Tag Archives: David Bushnell

Gold nanoparticle clusters: four new models

This research is being done at the University of Nebraska-Lincoln (UNL) which seems to be on a publishing tear lately. From an April 27, 2015 news item on Nanowerk, here’s the latest,

They may deal in gold, atomic staples and electron volts rather than cement, support beams and kilowatt-hours, but chemists have drafted new nanoscale blueprints for low-energy structures capable of housing pharmaceuticals and oxygen atoms.

Led by UNL’s Xiao Cheng Zeng and former visiting professor Yi Gao, new research has revealed four atomic arrangements of a gold nanoparticle cluster. The arrangements exhibit much lower potential energy and greater stability than a standard-setting configuration reported last year by a Nobel Prize-winning team from Stanford University.

The modeling of these arrangements could inform the cluster’s use as a transporter of pharmaceutical drugs and as a catalyst for removing pollutants from vehicular emissions or other industrial byproducts, Zeng said.

An April 24, 2015 UNL news release (also on EurekAlert), which originated the news item, provides more technical details about the work,

Led by UNL’s Xiao Cheng Zeng and former visiting professor Yi Gao, new research has revealed four atomic arrangements of a gold nanoparticle cluster. The arrangements exhibit much lower potential energy and greater stability than a standard-setting configuration reported last year by a Nobel Prize-winning team from Stanford University.

The modeling of these arrangements could inform the cluster’s use as a transporter of pharmaceutical drugs and as a catalyst for removing pollutants from vehicular emissions or other industrial byproducts, Zeng said.

Zeng and his colleagues unveiled the arrangements for a molecule featuring 68 gold atoms and 32 pairs of bonded sulfur-hydrogen atoms. Sixteen of the gold atoms form the molecule’s core; the remainder bond with the sulfur and hydrogen to form a protective coating that stems from the core.

Differences in atomic arrangements can alter molecular energy and stability, with less potential energy making for a more stable molecule. The team calculates that one of the arrangements may represent the most stable possible structure in a molecule with its composition.

“Our group has helped lead the front on nano-gold research over the past 10 years,” said Zeng, an Ameritas University Professor of chemistry. “We’ve now found new coating structures of much lower energy, meaning they are closer to the reality than (previous) analyses. So the deciphering of this coating structure is major progress.”

The structure of the molecule’s gold core was previously detailed by the Stanford team. Building on this, Zeng and his colleagues used a computational framework dubbed “divide-and-protect” to configure potential arrangements of the remaining gold atoms and sulfur-hydrogen pairs surrounding the core.

The researchers already knew that the atomic coating features staple-shaped linkages of various lengths. They also knew the potential atomic composition of each short, medium and long staple — such as the fact that a short staple consists of two sulfur atoms bonded with one gold.

By combining this information with their knowledge of how many atoms reside outside the core, the team reduced the number of potential arrangements from millions to mere hundreds.

“We divided 32 into the short, middle and long (permutations),” said Zeng, who helped develop the divide-and-protect approach in 2008. “We lined up all those possible arrangements, and then we computed their energies to find the most stable ones.

“Without those rules, it’s like finding a needle in the Platte River. With them, it’s like finding a needle in the fountain outside the Nebraska Union. It’s still hard, but it’s much more manageable. You have a much narrower range.”

The researchers resorted to the computational approach because of the difficulty of capturing the structure via X-ray crystallography or single-particle transmission electron microscopy, two of the most common imaging methods at the atomic scale.

Knowing the nanoparticle’s most stable configurations, Zeng said, could allow biomedical engineers to identify appropriate binding sites for drugs used to treat cancer and other diseases. The findings could also optimize the use of gold nanoparticles in catalyzing the oxidation process that transforms dangerous carbon monoxide emissions into the less noxious carbon dioxide, he said.

Here’s an image illustrating the work,

This rendering shows the atomic arrangements of a gold nanocluster as reported in a new study led by UNL chemist Xiao Cheng Zeng. The cluster measures about 1.7 nanometers long -- roughly the same length that a human fingernail grows in two seconds. (Joel Brehm/Office of Research and Economic Development)

This rendering shows the atomic arrangements of a gold nanocluster as reported in a new study led by UNL chemist Xiao Cheng Zeng. The cluster measures about 1.7 nanometers long — roughly the same length that a human fingernail grows in two seconds. (Joel Brehm/Office of Research and Economic Development)

Here’s a link to and a citation for the paper,

Unraveling structures of protection ligands on gold nanoparticle Au68(SH)32 by Wen Wu Xu, Yi Gao, and Xiao Cheng Zeng. Science Advances 24 Apr 2015: Vol. 1 no. 3 e1400211 DOI: 10.1126/sciadv.1400211

This is an open access article.

As for the Stanford University team’s work mentioned in the news release, I believe it’s from the Roger Kornberg (Nobel laureate) Laboratory. There’s more about that team’s work in an Aug. 21, 2014 article (A new gold standard for nano; Note: A link has been removed) by David Bradley for Chemistry World,

Characterising gold nanoparticles at atomic resolution might improve our understanding of the catalytic activity of these materials, according to an international team. These researchers have now demonstrated that it is possible to use electron microscopy to obtain data on at least one gold cluster of greater than 1nm diameter and to validate the results by comparison with small-angle x-ray scattering data, infrared absorption spectra and density functional theory calculations.

Here’s a link to and a citation for the 2014 paper,

Electron microscopy of gold nanoparticles at atomic resolution by Maia Azubel, Jaakko Koivisto, Sami Malola, David Bushnell, Greg L. Hura, Ai Leen Koh, Hironori Tsunoyama, Tatsuya Tsukuda, Mika Pettersson, Hannu Häkkinen, & Roger D. Kornberg. Science 22 August 2014: Vol. 345 no. 6199 pp. 909-912 DOI: 10.1126/science.1251959

This paper is behind a paywall.

The most recent posting here about gold nanoparticles is an April 14, 2015 piece titled: Gold atoms: sometimes they’re a metal and sometimes they’re a molecule.