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New UW–PNNL project to illuminate design principles behind peptoid-generated plasmonic nanomaterials

By Lindsey Doermann
August 1, 2019

The Army Research Office (ARO) has awarded UW and PNNL researchers a three-year, $600,000 grant aimed at developing rules for designing peptoids that can produce programmable plasmonic nanomaterials. If engineers can mimic how living organisms produce inorganic substances — known as biominerals — they may be able to efficiently synthesize advanced composite materials with predictable structures and functions.

Specialized proteins and peptides govern how creatures from forams to corals to mollusks produce finely-tuned materials for shells and other rigid structures. But due to the complexity of protein folding, it has proven particularly difficult to parse out just how biomolecules control crystal nucleation, growth, and morphology.

In recent work, UW–PNNL Faculty Fellows Chun-Long Chen and Jim De Yoreo and their colleagues showed they could design peptoids to control the formation of plasmonic gold nanomaterials. In the new ARO-funded project, Chen, De Yoreo, and UW chemical engineering chair Jim Pfaendtner will broaden their scope to gain a more fundamental understanding of peptoid-directed synthesis of plasmonic nanocrystals. From this, they aim to establish design principles for peptoids that predictably produce plasmonic nanomaterials with designed morphology and functions.

"The particular focus of this research effort — integrating computation, synthesis, and state-of-the-art characterization techniques to elucidate the principles underlying polymer-directed nanomaterial formation — is quite intriguing," said Dr. Dawanne Poree, chemical science program manager at ARO, an element of the U.S. Army Combat Capabilities Development Command’s Army Research Laboratory. "If successful, this work will provide direct insights into how polymer structure can not only dictate, but also program nanomaterial morphology, resulting in predictable and tunable properties that could potentially be used to protect soldiers."

Plasmonic nanomaterials have a wide range of applications in sensing, photonics, and catalysis. In the defense realm, they may be used to detect certain nerve agents and neutralize harmful forms of E. coli. The ability to both efficiently synthesize these materials and incorporate chemical characteristics that recognize molecular targets with specificity rivaling that found in nature could open up a new realm of advanced, versatile materials.

In pursuit of this goal, the UW–PNNL group will approach peptoid design in two ways: varying side chains that mimic amino acids to control hydrophobic and electrostatic interactions; and screening a library of peptoids for the molecules that promote formation of plasmonic nanocrystals.

Then, they’ll use state-of-the-art imaging techniques, such as in situ transmission electron microscopy (TEM), to monitor crystal formation. In situ TEM will provide real time observations of how nanocrystals form, and atomic force microscopy (AFM) will be used to measure the binding free energy between peptoids and crystal surfaces.

Combining these experimental techniques with computer simulations, the researchers aim to elucidate the principles underlying peptoid-directed plasmonic nanomaterial formation. They anticipate that what they learn will bring them much closer to achieving their ultimate vision: using synthetic molecules that mimic proteins and peptides to produce advanced functional materials as well as nature does.

The project builds on collaborations and capabilities developed as part of the Northwest Institute for Materials Physics, Chemistry and Technology (NW IMPACT), which is a joint UW–PNNL institute dedicated to building collaborative research partnerships that advance the science of making materials and aid in workforce development across the northwest.

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This work is funded through the Polymer Chemistry Program of the Army Research Office, an element of U.S. Army Combat Capability Development Command’s Army Research Laboratory. The Polymer Chemistry Program identifies high-risk, high-payoff research that could lead to functional polymeric materials for improved protective and sensing capabilities.

Chen is a PNNL staff scientist and affiliate associate professor of chemical engineering at UW; De Yoreo is PNNL’s Chief Scientist for Materials Science, Physical and Computational Sciences (PCSD) and affiliate professor of materials science and engineering at UW; and Pfaendtner is the Bindra Endowed Associate Professor and Chair of the UW chemical engineering department and a PNNL staff scientist in PCSD.

Header image: gold nanoparticle synthesis, courtesy of Chun-Long Chen/PNNL