International audienceno abstrac

This review presents an extensive discussion on the major advances in the field of periodically organized mesoporous thin films (POMTFs) obtained via surfactant templated growth of inorganic or hybrid polymers. A large variety of templating agents can be coupled with inorganic polymerization reactions for the design of periodically organized nanostructured hybrid phases that yield POMTFs. The tuning of the interface between the template and the polymerizing phase and the control over chemical and processing conditions are the key parameters in producing tailor-made POMTFs with a high degree of reproducibility. This dynamic coupling between chemical and processing conditions dictates extensive use of complementary ex situ measurements with in situ characterization techniques that follow, in real time, film formation from the molecular precursor solutions to the final stabilized POMTF. Among modern analytical tools, 2D-GISAXS, ellipsoporosimetry, HRTEM, X-ray reflectometry, WAXS, time-resolved infrared spectroscopy, SAW, and optically polarized xenon NMR have proved to be highly relevant for this purpose. POMTFs combine the intrinsic physical and chemical properties of the inorganic or hybrid matrices with a highly defined nanoporous network having a tunable pore size and connectivity, high surface area and accessibility, and a specific orientation with respect to the substrate. As such, POMTFs are a promising family of advanced materials for a host of future applications including micro-optics and photonic devices, microelectronics, nanoionics and energy, environment, functional and protective coatings, biomaterials, environmentally responsive materials, and biomicrofluidics, among others.

Mesoordered silica thin films with cubic structures were prepared by evaporation induced self-assembly (EISA) with two types of structuring agent (CTAB and block copolymer F127). A complete and accurate description of these films was obtained by combining 2D-SAXS analyses, variable angle spectroscopic ellipsometry, and a specially designed environmental ellipsometric porosimetry (EEP) experiment. The EEP analysis is rapid and cheap and operates at ambient pressure and temperature. This latter experiment was performed with water and produced a set of water adsorption-desorption isotherms. A modified Kelvin equation, coupled with a modelisation of pores contraction, enabled the determination of the structural parameters of films porous networks: ellipsoidal pore diameters, porous volume, and surface area. Young moduli of films in the direction perpendicular to the substrates were calculated from these parameters.

We present here a complete study on a synthesis of nickel nanoparticles involving the reaction of [Ni(acac)2] with oleylamine (OA) and trioctylphosphine (TOP) reactants, whose simultaneous presence and relative amounts are paramount. The role of every reactant in the nucleation and growth of the nanoparticles has been delineated: OA is the reductant and thus controls the nucleation rate, meanwhile TOP provides a tunable surface stabilization through coordination on the Ni(0) surface. This result leads us to a design synthesis providing tailored monodispersed nanoparticles in a wide range (2−30 nm), which allows self-consistent studies of size-induced changes in catalytic and magnetic properties. Additionally, the growth mechanism is demonstrated to include an aggregation step which thus correlates with the polycrystalline feature of the nanoparticles obtained through this process. Moreover, the critical influence of the phosphine in this system was demonstrated a) for the outcome of the ripening mechanisms: defocusing effect and/or reshaping of the particles and b) for the surface properties: binding of the phosphine to the surface and its behavior toward oxidation was investigated by FTIR. Preliminary SQUID measurements show the impact of crystallites size on the magnetic properties.

The major advances in the field of the designed construction of hierarchically structured porous inorganic or hybrid materials wherein multiscale texturation is obtained via the combination of aerosol or spray processing with sol-gel chemistry, self-assembly and multiple templating are the topic of this review. The available materials span a very large set of structures and chemical compositions (silicates, aluminates, transition metal oxides, nanocomposites including metallic or chalcogenides nanoparticles, hybrid organic-inorganic, biohybrids). The resulting materials are manifested as powders or smart coatings via aerosol-directed writing combine the intrinsic physical and chemical properties of the inorganic or hybrid matrices with defined multiscale porous networks having a tunable pore size and connectivity, high surface area and accessibility. Indeed the combination of soft chemical routes and spray processing provides "a wind of change" in the field of "advanced materials". These strategies give birth to a promising family of innovative materials with many actual and future potential applications in various domains such as catalysis, sensing, photonic and microelectronic devices, nano-ionics and energy, functional coatings, biomaterials, multifunctional therapeutic carriers, and microfluidics, among others.

Innovative strategies to produce well-defined nanoparticles and other nanostructures such as nanofibres, quantum wells and mesoporous materials have revitalized materials science for the potential benefit to society. Here, we report a controlled process, involving soft-chemistry-based deposition, template-assisted mesostructured growth, and tuned annealing conditions that allows the preparation of ordered mesoporous crystalline networks and mesostructured nano-island single layers, composed of multicationic metal oxides having perovskite, tetragonal or ilmenite structures. This strategy to obtain meso-organized multi-metal-oxide nanocrystalline films (M(3)NF) bridges the gap between conventional mesoporous materials and the remarkable properties of crystalline ternary or quaternary metallic oxides. Nanocrystalline mesoporous films with controlled wall thickness (10-20 nm) of dielectric SrTiO(3), photoactive MgTa(2)O(6) or ferromagnetic semi-conducting Co(x)Ti(1-x)O(2-x) were prepared by evaporation-induced self-assembly (EISA) using a specially designed non-ionic block-copolymer template. A tuned thermal treatment of the mesoporous films permits the transfer of the wall structure into nanocrystallites, with all tectonic units being tightly incorporated into mechanically stable ordered tri- or bidimensional nanocrystalline networks. This methodology should allow multifunctionalization, miniaturization and integration during development of devices such as smart sensors and actuators, better-performing photocatalysts, and fast electrochromic devices. On the other hand, organized arrays of dispersed ferromagnetic or ferroelectric nanoparticles are promising materials for spintronics and for cheap, non-volatile 'flash' memories.

No abstract

A strategy is shown to fabricate highly organized mesoporous anatase films exhibiting favorable properties for photocatalysis and photovoltaic applications by the hydrolysis/condensation of TiCl4 in the presence of PHB−PEO block copolymer templates. Dipcoating for evaporation-induced-self-assembly followed by a straight thermal treatment was employed. The evaporation/structuration process and the thermal treatment were mechanistically followed by in situ GISAXS/WAXS measurements, and the final product was carefully analyzed by spectroscopic ellipsometry and transmission electron microscopy to reveal the consequences of crystallization onto the micro-, the meso-, and the macroscale.