Different types of nanoscale lattice formed with polyhedra DNA nano-frames (tetrahedra, cubes and octahedra) and gold nanoparticles are mineralized with controllable silica coatings. Image: Oleg Gang/Columbia Engineering.
Different types of nanoscale lattice formed with polyhedra DNA nano-frames (tetrahedra, cubes and octahedra) and gold nanoparticles are mineralized with controllable silica coatings. Image: Oleg Gang/Columbia Engineering.

Researchers at Columbia Engineering, working with colleagues at Brookhaven National Laboratory, have fabricated nanoparticle-based 3D materials that can withstand a vacuum, high temperatures, high pressure and high radiation. This new fabrication process results in robust and fully engineered nanoscale frameworks that can not only accommodate a variety of functional nanoparticle types but can also be quickly processed with conventional nanofabrication methods.

"These self-assembled nanoparticles-based materials are so resilient that they could fly in space," says Oleg Gang, professor of chemical engineering and of applied physics and materials science at Columbia Engineering, who led the study. "We were able to transition 3D DNA-nanoparticle architectures from liquid state – and from being a pliable material – to solid state, where silica re-enforces DNA struts. This new material fully maintains its original framework architecture of DNA-nanoparticle lattice, essentially creating a 3D inorganic replica. This allowed us to explore – for the first time – how these nanomaterials can battle harsh conditions, how they form and what their properties are." Gang and his colleagues report their work in a paper in Science Advances.

Material properties are different at the nanoscale and researchers have long been exploring how to use nanomaterials in all kinds of applications, from making sensors for phones to building faster chips for laptops. Developing fabrication techniques for realizing 3D nano-architectures has, however, proved challenging.

DNA nanotechnology allows complexly organized materials to be created from nanoparticles through self-assembly. But given the soft and environment-dependent nature of DNA, such materials are often only stable under a narrow range of conditions. In contrast, these newly formed materials can be used in a broad range of applications where engineered structures are required. While conventional nanofabrication excels in creating planar structures, Gang's new method can fabricate the 3D nanomaterials that are becoming essential to so many electronic, optical and energy applications.

Gang, who holds a joint appointment as group leader of the Soft and Bio Nanomaterials Group at Brookhaven Lab's Center for Functional Nanomaterials, is at the forefront of DNA nanotechnology, which relies on folding DNA chains into desired 2D and 3D nanostructures. These nanostructures become building blocks that can be programmed via Watson-Crick interactions to self-assemble into 3D architectures.

His group designs and forms these DNA nanostructures, integrates them with nanoparticles and directs the assembly of targeted nanoparticle-based materials. And now, with this new technique, the team can transition these materials from being soft and fragile to solid and robust.

This new study demonstrates an efficient method for converting 3D DNA-nanoparticle lattices into silica replicas, while maintaining the topology of the interparticle connections between DNA struts and the integrity of the nanoparticle organization. Silica works well because it helps retain the nanostructure of the parent DNA lattice, forms a robust cast of the underlying DNA and does not affect the arrangement of the nanoparticles.

"The DNA in such lattices takes on the properties of silica," says Aaron Michelson, a PhD student from Gang's group. "It becomes stable in air and can be dried and allows for 3D nanoscale analysis of the material for the first time in real space. Moreover, silica provides strength and chemical stability, it's low-cost and can be modified as needed – it's a very convenient material."

To learn more about the properties of their nanostructures, the team exposed the silica-coated DNA-nanoparticle lattices to extreme conditions: high temperatures above 1000°C and high mechanical stresses over 8GPa (about 80,000 times more than atmosphere pressure), and studied these processes in situ. To gauge the structures' viability for applications and further processing steps, the researchers also exposed them to high doses of radiation and focused ion beams.

"Our analysis of the applicability of these structures to couple with traditional nanofabrication techniques demonstrates a truly robust platform for generating resilient nanomaterials via DNA-based approaches for discovering their novel properties," Gang notes. "This is a big step forward, as these specific properties mean that we can use our 3D nanomaterial assembly and still access the full range of conventional materials processing steps. This integration of novel and conventional nanofabrication methods is needed to achieve advances in mechanics, electronics, plasmonics, photonics, superconductivity and energy materials."

Collaborations based on Gang's work have already led to novel superconductivity, and conversion of the silica to conductive and semiconductive media for further processing. This work is reported in papers in Nature Communications and Nano Letters. The researchers are also planning to modify the structure to make a broad range of materials with highly desirable mechanical and optical properties.

"Computers have been made with silicon for over 40 years," Gang adds. "It took four decades to push the fabrication down to about 10nm for planar structures and devices. Now we can make and assemble nano-objects in a test tube in a couple of hours without expensive tools. Eight billion connections on a single lattice can now be orchestrated to self-assemble through nanoscale processes that we can engineer. Each connection could be a transistor, a sensor or an optical emitter – each can be a bit of data stored. While Moore's law is slowing, the programmability of DNA assembly approaches is there to carry us forward for solving problems in novel materials and nanomanufacturing. While this has been extremely challenging for current methods, it is enormously important for emerging technologies."

This story is adapted from material from Columbia Engineering, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.