U. MICHIGAN (US) — By exploiting a delicate balance of atomic forces, researchers can create nanoparticle superclusters that are uniform in size—an important factor in a variety of nanotech applications.
In another instance of forces behaving in unexpected ways at the nanoscale, scientists discovered that if you start with small nanoscale building blocks that are varied enough in size, the electrostatic repulsion force and van der Waals attraction force will balance each other and limit the growth of the clusters, enabling formations that are uniform in size. The findings are published in the Nature Nanotechnology.
“The breakthrough here is that we’ve discovered a generic mechanism that causes these nanoparticles to assemble into near perfect structures,” says Sharon Glotzer, chemical engineering professor at the University of Michigan.
“The physics that we see is not special to this system, and could be exploited with other materials. Now that we know how it works, we can design new building blocks that will assemble the same way.”
Researchers created the inorganic superclusters—technically called “supraparticles”—out of red, powdery cadmium selenide In many ways the structures are similar to viruses. They share many attributes with the simplest forms of life, including size, shape, core-shell structure, and the abilities to both assemble and dissemble, says co-author Nicholas Kotov.
“Having these functionalities in totally inorganic system is quite remarkable,” Kotov says. “There is the potential to combine them with the beneficial properties of inorganic materials such as environmental resilience, light adsorption, and electrical conductivity.”
Zhiyong Tang, a collaborating professor at the National Center of Nanoscience and Technology in China, says, “It is also very impressive that such supraparticles can be further used as the building blocks to fabricate three-dimensional ordered assemblies. This secondary self-assembly behavior provides a feasible way to obtain large-scale nanostructures that are important for practical application.”
Kotov is currently working on “breeding” these supraparticles to produce synthetic fuels from carbon dioxide. The work also has applications in drug delivery and solar cell research and it could dramatically reduce the cost of manufacturing large quantities of supraparticles, he says.
“By replicating the self-assembly processes that allow living organisms to grow and heal, we can simplify the production of many useful nanostructured systems from semiconductors and metals so much so that they can be made in any high school laboratory.”
This research is funded by the Department of Defense, the National Science Foundation, and the U.S. Army Research Office.
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