Posted in | Nanomaterials

ESRF X-ray Beams Reveal ‘Electron Sponge’ Behavior of Nanoparticles

Published on November 13, 2013 at 4:01 AM

A new chapter has been opened in our understanding of the chemical activity of nanoparticles says a team of international scientists. Using the X-ray beams of The European Synchrotron (ESRF) they showed that the electrons absorbed and released by cerium dioxide nanoparticles during chemical reactions behave in a completely different way than previously thought: the electrons are not bound to individual atoms but, like a cloud, distribute themselves over the whole nanoparticle.


Time dependent cerium high energy resolution fluorescence detection X-ray adsorption spectroscopy (HERFD-XAS) of 3nm cerium dioxide particles before any chemical reaction (red curve) and during the catalase mimetic activity (bleu curve).

The team of scientists was led by Pieter Glatzel from The European Synchrotron (ESRF), in Grenoble (France), and Victor Puntes from the Universitá Autònoma of Barcelona, Catalan Institute of Nanotechnologies (Spain). The first author is Jean-Daniel Cafun from the ESRF.


The element Cerium is abundant in the Earth’s crust and can easily be mined and purified. However, without a thorough understanding of the chemical processes that take place on the surface of cerium dioxide nanoparticles, it is impossible to optimise their current and future use. And to address a more complex issue, it is also impossible to assess the limits of their safe use.



X-rays reveal an unexpected property of widely used nanoparticles


"Scientists have been discussing the question: What happens when electrons are added to ceria nanoparticles? The work by Cafun et al. is a key study because it questions the present, widely accepted model and will lead the research in a new direction," says Frank de Groot, an expert on nanomaterials at Utrecht University who did not take part in the experiment.

The next step, which has already been initiated, will be to assess whether non-localised electrons are a property of cerium dioxide only or also of other widely used nanoparticles like titanium dioxide. “In parallel, chemists have to revisit their theoretical models to explain the chemical behaviour of nanoparticles and to better understand how electrons are transferred in chemical reactions taking place on their surface,” concludes Pieter Glatzel.


Jean-Daniel Cafun et al., Absence of Ce3+ Sites in Chemically Active Colloidal Ceria Nanoparticles, ACS Nano 12 November 2013, DOI:10.1021/nn403542p


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