“Seeing” More Sharply into Self-Assembled Nanomaterials

The Science

Three-dimensional nanostructures are key to advances in many applications. Nanostructures are built from nanomaterials, natural and artificial materials that are more than 10,000 times smaller than the width of a human hair. Nanostructures are important to everything from new biomaterials to catalysts to solar cells and other devices that interact with light. One way to create these nanostructures is using tailored DNA to program the materials’ assembly. This opens a path to new materials with properties that can be tuned at the nanoscale. To aid in this work, researchers have developed a new record-setting, 3D imaging tool. The tool uses high energy X-rays to reveal or “visualize” the internal structure of nanomaterials.

The Impact

To build nanostructures, researchers need  to probe these structures’ internal architecture at various states of assembly in three dimensions. Current probing methods at the nanoscale have limitations. The researchers used several methods including powerful light sources to produce X-ray computed tomography (CT) scans. The scans provided record-setting, 7-nanometer resolution and information on the elements in the materials. The researchers then constructed 3-D frameworks to reveal the nanostructures’ imperfections and interfaces. This also helped to clarify how the nanostructures had assembled.

Summary

Bottom-up nanofabrication is an attractive strategy for creating complex 3D materials through the self-assembly of functional nanocomponents. In particular, DNA-encoding can offer a tremendous level of structural and compositional control for programming unique and specific material organization. In this study, the team designed a new, self-assembled nanomaterial that has novel catalytic, mechanical, and electronic properties. The research leveraged the capabilities of the Center for Functional Nanomaterials (CFN), a Department of Energy (DOE) user facility at Brookhaven National Laboratory (BNL). While this technique offered the researchers tremendous control over the designed material, it was not clear how different designs and fabrication protocols affected the structure and functionality of the material. By combining the brilliant X-ray source of the National Synchrotron Light Source II (NSLS-II), another DOE user facility at BNL, with nanofocusing multilayer Laue lenses, the team developed an X-ray CT tool at the Hard X-ray Nanoprobe (HXN) beamline at NSLS-II that enabled imaging of the inner architecture of the nanomaterials. One essential step in this study was the development of new software tools to help untangle the large amount of data into pieces that could be processed and understood. The team overcame the major challenge of identifying different types of defects in a formed structure through an iterative process that led to the 3D visualization of individual nanoparticles and frameworks. Through this process the team also verified the record-setting resolution of the X-ray microscopy through standard analysis and machine-learning approaches.

The combination of the new functional nanomaterials created via bottom-up fabrication, the advanced 3D X-ray CT tool, and the novel analysis software opens the door to faster materials development and characterization afforded by the synergistic user facilities.

Funding

Funding for this research was provided by the Department of Energy (DOE) Office of Science, Office of Basic Energy Sciences and by the Department of Defense, Army Research Office. This research used resources of the Center for Functional Nanomaterials and National Synchrotron Light Source II, both of which are DOE Office of Science user facilities.