The authors describe being able to see how the atoms of a platinum nanoparticle—only 10 nm in diameter—are arranged in three dimensions. They also identify how the atoms are arranged around defects in the platinum nanoparticle.
Similar to how CT scans of the brain and body are done in a hospital, the scientists took images of a platinum nanoparticle from many different directions and then pieced the images together using a new method that improved the quality of the images.
This novel method is a combination of three techniques: scanning transmission electron microscopy, equally sloped tomography (EST) and three-dimensional Fourier filtering. Compared to conventional CT, the combined method produces much higher quality 3D images and allows the direct visualization of atoms inside the platinum nanoparticle in three dimensions.
“Visualizing the arrangement of atoms in materials has played an important role in the evolution of modern science and technology,” said Jianwei (John) Miao, who led the work. He is a professor of physics and astronomy at UCLA and a researcher with the California NanoSystems Institute at UCLA.
“Our method allows the 3D imaging of the local structures in materials at atomic resolution, and it is expected to find application in materials sciences, nanoscience, solid state physics and chemistry,” he said.
“It turns out that there are details we can only see when we can look at materials in three dimensions,” said co-author Laurence D. Marks, a professor of materials science and engineering at Northwestern’s McCormick School of Engineering and Applied Science.
“We have had suspicions for a long time that there was more going on than we could see from the flat images we had,” Marks said. “This work is the first demonstration that this is true at the atomic scale.”
Nanotechnology expert Pulickel M. Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor of Engineering at Rice University complimented the research.
“This is the first instance where the three-dimensional structure of dislocations in nanoparticles has been directly revealed at atomic resolution,” Ajayan said. “The elegant work demonstrates the power of electron tomography and leads to possibilities of directly correlating the structure of nanoparticles to properties, all in full 3-D view.”
Defects can influence many properties of materials, and a technique for visualizing these structures at atomic resolution could lead to new insights beneficial to researchers in a wide range of fields.
“Much of what we know about how materials work, whether it is a catalyst in an automobile exhaust system or the display on a smartphone, has come from electron microscope images of how the atoms are arranged,” Marks said. “This new imaging method will open up the atomic world of nanoparticles.”
The experimental images were acquired at the Electron Imaging Center for NanoMachines of California NanoSystems Institute. The work at UCLA was supported by UC Discovery/TomoSoft Technologies (IT107-10166). The work at Northwestern University was supported by the Materials Research Center, which is funded by the National Science Foundation.
Source: Northwestern University