UNIVERSITY PARK, Pa. — Inspired by an artist’s stencils, researchers have developed atomic-level precision patterning on nanoparticle surfaces, allowing them to “paint” gold nanoparticles with polymers, or long chains of small molecules, to give them an array of new shapes and functions. The “patchy nanoparticles” developed by a multi-institutional team that includes researchers at Penn State can be made in large batches, used for a variety of electronic, optical or biomedical applications, or used as building blocks for new complex materials and metamaterials.
Co-led by Kristen Fichthorn, Merrell Fenske Professor of Chemical Engineering and professor of physics at Penn State, the team includes collaborators at the University of Illinois Urbana-Champaign and the University of Michigan. The researchers reported their findings in the journal Nature.
“One of the holy grails in the field of nanomaterials is making complex, functional structures from nanoscale building blocks. But it's extremely difficult to control the direction and organization of each nanoparticle, especially in achieving materials beyond simple close packing,” said co-corresponding author Qian Chen, professor of materials science and engineering at the University of Illinois Urbana-Champaign. “Then we got this idea from nature: Proteins have different surface domains, and by their interaction, they can make all the intricate machines we see in biology. So, we are adopting that strategy, having patches or distinct domains on the surface of the nanoparticles.”
However, the problem of how to attach the patches in a controlled design or at large scales proved a challenge, the researchers said. While wrestling with the problem as a graduate student in Chen’s lab, Ahyoung Kim, the co-first author of the paper, took an art class. In the class, she learned a stenciling technique that used a mask to paint a complex design on a curved piece of pottery. She realized such a technique could work on nanoparticle surfaces, too.
Working with Chen, Fichthorn’s group employed quantum mechanical calculations to develop masking designs by exploring the competitive binding of iodide and organic primer to faceted gold nanoparticles.
“Ionic adsorption is a classical question in surface science,” Fichthorn said, explaining that adsorption is the binding of atoms and molecules to a solid surface. “We computed, at the atomic level, the energetically preferred configurations of iodide and organic primer on various gold facets and predicted a phase diagram for atomic stenciling to occur.”