Fig. 3. (a) TEM image of a calcium carbonate (CaCO₃)-based nanodisk. (b) Selected-area electron diffraction (SAED) pattern of the nanodisk. (c) Cryogenic high-resolution TEM (cryo-HRTEM) image of a CaCO₃-based nanodisk corresponding to the red square in (d). (d) TEM image of CaCO₃-based nanodisks at low magnification. (e) Fast Fourier transform (FFT) pattern corresponding to the black square in (c). (f) TEM image of a CaCO₃-based nanorod. (g) SAED pattern of the nanorod. (h) HRTEM image of a CaCO₃-based nanorod corresponding to the red square in (i). (i) TEM image of CaCO₃-based nanorods at low magnification. (j) Fast FFT pattern corresponding to the black square in (h). Amorphous layers are surrounded by red dashed lines.