Extended Data Fig. 5: EELS analysis of the DOs region and a multicycle fracture and healing test showing the region of DOs expands.
a, EELS from the DOs region in comparison with raw glassy carbon and ntDC. The lavender and aqua regions represent 1s-π* and 1s-σ* transitions of carbon, respectively. The DOs show substantially higher fraction of sp2 (at 285 eV) and lower fraction of sp3 (at 292 eV) than those of ntDC, indicating substantial sp2 bonding in DOs. The sp3 content in DO was roughly estimated with raw glassy carbon with the two-windows method using EELS information. For two-windows method, Iπ* and Iσ* were calculated by integrating the intensity over 4 eV (283−287 eV) and 10 eV window (288−298 eV), respectively39. The sp2 ratio was calculated using the equation \({N}_{{int}\,{ratio}}=\frac{{I}_{\pi * }^{{DOs}}/{I}_{\sigma * }^{{DOs}}}{{I}_{\pi * }^{{GC}}/{I}_{\sigma * }^{{GC}}}\) and \({N}_{{int}\,{ratio}}=3x/(4-x)\), where x represents the sp2 fraction38. The estimated content of sp3 in DOs (that is, 1-x) is about 34.5% ± 3.0%. b to d, TEM images of the NB after healing duration of 10 min, 20 min and 30 min before the 1st, 2nd and 3rd healing tests, respectively. The DOs content kept increasing with fracture cycles.
