Gold nanoparticles are widely used by researchers around the
globe. Because they are stable and have defined electronic, electrochemical,
and optical properties; they are useful for a great many types of work.
However, until recently, how the particles' structures were as stable as they
are has been a mystery. These superatoms, often composed of gold and one or
more additional elements, hid their molecular and electronic structures from
scientists quite well.
Research done by a collection of universities including Georgia Tech University,
Stanford University, the University of Jyväskylä in Finland, and Chalmers
University of Technology in Sweden broke
through the haze of the mysterious atomic clusters. Earlier work at
Stanford in 2007 disproved a popular theory that secondary atoms, in this case
sulfur atoms, simply sat atop a structure of pure gold, connected to multiple
atoms of the core.
Instead, the organic sulfer molecules, known as thiolates, stole gold atoms
from the core forming a protective cover around it attached by the
thiolate-gold-thiolate bonds. This confirmed, instead, a “divide and protect”
theory predicted by Hannu Häkkinen, a professor at the University of Jyväskylä,
formerly of Georgia Tech.
The accumulated work has been used to predict the structures of different gold
nanoclusters involving various amounts of gold atoms. At least one of these
structures, a 25 gold atom cluster, has been confirmed by another group of
researchers.
Further understanding the complex gold nanoparticles will aid scientists in
designing custom gold nanoparticles for use in various areas of research. “We
now have a unified model that provides a solid background for nanoengineering
ligand-protected gold clusters for applications in catalysis, sensing,
photonics, bio-labeling and molecular electronics,” Häkkinen explained.