Fig. 1

Reduction of GO under the beam. Lower magnification (lattice resolution) STEM images: a initial and b after ~50 scans. Adsorbates shrink under observation, and the clean lattice area increases. The insets show a model with and without functional groups attached to the graphene sheet (reduced GO). The upper left section of the image contains the supporting carbon film. c EEL spectra after different electron doses showing the loss of the oxygen K-edge. d EEL intensity of the oxygenK-edge as a function of electron dose. e High magnification double-Gaussian filtered image where the graphene lattice with defects and impurities is resolved. The bright atoms (red dashed circles) can be identified as oxygen. The atom in the blue dashed circle is at the edge of the intensity distribution and might be either nitrogen or oxygen. f Histogram of the ADF intensities of carbon (gray) and oxygen atoms (red). g Magnified histogram of panel f. Insets in a, b are reprinted from ref. ¹⁰ with permission. Scale bars are 2 nm