Dig deeper into nanomaterials — ScienceDaily

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From the design of new biomaterials to new photonic devices, new materials constructed through a process called bottom-up nanofabrication, or self-assembly, are paving the way for new technologies with properties tailored to the nanoscale. However, to fully unlock the potential of these new materials, researchers must “see” into their tiny creations so they can control the design and manufacturing to activate the material’s desired properties.

It’s a complex challenge that researchers from Columbia Engineering and the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have tackled for the first time, imagining the interior of a new self- assembled from nanoparticles with a resolution of seven nanometers, about 1/100,000 the width of a human hair. In a new article published on April 6, 2022, in Science, the researchers present the power of their new high-resolution X-ray imaging technique to reveal the internal structure of the nanomaterial.

The team designed the new nanomaterial using DNA as a programmable building material, allowing them to create new engineering materials for catalysis, optics and extreme environments. During the process of creating these materials, the various building blocks made of DNA and nanoparticles fall into place on their own based on a defined “blueprint” – called a template – devised by the researchers. However, to image and operate these tiny structures with X-rays, they needed to convert them into inorganic materials that could withstand X-rays while still providing useful functionality. For the first time, the researchers were able to see the details, including the imperfections, of their newly arranged nanomaterials.

“Although our assembly of DNA-based nanomaterials offers a considerable level of control to fine-tune the properties we desire, they do not form perfect structures that fully fit the plan. Thus, without detailed 3D imaging with resolution at one single particle, it is impossible to understand how to design efficient self-assembled systems, how to tune the assembly process, and how the performance of a material is affected by imperfections,” said corresponding author Oleg Gang, professor of chemical engineering and applied physics and materials scientist at Columbia Engineering and scientist at the Center for Functional Nanomaterials (CFN) at Brookhaven.

Creation of new nanostructures at Columbia and Brookhaven laboratories

As a user facility of the DOE Office of Science, the CFN offers a wide range of tools to create and study new nanomaterials. It was in the CFN and Columbia Engineering laboratories that Gang and his team first constructed and studied new nanostructures. Using both DNA-based assembly as a novel tool for nanoscale fabrication and precise modeling with inorganic materials that can coat DNA and nanoparticles, researchers were able to demonstrate a new type of complex 3D architecture.

“When I joined the research team five years ago, we had studied the surface of our assemblies very well, but the surface is only superficial. If you can’t go deeper, you’ll never see that there is a blood system or bones. Since the assembly inside our materials determines their performance, we wanted to dig deeper to understand how it works,” said Aaron Noam Michelson, first author of the study who was a PhD student with Gang and is now a postdoctoral fellow at CFN.

And the team went further, collaborating with researchers from the Hard X-ray Nanoprobe (HXN) beamline at the National Synchrotron Light Source II (NSLS-II), another DOE Office of Science user facility located at Brookhaven Lab. NSLS-II enables researchers to study materials with nanoscale resolution and exquisite sensitivity by delivering ultra-bright light ranging from infrared to hard X-rays.

“At NSLS-II we have many tools that can be used to learn more about a material depending on what interests you. What made HXN interesting for Oleg and his work is that you can see the real spatial relationships between objects in the structure at the nanoscale But, at the time when we first talked about this research, “seeing into” these tiny structures was already at the limit of what the line beamline could do,” Hanfei Yan, also the corresponding author of the study and a beamline scientist at HXN, told HXN.

Overcome the obstacles

To meet this challenge, the researchers discussed the various obstacles they had to overcome. At CFN and Columbia, the team had to figure out how to build the structures with the desired organization and how to convert them into an inorganic replica capable of withstanding powerful X-ray beams, while at NSLS-II, the researchers had to adjust the beamline by improving resolution, data acquisition and many other technical details.

“I think the best way to describe our progress is in terms of performance. When we first tried to take data from HXN, it took us three days and we got part of a data set. The second time we did it, it took us two days, and we got most of a data set, but our sample got destroyed in the process. a little over 24 hours, and we got a full data set. Each of those steps took about six months apart,” Michelson said.

Yan added: “Now we can complete it in one day. The technique is mature enough that we also offer it to other users who would like to use our beamline to study their sample. See samples at this scale is interesting for areas such as microelectronics and battery research.”

Leveraging the Brookhaven Lightline

The team leveraged the beamline’s capabilities in two ways. They not only measured the phase contrast of X-rays passing through the samples, but they also collected the X-ray fluorescence – the light emitted – from the sample. By measuring the phase contrast, the researchers were able to better distinguish the foreground from the background of their sample.

“Measuring the data was only half the battle; now we needed to translate the data into meaningful insights into the order and imperfection of self-assembled systems. We wanted to understand what kind of faults can occur in these systems and what is the origin of it. Until this point, this information was only available by calculation. Now we can really see this experimentally, which is super exciting and, literally, revealing for the future development of nanomaterials of design complex,” Gang said.

New software tools to manage data

Together, the researchers developed new software tools to help unravel the vast amount of data into chunks that could be processed and understood. One of the main challenges was to be able to validate the resolution obtained. The iterative process that ultimately led to the groundbreaking new resolution spanned several months before the team verified the resolution through both standard analytics and machine learning approaches.

“It took me all my PhD to get here, but I personally feel very happy to be part of this collaboration. beamline. All the new skills I’ve learned on this journey will come in handy for whatever lies ahead,” Michelson said.

Next steps

Even though the team has reached this impressive milestone, it is far from done. They have already set their sights on the next steps to further push the limits of the possible.

“Now that we’ve gone through the data analysis process, we plan to make this part easier and faster for future projects, especially when further improvements to the beamline allow us to collect even more data. Scanning is currently the bottleneck when doing high-resolution tomography work at HXN,” Yan said.

Gang added, “In addition to continuing to improve beamline performance, we also plan to use this new technique to further explore the relationships between defects and properties of our materials. We plan to design more complex nanomaterials. using DNA self-assembly which can be studied using HXN. This way we can see how much structure is built internally and relate it to the assembly process. We are developing a new bottom-up manufacturing platform that we wouldn’t be able to image without this new capability.”

By understanding this link between material properties and the assembly process, researchers hope to unlock the path to refining these materials for future applications in nanomaterials designed for batteries and catalysis, for light manipulation, and for desired mechanical responses.

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