Fig. 3: Structural comparison.

a Schematic illustration highlighting the differences among Model-1, Model-2, and Model-3. Here, Model-2 was obtained by eliminating the multiscale defects of Model-1 via the template-free method. Model-3 was then achieved by preventing the nanocrystal aggregation through the nucleation-regulation strategy. b Field emission scanning electron microscopy images showing cross-sectional morphologies (scale bar = 200 nm) of Model-1, Model-2, and Model-3 (top). Small-angle X-ray scattering patterns of Model-1, Model-2, and Model-3 (bottom). c N₂ adsorption-desorption isotherms. d Pore size distribution curves. e High-resolution transmission electron microscopy observations (inset: selected area electron diffraction patterns) of Model-2 and Model-3, and the fast-Fourier-transform images of amorphous and crystalline regions, respectively. f X-ray diffraction patterns of Model-2 and Model-3, all showing the sharp peak at ~25.5°, corresponding to the (101) plane of anatase. g Size distributions of nanograins in Model-2 and Model-3, based on statistical analysis, exhibiting similar average sizes but differing levels of uniformity.