What is it about?

Superfluid helium droplets of an internal temperature of 0.4 Kelvin (i.e. minus 273 degrees Celsius) fly through a vacuum chamber where individual atoms or molecules are selectively introduced into these droplets. There, they coalesce into a new aggregate and can be deposited on different substrates. In the published work, the synthesized clusters have a 3-nanometer core of silver and a 1.5-nanometer-thick shell of zinc oxide. Zinc oxide is a semiconductor that is used, for example, in radiation detectors for measuring electromagnetic radiation or in photocatalysts for breaking down organic pollutants. The special thing about the material combination is that the silver core provides a plasmonic resonance, i.e. it absorbs light and thus causes a high light field amplification. This puts electrons in an excited state in the surrounding zinc oxide, thereby forming electron-hole pairs – small portions of energy that can be used elsewhere for chemical reactions, such as catalysis processes directly on the cluster surface.

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Why is it important?

Whether in innovative high-tech materials, more powerful computer chips, pharmaceuticals or in the field of renewable energies, nanoparticles – smallest portions of bulk material – form the basis for a whole range of new technological developments. Due to the laws of quantum mechanics, such particles measuring only a few millionths of a millimetre can behave completely differently in terms of conductivity, optics or robustness than the same material on a macroscopic scale. In addition, nanoparticles or nanoclusters have a very large catalytically effective surface area compared to their volume. For many applications this allows material savings while maintaining the same performance.

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