Fig. 4

Catalysis by 14 metal nanoclusters. a Representative examples of 80 keV AC-HRTEM images of the 14 transition metal nanoclusters in carbon nanotubes highlighting different examples of catalytic behaviour that are manifested as the rearrangement and formation of a variety of carbon nanostructures. b Time-series AC-HRTEM images illustrating three fundamental types of metal nanocluster activities. ‘Process 1′: a Mn nanocluster promotes incorporation of the native carbon shell into the nanotube sidewall, which causes the lower part of the NT to warp, as indicated by the red arrows. ‘Process 2′: a Ni nanocluster abstracts carbon atoms from a point of contact with the host NT and promotes the formation of a new carbon structure. The direction in which the carbon shell grows is dictated by steric hindrance imposed by the host nanotube (indicated with blue arrows). The loss of carbon atoms from the host NTs leads to structural deformation (indicated with red arrow). ‘Process 3′ (a combination of ‘Process 1′ and ‘Process 2′): a Pt nanocluster abstracts carbon atoms from the host NT and restructures them into a carbon shell and simultaneously promotes incorporation of the native carbon shell into the host NT (areas of new carbon structure formation and sealing of a loop-and-hole structure are indicated by red arrows, individual Pt atoms dissociated from the nanocluster are indicated by green arrows). The scale bar is 1 nm