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Hierarchical porous materials have attracted a considerable attention owing to the increased interest in their applications. Hierarchical Porous Silica (HPS) was synthesized by combining the sol‐gel of sodium silicate (SS) and oil in water nanoemulsion (O/W‐NE) templating. The oil droplets of NE acted as pore forming agent and the sol‐gel built the silica framework. The O/W‐NE was prepared by a low energy method, i. e. the phase inversion composition (PIC) method. The influence of pH of SS and NE on HPS was studied. The volume of ammonia, used to induce gelling, was studied as a factor influencing the HPS. The calcined samples were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), FTIR, N2 adsorption and small‐angel X‐ray scattering (SAXS). The results show that the microstructure is highly affected by pH and can be; macropores inserted in a dense matrix; a blend of a dense and a porous structure; or fully hierarchical porous silica. HPS has a specific surface area of 240 m2/g and a large pore volume (1.5 cm3/g) and a surface roughness of 2.95. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Sustainable preparation of mesoporous silica. • ScCO 2 extraction of non-ionic templates. • Fast extraction of the organic template. • Improvement of material crystallinity. • Hydrothermal resistance of mesoporous silica. Abstract We report how we could circumvent two major drawbacks in the potential scale up synthesis of mesoporous silica via the surfactant-based templating route. First, burning the organic templates to free porosity is costly and not environmental friendly. Most of the mesoporous silica materials show also extremely poor resistance to hydrothermal environments. These drawbacks have certainly contributed to prevent these materials meet practical use, and hampered any possible large-scale manufacturing. Unlike previous reports that claimed that supercritical carbon dioxide (scCO 2) was ineffective in removing most of the organic templates, except amines, we describe how the unique synergy we achieved between scCO 2 extraction and our two-step synthesis of mesoporous silica with nonionic templates allowed us to overcome these drawbacks. We conducted different tests, and we report here the preparation of mesoporous materials with tunable pore size between 1 and 10 nm, structure varying from 3D wormhole to hexagonal, and hydrothermal resistance. [ABSTRACT FROM AUTHOR]

The formation of silicate/organic hybrid micelles is an important milestone in the two-step synthesis of mesoporous silica with polyethyleneoxide (PEO) nonionic structure directing agents (C.R. Chimie 8 (2005) 579). Unlike many inorganic/organic hybrid micelles, these objects have the inorganic component as a diffuse layer positioned at the periphery of the initial micelles and interacting with the hydrophilic polyoxyethylene palisade. We studied how this additional inorganic layer can modify the structure and dynamics of micelles prepared with different types of nonionic surfactants using steady-state and time-resolved fluorescence and dynamic light scattering. Our results show that these hybrid micelles still possess a versatile behavior, which allows them to adapt reversibly to temperature changes. This silicate layer tends to stabilize and consolidate the micelle structure, especially close to the cloud point of critical micelle temperature for polypropyleneoxide (PPO)-based triblock copolymers. Their internal structure is only slightly disturbed by the silicate layer, which reduces the molecular exchanges a little bit. Among other results, we managed to elucidate why mesoporous silica prepared with Pluronic P123, according to our synthesis, stands a dramatic structural change from wormhole to hexagonal structure at 40 °C. Our dynamic light scattering study shows that 40 °C is a critical temperature corresponding to a sphere-to-rodlike structural transition of hybrid micelles, which is not observed with pure micelles. [ABSTRACT FROM AUTHOR]

Membranes are vital and touch every aspect of our daily lives. For instance, they ensure that clean or pure drinking water can be produced, or they can purify our air. However, there is no one-membrane material that can perform all these objectives, and they must be catered for each specific application. As more traditional membrane materials are either polymer based or inorganic/ceramic based, each application will require a different material that can use one or both of these components. Currently, much research is dedicated to combining both polymer and inorganic based materials to form hybrid membranes that could “have the best of both worlds”. The most common form of hybrid membranes are mixed matrix membranes, or MMM. However, their synthesis normally involves the direct addition of inorganic particles into an existing polymeric solution, leading to composite materials without strong interaction between organic and inorganic moieties. In this work, we explore the reversal of this process; that is, the formation of the polymeric component directly from the surface of these particles using surface-initiated atom-transfer radical polymerization, or si-ATRP. Such a method intends to provide a high intimacy between polymers and ceramics, and strong interconnection via covalent bonds. Using a latex based solution of these functionalized titania particles, we present two pathways, known as “Coating Onto” and “Grafting From” pathways, in which these latexes can be applied to larger, tubular membrane coatings. These latexes were first analyzed by TGA to determine their functionalization densities and degree of polymerization. SEM was then employed to visually assess the membrane surfaces to determine the final optimal conditions used for preliminary gas separation tests. [ABSTRACT FROM AUTHOR]

Hybrid materials that are composed of a polymeric material interfaced with an inorganic, metal oxide material have been a rapidly expanding research area in the last few decades. However, interfacial regions remain an important area of focus, and as such hybrid materials do not always possess a very robust or stable interface. Tailor-made interfacial molecules have been successfully reported but material scientists wishing to develop composite interfacial materials would favorably use commercial solutions. Our study shows how we can leverage a commercially available organophosphonic acid group that is coupled with a 2-bromo isobutyrate initiator for surface initiated atom transfer radical polymerization (SI-ATRP) for use as a strong interfacial molecule. We illustrate this mechanism with both nanoparticles of titania and flat titania substrates used as the grafting support and polymerization anchoring points. We demonstrate that the size of the organophosphonic acid initiator, specifically the carbon spacer between the reactive groups, controls the stability of the molecule. The actual covalent linkage between the phosphonic acid group and the titania surface while also leaving the ATRP initiating group able to start the polymerization, is confirmed via31P solid state NMR spectroscopy, liquid 1H NMR spectroscopy XPS, DLS and SEM. [ABSTRACT FROM AUTHOR]

Abstract: Nb3Sn is a superconductor that exhibits higher performances than NbTi alloy currently used in superconducting magnets, regarding both the critical magnetic field and critical current. However, Nb3Sn is an intermetallic compound prepared by thermal treatment, which loses ductility and plasticity once reacted. Since organic materials cannot be used as insulating sheaths and applied before the thermal treatment required for the synthesis of Nb3Sn, a clay mineral-based organic-free sheath was prepared, which can be applied to Nb3Sn magnetic coils prepared by the wind & react method, before the thermal process. This process allows for facile shaping of the superconductor precursor, before reaction, along with the application of the insulating coating, the sintering of this coating being achieved by the thermal treatment required for the synthesis of Nb3Sn. This process has been designed for industrial developments and facile scale-up. The final material is an organic-free ceramic ribbon that can be stored before further use as an insulating sheath of Nb3Sn wires, and electrical and magnetic tests on both the material and a specific demonstrator made with a 20m superconducting reel, demonstrate that this material can be used as an insulating sheath, with no side-effect on superconductor properties. [Copyright &y& Elsevier]

Abstract: We used a new synthesis of TiO2 anatase 6nm nanocrystals prepared at room temperature (Hegazy and Prouzet, 2012 [10]) to explore the influence of different physical-chemical parameters on photocatalysis, and bench-tested the material against two commercial powders made of either pure anatase (Sigma™), or composite anatase–rutile particles (P25 Degussa™). The initial as-synthesised material demonstrates a low photocatalytic activity, which is greatly improved after thermal activation as a result of improved crystallinity without any drastic change in crystal size. The influence of several other parameters was studied, the resulting tests being compared with commercial products. The cumulative improvement provided by these different parameters led finally to a material that exhibits a higher photocatalysis compared to commercial anatase, and similar to the commercial material usually used for reference (P25). This study, which can apply to other titania materials, illustrates how the post-treatment and process adaptation can help to optimise an initial material. [Copyright &y& Elsevier]

TiO2 nanoparticles are a major component in many areas, and especially for dye-sensitized solar cells (DSSC) as a result of their electronic structure that allows them to collect the electrons transferred from the dye molecules after sunlight irradiation, as well as of their semiconducting properties, which provide the surface transport of these electrons up to the collecting electrode. However, for this application or others, the optimization of both structural and electronic properties of titanium oxide is still a challenge because it depends on both crystalline structure and material nano/mesostructure. We report how small (<6 nm) titanium oxide nanoparticles were synthesized by a single step method, with the anatase crystalline phase obtained at room temperature, and an opened nanostructure. A mixture design method was required to identify the precise composition that led to the suitable material. Mesoporous materials made of pure anatase nanocrystals were obtained with the suitable porosity (5 nm pore diameter, 190 m2/g, 0.3 mL/g porous volume) without any surfactant agent. Both the evolution of the crystal size and nature of the phases were studied as a function of heating temperatures ranging from 20 to 800 °C. These materials display a good thermal stability up to 400 °C, in term of crystal size, and up to 700 °C, regarding the crystalline phase. Finally, the study of their semiconducting properties as a function of the crystal size allowed us to confirm the previous theoretical models regarding the crystal size-dependence of band gap and to set the limit of the size quantum confinement effect around 7 nm. The parameters for the synthesis of mesoporous nanocrystalline anatase made of 4 nm nanocrystals were identified via a mixture design method. This surfactant-free room temperature synthesis gives mesoporous materials (5 nm pore size, 190 m2/g, 0.3 mL/g porous volume), which display band gap size quantum confinement, that were tested more specifically for dye-sensitized solar cell applications. [ABSTRACT FROM AUTHOR]

Abstract: The complete understanding of the properties of a material goes in close relationship with a correct description of their structure. This is particularly true for mesoporous silica that exhibits different shapes and sizes of the porous framework as well as different degrees of crosslinking of the silica network itself. These variations can affect drastically the specific properties of these materials as well as their hydrothermal resistance. Hydrothermal resistance and adsorption properties are governed by the surface structure, but the later parameter is not frequently studied because it can be difficult to characterize. Therefore a simple parameter such as surface roughness could be helpful in relating the properties of materials with their surface structure. The direct determination of surface roughness is impossible, but it has been demonstrated that a single mathematical parameter, the surface fractal dimension Ds, can be related within a certain limit with surface roughness. Here we demonstrate using nitrogen adsorption data that a correlation can be drawn between the values of the surface fractal dimension Ds used as a gauge of the surface roughness and the structural evolution of a series of mesoporous silicas. Among the different adsorption models for obtaining Ds that are available nowadays, we selected the one proposed by Avnir and Jaroniec. We demonstrate in this report that there exists a real correlation between the evolution of Ds, when applied to a series of samples prepared under different synthesis conditions, with the evolution of their structure and properties. By example, this study allowed us to link the range of hydrothermal resistance of different mesoporous silicas (e.g. the HMS, MSU, MCM, SBA families of silicas) with their surface roughness. Moreover, we found that HMS silica, a very resistant material toward hydrothermal treatment, exhibits actually the lowest surface roughness. We could demonstrate too how different synthesis parameters such as temperature, can modify this surface roughness, hence the final properties of the mesoporous silica. Finally, we show that this method can even be applied to water ellipsoporometry and help to follow the crystallization of thin layers of metal oxide. Bearing in mind that Ds is a parameter that can readily be determined using the existing software – based on different models – associated with most commercial adsorption equipment, we urge the broader use of the Ds parameter for the structural characterization of surface roughness in mesoporous materials and metal oxide thin layers. [Copyright &y& Elsevier]

Abstract: We describe in the present report how the production of millimetric beads containing porous aluminum oxihydroxide (boehmite) can be obtained easily by taking advantage of the fast gelation process of sodium alginate by ion exchange. The combination of two gelation mechanisms led us to the preparation of objects that can be more easily manipulated than powder and still exhibit the porous properties of this latter, with similar surface area. This pathway can be extended to various systems and it constitutes an additional example of a recent concept called “integrative chemistry” [R. Backov, Soft Matter 2 (2006) 452–464]. [Copyright &y& Elsevier]

Describes the templating of mesoporous molecular sieves by nonionic polyethylene oxide (PEO) surfactants. Applications of mesoporous molecular sieves; Powder x-ray diffraction (XRD) patterns; N2 adsorption-desorption isotherm; Horvath-Kawazoe (HK) pore size distribution.

Abstract: Magnetic behavior of molecular magnets-based nanocomposite materials was investigated as a function of the molecular materials’ concentration. These materials, made of transition metal ions connected via cyano-bridging ligands, Co3[Fe(CN)6]2, were synthesized simultaneously with MSU-type mesoporous silica as a confinement matrix. This synergetic synthesis led to Co3[Fe(CN)6]2 nanoparticles of ca. 2–3nm. Their magnetic properties were investigated as a function of their concentration. These analyses, including dc and ac vs temperature, as well as frequency measurements, reveal a superspin-glass like transition at low temperature. The aging and memory effects observed demonstrate that the superspin-glass behavior for nanocomposites containing the lowest amount of nanoparticles is due principally to spin frustration on the surface of the nanoparticles while for the nanocomposites containing the largest amount of nanoparticles, both surface spin-frustration and dipolar interparticle interactions influence the magnetic regime. [Copyright &y& Elsevier]

Dye-sensitized solar cells (DSSCs) are still attracting great attention as a potential alternative to conventional silicon solar cells, and a lot of current research is focusing on enhancing their efficiency through the individual improvement of the DSSCs components, as well as their integration. Among all components, mesoporous TiO 2 plays a major role, because it is the charge collector for the dye molecules or perovskite in liquid and solid DSSCs, respectively. Specificities of TiO 2 are now well-known: an anatase crystalline structure for an optimized bandgap, small particle size to shorten the charge diffusion path, reduced grain boundaries to limit current resistivity, significant porosity to enhance integration and interaction between the photon absorbers and the charge-collecting anode. We reported previously how well-crystallized small nanoparticles were successfully synthesized via a room temperature synthesis by Hegazy and Prouzet (2012) [ 10 ], leading to very small crystallites (4–10 nm) of pure TiO 2 anatase. Since as-synthesized materials still contain hydration water, a major drawback in DSSCs, we report here how dehydration and crystallinity can be improved by annealing at a moderate temperature, without any sintering or significant particle coarsening. The resulting impact on properties is confirmed by testing the resulting annealed TiO 2 nanopowder in photovoltaic liquid DSSCs. In addition, we describe a comprehensive study of the preparation and test of TiO 2 based photoanodes, including UV exposure and HCl treatment. Photovoltaic tests were conducted on a large active surfaces (5 cm 2 ) cells to give a more realistic picture of the influence of each parameter involved in the cell performance, characterized under AM 1.5 illumination with 100 mWcm −2 light intensity. The specific contribution of each parameter on the cell performance is discussed. We demonstrate why the TiO 2 nanopowder developed in our previous synthesis, in connection with the suitable treatments during the photoanode preparation, can replace commercial powders, with a greater success in cell photoefficiency. [ABSTRACT FROM AUTHOR]

We report how the control of a single parameter, the co-surfactant, determines the phase transitions of oil-in-water swollen liquid crystals (SLCs) prepared with cetyltrimethylammonium bromide (CTAB), from cubic to hexagonal, lamellar, and finally sponge-like structures. SLCs are complex mixtures (surfactant + co-surfactant + water + salt + oil) usually prepared to form hexagonal mesophases, with cell parameters tunable between 3 and 30 nm. These hexagonal mesophases were successfully used as nanoreactors to prepare a broad range of nanostructured materials. Because the potential of these mesophases as adaptive nanoreactors has not been extended to other liquid crystal geometries than the hexagonal, we studied in a first step the structure evolution of SLCs made with CTAB, cyclohexane, pentanol-1, water and different stabilising salts. We used small-angle X-ray scattering (SAXS), polarised light microscopy and Freeze-Fracture TEM to provide a partial phase diagram and list the different mesophases obtained as a function of composition. We report that the adjustment of a single parameter, the co-surfactant (pentanol-1), determines the phase transition between cubic, hexagonal, lamellar, and sponge-like structures, all other parameters such as the nature and concentration of salt, or amount of oil being constant. [ABSTRACT FROM AUTHOR]

We report the experimental evidence of a new form of room-temperature ferromagnetism in high surface area nanocrystalline manganese-doped In2O3, prepared from colloidal nanocrystals as building blocks. The nanocrystal structure (bixbyite or corundum) and assembly were controlled by their size, and the type and concentration of dopant precursors. The existence of substitutional paramagnetic Mn dopant ions in mixed valence states (Mn2+ and Mn3+) was confirmed and quantified by different spectroscopic methods, including X-ray absorption and magnetic circular dichroism. The presence of different oxidation states is the basis of ferromagnetism induced by Stoner splitting of the local density of states associated with extended structural defects, due to charge transfer from the Mn dopants. The extent of this charge transfer can be controlled by the relationship between the electronic structures of the nanocrystal host lattice and dopant ions, rendering a higher magnetic moment in bixbyite relative to corundum Mn-doped In2O3. Charge-transfer ferromagnetism assumes no essential role of dopant as a carrier of the magnetic moment, which was directly confirmed by X-ray magnetic circular dichroism, as an element-specific probe of the origin of ferromagnetism. At doping concentrations approaching the percolation limit, charge-transfer ferromagnetism can switch to a double exchange mechanism, given the mixed oxidation states of Mn dopants. The results of this work enable the investigations of the new mechanisms of magnetic ordering in solid state and contribute to the design of new unconventional magnetic and multifunctional materials. [ABSTRACT FROM AUTHOR]

Metalcyanobridged coordination polymersor Prussian blueanalogues (PBA)nanoparticles have been synthesized along witha mesostructured MSU-type silica matrix. This synthesis was appliedto several M(II)3[M′(III)(CN)6]2, (M = Co, Ni, Fe; M′ = Co, Fe) and ahomogeneous distribution of PBA nanometric particles was obtained,even at high concentration (>20 wt %) within a silica matrix thatexhibits long-range order as the result of the concomitant increasein concentration of nonionic surfactants templates during the synthesis.The same magnetic behavior as observed for bulk materials was observedwith the magnetic PBA nanoparticles and thermal treatment under differentatmospheres leads to the formation of bimetallic oxides or alloys,which display magnetic properties. [ABSTRACT FROM AUTHOR]

The photocatalytic properties of titanium dioxide depend not only on its electronic properties, but also on the material size and shape, which can increase interactions between the reactants and catalyst. Most studies to date show that reducing the particle size down to the nanoscale increases photocatalytic efficiency, as a result of a higher surface to volume ratio and because a larger proportion of the material is actually irradiated by light. We demonstrate that a multiscale shape design, which integrates surface roughness, particle shape, and 1D material processing and orientation, can favor photocatalytic properties in the solid-gas regime, especially mineralization (conversion into CO2), when the hierarchical 1D orientation of the material is combined with unidirectional gas flow. Several materials with hierarchical structure were prepared and characterized. They have been tested for the photocatalytic mineralization of gaseous acetone and compared with commercial catalysts. Our study reveals that a suitable combination of multiscale design and optimization of the material orientation and gas flow favors high mineralization. [ABSTRACT FROM AUTHOR]

Abstract: A lot of experiments were investigated to show the behaviour of an ultrafiltration membrane during the filtration of pure salt solutions. What happens when the filtered solution contains several ions? In this paper, results are given concerning the filtration of mixtures of two salts solutions, salts with a common anion: NaCl+CaCl2 and Na2SO4 +CaSO4. The surface charge of the membrane is characterized by streaming potential measurements and rejection rates by means of chromatography. These results confirm the adsorption of divalent ions on the surface and a good selectivity for divalent cations. [Copyright &y& Elsevier]

Abstract: We report the singular filtration properties of an ultrafiltration membrane made with mesoporous silica that exhibits cylindrical pores aligned mostly normal to the support. This membrane supported on tubular commercial macroporous alumina supports was prepared by the interfacial growth mechanism between stable silica–surfactant hybrid micelles made of the association of silica oligomers with polyethyleneoxide-based (PEO) surfactants and sodium fluoride, a well-known silica condensation catalyst [Boissière et al., An ultrafiltration membrane made with mesoporous MSU-X silica, Chem. Mater. 15 (2003) 460–463]. It appears that the combined effect of the silica nature of the membrane, whose surface charge can be easily adjusted by changing the pH and the non-connected cylindrical shape of the pores provides a new behavior in the retention properties, as proved by the filtration of polyoxyethylene polymers (PEO) with different molecular weights. Depending on the filtration conditions, a rejection rate of 80% and a steep cut-off at 2000Da can be obtained or, on the reverse, polymers three times bigger than the pore diameter can diffuse through the membrane. This new filtration mechanism, which opens up new modes of separation modes, is explained in the light of both topology of the porous network and pH-dependent interactions between PEO polymers and silica porous media. [Copyright &y& Elsevier]

Abstract: We report the preparation of a novel type of mesoporous silica of the MSU-type family. This material was prepared with Pluronic P123 copolymer in mild acidity according to a two-step process. Its structure was explored by X-ray diffraction, N2 isotherms, SEM and TEM. The TEM study was completed by a 3D tomography analysis that allowed us to obtain information on the morphology of the pore-and-void system. The powder is homogeneous and made of nanoparticles (200 nm in size) built by the folding of ribbons with hexagonally-packed pores (pore diameter of 8.6 nm). This folding creates microvoids in the particles that give rise to an additional porosity. The properties of adsorption/separation of this new type of silica were tested for HPLC. Although the powder was not optimized for this application, the first results on ungrafted silica appear equivalent to those obtained with a commercial HPLC silica powder. To cite this article: M.U. Martines et al., C. R. Chimie 8 (2005). [Copyright &y& Elsevier]

MSU-type mesoporous silica prepared with nonionic surfactants according to the two-step pathway, exhibits a specific feature that makes its structure sensitive to the synthesis temperature. Until now, this factor had been demonstrated to affect the pore structure in the mesoporous range, between 2 and 5 nm. We describe in the present report that this parameter affects drastically syntheses of MSU-3 silica made with the block copolymer Pluronic 123 within a temperature range of 5–75 °C. Depending on the synthesis temperature, the pore size can vary from microporous (below 2 nm) to mesoporous (close to 9 nm) in a steady-like evolution. However, two properties of block copolymers must be addressed for a full understanding of this evolution: the solubility limit of nonionic templates at higher temperatures, which prevents the formation of micelles because a too high hydrophobicity, and the Critical Micelle Temperature (CMT) at lower temperatures, which prevents the formation of micelles because a too high hydrophilicity. These results confirm that the assembly mechanism that leads to mesostructured materials requires a fine balance of interactions, not only between inorganic and organic reagents but also between the organic templates themselves. [Copyright &y& Elsevier]

In this work, we shall expose the main results obtained with ceramic air filters (CAF) having different characteristics. CAF are discs in which the filtration area is equal to 130 cm2. The influence of face velocities of the aerosols varying from 0.5 to 14 cm/s, of porous volume, ranging from 48 to 58%, of pore diameters ranging from 11 to 14.8 μm and of thickness of the filters (from 1 to 3.2 mm) on the values of the penetration and the pressure drop will be pointed out. Particle penetration which depends on the values of these parameters have been measured in the range from 10−6 to 5×10−2 which corresponds to an efficiency varying from 99.999999 to 99.95%. Relative performances of filters have been analyzed in terms of figure of merit. [Copyright &y& Elsevier]