Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

Highly monodisperse spherical silica nanoparticles with diameters ranging from ca. 15 to 200 nm were prepared using an environmentally friendly water-based synthesis. The size of the spheres can be precisely controlled by using a facile regrowth procedure in the same reaction media. Furthermore, these monodisperse silica spheres can be successfully used as seeds in the well-established Stober silica preparation. The regrowth approach allows for easy incorporation of functional additives. High monodispersity and charge stabilization renders these nanoparticles highly suitable for close-packed array formation and colloidal templating.

Facile preparation of highly monodisperse small silica spheres (15 to >200 nm) suitable for colloidal templating and formation of ordered arrays.

Three-Dimensional Titanium Dioxide Nanomaterials

The beauty of opals results from a densely packed, highly ordered arrangement of silica spheres with a diameter of several hundred nanometers. Such ordered nanostructures are typical examples of materials called photonic crystals, which can be formed by known microstructuring methods and by self-assembly. Opals represent a self-assembly approach to these structured media; such an approach can lead to novel materials for photonics, photocatalysis, and other areas. Although self-assembly leads to many types of defects, resulting in the surprising and very individual appearance of natural opals, it causes also difficulties in technological applications of opal systems.

Opals: Status and Prospects

This Article focuses on the fabrication of highly ordered nanotubes and some novel nanostructures of titania (TiO2) with a two-step anodization method. The first-step anodization was actually a pretreatment of the Ti foil surface and provided well-ordered imprints that served as a template for the further growth of nanotubes. As a result, the TiO2 nanotubes growing in the second-step anodization appreciably outperformed those fabricated with the conventional one-step Ti anodization in terms of size uniformity and arrangement orderliness. The parameters of the anodization were then modulated to obtain more complex structures. When the voltage in the second-step anodization was lower than that in the first-step anodization, a lotus root-shaped TiO2 nanostructure, in which each imprint contained several smaller nanopores, was achieved. When the second anodization was further divided into two stages, double-layered nanotube arrays were synthesized. They contained two distinctly separated parts, i.e., the bamb...

Anodization Fabrication of Highly Ordered TiO2 Nanotubes

High-quality colloidal photonic crystals obtained by optimizing growth parameters in a vertical deposition technique

Preparation of Large‐Area 3D Ordered Macroporous Titania Films by Silica Colloidal Crystal Templating

Synthesis of thin film titania photonic crystals through a dip-infiltrating sol–gel process

Photonic crystals with an inverted-opal structure using polymer and silica colloidal crystal templates were prepared and compared. We show that the behaviors of the template during the removal process and heat treatment are determinant factors on the crystal formation. While both templates result in ordered macroporous structures, the optical quality in each case is quite different. The removal of the polymer template by sintering causes a large shrinkage of the inverted framework and produces a high density of cracks in the sample. With a silica template, sintering actually improves the quality of the inverted structure by enhancing the template’s mechanical stability, helping increase the filling fraction, and consolidating the titania framework. The role of the other important factors such as preheating and multiple infiltrations is also investigated.

Xing-Fang Hu

Papers

High-quality colloidal photonic crystals obtained by optimizing growth parameters in a vertical deposition technique

Preparation of Large‐Area 3D Ordered Macroporous Titania Films by Silica Colloidal Crystal Templating

Synthesis of thin film titania photonic crystals through a dip-infiltrating sol–gel process

A comparative study of inverted-opal titania photonic crystals made from polymer and silica colloidal crystal templates

High quality ordered macroporous titania films with large filling fraction