Porous TiO₂ Photonic Band Gap Materials by Anodization

Abstract

Self-organized TiO 2 nanomaterials grown by anodic oxidation of Ti foils have attracted broad scientific interest due to their wide potential applications. The majority of anodic TiO 2 nanostructures studied to date are in the form of self-ordered nanotube arrays. Here we report an exotic type of multilayered nanoporous TiO 2 films that are conveniently fabricated by anodizing Ti foils of high imperfection levels using a novel multipulse anodization method. The fabricated TiO 2 films feature tens of welldefined layers whose long-range structural periodicity leads to photonic band gaps in the visible wavelengths and vivid film colors. Moreover, the optical responses (or the film color) of the fabricated TiO 2 multilayers not only are sensitive to environmental chemicals but also can be electrically switched on and off repeatedly, demonstrating their novel potential applications for, e.g., colored smart windows or electric display boards.

TiO2 nanotube structures for the enhancement of photon utilization in sensitized solar cells

“…The detailed morphologies in the interface region using triangular, sinusoidal or square current profiles show great disparity, which would affect the dye loading capacity when applied in sensitized solar cells [233]. Li et al fabricated periodic structures in Si, Fe and Ti substrates by anodization etching using sinusoidal, square or multi-step voltage or current pulses, and various porous structures of these materials with structural colors can be obtained [234][235][236]. Table 2 summarizes some representative oxide periodic structures with broad applications.…”

Electrochemical fabrication and optical properties of porous tin oxide films with structural colors

“…Similar to some previously reported photonic sensing systems, 11,12,30 the sensing mechanism is based on the fact that the average index of refraction of a porous photonic crystal will increase with foreign species filling in its pores, resulting in a red-shift of its PBG. To illustrate the sensing capability of the porous SnO 2 photonic films reported here, we exposed the SnO 2 films to ethanol (index of refraction, 1.36) which has a low surface tension to infiltrate the nanostructured lattice due to the capillary condensation effect.…”

“…[1][2][3] There have been many attempts to generate artificial structural color through various technological approaches such as, 4,5 layer by layer technical, 6,7 self-assembly of colloid particles, 8,9 lithographic patterning, 10 and anodization. [11][12][13][14] Among these methods, anodization has attracted considerable attention because it offers the advantages of low cost, high process controllability, and convenience in obtaining periodic structures over a large area. Anodic structures of brilliant colors based on periodic porous Si, 15 TiO 2 ,11,13,14 Fe 2 O 3 , and Fe 3 O 4 (Ref.…”

“…[11][12][13][14] Among these methods, anodization has attracted considerable attention because it offers the advantages of low cost, high process controllability, and convenience in obtaining periodic structures over a large area. Anodic structures of brilliant colors based on periodic porous Si, 15 TiO 2 ,11,13,14 Fe 2 O 3 , and Fe 3 O 4 (Ref. 12) have been achieved using the periodically modulated anodization voltage or current waveforms.…”

Selective Removal of the Outer Shells of Anodic TiO2 Nanotubes

“…Moreover, pretreatments of the Ti foils (e.g., cold working) can also be used to adjust the morphology of anodic TiO 2 nanomaterials. The efficacy of the anodization method is highlighted in the diverse anodic nanostructures achieved, including nanobamboos, nanolaces, branched tubes, and multi‐layers 25–30…”