Controlled Formation of Highly Organized Mesoporous Titania Thin Films:  From Mesostructured Hybrids to Mesoporous Nanoanatase TiO₂

Abstract

In this paper, we report the complete synthesis and characterization procedures to generate highly organized and oriented mesoporous titania thin films, using poly(ethylene oxide) (PEO)-based templates. Controlled conditions in the deposition, postsynthesis, and thermal treatment steps allow one to tailor the final mesostructure (2D hexagonal, p6m, or 3D cubic, Im3m). Various techniques were used to determine the time evolution of the mesostructure. Spectroscopic techniques (UV/vis, (17)O NMR) and EXAFS/XANES have been used to follow the chemical changes in the Ti(IV) environment. Crossing these techniques spanning all ranges permits a complete description of the chemistry all the way from solution to the mesostructured metal oxide. A critical discussion on all important chemical and processing parameters is provided; the understanding of these features is essential for a rational design and the reproducible construction of mesoporous materials.

Pore-size expansion of hexagonal-structured nanocrystalline titania/CTAB Nanoskeleton using cosolvent organic molecules

“…[10][11][12][13][14][15][16][17][18][19][20][21][22]. Therefore, thermal stability of the mesostructured titania materials is one of the important issues to be addressed.…”

“…[10][11][12][13][14][15][16][17][18][19][20][21][22] This is most likely due to the non-crystallization and -crystal growth of the Hex-ncTiO 2 /CTAB Nanoskeleton and Hex-ncTiO 2 /CTAB/COM Nanoskeleton during thermal treatment. Wide-angle XRD patterns of Hex-ncTiO 2 /CTAB Nanoskeleton and Hex-ncTiO 2 /CTAB/COM Nanoskeleton hardly changed in the temperature range of 150-450 °C (see Figure 12).…”

“…[10][11][12][13][14][15][16][17][18][19][20][21][22] In addition, preparation of mesostructured crystalline titania typically requires alcohol-based solvents, [10][11][12][13][14][15][16][17][18][19][20][21][22] so the replacement of many conventional alcohols as solvents used in the sol-gel reaction to the environmental benign alternatives is also an important challenge toward achieving the goal of green chemical processing.…”

“…[30][31][32][33] Compared with the reported methods, [10][11][12][13][14][15][16][17][18][19][20][21] our synthetic system involves benefits, for example, spontaneous formation of hexagonal structure and crystallization of titania (anatase formation) in aqueous solutions…”

General Synthesis of Ordered Nonsiliceous Mesoporous Materials

“…Upon solvent evaporation, the inorganic-organic composite liquid crystal mesophases are induced. The inorganic species are further polymerized and condensed, gradually forming the mesostructures (Figure 3) (54)(55)(56). Semicrystalline frameworks were obtained where nanocrystallites nucleated within the amorphous inorganic matrices (50).…”