Cédric Boissière

Nanoscaled Metal Borides and Phosphides: Recent Developments and Perspectives

and Perspectives Sophie Carenco,†,‡,§,∥,⊥ David Portehault,*,†,‡,§ Ced́ric Boissier̀e,†,‡,§ Nicolas Meźailles, and Cleḿent Sanchez*,†,‡,§ †Chimie de la Matier̀e Condenseé de Paris, UPMC Univ Paris 06, UMR 7574, Colleg̀e de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France ‡Chimie de la Matier̀e Condenseé de Paris, CNRS, UMR 77574, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Chimie de la Matier̀e Condenseé de Paris, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Laboratory Heteroelements and Coordination, Chemistry Department, Ecole Polytechnique, CNRS-UMR 7653, Palaiseau, France

Optimised photocatalytic activity of grid-like mesoporous TiO2 films: effect of crystallinity, pore size distribution, and pore accessibility

Photocatalytic activity of anatase cubic-based ordered mesoporous thin films was related to the morphology of the crystalline porous network obtained upon thermal treatment with a specific incremented sequence. The porosity and pore size distribution of these thin films were investigated with a novel Environmental Ellipsometric Porosimetry (EEP) technique. Network crystallinity was assessed by XRD. In parallel, the evolution of the photocatalytic activity was studied through UV-induced photodegradation of methylene blue and lauric acid within the films at the various steps of the temperature treatment. The photoactivity was linked to the porous characteristics of the films and we concluded that the activity is optimal when the porosity is high and completely accessible, and when the nanoparticle and pore size have dimensions of 7.5 and 5.5 nm respectively. Such an optimal system was obtained after a sequential thermal treatment ending with 10 min at 600 °C in air, for which the films adopts an ordered bidirectional grid-like structure.

Mesostructured hybrid organic–inorganic thin films

This review discussed the design and different synthetic routes that lead to hybrid thin films that have a periodically organised porosity. The mechanism of formation, the role of the organic functionality and the resulting mesophase, the comparison between one-pot and post-synthesis approaches and the applications domain of this mesostructured hybrid film are described and discussed in this article.

Spherical MSU-1 Mesoporous Silica Particles Tuned for HPLC

Among the mesoporous silica micellar templated structures (MTSs), MSU-X silica, obtained through an N0I0 assembly between non-ionic polyethyleneoxide-based surfactants (N0) and silica neutral inorganic precursors (I0), exhibits a regular ordered structure with a 3D wormhole porous framework and an easily controlled pore size. These materials have been tested for applications requiring both a narrow mesopore size distribution and isotropic properties. A specific double-step synthesis that we developed recently for MSU-X materials has allowed us to prepare mesoporous silica particles with the required shape, size, and properties. Both the particles’ synthesis and comparative HPLC separation tests with a commercial ungrafted silica HPLC powder of identical shape and size are reported.

Elaboration of Monodisperse Spherical Hollow Particles with Ordered Mesoporous Silica Shells via Dual Latex/Surfactant Templating: Radial Orientation of Mesopore Channels

Monodisperse spherical hollow nanoparticles of mesoporous silica featuring mesopores with a radial orientation in the silica shell were synthesized via a dual-templating method. Specifically designed polystyrene latexes with anionic or cationic surface charges acted as the core templates, while cetyltrimethylammonium bromide served as a co-template to structure the mesopore formation during tetraethoxysilane hydrolysis/condensation. The particles were well-separated and presented homogeneous mesoporous silica shells. Average particle diameters were less than 200 nm, and the particles displayed high values of specific surface area and pore volume. The shell thickness and the hollow core diameter could be tuned independently while the radial pore structure was preserved. A detailed analysis of the nitrogen adsorption-desorption isotherms proved that the central cavity was completely isolated from the external medium, that is, only accessible through the radial mesopores of the shell. Consequently, our particles gather the advantages of a well-defined structure, straight penetrating channels across the silica shell, and a high accessible porous volume of the central core. These properties make them far better candidates than simple mesoporous particles for any storage and/or controlled release applications.

Mesoporous maghemite–organosilica microspheres: a promising route towards multifunctional platforms for smart diagnosis and therapy

We report facile fabrication of advanced hybrid silica–spinel iron oxide (maghemite) composite microspheres built with both superparamagnetic nanoparticles for MR imaging, hyperthermia, and a hybrid mesoporous matrix enabling the transport of bioactive molecules for in vivo biomedical applications. Elaboration of such multifunctional platforms is performed by spray drying a sol of tunable composition that allows one to control the size and amount of magnetic particles embedded in the matrix, without aggregation, and to adjust the size and the surface chemical properties of the porous silica cavities. The resulting nanocomposites (γ-Fe2O3 8 nm particles in silica matrices from TEOS templated by CTAB or P123, without or with functionalisation with –Ph, –SH or –NH2) were characterised by chemical analysis, XRD, TEM, BET, FTIR and magnetisation measurements. Tests of the materials both as MRI T2-contrast agents and as heating sources of hyperthermia are presented in support of potential applications in diagnosis and therapy.

Adsorption properties in high optical quality nanoZIF-8 thin films with tunable thickness

We report processing of a thin film by chemical solution deposition of a microporous ZIF-8 nanoparticle dispersion. By using the drain and capillary regimes involved in the dip-coating process, we tuned the thickness of the films from 40 nm to 1 μm and controlled the packing of the nanoparticles on the substrate. The high optical quality thin films show a dual hierarchical porous structure from the micropores of the framework and the mesoporous interparticular voids. Moreover, vapor sorption properties of the microporous ZIF-8 based thin films have been evaluated by ellipsometric porosimetry. The hydrophobic films show alcohol, THF and hydrocarbon adsorption. Experiments for isopropanol/water separation have been carried out and the selective adsorption of the alcohol versus the water makes these thin films good candidates for vapor sensors.

Pyrolysis, Crystallization, and Sintering of Mesostructured Titania Thin Films Assessed by in Situ Thermal Ellipsometry

In-situ thermal ellipsometric analysis is used to elucidate new and fine-scale details on the thermally driven densification, pyrolysis, crystallization, and sintering of dense and ordered mesoporous titania thin films prepared by evaporation-induced self-assembly. The role of the heating schedule, initial film thickness, nature of the substrate and templating agent, solution aging, and presence of water and other additives in the calcination environment is examined. Each of these parameters is shown to have unique and often substantial effects on the final film structure, while the technique itself provides detailed insight into the chemical origin and evolution of these effects. In-situ monitoring and control over the governing chemical processes, such as high-temperature adsorption phenomena that impact nanocrystal growth, is also demonstrated. The evolution of both the porosity and chemical processes occurring inside these materials are evaluated, including extraction of kinetic parameters for the pyrolysis of the template and crystallization of the matrix walls. The latter is shown to be strongly dependent on the presence of mesoscale ordering with ordered cubic films indicating a 1D diffusion-limited crystallization process and dense films following a 3D diffusion-limited process. Less well-ordered mesoporous films, despite similarities in pore volume and pore size distributions, are kinetically more reminiscent of dense films in terms of crystallization. In-situ thermal ellipsometry, by detailing the evolution of the thermally driven chemistry and ceramization that dictate the final film properties, provides immensely important insight into the synthesis and optimization of advanced functional materials based on titania and other metal oxide thin films.

Critical aspects in the production of periodically ordered mesoporous titania thin films

Periodically ordered mesoporous titania thin films (MTTF) present a high surface area, controlled porosity in the 2-20 nm pore diameter range and an amorphous or crystalline inorganic framework. These materials are nowadays routinely prepared by combining soft chemistry and supramolecular templating. Photocatalytic transparent coatings and titania-based solar cells are the immediate promising applications. However, a wealth of new prospective uses have emerged on the horizon, such as advanced catalysts, perm-selective membranes, optical materials based on plasmonics and photonics, metamaterials, biomaterials or new magnetic nanocomposites. Current and novel applications rely on the ultimate control of the materials features such as pore size and geometry, surface functionality and wall structure. Even if a certain control of these characteristics has been provided by the methods reported so far, the needs for the next generation of MTTF require a deeper insight in the physical and chemical processes taking place in their preparation and processing. This article presents a critical discussion of these aspects. This discussion is essential to evolve from know-how to sound knowledge, aiming at a rational materials design of these fascinating systems.

Advanced selective optical sensors based on periodically organized mesoporous hybrid silica thin films.

Mesoporous thin films functionalized with silylated [small beta]-diketone compounds with symmetry mesostructure dependent on the probe quantity were used as fast uranyl species sensors with high selectivity and sensitivity.