Fig. 3

SEM images of TiO₂ nanotube arrays. SEM observations of the growth of TiO₂ nanotube arrays on the titanium plate surface after anodization for 10 h. Left: SEM surface view structure of titanium plate surface without anodization (×5000 magnification). Middle: SEM surface view structure of the TiO₂ nanotube array on the titanium plate surface (×5000 magnification). Right: SEM image showing the longitudinal structure of the TiO₂ nanotube array on the titanium plate surface (×5000 magnification)