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Today cross-cutting approaches, where molecular engineering and clever processing are synergistically coupled, allow the chemist to tailor complex hybrid systems of various shapes with perfect mastery at different size scales, composition, functionality, and morphology. Hybrid materials with organic-inorganic or bio-inorganic character represent not only a new field of basic research but also, via their remarkable new properties and multifunctional nature, hybrids offer prospects for many new applications in extremely diverse fields. The description and discussion of the major applications of hybrid inorganic-organic (or biologic) materials are the major topic of this critical review. Indeed, today the very large set of accessible hybrid materials span a wide spectrum of properties which yield the emergence of innovative industrial applications in various domains such as optics, micro-electronics, transportation, health, energy, housing, and the environment among others (526 references).

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Organic-inorganic hybrid membranes of Nafion and mesoporous silica containing sulfonic acid groups were synthesized using the sol-gel process with the goal of increasing the proton conductivity and water retention at higher temperatures and lowering relative humidities as well as improving the dimensional stability. These hybrid membranes were prepared via in situ co-condensation of tetraethoxysilane and chlorosulfonylphenethylsilane via self-assembly route using organic surfactants as templates for the tuning of the architecture of the silica or hybrid organosilica components. In this paper, we describe the elaboration and characterization of new hybrid membranes all the way from the precursor solution to the evaluation of the fuel cell performances. These hybrid materials were extensively characterized with the determination of their physicochemical and electrochemical properties. The membrane containing functionalized silica showed a higher ionic exchange capacity and greater water management than standard Nafion. The hybrid membranes showed improved proton conductivity at 95 °C and over the whole range of relative humidity in comparison to recast Nafion and Nafion 112 membranes.

Fe(II) and Fe(III) in various proportions were coprecipitated by NH3 at pH ≈ 11. The Fe(II)/Fe(III) ratio (x) was varied from 0.10 to 0.50. After stabilization by aging at pH ≃ 8 in anaerobic conditions, hydrous precipitates were characterized by electron microscopy, Mössbauer spectroscopy, and kinetics of dissolution in acidic medium. At any x value, all stable products exhibited the structure of (oxidized) magnetite. For x ≤ 0.30, two distinct species were coexisting: the one (“m”) was made up of ca. 4nm-sized particles with a low Fe(II) content (Fe(II)/Fe(III) ≈ 0.07), and the other (“M”) consisted of particles of larger, more or less distributed sizes, and composition Fe(II)/Fe(III) ≈ 0.33; “M” increased relative amount with increasing x. For x ≥ 0.35, “M” was the only constituent and its Fe(II)/Fe(III) ratio was equal to x. “M” is identified with (nonstoichiometric) magnetite, whereas “m” is likely to be an oxyhydroxide. Mechanisms of formation are discussed, and a phase diagram is proposed which schematizes the evolution of the coprecipitation products with x and with time. Addition of Fe(II) after the precipitation of Fe(III), instead of coprecipitation, yielded very similar results.

The elaborate performances characterizing natural materials result from functional hierarchical constructions at scales ranging from nanometres to millimetres, each construction allowing the material to fit the physical or chemical demands occurring at these different levels. Hierarchically structured materials start to demonstrate a high input in numerous promising applied domains such as sensors, catalysis, optics, fuel cells, smart biologic and cosmetic vectors. In particular, hierarchical hybrid materials permit the accommodation of a maximum of elementary functions in a small volume, thereby optimizing complementary possibilities and properties between inorganic and organic components. The reported strategies combine sol-gel chemistry, self-assembly routes using templates that tune the material's architecture and texture with the use of larger inorganic, organic or biological templates such as latex, organogelator-derived fibres, nanolithographic techniques or controlled phase separation. We propose an approach to forming transparent hierarchical hybrid functionalized membranes using in situ generation of mesostructured hybrid phases inside a non-porogenic hydrophobic polymeric host matrix. We demonstrate that the control of the multiple affinities existing between organic and inorganic components allows us to design the length-scale partitioning of hybrid nanomaterials with tuned functionalities and desirable size organization from ångström to centimetre. After functionalization of the mesoporous hybrid silica component, the resulting membranes have good ionic conductivity offering interesting perspectives for the design of solid electrolytes, fuel cells and other ion-transport microdevices.

Tailoring physical and chemical properties at the nanoscale by assembling nanoparticles currently paves the way for new functional materials. Obtaining the desired macroscopic properties is usually determined by a perfect control of the contact between nanoparticles. Therefore, the physics and chemistry of nanocontacts are one of the central issues for the design of the nanocomposites. Since the birth of atomic force microscopy, crucial advances have been achieved in the quantitative evaluation of van der Waals and Casimir forces in nanostructures and of adhesion between the nanoparticles. We present here an investigation, by a noncontact method, of the elasticity of an assembly of nanoparticles interacting via either van der Waals-bonded or covalent-bonded coating layers. We demonstrate indeed that the ultrafast opto-acoustic technique, based on the generation and detection of hypersound by femtosecond laser pulses, is very sensitive to probe the properties of the nanocontacts. In particular, we observe and evaluate how much the subnanometric molecules present at nanocontacts influence the coherent acoustic phonon propagation along the network of the interconnected silica nanoparticles. Finally, we show that this ultrafast opto-acoustic technique provides quantitative estimates of the rigidity/stiffness of the nanocontacts.

Alternative energy sources, such as solar power and wind power, have received increasing attention over the past decades in order to replace the environmentally damaging and diminishing fossil fuels. Solar power is obviously one of the most attractive renewable energy sources. Up to now, the main photovoltaic (PV) devices have been based on solidstate junctions, usually made of silicon, and take advantage of the development of the semiconductor industry. A challenging new generation of solar cells is now emerging based on interpenetrating networks built from nanocrystalline sensitized oxides and conducting electrolytes. The so-called dye-sensitized solar cells (DSSCs), which use a liquid electrolyte associated with a redox couple, are easy to fabricate and lead to low-cost devices. Therefore, DSSCs constitute a promising alternative to silicon-based p-n junction PV devices. In solar cells that contain TiO 2 as a semiconductor, ruthenium-based complexes as a dye, and an iodide/iodine redox couple in acetonitrile as an electrolyte, excellent solar energy conversion performance is achieved (> 10 %).[1] Even though Grätzel's cells are now commercially available, market expansion is limited because of the use of a liquid electrolyte. Indeed, technological fabrication issues of cell sealing, handling, and maintenance, and the difficulty of marketing flexible PV cells with highly corrosive liquid electrolytes, are still of concern. A large number of alternative solutions have been proposed. These include replacement of the liquid redox electrolyte with i) ionically conductive gels, [2] ii) p-type inorganic materials such as CuI [3] and CuSCN, [4] and iii) molecular or macromolecular organic hole conductors such as triphenyldiamine, polypyrrole, [5] and p-phenylene vinylene based copolymers, [6] or substituted polythiophenes. [7] This third generation of all-solid-state PV cells is very promising and highly attractive. Overall efficiencies up to 4 % have been obtained for p-type inorganic materials [8] and up to 2.6 % for molecular organic hole-conducting materials. [9] Nevertheless, all these promising devices still exhibit poor long-term stability. This paper focuses on the sol-gel elaboration of homogeneous nanoporous TiO 2 films in which control of the architecture, porosity, and layer thickness allows optimization of the solid solar-cell efficiency and stability. A very effective design and processing of all-solid-state solar cells using high-quality TiO 2 -based mesoporous films as an n-type semiconductor layer, a Ru-based complex (Ru-dye) for visible-light absorption, [10] and regioregular poly(3-octylthiophene) (P3OT) as a hole conductor [7a,7b,11] is reported. A high current-density value and an unexpected solar-conversion efficiency (up to 3.90 mA cm -2 and 1.3 %, respectively) can be achieved, as well as a very robust device at a low cost. More than 60 cells were prepared and tested at the same time and reproducible results have been obtained. As a result, the industrial production of such solar cells has tr...