Mar 15, 2011
Digging up metallic nanoparticles with an electron beam
Researchers in New Zealand have designed a new synthesis process, which combines the advantages of low-depth low-concentration ion implantation and high-temperature electron beam annealing to produce surface metallic nanoclusters on silica. The method uses an electron beam to induce the selective desorption of molecules at the surface of the silica matrix. This reduces the silica surface level while the nanoclusters coalesce into bigger structures and result in bare nanoclusters on the surface. Surprisingly, the nanoparticles are not significantly oxidized when in contact with air.
Investigation of the magnetic properties of the samples reveals superparamagnetic behaviour and high magnetization. These properties are easily controllable through the synthesis parameters (implantation concentration, depth, annealing temperature, and duration). The remarkable properties of such a material have real potential to be used as a core for a small fluxgate magnetometer. In addition, having an insulator, air or silica, separating highly spin polarized nano magnetic nanoparticles means that they can be used as magnetoresistance magnetic field sensors.
The Ion Beam Analysis and New Materials team at GNS Science, New Zealand, is developing new materials using ion implantation, electron beam and arc discharge methods. The group is studying the mechanism underlying the synthesis of the materials, as well as investigating the properties and potential uses across a wide range of applications from gas sensor to magnetic devices.
More details can be found in the journal Nanotechnology.
About the author
John Kennedy, PhD, is a senior scientist at GNS Science and associate investigator in the MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand, and co-supervises the thesis work performed by Jérôme Leveneur, a PhD student in the Chemistry Department at the University of Auckland. Leveneur's thesis involves the understanding of the synthesis, properties and applications of nanostructured materials fabricated using this method. This study was conducted in collaboration with Grant Williams, PhD, from Industrial Research Ltd and Principal Investigator in the MacDiarmid institute, New Zealand, David Mitchell, PhD, from the Australian Centre for Microscopy and Microanalysis at the University of Sydney and Andreas Markwitz, PhD principal scientist at GNS Science and principal investigator in the MacDiarmid Institute.