Crucially, the research led by the University of York and reported in Nature Materials, shows that oxidation of metals - the process that describes, for example, how iron reacts with oxygen, in the presence of water, to form rust - proceeds much more rapidly in nanoparticles than at the macroscopic scale.
This is due to the large amount of strain introduced in the nanoparticles due to their size which is over a thousand times smaller than the width of a human hair.
Improving the understanding of metallic nanoparticles – particularly those of iron and silver - is of key importance to scientists because of their many potential applications. For example, iron and iron oxide nanoparticles are considered important in fields ranging from clean fuel technologies, high density data storage and catalysis, to water treatment, soil remediation, targeted drug delivery and cancer therapy.
The research team, which also included scientists from the University of Leicester, the National Institute for Materials Science, Japan and the University of Illinois at Urbana-Champaign, USA, used the unprecedented resolution attainable with aberration-corrected scanning transmission electron microscopy to study the oxidisation of cuboid iron nanoparticles and performed strain analysis at the atomic level.
Lead investigator Dr Roland Kröger, from the University of York's Department of Physics, said: "Using an approach developed at York and Leicester for producing and analysing very well-defined nanoparticles, we were able to study the reaction of metallic nanoparticles with the environment at the atomic level and to obtain information on strain associated with the oxide shell on an iron core.
"We found that the oxide film grows much faster on a nanoparticle than on a bulk single crystal of iron – in fact many orders of magnitude quicker. Analysis showed there was an astonishing amount of strain and bending in nanoparticles which would lead to defects in bulk material."
The scientists used a method known as Z-contrast imaging to examine the oxide layer that forms around a nanoparticle after exposure to the atmosphere, and found that within two years the particles were completely oxidised.
Corresponding author Dr Andrew Pratt, from York's Department of Physics and Japan's National Institute for Materials Science, said: "Oxidation can drastically alter a nanomaterial's properties - for better or worse - and so understanding this process at the nanoscale is of critical importance. This work will therefore help those seeking to use metallic nanoparticles in environmental and technological applications as it provides a deeper insight into the changes that may occur over their desired functional lifetime."
The experimental work was carried out at the York JEOL Nanocentre and the Department of Physics at the University of York, the Department of Physics and Astronomy at the University of Leicester and the Frederick-Seitz Institute for Materials Research at the University of Illinois at Urbana-Champaign.
The scientists obtained images over a period of two years. After this time, the iron nanoparticles, which were originally cube-shaped, had become almost spherical and were completely oxidised.
Professor Chris Binns, from the University of Leicester, said: "For many years at Leicester we have been developing synthesis techniques to produce very well-defined nanoparticles and it is great to combine this technology with the excellent facilities and expertise at York to do such penetrating science. This work is just the beginning and we intend to capitalise on our complementary abilities to initiate a wider collaborative programme."
The research was supported by a Max-Kade Foundation Visiting Professorship stipend to Dr Kröger and financial support from the World Universities Network (WUN). The Engineering and Physical Sciences Research Council (EPSRC) funded the initial stages of the project (EP/D034604/1).
Caron Lett | EurekAlert!
One in 5 materials chemistry papers may be wrong, study suggests
15.12.2017 | Georgia Institute of Technology
Scientists channel graphene to understand filtration and ion transport into cells
11.12.2017 | National Institute of Standards and Technology (NIST)
A study carried out by an international team of researchers and published in the journal Physical Review X shows that ion-trap technologies available today are suitable for building large-scale quantum computers. The scientists introduce trapped-ion quantum error correction protocols that detect and correct processing errors.
In order to reach their full potential, today’s quantum computer prototypes have to meet specific criteria: First, they have to be made bigger, which means...
Since 2016, German and Spanish researchers, among them scientists from the University of Göttingen, have been hunting for exoplanets with the “Carmenes”...
DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.
Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
18.12.2017 | Physics and Astronomy
18.12.2017 | Studies and Analyses
18.12.2017 | Medical Engineering