Dr. Amanda S. Barnard

CSIRO Materials Science & Engineering, Australia Authors | Amanda S. Barnard, Neil P. Young, Angus I. Kirkland, Marijn A. van Huis and Huifang Xu. Email | Amanda.Barnard@csiro.au

ApplicationNanogold – A Qualitative Phase Map (cited 86 times)
AuthorsAmanda S. Barnard, Neil P. Young, Angus I. Kirkland, Marijn A. van Huis and Huifang Xu.
JournalACS Nano, 2009, 3 (6), pp 1431–1436
SampleNanoparticles
TopicCatalyst Stability, Phase Transformation
TechniquesHRTEM
KeywordsGold; Nanoparticles; Shape; Phase diagram; Thermodynamics; Modeling
Publication / D.O.I.Full publication here DOI: 10.1021/nn900220k

Nanogold – A Qualitative Phase Map

ABSTRACT: The development of the next generation of nanotechnologies requires precise control of the size, shape, and structure of individual components in a variety of chemical and engineering environments. This includes synthesis, storage, operational environments and, since these products will ultimately be discarded, their interaction with natural ecosystems.

Much of the important information that determines these properties is contained within nanoscale phase diagrams, but quantitative phase maps that include surface effects and critical diameter (along with temperature and pressure) remain elusive. Here we present the first quantitative equilibrium phase map for gold nanoparticles together with experimental verification, based on relativistic ab initio thermodynamics and in situ high-resolution electron microscopy at elevated temperatures.

Figure: “Until recently growing gold nanoparticles was a little like a box of chocolates – you never know what you were going to get!”

DENSsolutions Comments

Nanoparticles of gold are currently attracting considerable attention for use in biomedical applications including drug delivering, heating, sensing and in nanocatalysis. However, our ability to control the properties upon which these applications are based is still intrinsically linked to the nanomorphology of individual particles.

Most theoretical models predict that, in general, the more perfect the nanoparticles, the better they perform. However, real nanoparticles are rarely crystallographically ideal, and planar defects such as contact twins and intrinsic or extrinsic stacking faults, form during growth in materials with low stacking fault or twin boundary energy, and surface energy anisotropy.  Gold features in this group, often exhibiting structural and morphological modifications including single or multiple (parallel, contact) twinning and cyclic twinning resulting in decahedral and truncated decahedral structures. Verifying a phase map given by theoretical simulation is very challenging undertaking, which requires mapping gold particles at various elevated temperatures.

The researchers using a range of DENSsolutions heating systems were able to observe gold particles at various elevated temperature. The extreme low drift at elevated temperature allows structural and shape transformations in individual gold particles that could be imaged with atomic resolution. By using approach, the researchers succeed in mapping the gold phase diagram experimentally.

Download the full publication here at the ACS Nano Journal

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