A new collaborative study led by a research team at the Department of Energy’s , University of California, Los Angeles and the ÌìÃÀÓ°ÊÓ´«Ã½ could provide engineers new design rules for creating microelectronics, membranes and tissues, and open up better production methods for new materials. At the same time, the research, Dec. 6 in the journal , helps uphold a scientific theory that has remained unproven for over a century.

Just as children follow a rule to line up single file after recess, some materials use an underlying rule to assemble on surfaces one row at a time, according to the study.

Nucleation — that first formation step — is pervasive in ordered structures across nature and technology, from cloud droplets to rock candy. Yet despite some predictions made in the 1870s by the American scientist , researchers are still debating how this basic process happens.

The new study verifies Gibbs’ theory for materials that form row by row. Led by UW graduate student Jiajun Chen, working at PNNL, the research uncovers the underlying mechanism, which fills in a fundamental knowledge gap and opens new pathways in materials science.

Chen used small protein fragments called peptides that show specificity, or unique belonging, to a material surface. The UCLA collaborators have been identifying and using such material-specific peptides as control agents to force nanomaterials to grow into certain shapes, such as those desired in catalytic reactions or semiconductor devices. The research team made the discovery while investigating how a particular peptide — one with a strong binding affinity for molybdenum disulfide — interacts with the material.

“It was complete serendipity,” said PNNL materials scientist , co-corresponding author of the paper and Chen’s doctoral advisor. “We didn’t expect the peptides to assemble into their own highly ordered structures.”

That may have happened because “this peptide was identified from a molecular evolution process,” adds co-corresponding author , a professor of materials science and engineering at UCLA. “It appears nature does find its way to minimize energy consumption and to work wonders.”

The transformation of liquid water into solid ice requires the creation of a solid-liquid interface. According to Gibbs’ classical nucleation theory, although turning the water into ice saves energy, creating the interface costs energy. The tricky part is the initial start — that’s when the surface area of the new particle of ice is large compared to its volume, so it costs more energy to make an ice particle than is saved.

Gibbs’ theory predicts that if the materials can grow in one dimension, meaning row by row, no such energy penalty would exist. Then the materials can avoid what scientists call the nucleation barrier and are free to self-assemble.

There has been recent controversy over the theory of nucleation. Some researchers have found evidence that the fundamental process is actually more complex than that proposed in Gibbs’ model.

But “this study shows there are certainly cases where Gibbs’ theory works well,” said De Yoreo, who is also a UW affiliate professor of both chemistry and materials science and engineering.

Previous studies had already shown that some organic molecules, including peptides like the ones in the Science paper, can self-assemble on surfaces. But at PNNL, De Yoreo and his team dug deeper and found a way to understand how molecular interactions with materials impact their nucleation and growth.

They exposed the peptide solution to fresh surfaces of a molybdenum disulfide substrate, measuring the interactions with atomic force microscopy. Then they compared the measurements with molecular dynamics simulations.

De Yoreo and his team determined that even in the earliest stages, the peptides bound to the material one row at a time, barrier-free, just as Gibbs’ theory predicts.

The atomic force microscopy’s high-imaging speed allowed the researchers to see the rows just as they were forming. The results showed the rows were ordered right from the start and grew at the same speed regardless of their size — a key piece of evidence. They also formed new rows as soon as enough peptide was in the solution for existing rows to grow; that would only happen if row formation is barrier-free.

This row-by-row process provides clues for the design of 2D materials. Currently, to form certain shapes, designers sometimes need to put systems far out of equilibrium, or balance. That is difficult to control, said De Yoreo.

“But in 1D, the difficulty of getting things to form in an ordered structure goes away,” De Yoreo added. “Then you can operate right near equilibrium and still grow these structures without losing control of the system.”

It could change assembly pathways for those engineering microelectronics or even bodily tissues.

Huang’s team at UCLA has demonstrated new opportunities for devices based on 2D materials assembled through interactions in solution. But she said the current manual processes used to construct such materials have limitations, including scale-up capabilities.

“Now with the new understanding, we can start to exploit the specific interactions between molecules and 2D materials for automatous assembly processes,” said Huang.

The next step, said De Yoreo, is to make artificial molecules that have the same properties as the peptides studied in the new paper — only more robust.

At PNNL, De Yoreo and his team are looking at stable peptoids, which are as easy to synthesize as peptides but can better handle the temperatures and chemicals used in the processes to construct the desired materials.

Co-authors are Enbo Zhu, Zhaoyang Lin and Xiangfeng Duan at UCLA; Juan Liu and Hendrik Heinz at the University of Colorado, Boulder; and Shuai Zhang at PNNL. Simulations were performed using the Argonne Leadership Computing Facility, a Department of Energy Office of Science user facility. The research was funded by the National Science Foundation and the Department of Energy.

###

Grant numbers: EFRI-1433541, 1530790, 1623947, CNS-0821794, DE-AC02-06CH11357

Adapted from a PNNL written by Laura Shields.

The United States Department of Energy has awarded an expected $10.75 million, four-year grant to the ÌìÃÀÓ°ÊÓ´«Ã½, the and other partner institutions for a new interdisciplinary research center to define the enigmatic rules that govern how molecular-scale building blocks assemble into ordered structures — and give rise to complex hierarchical materials.

The Center for the Science of Synthesis Across Scales, or CSSAS, will bring together researchers from biology, engineering and the physical sciences to uncover new insights into how molecular interactions control assembly and apply these principles toward creating new materials with novel and revolutionary properties for applications in energy technology.

“This center seeks to understand the fundamental rules of how order emerges from the interaction of simple building blocks,” said CSSAS Director , the Matthaei Professor and Chair of the UW Department of Chemical Engineering. “What are the energetics, rates and pathways involved, and what properties emerge when simple components come together in increasingly complex layers? Those are some of our driving questions.”

The UW-based CSSAS is among the newest members of the Energy Frontier Research Centers by the Department of Energy. These centers, operated out of universities and national labs, are funded by the Department of Energy and devoted to specific goals in energy science. The work at the CSSAS will focus on understanding the principles of “hierarchical synthesis” — the process by which molecules come together, bind, interact and create layer upon layer of higher-ordered structures.

CSSAS experiments will focus on protein-based building blocks, but will also probe protein-like synthetic compounds called peptoids as well as inorganic nanoparticles. Studying the biologically inspired assembly of these systems individually and in combination will shed new light on how living organisms, through billions of years of adaptation and evolution, have created complex hierarchical systems to solve a host of challenges, said Baneyx.

Understanding hierarchical synthesis would allow engineers to design and build new materials with unique properties for innovative technological advancements that can come about only when scientists exert precise control over a material. For example, controlling how charges move precisely through a material — or how a substrate is shuttled between the active sites of a series of enzymes positioned with nanoscale precision — could be key to creating new materials for energy storage, transmission and generation. The precision control that scientists envision could also yield functional materials that are self-healing or self-repairing, and have other custom physical properties designed within them.

“Scientists have been trying to create these types of innovative materials largely through ‘top-down’ approaches, and often by reverse engineering an interesting biological material,” said Baneyx. “We will begin with the blocks themselves, exploring how order evolves in the synthesis process when the blocks are put together and interact.”

CSSAS research will focus on three major areas:

• Investigating the emergence of order from the interactions of individual building blocks, be they peptoids, inorganic nanoparticles or protein-based particles
• Probing how hierarchy unfolds as these building blocks are combined to construct lattices, active structures and hybrid materials
• Using machine learning, computational simulations and big data analytics to learn new ways to control the assembly dynamics of hierarchical structures

These investigations will build upon work conducted at the UW , led by UW biochemistry professor and Howard Hughes Medical Institute investigator , and harness the expertise of researchers at the University of Chicago, the Oak Ridge National Laboratory and the University of California, San Diego.

The CSSAS effort was enabled by , or NW IMPACT, which was formally launched earlier this year by UW President Ana Mari Cauce and PNNL Director Steven Ashby to fertilize cross-disciplinary collaborations between UW and PNNL researchers. NW IMPACT co-director , who is the PNNL chief scientist for materials synthesis and simulation across scales and also holds a joint appointment at the UW in both chemistry and materials science and engineering, will serve as the deputy director of the CSSAS.

“This center’s focus is ultimately on unlocking potential,” said Baneyx. “Once we understand the fundamental rules governing the assembly of bioinspired building blocks, we will be able to design new materials to meet a broad range of technological needs.”

###

For more information, contact Baneyx at 206-685-7659 or baneyx@uw.edu and De Yoreo at 509-375-6494 or james.deyoreo@pnnl.gov.

Many innovations of 21st century life, from touch screens and electric cars to fiber-optics and implantable devices, grew out of research on new materials. This impact of materials science on today’s world has prompted two of the leading research institutions in the Pacific Northwest to join forces to research and develop new materials that will significantly influence tomorrow’s world.

With this eye toward the future, the Department of Energy’s and the announced the creation of the — or NW IMPACT — a joint research endeavor to power discoveries and advancements in materials that transform energy, telecommunications, medicine, information technology and other fields. UW President and PNNL Director formally launched NW IMPACT during a ceremony Jan. 31 at the PNNL campus in Richland, Washington.

“This partnership holds enormous potential for innovations in materials science that could lead to major changes in our lives and the world,” said Cauce. “We are excited to strengthen the ties between our two organizations, which bring complementary strengths and a shared passion for ground-breaking discovery.”

“The science of making new materials is vital to a wide range of advancements, many of which we have yet to imagine,” said Ashby. “By combining ideas, talent and resources, I have no doubt our two organizations will find new ways to improve lives and provide our next generation of materials scientists with valuable research opportunities.”

The institute builds on a history of successful partnerships between the UW and PNNL, including joint faculty appointments and past collaborations such as the , the PNNL-led and a new UW-based . But NW IMPACT is the beginning of a long-term partnership, forging deeper ties between the UW and PNNL.

The goal is to leverage these respective strengths to enable discoveries, innovations and educational opportunities that would not have been possible by either institution alone.

“By partnering the UW and PNNL together through NW IMPACT, the sum will truly be greater than the parts,” said David Ginger, a UW professor of chemistry and chief scientist at the UW .  “We are joining together our expertise and experiences to create the next generation of leaders who will create the materials of the future.”

Ginger will co-lead the institution in its initial phase with Jim De Yoreo, chief scientist for materials synthesis and simulation across scales at PNNL and a joint appointee at the UW.

Over its first few years, NW IMPACT aims to hire a permanent institute director, who will be based at both PNNL and the UW; create at least 20 new joint UW-PNNL appointments among existing researchers; streamline access to research facilities at the UW’s Seattle campus and PNNL’s Richland campus for institute projects; involve at least 20 new UW graduate students in PNNL-UW collaborations; and provide seed grants to institute-affiliated researchers to tackle new scientific frontiers in a collaborative fashion.

Some of the areas in which NW IMPACT will initially focus include:

• Materials for energy conversion and storage, which can be applied to more efficient solar cells, batteries and industrial applications. These include innovative approaches to create flexible, ultrathin solar cells for buildings or fabrics, long-lasting batteries for implantable medical devices, catalysts to enable high efficiency energy conversion and industrial processes, and manufacturing methods to synthesize these materials efficiently for commercial applications.
• Quantum materials, such as ultrathin semiconductors or other materials that can harness the rules of quantum mechanics at subatomic-level precision for applications in quantum computing, telecommunications and beyond.
• Materials for water separation and utilization, which include processes to make water purification and ocean desalination methods faster, cheaper and more energy-efficient.
• Biomimetic materials, which are synthetic materials inspired by the structures and design principles of biological molecules and materials within our cells — including proteins and DNA. These materials could be applicable in medical settings for implantable devices or tissue engineering, and for self-assembled protein-like scaffolds in industrial settings.

“The science of making materials involves understanding where the atoms must be placed in order to obtain the properties needed for specific applications, and then understanding how to get the atoms where they need to be,” said De Yoreo.

NW IMPACT will draw on the unique strengths and talents of each institution for innovative collaborations in these areas. For example, PNNL has broad expertise in materials for improved batteries. The lab also offers best-in-class imaging, NMR and mass spectrometry capabilities at , a DOE Office of Science user facility. DOE supports fundamental research at PNNL in chemistry, physics and materials sciences that are key to materials development. The UW brings complementary facilities and equipment to the partnership, such as the and a cryo-electron microscopy facility, as well as expertise in a variety of “big data” research and training endeavors, highly rated research and education programs, and ongoing materials research projects through the National Science Foundation-funded .

###

For more information, contact James Urton with the UW News Office at 206-543-2580 or jurton@uw.edu and Susan Bauer with the PNNL News & Media Relations Office at 509-372-6083 or susan.bauer@pnnl.gov.

“Because crystallization is a ubiquitous phenomenon across a wide range of scientific disciplines, a shift in the picture of how this process occurs has far-reaching consequences,” said , a materials scientist and physicist at the Department of Energy’s Pacific Northwest National Laboratory and affiliate UW and .

These conclusions, with De Yoreo as lead author, have implications for decades-old questions in crystal formation, such as how animals and plants form minerals into shapes that have no relation to their original crystal symmetry or why some contaminants are so difficult to remove from stream sediments and groundwater.

Their findings crystalized during discussions among 15 scientists from diverse fields such as geochemistry, physics, biology and the earth and materials sciences. At their home institutions, these researchers conduct experiments, investigate animal skeletons, study soils and streams or use computer simulations to visualize how particles can form and attach. They met for a three-day workshop in Berkeley, California, that was sponsored by the Council on Geosciences from the Department of Energy’s .

“Researchers across all disciplines have made observations of skeletons and laboratory-grown crystals that cannot be explained by traditional theories,” said senior author , a professor of geosciences at Virginia Tech. “We show how these crystals can be built up into complex structures by attaching particles — as nanocrystals, clusters, or droplets — that become organized into complex shapes. Many scientists have contributed to identifying these particles and pathways to becoming a crystal — our challenge was to put together a framework to understand them.”

In animal and laboratory systems alike, the crystal formation process begins by constructing their constituent particles. These can be small molecules, clusters, droplets or nanocrystals. These particles are unstable and begin to combine with each other, nearby crystals and other surfaces. For example, nanocrystals prefer to orient themselves along the same direction as a larger crystal before attaching, much like adding Legos. In contrast, amorphous conglomerates can simply aggregate. Their atoms later become organized by “doing the wave” through the mass to rearrange into a single crystal.

“Because we largely show a community consensus on this topic, the study has the potential to define the directions of future research on crystallization,” said De Yoreo.

The authors say much work remains to understand the forces that cause these particles to move and combine. It is one of the driving forces behind new research.

“Particle pathways are tricky because they can form what appear to be crystals with the traditional faceted surfaces or they can have completely unexpected shapes and chemical compositions,” said Dove. “Our group synthesized the evidence to show these pathways to growing a crystal become possible because of interplays between of thermodynamic and kinetic factors.”

The implications of these discussions span diverse scientific fields. By understanding how animals form crystals into working structures such as shells, teeth and bones, scientists will have a bigger and better toolbox to interpret crystals formed in nature. These insights may also help design novel materials and explain unusual mineral patterns in rocks. In addition, knowledge of how pollutants are transported or trapped in the minerals of sediments has implications for environmental management of water and soil.

“How we think about the ways to crystallization impacts how we interpret natural crystallization processes in geochemical and biological environments, as well as how we design and control synthetic crystal growth processes,” said De Yoreo. “I was surprised at how widespread a phenomenon particle-mediated crystallization is and how easily one can create a unified picture that captures its many styles.”

The work was supported by the Council on Geosciences of the U.S. Department of Energy’s office of Science. All co-authors and their affiliations .

###

For more information, contact De Yoreo at James.DeYoreo@pnnl.gov.

Adapted from PNNL press release: ““