Three-dimensional atomic imaging of crystalline nanoparticles

Many engineering and chemical applications make use of crystalline nanoparticles, harnessing properties that are controlled by their precise three-dimensional morphology, structure and composition. Sandra Van Aert and colleagues demonstrate that it is possible to obtain full three-dimensional structural information for such particles at atomic resolution using a mix of electron tomography and electron microscopy, coupled with separately available knowledge of the crystallographic structure of the target nanoparticle. Such information should ultimately lead to a better understanding of the desirable properties of these systems. This study demonstrates how it is possible to extract full three-dimensional structural information at atomic resolution using a combination of electron tomography and electron microscopy, coupled with separately available knowledge of the crystallographic structure adopted by the target nanoparticle. Such information should ultimately lead to a better understanding of the desirable properties of these systems. Determining the three-dimensional (3D) arrangement of atoms in crystalline nanoparticles is important for nanometre-scale device engineering and also for applications involving nanoparticles, such as optoelectronics or catalysis. A nanoparticle’s physical and chemical properties are controlled by its exact 3D morphology, structure and composition1. Electron tomography enables the recovery of the shape of a nanoparticle from a series of projection images2,3,4. Although atomic-resolution electron microscopy has been feasible for nearly four decades, neither electron tomography nor any other experimental technique has yet demonstrated atomic resolution in three dimensions. Here we report the 3D reconstruction of a complex crystalline nanoparticle at atomic resolution. To achieve this, we combined aberration-corrected scanning transmission electron microscopy5,6,7, statistical parameter estimation theory8,9 and discrete tomography10,11. Unlike conventional electron tomography, only two images of the target—a silver nanoparticle embedded in an aluminium matrix—are sufficient for the reconstruction when combined with available knowledge about the particle’s crystallographic structure. Additional projections confirm the reliability of the result. The results we present help close the gap between the atomic resolution achievable in two-dimensional electron micrographs and the coarser resolution that has hitherto been obtained by conventional electron tomography.