From The University of Michigan (US): “Nanostructures get complex with electron equivalents” 

U Michigan bloc

From The University of Michigan (US)

January 13, 2022

Kate McAlpine

The structural illustration shows the triple-double-gyroid, a new crystal structure discovered by the researchers at Northwestern University (US), the University of Michigan (US) and Argonne National Laboratory (US). It has never been found in nature or synthesized before. The translucent balls in red, green and blue show the positions of large nanoparticles. Each color represents a double-gyroid structure. The dark grey balls and sticks show the locations of the smaller, electron-like particles in one of three types of sites in which those particles appear. The formation of this new crystal structure is a result of the way electron-like nanoparticles control the number of neighbors around the larger nanoparticles. Image credit: Sangmin Lee, Glotzer Group.

Complex crystals that mimic metals—including a structure for which there is no natural equivalent—can be achieved with a new approach to guiding nanoparticle self-assembly.

Rather than just nanoparticles that serve as “atom equivalents,” the crystals produced and interpreted by Northwestern University (US), University of Michigan and DOE’s Argonne National Laboratory(US) rely on even smaller particles that simulate electrons.

“We’ve learned something fundamental about the system for making new materials,” said Northwestern’s Chad Mirkin, the George B. Rathmann Professor of Chemistry in the Weinberg College of Arts and Sciences and a co-corresponding author of the paper in Nature Materials. “This strategy for breaking symmetry rewrites the rules for material design and synthesis.”

Nanoparticles have the potential to enable new materials with properties that can be carefully designed, but one of the big challenges is making these materials self-assemble. Nanoparticles are too small and numerous to build brick by brick.

Colloidal crystals are a family of self-assembled arrays made by nanoparticles, with potential applications in photonics. Crystals that can transform light may be engineered for everything from light sensors and lasers to communications and computing.

“Using large and small nanoparticles, where the smaller ones move around like electrons in a crystal of metal atoms, is a whole new approach to building complex colloidal crystal structures,” said Sharon Glotzer, the Anthony C. Lembke Department Chair of Chemical Engineering at U-M and a co-corresponding author.

Mirkin’s team created colloidal crystals by coating metal nanoparticles with DNA to make them stick to one another. The DNA strands are self-complementary, which means they bond to one another. By tuning parameters like the length of the DNA and how densely the nanoparticles are coated, the metal nanoparticles can be “programmed” to arrange themselves in specified ways. As a result, they are called programmable atom equivalents.

However, the “atoms” in this crystal—spheres with an even coating of DNA—are the same in all directions, so they tend to build symmetric structures. To build less symmetric structures, they needed something to break the symmetry.

“Building on Chad’s prior discovery of ‘electron equivalents’ with Northwestern’s Monica Olvera De La Cruz, we explored more complex structures where control over the number of neighbors around each particle produced further symmetry-breaking,” Glotzer said.

Smaller metal spheres, with fewer DNA strands to make them less sticky, end up acting like electrons in an arrangement of larger nanoparticle “atoms.” They roved around the interior of the structure, stabilizing the lattice of large nanoparticles. Mirkin’s team varied the stickiness of the “electron” nanoparticles to get different structures, as well as changing the temperature and the ratio of nanoparticle “atoms” and “electrons.”

They analyzed these structures aided by small-angle x-ray scattering studies carried out with Byeongdu Lee, a physicist at Argonne National Laboratory and a co-corresponding author. That data revealed three complex, low-symmetry structures. One, whose twisted tunnels are known as a triple double-gyroid structure, has no known natural equivalent.

These new, low-symmetry colloidal crystals offer optical and catalytic properties that can’t be achieved with other crystals, and the symmetry-breaking method promises many more new structures. Glotzer’s team developed computer simulations to recreate the self-assembly results, helping to decipher the complicated patterns and revealing the mechanisms that enabled the nanoparticles to create them.

“We’re in the midst of an unprecedented era for materials discovery,” Mirkin said. “This is another step forward in bringing new, unexplored materials out of the sketchbook and into applications that can harness their incredible properties.”

The study was supported primarily by the Center for Bio-Inspired Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy and also by the Air Force Office of Scientific Research and the Sherman Fairchild Foundation.

Mirkin is also a professor of chemical and biological engineering, biomedical engineering, and materials science and engineering at the McCormick School of Engineering; and a professor of medicine at the Feinberg School of Medicine. He also is the founding director of the International Institute for Nanotechnology. Glotzer is also the John Werner Cahn Distinguished University Professor of Engineering, the Stuart W. Churchill Collegiate Professor of Chemical Engineering, and a professor of material science and engineering, macromolecular science and engineering, and physics at U-M.

See the full article here .


Please support STEM education in your local school system

Stem Education Coalition

U MIchigan Campus

The University of Michigan (US) is a public research university located in Ann Arbor, Michigan, United States. Originally, founded in 1817 in Detroit as the Catholepistemiad, or University of Michigania, 20 years before the Michigan Territory officially became a state, the University of Michigan is the state’s oldest university. The university moved to Ann Arbor in 1837 onto 40 acres (16 ha) of what is now known as Central Campus. Since its establishment in Ann Arbor, the university campus has expanded to include more than 584 major buildings with a combined area of more than 34 million gross square feet (781 acres or 3.16 km²), and has two satellite campuses located in Flint and Dearborn. The University was one of the founding members of the Association of American Universities (US).

Considered one of the foremost research universities in the United States, the university has very high research activity and its comprehensive graduate program offers doctoral degrees in the humanities, social sciences, and STEM fields (Science, Technology, Engineering and Mathematics) as well as professional degrees in business, medicine, law, pharmacy, nursing, social work and dentistry. Michigan’s body of living alumni (as of 2012) comprises more than 500,000. Besides academic life, Michigan’s athletic teams compete in Division I of the NCAA and are collectively known as the Wolverines. They are members of the Big Ten Conference.

At over $12.4 billion in 2019, Michigan’s endowment is among the largest of any university. As of October 2019, 53 MacArthur “genius award” winners (29 alumni winners and 24 faculty winners), 26 Nobel Prize winners, six Turing Award winners, one Fields Medalist and one Mitchell Scholar have been affiliated with the university. Its alumni include eight heads of state or government, including President of the United States Gerald Ford; 38 cabinet-level officials; and 26 living billionaires. It also has many alumni who are Fulbright Scholars and MacArthur Fellows.


Michigan is one of the founding members (in the year 1900) of the Association of American Universities (US). With over 6,200 faculty members, 73 of whom are members of the National Academy and 471 of whom hold an endowed chair in their discipline, the university manages one of the largest annual collegiate research budgets of any university in the United States. According to the National Science Foundation (US), Michigan spent $1.6 billion on research and development in 2018, ranking it 2nd in the nation. This figure totaled over $1 billion in 2009. The Medical School spent the most at over $445 million, while the College of Engineering was second at more than $160 million. U-M also has a technology transfer office, which is the university conduit between laboratory research and corporate commercialization interests.

In 2009, the university signed an agreement to purchase a facility formerly owned by Pfizer. The acquisition includes over 170 acres (0.69 km^2) of property, and 30 major buildings comprising roughly 1,600,000 square feet (150,000 m^2) of wet laboratory space, and 400,000 square feet (37,000 m^2) of administrative space. At the time of the agreement, the university’s intentions for the space were not set, but the expectation was that the new space would allow the university to ramp up its research and ultimately employ in excess of 2,000 people.

The university is also a major contributor to the medical field with the EKG and the gastroscope. The university’s 13,000-acre (53 km^2) biological station in the Northern Lower Peninsula of Michigan is one of only 47 Biosphere Reserves in the United States.

In the mid-1960s U-M researchers worked with IBM to develop a new virtual memory architectural model that became part of IBM’s Model 360/67 mainframe computer (the 360/67 was initially dubbed the 360/65M where the “M” stood for Michigan). The Michigan Terminal System (MTS), an early time-sharing computer operating system developed at U-M, was the first system outside of IBM to use the 360/67’s virtual memory features.

U-M is home to the National Election Studies and the University of Michigan Consumer Sentiment Index. The Correlates of War project, also located at U-M, is an accumulation of scientific knowledge about war. The university is also home to major research centers in optics, reconfigurable manufacturing systems, wireless integrated microsystems, and social sciences. The University of Michigan Transportation Research Institute and the Life Sciences Institute are located at the university. The Institute for Social Research (ISR), the nation’s longest-standing laboratory for interdisciplinary research in the social sciences,[123] is home to the Survey Research Center, Research Center for Group Dynamics, Center for Political Studies, Population Studies Center, and Inter-Consortium for Political and Social Research. Undergraduate students are able to participate in various research projects through the Undergraduate Research Opportunity Program (UROP) as well as the UROP/Creative-Programs.

The U-M library system comprises nineteen individual libraries with twenty-four separate collections—roughly 13.3 million volumes. U-M was the original home of the JSTOR database, which contains about 750,000 digitized pages from the entire pre-1990 backfile of ten journals of history and economics, and has initiated a book digitization program in collaboration with Google. The University of Michigan Press is also a part of the U-M library system.

In the late 1960s U-M, together with Michigan State University (US) and Wayne State University (US), founded the Merit Network, one of the first university computer networks. The Merit Network was then and remains today administratively hosted by U-M. Another major contribution took place in 1987 when a proposal submitted by the Merit Network together with its partners IBM, MCI, and the State of Michigan won a national competition to upgrade and expand the National Science Foundation Network (NSFNET) backbone from 56,000 to 1.5 million, and later to 45 million bits per second. In 2006, U-M joined with Michigan State University and Wayne State University to create the University Research Corridor. This effort was undertaken to highlight the capabilities of the state’s three leading research institutions and drive the transformation of Michigan’s economy. The three universities are electronically interconnected via the Michigan LambdaRail (MiLR, pronounced ‘MY-lar’), a high-speed data network providing 10 Gbit/s connections between the three university campuses and other national and international network connection points in Chicago.