Exploring the frontiers of nano-imaging

Metallic nanoparticles are among the smallest particles in existence – measuring 1-100 nanometres, where each nanometre is a millionth of a millimetre. Associate Professor Hans Elmlund from Monash University, and collaborators in the US and South Korea, have developed a novel technique to study the 3D structure of platinum nanoparticles at a level of detail never seen before.

Despite their miniscule size, metallic nanoparticles have huge potential in nanotechnology and are heavily used in biomedical sciences and engineering. In a new paper published in Science, Elmlund and colleagues at Princeton, Berkeley, Harvard, Ulsan National Institute of Science and Technology and Amore-Pacific Corp. R&D Center demonstrate their powerful method: 3D Structure Identification of Nanoparticles by Graphene Liquid Cell EM (SINGLE). The ingenious technique combines three components: a graphene liquid cell, which is a one carbon-atom thick bag able to hold liquid that remains visible under an electron microscope; an extremely sensitive direct electron detector that captures movies of nanoparticles spinning in solution; and PRIME, a 3D modelling approach that enables the creation of 3D computer models of individual nanoparticles from such movies.

The crystalline arrangements of atoms in nanoparticles are variable, and until now, their highly complex and unpredictable structures have remained a mystery. Using their newly described method, the international collaborators were able to extract detailed information on the formation of platinum nanoparticles. Interestingly, instead of the anticipated cubical or highly symmetrical arrangement, they discovered that the particles are in fact made up of asymmetrical multi-domain structures.

The researchers chose to work with platinum nanocrystals due to their excellent catalytic capabilities, the atomic arrangement on the surface and at the core influences particles’ effectiveness in such reactions. Detailing the structure of platinum nanoparticles therefore has significant implications for their future applications in catalysis.

Since nanoparticles are exploited for such a vast range of applications – diagnostic imaging, renewable energy storage and targeted drug delivery, for example – the researchers’ innovative, hybrid method to reconstruct the particles’ 3D atomic structure and understand the intricacies of their formation will play an important role in the development of new technologies and materials.

For Elmlund and his colleagues, the next steps will involve investigating the formation and evolution of nanoparticles, and characterising the transitions they go through to reach their final form. “It is important for us to understand this so that we can design new materials, for example, to build better or more efficient solar cells, or make better and more economical use of fossil fuels,” says Elmlund.

The paper was published in the July 2015 edition of Science, and the abstract can be read here.

The research was also featured as a national research highlight by the Australian Research Council (ARC) for the month of July. You can find all the ARC’s July research highlights here.