Figure 5.

(a,b) Scanning electron microscopy images of the Platanus acerifolia seed fibers, (c,d) titanium sol-impregnated fibers (TIF), (e) titanium fiber hybrid (TFH), (f–i) hollow tubular TiO₂ microtubes, and (j) an inner wall of the TiO₂ microtubes. (k) Schematic of the double soaking sol-gel route for the preparation of TiO₂ microtubes. (l) The XRD pattern of the TiO₂ microtubes (a,b) their inner wall. (m) The FTIR spectra of the natural SFs (a) and TIF (b), TFH (c), and TiO₂ microtubes (d) prepared from the natural SFs. (n) The BET surface is a pore-size distribution of the TiO₂ microtubes. (o) UV-Vis spectra of the commercially available TiO₂ (a) and synthesized TiO₂ microtubes (b). Figure adapted with permission from Reference [89]. Copyright 2017 Elsevier.