How do you build a metal nanoparticle?

July 10, 2017, University of Pittsburgh
A structure of a ligand-protected Au25 nanocluster. Credit: Computer-Aided Nano and Energy Lab (C.A.N.E.LA.)

Although scientists have for decades been able to synthesize nanoparticles in the lab, the process is mostly trial and error, and how the formation actually takes place is obscure. However, a study recently published in Nature Communications by chemical engineers at the University of Pittsburgh's Swanson School of Engineering explains how metal nanoparticles form.

"Thermodynamic Stability of Ligand-Protected Metal Nanoclusters" (DOI: 10.1038/ncomms15988) was co-authored by Giannis Mpourmpakis, assistant professor of chemical and petroleum engineering, and PhD candidate Michael G. Taylor. The research, completed in Mpourmpakis' Computer-Aided Nano and Energy Lab (C.A.N.E.LA.), is funded through a National Science Foundation CAREER award and bridges previous research focused on designing nanoparticles for catalytic applications.

"Even though there is extensive research into nanoparticle synthesis, there really isn't a rational explanation why a nanoparticle is formed," Dr. Mpourmpakis said. "We wanted to investigate not just the catalytic applications of , but to make a step further and understand nanoparticle stability and formation. This new theory explains why ligand-protected metal nanoclusters are stabilized at specific sizes."

A ligand is a molecule that binds to metal atoms to form metal cores that are stabilized by a shell of ligands, and so understanding how they contribute to nanoparticle stabilization is essential to any process of nanoparticle application. Dr. Mpourmpakis explained that previous theories describing why nanoclusters stabilized at specific sizes were based on empirical electron counting rules - the number of electrons that form a closed shell electronic structure, but show limitations since there have been metal nanoclusters experimentally synthesized that do not necessarily follow these rules.

"The novelty of our contribution is that we revealed that for experimentally synthesizable nanoclusters there has to be a fine balance between the average bond strength of the nanocluster's metal core, and the binding strength of the ligands to the metal core," he said. "We could then relate this to the structural and compositional characteristic of the nanoclusters, like size, number of , and number of ligands.

"Now that we have a more complete understanding of this stability, we can better tailor the nanoparticle morphologies and in turn properties, to applications from biolabeling of individual cells and targeted drug delivery to catalytic reactions, thereby creating more efficient and sustainable production processes."

Explore further: Facile decomposition of metal-NHC complexes under catalytic conditions and the key role of NHC-stabilized nanoparticles

More information: Michael G. Taylor et al, Thermodynamic stability of ligand-protected metal nanoclusters, Nature Communications (2017). DOI: 10.1038/ncomms15988

Related Stories

Custom designing silver nanoclusters

July 15, 2016

Altering a single atom in a silver nanocluster considerably changes its properties, creating an exciting opportunity to design these clusters.

Closer ties for silver clusters

December 20, 2016

Tiny clusters of silver atoms arranged with atomic level precision could become more versatile and useful due to a simpler way to hold them together.

Recommended for you

Engineers develop technique to make adaptive materials

April 17, 2018

Engineers at the U.S. Army Research Laboratory and the University of Maryland have developed a technique that causes a composite material to become stiffer and stronger on-demand when exposed to ultraviolet light.

New type of opal formed by common seaweed discovered

April 17, 2018

Scientists have discovered a completely new type of opal formed by a common seaweed which harnesses natural technology by self-assembling a nanostructure of oil droplets to control how light reflects from its cells to display ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.