Scientists mix the unmixable to create 'shocking' nanoparticles

March 29, 2018

College Park, Md. -- Making a giant leap in the 'tiny' field of nanoscience, a multi-institutional team of researchers is the first to create nanoscale particles composed of up to eight distinct elements generally known to be immiscible, or incapable of being mixed or blended together. The blending of multiple, unmixable elements into a unified, homogenous nanostructure, called a high entropy alloy nanoparticle, greatly expands the landscape of nanomaterials--and what we can do with them.

This research makes a significant advance on previous efforts that have typically produced nanoparticles limited to only three different elements and to structures that do not mix evenly. Essentially, it is extremely difficult to squeeze and blend different elements into individual particles at the nanoscale. The team, which includes lead researchers at University of Maryland, College Park (UMD)'s A. James Clark School of Engineering, published a peer-reviewed paper based on the research featured on the March 30 cover of Science.

"Imagine the elements that combine to make nanoparticles as Lego building blocks. If you have only one to three colors and sizes, then you are limited by what combinations you can use and what structures you can assemble," explains Liangbing Hu, associate professor of materials science and engineering at UMD and one of the corresponding authors of the paper. "What our team has done is essentially enlarged the toy chest in nanoparticle synthesis; now, we are able to build nanomaterials with nearly all metallic and semiconductor elements."

The researchers say this advance in nanoscience opens vast opportunities for a wide range of applications that includes catalysis (the acceleration of a chemical reaction by a catalyst), energy storage (batteries or supercapacitors), and bio/plasmonic imaging, among others.

To create the high entropy alloy nanoparticles, the researchers employed a two-step method of flash heating followed by flash cooling. Metallic elements such as platinum, nickel, iron, cobalt, gold, copper, and others were exposed to a rapid thermal shock of approximately 3,000 degrees Fahrenheit, or about half the temperature of the sun, for 0.055 seconds. The extremely high temperature resulted in uniform mixtures of the multiple elements. The subsequent rapid cooling (more than 100,000 degrees Fahrenheit per second) stabilized the newly mixed elements into the uniform nanomaterial.

"Our method is simple, but one that nobody else has applied to the creation of nanoparticles. By using a physical science approach, rather than a traditional chemistry approach, we have achieved something unprecedented," says Yonggang Yao, a Ph.D. student at UMD and one of the lead authors of the paper.

To demonstrate one potential use of the nanoparticles, the research team used them as advanced catalysts for ammonia oxidation, which is a key step in the production of nitric acid (a liquid acid that is used in the production of ammonium nitrate for fertilizers, making plastics, and in the manufacturing of dyes). They were able to achieve 100 percent oxidation of ammonia and 99 percent selectivity toward desired products with the high entropy alloy nanoparticles, proving their ability as highly efficient catalysts.

Yao says another potential use of the nanoparticles as catalysts could be the generation of chemicals or fuels from carbon dioxide.

"The potential applications for high entropy alloy nanoparticles are not limited to the field of catalysis. With cross-discipline curiosity, the demonstrated applications of these particles will become even more widespread," says Steven D. Lacey, a Ph.D. student at UMD and also one of the lead authors of the paper.

This research was performed through a multi-institutional collaboration of Prof. Liangbing Hu's group at the University of Maryland, College Park; Prof. Reza Shahbazian-Yassar's group at the University of Illinois at Chicago; Prof. Ju Li's group at the Massachusetts Institute of Technology; Prof. Chao Wang's group at Johns Hopkins University; and Prof. Michael Zachariah's group at the University of Maryland, College Park.

What outside experts are saying about this research:

"This is quite amazing; Dr. Hu creatively came up with this powerful technique, carbo-thermal shock synthesis, to produce high entropy alloys of up to eight different elements in a single nanoparticle. This is indeed unthinkable for bulk materials synthesis. This is yet another beautiful example of nanoscience!," says Peidong Yang, the S.K. and Angela Chan Distinguished Professor of Energy and professor of chemistry at the University of California, Berkeley and member of the American Academy of Arts and Sciences.

"This discovery opens many new directions. There are simulation opportunities to understand the electronic structure of the various compositions and phases that are important for the next generation of catalyst design. Also, finding correlations among synthesis routes, composition, and phase structure and performance enables a paradigm shift toward guided synthesis," says George Crabtree, Argonne Distinguished Fellow and director of the Joint Center for Energy Storage Research at Argonne National Laboratory.
-end-
The A. James Clark School of Engineering at the University of Maryland serves as the catalyst for high-quality research, innovation, and learning, delivering on a promise that all graduates will leave ready to impact the Grand Challenges (energy, environment, security, and human health) of the 21st century. The Clark School is dedicated to leading and transforming the engineering discipline and profession, to accelerating entrepreneurship, and to transforming research and learning activities into new innovations that benefit millions. Visit us online at http://www.eng.umd.edu and follow us on Twitter @ClarkSchool.

University of Maryland

Related Nanoparticles Articles from Brightsurf:

An ionic forcefield for nanoparticles
Nanoparticles are promising drug delivery tools but they struggle to get past the immune system's first line of defense: proteins in the blood serum that tag potential invaders.

Phytoplankton disturbed by nanoparticles
Products derived from nanotechnology are efficient and highly sought-after, yet their effects on the environment are still poorly understood.

How to get more cancer-fighting nanoparticles to where they are needed
University of Toronto Engineering researchers have discovered a dose threshold that greatly increases the delivery of cancer-fighting drugs into a tumour.

Nanoparticles: Acidic alert
Researchers of Ludwig-Maximilians-Universitaet (LMU) in Munich have synthesized nanoparticles that can be induced by a change in pH to release a deadly dose of ionized iron within cells.

3D reconstructions of individual nanoparticles
Want to find out how to design and build materials atom by atom?

Directing nanoparticles straight to tumors
Modern anticancer therapies aim to attack tumor cells while sparing healthy tissue.

Sweet nanoparticles trick kidney
Researchers engineer tiny particles with sugar molecules to prevent side effect in cancer therapy.

A megalibrary of nanoparticles
Using straightforward chemistry and a mix-and-match, modular strategy, researchers have developed a simple approach that could produce over 65,000 different types of complex nanoparticles.

Dialing up the heat on nanoparticles
Rapid progress in the field of metallic nanotechnology is sparking a science revolution that is likely to impact all areas of society, according to professor of physics Ventsislav Valev and his team at the University of Bath in the UK.

Illuminating the world of nanoparticles
Scientists at the Okinawa Institute of Science and Technology Graduate University (OIST) have developed a light-based device that can act as a biosensor, detecting biological substances in materials; for example, harmful pathogens in food samples.

Read More: Nanoparticles News and Nanoparticles Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.