Researchers from the Pacific Northwest National Laboratory (PNNL) and the University of Washington (UW) have created a bio-inspired molecule that can guide gold atoms to make flawless nanoscale stars. The research is a significant step toward better understanding and manipulating the form of metal nanoparticles and developing new materials with customizable properties.
According to Chun-Long Chen, a PNNL senior research scientist, UW affiliate professor of chemical engineering and chemistry, and UW–PNNL Faculty Fellow, metallic nanoparticles have fascinating optical features called plasmonic capabilities. Star-shaped metallic nanoparticles, in particular, have been shown to have unique properties that can be used for sensing and detecting harmful microorganisms, as well as other national security and health applications.
“Peptoid-Directed Formation of 5-Fold Twinned Au Nanostars via Particle Attachment and Side Stabilization”Angewandte Chemie
The scientists meticulously tweaked sequences of peptoids, a sort of programmable protein-like synthetic polymer, to make these remarkable nanoparticles. “Peptoids have a distinct advantage when it comes to obtaining molecular-level controls,” Chen explains. The peptoids in this example guide small gold particles to bind and relax, forming larger five-fold twinned ones while also stabilizing the crystal structure’s facets. Their idea was inspired by nature, where proteins have the ability to govern the production of innovative functional materials.
Advanced in situ transmission electron microscopy (TEM) was used by Jim De Yoreo and Biao Jin to “see” the stars forming in solution at the nanoscale. The technique demonstrated the functions of particle attachment and facet stability in determining shape while also providing an in-depth mechanistic insight into how peptoids direct the process. Jin is a postdoctoral research associate at PNNL and a Battelle Fellow at PNNL. De Yoreo is an affiliate professor of materials science and engineering at UW.
After assembling their nanoscale constellation, the researchers used molecular dynamics simulations to capture a degree of detail that experiments couldn’t—and to explain why specific peptoids regulated the production of flawless stars. This research was spearheaded by Xin Qi, a chemical engineering postdoctoral researcher in Professor Jim Pfaendtner’s group at UW. Qi modeled interfacial interactions between numerous distinct peptoids and particle surfaces using the UW’s Hyak supercomputer cluster.
The simulations are essential for learning how to create plasmonic nanoparticles that absorb and scatter light in novel ways. To generate this attractive star-shaped particle with fascinating plasmonic features, you need a molecular-level understanding, “Cheney explained.” Simulations can help researchers better understand why certain peptoids produce certain forms.
According to the researchers, we are striving toward a future in which simulations influence experimental design, resulting in the predictive synthesis of nanomaterials with targeted plasmonic improvements, according to the team. They want to start by using computational methods to find peptoid side chains and sequences with the appropriate facet selectivity. They’d next use cutting-edge in situ imaging techniques like liquid-cell TEM to track direct facet expression, stability, and particle attachment. To put it another way, Chen asks, “Can we employ a peptoid-based strategy to predictably construct a structure of plasmonic nanoparticles with interesting optical properties?”
They aren’t quite there yet, but this successful experimental-computational effort brings them closer. Additionally, the team’s ability to consistently synthesize nice star shapes is critical; more homogeneous particles translate to more predictable optical properties.
This research, which was just published in the journal Angewandte Chemie, is the result of a 2019 award from the Army Research Laboratory of the US Army Combat Capability Development Command to create design guidelines for peptoids that produce programmable nanomaterials. It’s the result of growing materials synthesis collaborations between UW and PNNL, such as the joint initiatives Northwest Institute for Materials Physics, Chemistry, and Technology (NW IMPACT) and Materials Synthesis and Simulations Across Scales (MS3), as well as DOE-funded research through the Center for the Science of Synthesis Across Scales (CSSAS). The dual appointment scheme at these universities is extremely beneficial to these relationships.
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