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

Mesoporous organic-inorganic hybrid materials, a new class of materials characterized by large specific surface areas and pore sizes between 2 and 15 nm, have been obtained through the coupling of inorganic and organic components by template synthesis. The incorporation of functionalities can be achieved in three ways: by subsequent attachment of organic components onto a pure silica matrix (grafting), by simultaneous reaction of condensable inorganic silica species and silylated organic compounds (co-condensation, one-pot synthesis), and by the use of bissilylated organic precursors that lead to periodic mesoporous organosilicas (PMOs). This Review gives an overview of the preparation, properties, and potential applications of these materials in the areas of catalysis, sorption, chromatography, and the construction of systems for controlled release of active compounds, as well as molecular switches, with the main focus being on PMOs.

Silica-based mesoporous organic-inorganic hybrid materials.

A simple one-step NaCl-assisted microwave-solvothermal method has been developed for the preparation of monodisperse α-Fe2O3 mesoporous microspheres. In this approach, Fe(NO3)3 · 9H2O is used as the iron source, and polyvinylpyrrolidone (PVP) acts as a surfactant in the presence of NaCl in mixed solvents of H2O and ethanol. Under the present experimental conditions, monodisperse α-Fe2O3 mesoporous microspheres can form via oriented attachment of α-Fe2O3 nanocrystals. One of the advantages of this method is that the size of α-Fe2O3 mesoporous microspheres can be adjusted in the range from ca. 170 to ca. 260 nm by changing the experimental parameters. High photocatalytic activities in the degradation of salicylic acid are observed for α-Fe2O3 mesoporous microspheres with different specific surface areas.

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Monodisperse α-Fe2O3 Mesoporous Microspheres: One-Step NaCl-Assisted Microwave-Solvothermal Preparation, Size Control and Photocatalytic Property

On the Controllable Soft-Templating Approach to Mesoporous Silicates

Materials found in nature combine many inspiring properties such as sophistication, miniaturization, hierarchical organizations, hybridation, resistance and adaptability. Elucidating the basic components and building principles selected by evolution to propose more reliable, efficient and environment-respecting materials requires a multidisciplinary approach.

Biomimetism and bioinspiration as tools for the design of innovative materials and systems.

Rational Design and X-ray Molecular Structure of the First Irido-Cryptand and Encapsulation of a Tetrafluoroborate Anion The CNRS and UPMC are gratefully acknowledged for supporting this work. We thank Prof. D. Davoust and Dr. E. Condamine (IRCOF-Université de Rouen, France) for carrying out the special 13C{19F} NMR experiments on a 600 MHz Bruker instrument equipped with a TXO probe 13C/19F,1H.

Rational Design and X‐ray Molecular Structure of the First Irido‐Cryptand and Encapsulation of a Tetrafluoroborate Anion

Mesostructured transition metal (Ti, Zr, V, Al and Ce-Zr) oxide-based hybrid thin films, templated by poly(ethylene oxide)-based surfactants or block copolymers, have been prepared reproducibly, displaying 2D-hexagonal (p6m) or 2D-centred rectangular (c2m) structure. By carefully adjusting the variables involved it is possible to combine both high organisation and excellent optical quality. TiO2 and ZrO2-based materials show thermal stability up to 400-550°C. The elimination of the template can be conducted efficiently and gives rise to high surface area mesoporous films. For the other metal oxide hybrids the inorganic framework is much more fragile, and requires a precise sequence of post-treatments to be stabilised. In addition, original and homogeneous macrotextures shaped with coral-like, helical or macroporous sieves morphologies have been obtained following a nanotectonic approach based on the template-directed assembly by poly-γ-benzyl-L-glutamate (PBLG) of organically functionalised CeO2 crystalline nanoparticles.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400130234

Design of Transition Metal Oxide and Hybrid Mesoporous Materials

Because of the increasing interest in nanoscale technologies, many groups have taken part in the recent development of nanostructured materials that may be preserved in a robust form for designed applications. Amongst the various possible synthesis paths, the Evaporation Induced Self Assembly (EISA), leading to surfactant templated materials in the shape of thin films (liquid deposition), spheres (spray-drying) or monolith (slowevaporation), is one of the most promising since it enables to control morphologies and allows keeping the stoichiometry in non-volatile species homogeneously distributed in the final materials. The elaboration of the desired mesoporous materials passes by the control of the three steps involved in such a process: The control on the precursor chemical reactivity in the initial solution, the control of all processing parameters during evaporation and the control during consolidation by thermal decomposition of the organic phase and the potential crystallisation of the inorganic network. Through the use of complementary in-situ experiments and conventional characterisation techniques (NMR, 2D-SAXS, interferometry, TEM, ellipsometry, N2-BET), the present paper recalls the top-to-bottom studies of the EISA process applied to two different systems (SiO2 and TiO2) as thin films and spherical sub-micronic particles. In addition, the preparation of ordered mesoporous pure anatase thin films stable up to 700°C will be presented in details at the end of this work.

Amorphous and Crystalline Mesoporous Materials Prepared Via Evaporation

Mesostructured TiO2-surfactant hybrid xerogels and thin films are prepared by Evaporation-Induced Self Assembly (EISA). These organized structures are reproducibly formed through cooperative self-assembly between hydrophilic Ti-oxo species and a micellar template after selective solvent evaporation from ethanol/HCl/H2O media. The construction of these networks is tailored by tuning the hydrolysis-condensation of the metallic cations with the self-assembly of the organic counterparts (“hydrophilic matching” approach). The hybrids present hexagonal mesostructure ( p6m). The formation kinetics of the mesophase is followed by SAXS, interferometry and mass spectrometry (MS) analysis of the vapor phase. An adequate thermal treatment of the organized hybrids leads to high surface (150-400m2 g-1) phosphorus-free mesoporous titania films or powders, with walls containing anatase nanocrystallites. This approach can be successfully extended to other non-silicate based meso-structured materials.

Florence Cagnol

Papers

Rational Design and X‐ray Molecular Structure of the First Irido‐Cryptand and Encapsulation of a Tetrafluoroborate Anion

Design of Transition Metal Oxide and Hybrid Mesoporous Materials

Amorphous and Crystalline Mesoporous Materials Prepared Via Evaporation

Controlled Design of Mesostructured Titania Based Materials