Fig. 2: Structure analysis of the twisted graphene spiral.

a The CLSM image provides height information, illustrating the central region of an individual GS. In the image, blue denotes lower heights; scale bar, 50 μm. b confirming an average twist angle of Ψ ≈ 7.3°, which is consistent with the measurements obtained from AFM (shown in Supplementary Fig. 9). The red rectangle in (b) highlights the presence of diffraction points corresponding to the moiré pattern, as further depicted in Supplementary Fig. 9; scale bar, 2 1/nm. c The moiré pattern is a periodic arrangement of bright (AA stacking area) and dark (AB stacking area) regions; scale bar, 2 nm. d Schematic diagram illustrating the structure of the GS; scale bar, 5 nm. e Side view of the double helix GS model and the corresponding simulated STEM image. g Contrast line profile along the perpendicular plane across the colored strips in (e). A staggered series of graphene planes are signatures of double helical organization, as its simulated STEM images show. f Magnified STEM image of GS showing double helix feature. h The contrast line profile analysis of (f) exhibits similar features as shown in the simulated images (e, g). TEM operating voltage was 80 kV in order to minimize beam damage; scale bar, 1 nm.