New Hollow Metal Superlattices Created for Optical Applications

According to Northwestern University researchers, the method for creating unique hollow metal nanoparticle-based open-framework superlattices has significantly improved.

New Hollow Metal Superlattices Created for Optical Applications

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The team discovered that they could create open-channel superlattices with pores ranging from 10 to 1000 nm in size, sizes that had previously been impossible to reach, by using small hollow particles known as metallic nanoframes and altering them with suitable DNA sequences.

Researchers will be able to employ these colloidal crystals for molecular absorption and storage, separations, chemical sensing, catalysis, and numerous optical applications due to their newly discovered control over porosity.

The new study highlights the generalizability of new design principles to produce novel materials by identifying 12 distinct porous nanoparticle superlattices with control over symmetry, geometry, and pore connectivity.

Nature published the study on October 26th, 2022.

The new results will have broad-ranging effects for nanotechnology and beyond, according to Chad A. Mirkin, the George B. Rathmann Professor of Chemistry in the Weinberg College of Arts and Sciences at Northwestern and the head of the International Institute for Nanotechnology.

We had to rethink what we knew about DNA bonding with colloidal particles. With these new types of hollow nanocrystals, the existing rules for crystal engineering were not adequate.

Chad A. Mirkin, George B. Rathmann Professor, Chemistry, Weinberg College of Arts and Sciences, Northwestern University

Nanoparticle assembly driven by ‘edge-bonding’ allows us to access a breadth of crystalline structures that we cannot access through conventional ‘face-bonding,’ the traditional way we think of structure formation in this field. These new structures lead to new opportunities both from scientific and technological standpoints,” Mirkin added.

In addition to being a professor of chemical and biological engineering, biomedical engineering, and materials science and engineering at Northwestern University’s McCormick School of Engineering, Mirkin, a pioneer in nanochemistry, is also a professor of medicine at the Feinberg School of Medicine.

For more than 20 years, Mirkin’s team has used the programmability of DNA to create crystals with unexpected and beneficial features, expanding the idea to include hollow particles as a significant step toward a more comprehensive strategy for comprehending and managing colloidal crystal formation.

Colloidal crystals are used in nature to regulate the colors of many creatures, such as the variable color of a chameleon’s skin and butterfly wings. Mirkin’s laboratory-produced structures will challenge scientists and engineers to create new devices, particularly the porous ones that allow molecules, materials, and even light to pass through them.

Another family of synthetic porous materials called zeolites is used in several industrial chemical processes, according to Vinayak Dravid, the Abraham Harris Professor of Materials Science and Engineering at McCormick and one of the study’s authors.

There are many limitations to zeolites because these are made by physical rules that limit options. But when DNA is used as a bond, it allows for a greater diversity of structures and much larger variety of pore sizes, and thus a diverse range of properties.

Vinayak Dravid, Study Author and Abraham Harris Professor, Materials Science and Engineering, McCormick School of Engineering, Northwestern University

A variety of applications are made possible by the ability to regulate pore size and connections between pores. For instance, the authors demonstrate an intriguing optical property of porous superlattices known as a negative refractive index that is not present in nature and is only possible with artificial materials.

In this work, we discovered how open-channel superlattices can be new types of optical metamaterials that allow for a negative index of refraction. Such metamaterials enable exciting applications such as cloaking and superlensing, the imaging of super small objects with microscopy.

Koray Aydin, Study Author and Associate Professor, Electrical and Computer Engineering, McCormick School of Engineering, Northwestern University

The scientists continue to work together to develop the project.

Mirkin added, “We need to apply these new design rules to nanoporous metallic structures made of others metals, like aluminum, and we need to scale the process. These practical considerations are very important in the context of high-performance optical devices. Such an advance could be truly transformative.

The study was supported by the Center for Bio-Inspired Energy Science, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences (award number DE-SC0000989), and the Air Force Office of Scientific Research (award numbers FA9550-17-1-0348 and FA9550-16-1-0150).

Journal Reference

Li, Y., et al. (2022) Open-channel metal particle superlattices. Nature. doi:10.1038/s41586-022-05291-y


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