The structure-function relationship understanding of a nanomaterial requires an accurate map of its shape, strain and surface/interface structure. Electron diffractive imaging (EDI) has recently proved to be a powerful method to image shape and internal structure of Au  and CdS  nanocrystals of few nm diameters with a spatial resolution of 80-100 pm. A synergic use of measured diffraction patterns and phase retrieval techniques allowed to bypass the need for imaging lenses, avoiding the resolution limits associated to their aberrations. We here phase-retrieved electron diffractive HRTEM images of individual TiO2 nanocrystals at 70 pm resolution, even exposing the specimen to a low electron dose . For the first time, while retrieving the detailed crystal structure of the oxide nanomaterial, O atomic columns were visualized in the coupled EDI-HRTEM experiment without the need for any lens aberration corrector . In addition, our approach allowed us to reveal subtle deviation of the nanocrystal unit cell structure from the bulk counterpart. These highlithing results demonstrate EDI-HRTEM as a unique tool to study the actual atomic structure of nanomaterials with an unprecedented level of accuracy and sensitivity to light atomic elements. In principle, the resolution is only diffraction and dose limited (dependent on wavelength, detector aperture size and exposure time), giving to EDI-HRTEM the potential to achieve record sub-atomic resolutions and promising numerous applicationsin life and materials sciences.
Cozzoli, P. D.
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