Bio-inspired method to create nanoscale gold stars

Scientists from the Department of Energy’s Pacific Northwest National Laboratory (PNNL) and the University of Washington (UW) have succeeded in designing a nature-inspired molecule that can guide gold atoms to form nanoscale stars without fault.

Peptoid-directed formation of twinned quintuple nanostars by particle attachment and facet stabilization. Image credit: Dr. Biao Jin, et al (2022)

The study is an important step towards understanding and regulating the shape of metallic nanoparticles and developing innovative materials with tunable characteristics.

Metallic nanomaterials possess interesting optical characteristics, known as plasmonic properties, says Chun-Long Chen, principal investigator at PNNL, affiliate professor of chemical engineering and chemistry at UW, and UW-PNNL faculty member.

Specifically, star-shaped metallic nanomaterials are already said to exhibit proprietary enhancements that are beneficial for the detection and discovery of pathogenic bacteria, among other health and national security applications.

To form these remarkable nanoparticles, the researchers carefully tuned sequences of peptoids, a type of artificial polymer resembling an adjustable protein.

Peptoids offer a unique advantage in achieving molecular level controls.

Chun-Long Chen, Senior Researcher and Faculty Member, UW-PNNL

In this case, the peptoids direct the small gold particles to attach and relax to develop larger quintuple twins, while stabilizing the facets of the crystal structure. Their method was inspired by nature, where proteins can regulate the formation of materials with innovative functionalities.

Jim De Yoreo and Biao Jin have used state-of-the-art in situ transmission electron microscopy (TEM) to “see” the creation of stars in solution at the nanometer scale. The technique not only offered a full mechanistic understanding of how peptoids drive the process, but also exposed the roles of facet stabilization and particle attachment in shape regulation.

De Yoreo is a Battelle Fellow at PNNL and an Affiliate Professor of Materials Science and Engineering at UW, and Jin is a Postdoctoral Research Associate at PNNL.

After assembling their nanoscale constellation, the scientists then used molecular dynamics simulations to absorb a level of detail that cannot be derived from experiments – and to demonstrate why particular peptoids regulated flawless star formation. .

Xin Qi, a postdoctoral researcher in chemical engineering in Professor Jim Pfaendtner’s group, led the study at UW. Qi used the Hyak supercomputer cluster at UW to model the interfacial occurrences between many different particle surfaces and peptoids.

Simulations have an important role to play in learning how to design plasmonic nanomaterials that distinctly capture and scatter light.

You need to have an understanding at the molecular level to form this beautiful star-shaped particle with interesting plasmonic properties.

Chun-Long Chen, Senior Researcher and Faculty Member, UW-PNNL

Simulations can build the theoretical understanding of why specific peptoids form specific shapes.

Scientists hope to help establish a future where simulations drive experimental design, in a cycle the team hopes will lead to the predictive production of nanomaterials with preferred plasmonic enhancements. In this way, they want to use computational instruments to detect side chains and peptoid sequences with facet-preferred selectivity.

Next, they would use advanced in situ imaging methods, such as liquid cell TEM, to track direct facet expression, stabilization, and particle attachment.

If someone can tell us that a plasmonic nanomaterial structure has interesting optical properties, can we use a peptoid-based approach to do it in a predictable way?

Chun-Long Chen, Senior Researcher and Faculty Member, UW-PNNL

Although they are not there yet, this fruitful experimental-computing research is helping to bring them closer to this reality. Additionally, the team’s ability to reliably create perfect star shapes is an essential step; more homogeneous particles could mean more predictable optical properties.

This study, recently published in the journal Angewandte Chemiebegan with a grant in 2019 from the U.S. Army Combat Capability Development Command’s Army Research Laboratory to create design guidelines for peptoids that create modifiable nanomaterials.

This is due to growing partnerships between UW and PNNL in the field of materials synthesis, including the cooperative initiatives of the Northwest Institute for Materials Physics, Chemistry, and Technology (NW IMPACT) and Materials Synthesis and Simulations Across Scales (MS3); and DOE-funded research through the Center for the Science of Synthesis Across Scales (CSSAS). These partnerships greatly benefit from the establishments’ dual meeting programme.

Journal reference:

Jin, B. et al. (2022) Peptoid-directed formation of five-twin Au nanostars by particle attachment and facet stabilization. Angewandte Chemie.


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