Fig. 3.

a Schematic illustration YS Fe₃O₄@C nanobox following 1-, 2- and 3-h etching time. The TEM images (b₁, b₂, b₃) of Fe₃O₄@C nanobox are shown in the dashed box corresponding to 1-, 2- and 3-h etching, respectively. Reprinted with permission from Ref. [84]. Graphical illustrations of c YS nanoprism of Ni–Co mixed oxide, d YS octahedral Fe₂P@C, and e YS octahedral Au nanorod@Cu₇S₄. f TEM image of YS Ni–Co mixed oxide nanoprism. g₁ SEM image and g₂ TEM octahedral Fe₂P@C. h TEM octahedral Cu₇S₄ shell with Au nanorod yolk. Reprinted with permission from Refs. [80, 82, 88]