Abstract: Ceria nanoparticles (NPs) are fundamental in heterogeneous catalysis because of their ability to store or release oxygen depending on the ambient conditions. Their oxygen storage capacity is strictly related to the exposed planes, crystallinity, density and distribution of defects. In this work a study of ceria NPs produced with a ligand-free, physical synthesis method is presented. The NP films were grown by a magnetron sputtering based gas aggregation source and studied by high resolution- and scanning-transmission electron microscopy and x-ray photoelectron spectroscopy. In particular, the influence of the oxidation procedure on the NP reducibility has been investigated. The different reducibility has been correlated to the exposed planes, crystallinity and density and distribution of structural defects. The results obtained in this work represent a basis to obtain cerium oxide NP with desired oxygen transport properties.

Abstract: Deactivation was investigated in Fe2O3-CeO2 oxygen storage materials during repeated H-2-reduction and CO2-reoxidation. In situ XRD, XAS, and TEM were used to identify phases, crystallite sizes, and morphological changes upon cycling operation. The effect of redox cycling was investigated both in Fe-rich (80 wt % Fe2O3-CeO2) and Ce-rich (10 wt %Fe2O3-CeO2) materials. The former consisted of 100 nm Fe2O3 particles decorated with 5-10 nm Ce1-xFexO2-x. The latter presented CeO2 with incorporated Fe, i.e. a solid solution of Ce1-xFexO2-x, as the main oxygen carrier. By modeling the EXAFS Ce-K signal for as-prepared 10 wt %Fe2O3-CeO2, the amount of Fe in CeO2 was determined as 21 mol %, corresponding to 86% of the total iron content. Sintering and solid solid transformations, the latter including both new phase formation and element segregation, were identified as deactivation pathways upon redox cycling. In Ce-rich material, perovskite (CeFeO3) was identified by XRD. This phase remained inert during reduction and reoxidation, resulting in an overall lower oxygen storage capacity. Further, Fe segregated from the solid solution, thereby decreasing its reducibility. In addition, an increase in crystallite size occurred for all phases. In Fe-rich material, sintering is the main deactivation pathway, although Fe segregation from the solid solution and perovskite formation cannot be excluded.

Abstract: Barium titanate powder was processed by slip casting in a rotating strong magnetic field of 9.4 T. The orientation factor of the sintered compact was analyzed by the X-ray diffraction technique and the microstructure (grain-size) was analyzed by scanning electron microscope. The hydrothermally prepared barium titanate was used as matrix material and the molten-salt synthesized barium titanate, with a larger particle-size, was used as template for the templated grain-growth process. Addition of large template particles was observed to increase the orientation factor of the sintered cast (5 vol% loading). Template particles acted as starting grains for the abnormal grain-growth process and the average grain-size was increased after sintering. Increasing the solid loading (15 vol%) resulted in a similar orientation factor with a decrease of the average grain size by more than half. However, addition of templates to the 15 vol% cast had a negative effect on the orientation factor. The impingement of growing particles was stated as the primary cause of particle misorientation resulting in a low orientation factor after sintering. Different heating conditions were tested and it was determined that a slow heating rate gave the highest orientation factor, the smallest average grain-size and the highest relative density. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Abstract: An attempt to grow a thin epitaxial composite film of YBa2Cu3O7−δ (YBCO) with spinel MnFe2O4 (MFO) nanoparticles on a LAO substrate using the CSD approach resulted in a decomposition of the spinel and various doping modes of YBCO with the Fe and Mn cations. These nanostructural effects lead to a lowering of T c and a slight J c increase in field. Using a combination of advanced transmission electron microscopy (TEM) techniques such as atomic resolution high-angle annular dark field scanning TEM, energy dispersive x-ray spectroscopy and electron energy-loss spectroscopy we have been able to decipher and characterize the effects of the Fe and Mn doping on the film architecture. The YBaCuFeO5 anion-deficient double perovskite phase was detected in the form of 3D inclusions as well as epitaxially grown lamellas within the YBCO matrix. These nano-inclusions play a positive role as pinning centers responsible for the J c/J sf (H) dependency smoothening at high magnetic fields in the YBCO-MFO films with respect to the pristine YBCO films.

Abstract: High critical current densities can be realized in high-temperature superconductors such as YBa2Cu3O7-δ (YBCO) by controlling density, shape, size and direction of a secondary phase. Whereas the dependence on the growth rate and deposition temperature has been widely studied as key parameters for nano-engineering the pinning landscape, the vicinal tilt of the substrate surface might have an additional influence. Therefore, we deposited 6 mol% BaHfO3 (BHO) doped YBCO on SrTiO3 (STO) substrates with vicinal angles α between 0° and 40° to identify the influence of the tilt on the growth mode of BHO. An undisturbed epitaxial growth of the superconductor as well as an epitaxial integration of the BHO phase in the YBCO matrix is observed for all vicinal angles investigated. The critical temperature is constant up to α = 20°, whereas the self-field critical current density at 77 K starts to decrease above 10°. A detailed structural analysis of the film cross sections showed that the growth mode of BHO changes already for a vicinal tilt of 2° from a pure c-axis oriented growth to a layered structure with BHO aligned parallel to the YBCO ab-plane. We identified a strong influence of such a microstructure on the current flow in BHO doped YBCO films on STO substrates as well as on MgO based coated conductors prepared by inclined substrate deposition

Abstract: A series of BiVO4/3DOM TiO2 nanocomposites have been synthesized and their photocatalytic activity was investigated under visible light irradiation using the RhB dye as model pollutant molecule in an aqueous solution. The effect of the amount of BiVO4 as visible light sensitizer on the photocatalytic activity of BiVO4/3DOM TiO2 nanocomposites was highlighted. The heterostructured composite system leads to much higher photocatalytic efficiencies than bare 3DOM TiO2 and BiVO4 nanoparticles. As the proportion of BiVO4 in BiVO4/3DOM TiO2 nanocomposites increases from 0.04 to 0.6, the photocatalytic performance of the BiVO4/3DOM TiO2 nanocomposites increases and then decreases after reaching a maximum at 0.2. This improvement in photocatalytic perfomance is related to 1) the interfacial electron transfer efficiency between the coupled materials, 2) the 3DOM TiO2 inverse opal structure with interconnected pores providing an easy mass transfer of the reactant molecules and high accessibility to the active sites and large surface area and 3) the effect of light sensitizer of BiVO4. Intensive studies on structural, textural, optical and surface properties reveal that the electronic interactions between BiVO4 and TiO2 lead to an improved charge separation of the coupled BiVO4/TiO2 system. The photogenerated charge carrier densities increase with increasing the BiVO4 content, which acts as visible light sensitizer to the TiO2 and is responsible for the enhancement in the rate of photocatalytic degradation. However, the photocatalytic activity is reduced when the BiVO4 amount is much higher than that of 3DOM TiO2. Two reasons could account for this behavior. First, with increasing BiVO4 content, the photogenerated electron/hole pairs are accumulated at the surface of the BiVO4 nanoparticles and the recombination rate increases as shown by the PL results. Second, decreasing the amount of 3DOM TiO2 in the nanocomposite decreases the surface area as shown by the BET results. Moreover, the poor adsorptive properties of the BiVO4 photocatalyst also affect the photocatalytic performance, in particular at higher BiVO4 content. The present work demonstrates that BiVO4/3DOM TiO2 is a very promising heterojunction system for visible light photocatalytic applications.

Abstract: Heterogeneous metal catalysts enable the direct conjugation of linoleic acid tails in vegetable oil to their conjugated linoleic acid (CIA) isomers. CIA-enriched oils are useful as renewable feedstock for the chemical industry and as nutraceutical. Up to now, a solvent-free process for conjugated oils without significant formation of undesired hydrogenation products was not existing. This work shows the design of Ru/USY catalysts able to directly conjugate highly unsaturated vegetable oils such as safflower oil in absence of solvent and hydrogen. Key is fast molecular transport of the bulky reagent and reactive product triglycerides in the zeolite crystal. A two-step zeolite post-synthetic treatment (with NH4OH and acetate salt) was applied to create the necessary mesoporosity. More open zeolite structures allow for a faster conjugation reaction, while securing a fast removal of the reactive conjugated triglycerides, otherwise rapidly deactivating through fouling and pore blockage by polymers. The best Ru/USY catalyst in this contribution is capable of producing exceptionally high yields of conjugated oils, containing up to almost 30 wt% conjugated fatty acid tails in safflower oil, at an initial production rate of 328 g(CLA) mL(-1) h(-1) per gram metal catalyst. (C) 2016 Elsevier B.V. All rights reserved.

Abstract: The design of functional micro- and mesostructured composite materials is significantly important for separation processes. Mesoporous silica is an attractive material for fast diffusion, while microporous zeolitic imidazolate frameworks (ZIFs) are beneficial for selective adsorption and diffusion. In this work, ZIF-71 and ZIF-8 nanocrystals were grown on the surface of mesoporous silica spheres (MSS) via the seeding and regrowth approach in order to obtain monodispersed MSS-ZIF-71 and MSS-ZIF-8 spheres with a particle size of 2-3 mm. These MSS-ZIF spheres were uniformly dispersed into a polydimethylsiloxane (PDMS) matrix to prepare mixed matrix membranes (MMMs). These MMMs were evaluated for the separation of ethanol from water via pervaporation. The pervaporation results reveal that the MSS-ZIF filled MMMs substantially improve the ethanol recovery in both aspects viz. flux and separation factor. These MMMs outperforms the unfilled PDMS membranes and the conventional carbon and zeolite filled MMMs. As expected, the mesoporous silica core allows very fast flow of the permeating compound, while the hydrophobic ZIF coating enhances the ethanol selectivity through its specific pore structure, hydrophobicity and surface chemistry. It can be seen that ZIF-8 mainly has a positive impact on the selectivity, while ZIF-71 enhances fluxes more significantly.

Abstract: Towards the development of novel drug carriers for oral delivery of poorly soluble drugs mesoporous aerogel carbons (CAs), namely CA10 and CA20 with different pore sizes (10 and 20 nm, respectively), were evaluated. The non-steroidal anti-inflammatory lipophilic compound ibuprofen was incorporated via passive loading. The drug loaded carbon aerogels were systemically investigated by means of High-Resolution Transmission Electron Microscopy (HR-TEM), Nitrogen physisorption studies, X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), X-ray photon electron spectroscopy (XPS) and zeta-potential studies. In vitro release studies were performed in simulated intestinal fluids reflecting both fasted (FaSSIF) and fed (FeSSIF) state conditions. Cytotoxicity studies were conducted with human intestinal cells (Caco-2). Drug was in an amorphous state in the pores of the carbon carrier as shown from the physicochemical characterization studies. The results showed marked differences in the release profiles for ibuprofen from the two aerogels in the media tested whereas in vitro toxicity profiles appear to be compatible with potential therapeutic applications at low concentrations. (C) 2016 Elsevier B.V. All rights reserved.

Abstract: We present a green, biological production route for silica-titania photocatalysts using diatom microalgae. Diatoms are single-celled, eukaryotic microalgae (2-2000 mu m) that self-assemble soluble silicon (Si(OH)(4)) into intricate silica cell walls, called frustules. These diatom frustules are formed under ambient conditions and consist of hydrated silica with specific 3D morphologies and micro-meso or macroporosity. A remarkable characteristic of diatoms is their ability to bioaccumulate soluble titanium from cell culture medium and incorporate them into their nanostructured silica cell wall. Controlled cultivation of the diatom Pinnularia sp. on soluble titanium in a batch process resulted in the biological immobilisation of titanium dioxide in the porous 3D architecture of the frustules. Six different titanium sources are tested. The silica-titania frustules were isolated by treating the harvested Pinnularia cells with nitric acid (65%) or by high temperature treatment. Thermal annealing converted the amorphous titania into crystalline titania. The produced silica-titania material is evaluated towards photocatalytic activity for acetaldehyde (C2H4O) abatement. Frustules cultivated with TiBaldH showed the highest photocatalytic performance. Comparison of the photocatalytic activity with P25 reveals that P25 has a 4 fold higher photocatalytic activity, but when photocatalytic activity is normalized for titania content, the frustules show double activity. Further material characterization (morphology, crystallinity, surface area and elemental distribution) of the TiBaldH silica-titania frustules provides additional insight into their structure-activity relationship. These natural biosilicatitania materials have excellent properties for photocatalytic purposes, including high surface area (108 m(2) g(-1)) and good porosity, and show reliable immobilization of TiO2 in the ordered structure of the diatom frustule.

Abstract: We present the in situ synthesis of Au nanoparticles within the Zr based Metal Organic Framework, UiO-66. The resulting Au@UiO-66 materials were characterized by means of N-2 sorption, XRPD, UV-Vis, XRF, XPS and TEM analysis. The Au nanoparticles (NP) are homogeneously distributed along the UiO-66 host matrix when using NaBH4 or H-2 as reducing agents. The Au@UiO-66 materials were evaluated as catalysts in the oxidation of benzyl alcohol and benzyl amine employing O-2 as oxidant. The Au@MOF materials exhibit a very high selectivity towards the ketone (up to 100%). Regenerability and stability tests demonstrate that the Au@UiO-66 catalyst can be recycled with a negligible loss of Au species and no loss of crystallinity. In situ IR measurements of UiO-66 and Au@UiO-66-NaBH4, before and after treatment with alcohol, showed an increase in IR bands that can be assigned to a combination of physisorbed and chemisorbed alcohol species. This was confirmed by velocity power spectra obtained from the molecular dynamics simulations. Active peroxo and oxo species on Au could be visualized with Raman analysis.

Abstract: In this work we elucidate the elimination of mechanism Fe-antisite defects in lithium iron phosphate (LiFePO4) during the hydrothermal synthesis. Compelling evidence of this effect is provided by combining Neutron Powder Diffraction (NPD), High Resolution (Scanning) Transmission Electron Microscopy (HR-(S)TEM), Electron Energy Loss Spectroscopy (EELS), X-Ray Photoelectron Spectroscopy (XPS) and calculations. We found: i) the first intermediate vivianite inevitably creates Fe-antisite defects in LiFePO4; ii) the removal of these antisite defects by cation exchange is assisted by a nanometer-thick amorphous layer, rich in Li, that enwraps the LiFePO4 crystals.

Abstract: Self-assembly (SA) of nanostructures has recently gained increasing interest. A clear understanding of the process is not straightforward since SA of nanoparticles is a complex multiscale phenomenon including different driving forces. Here, we study the SA between aluminum doped ZnO nanopyramids into couples by combining inorganic chemistry and advanced electron microscopy techniques with atomistic simulations. Our results show that the SA of the coupled nanopyramids is controlled first by morphology, as coupling only occurs in the case of pyramids with well-developed facets of the basal planes. The combination of electron microscopy and atomistic modeling reveals that the coupling is further driven by strong ligandligand interaction between the bases of the pyramids as dominant force, while screening effects due to Al doping or solvent as well as corecore interaction are only minor contributions. Our combined approach provides a deeper understanding of the complex interplay between the interactions at work in the coupled SA of ZnO nanopyramids.

Abstract: The influence of neat and organically modified montmorillonite on the structureproperty relationships of a β-nucleated polypropylene matrix has been thoroughly investigated. High-angle annular dark field scanning transmission electron microscopy revealed that the organic modification of clay facilitated the dispersion of the clay, while X-ray diffractograms showed the α-nucleating effect of the clays on the β-nucleated matrix. The results from tensile tests showed that the organic modification of MMT affected profoundly only the tensile strength at yield and at break. The effect of the organic modification of the clay on the thermal stability of the composites was finally evaluated by thermogravimetric analysis, where the samples filled with oMMT decomposed faster than the ones filled with neat MMT, due to the decomposition of the organic salts that were initially used for the modification of MMT. A kinetics study of the thermal degradation of the composites was also performed, in order to export additional conclusions on the activation energy of the samples.