[en] The synthesis and functionalization of zeolite nanoparticles designed for laser-polarized ¹²⁹Xe NMR experiments in solution are described. These nanoparticles were functionalized by using original synthesis pathways through semicarbazide COCHO chemistry in order to ensure anchoring of a peptide for targeting biological receptors and attachment of PEG chains for in vivo experiments. Results demonstrated that accessibility of the dissolved noble gas to the micropores was maintained after functionalization. gamma Scintigraphy with ¹¹¹In linked to the zeolite particles has been investigated in order to follow the behaviour of the zeolite nanoparticles in mice. These preliminary ¹¹¹In scintigraphy experiments showed the localization of the nanoparticles after injection in mice and their biodistribution, as a first proof-of-concept towards in vivo ¹²⁹Xe MRI. (authors)

[en] The synthesis of a bis-zwitterionic lamellar hybrid material containing ammonium carboxylate groups is described. Cation-exchange properties of this material towards transition metal and lanthanide ions were studied as well as the regeneration and reuse of the material. (authors)

[en] Hydrogen production by radiolysis of water absorbed on solid is a major problem for nuclear waste management. In the present study, we demonstrate that controlling extreme surface properties of the irradiated material allows a direct tuning of the hydrogen production under irradiation. We achieve this control on a model system (silica fibers) using liquid phase atomic layer deposition (ALD) of titanium or zirconium oxide. The hydrogen production is strongly inhibited by the deposition of a sub-nano-metric layer of titanium oxide, whereas it is amplified upon zirconium oxide grafting. (authors)

[en] Atomistic simulation techniques have been used to study the insertion of lithium and sodium into α-U₃O₈. Calculations for isolated guest ions predict that lithium will occupy five-co-ordinate trigonal bipyramidal sites whereas sodium will occupy nine-co-ordinate sites. The modelling of the stoichiometric phases MU₃O₈ (M = Li, Na) reinforces these predictions. Calculations of ion migration are presented; lithium is demonstrated to be fairly mobile within the lattice whereas the diffusion of sodium is much more difficult. (author)

[en] Fibrous cerium hydrogenphosphate, CeP, has been treated hydrothermally in 1 mol dm^-3 phosphoric acid solution. CEP and its hydrothermally treated product, CeP(HT), have been characterized by X-ray powder diffractometry, scanning electron microscopy, solid-state ³¹P MAS NMR spectroscopy, FTIR spectroscopy, chemical and thermal analyses. A poorly crystalline fibrous CeP with a d-spacing of 1.1 nm converted into a highly crystalline CeP(HT) with platelet morphology by hydrothermal treatment. Solid-state ³¹P MAS NMR and FTIR measurements confirmed that one kind of phosphate (H₂PO₄) is present in CeP and two kinds of phosphate (HPO₄, PO₄) are present in CeP(HT), in which the integrated intensity ratio of HPO₄ to PO₄ is 2:1. From chemical and thermal analyses, structural formulae for CeP and CeP(HT) are assumed to be CeO(H₂PO₄)₂ ·2H₂O and Ce(HPO₄)(PO₄)_0.5, respectively. The Na⁺ exchange capacity of CeP amounted to 4.5 mmol g^-1 at pH 11 while that of CeP(HT) was less than 1.0 mmol g^-1 in the pH range 2-12. The pH dependence of the metal ion distribution coefficients exhibited ideal ion-exchange behaviour on CeP while metal ion distribution coefficients on CeP(HT) scarcely depended on pH. The metal ion selectivities of CeP and CeP(HT) increased in the order: Na⁺< Ca²⁺< Sr²⁺< K⁺, and Na⁺< K⁺< Ca²⁺< Sr²⁺, respectively. The distribution coefficient for the Sr²⁺ ion of CeP(HT) was higher than that of CeP under hydrothermal conditions. (Author)

[en] The synthesis, electron diffraction (ED), synchrotron X-ray and neutron structure, X-ray absorption spectroscopy (XAS) and magnetic property studies of La2MnVO6 double perovskite are described. Analysis of the synchrotron powder X-ray diffraction data for La2MnVO6 indicates a disordered arrangement of Mn and V at the B-site of the perovskite structure. Absence of super-lattice reflections in the ED patterns for La2MnVO6 supports the disordered cation arrangement. Room temperature time-of-flight (TOF) neutron powder diffraction (NPD) data show no evidence of cation ordering, in corroboration with the ED and synchrotron studies (orthorhombic Pnma, a = 5.6097(3), b = 7.8837(5) and c = 5.5668(3); 295 K, NPD). A comparison of XAS analyses of La2TVO6 with T = Ni and Co shows T2+ formal oxidation state while the T = Mn material evidences a Mn3+ admixture into a dominantly Mn2+ ground state. V-K edge measurements manifest a mirror image behavior with a V4+ state for T = Ni and Co with a V3+ admixture arising in the T = Mn material. The magnetic susceptibility data for La2MnVO6 show ferromagnetic correlations; the observed effective moment, μeff (5.72 μB) is much smaller than the calculated moment (6.16 μμB) based on the spin-only formula for Mn2+ (d5, HS)/V4+ (d1), supportive of the partly oxidized Mn and reduced V scenario (Mn3+/V3+).

[en] Graphene-modified LiFePO₄ composite has been developed as a Li-ion battery cathode material with excellent high-rate capability and cycling stability. The composite was prepared with LiFePO₄ nanoparticles and graphene oxide nanosheets by spray-drying and annealing processes. The LiFePO₄ primary nanoparticles embedded in micro-sized spherical secondary particles were wrapped homogeneously and loosely with a graphene 3D network. Such a special nanostructure facilitated electron migration throughout the secondary particles, while the presence of abundant voids between the LiFePO₄ nanoparticles and graphene sheets was beneficial for Li⁺ diffusion. The composite cathode material could deliver a capacity of 70 mAh g^-1 at 60C discharge rate and showed a capacity decay rate of <15% when cycled under 10C charging and 20C discharging for 1000 times.

[en] The dissolution of ceria is studied through a catalytic reduction process involving platinum nanoparticles in mild conditions at near ambient temperature. The deposition of platinum nanoparticles is made by sonication (Ar, 18 W cm^-2, 20 kHz), and further dissolution is studied as a function of different parameters such as stirring, sonication, dissolution media and temperature. The dissolution is evaluated using UV-vis spectrophotometry, ICP-AES, and SEM. The quantitative dissolution of ceria can be performed in HNO₃-HCOOH-[N₂H₅][NO₃], HNO₃-[N₂H₅][NO₃] or H₂SO₄-HCOOH mixtures at 40 degrees C. Nevertheless, it is shown that the combined use of ultrasound with nitric media in the presence of platinum nanoparticles can lead to passivating phenomena resulting in a decrease of the dissolution rate. (authors)

[en] We report the direct determination of surface enthalpies for nanophase TiO₂ anatase with different morphologies derived from drop solution calorimetry in a molten sodium molybdate (3Na₂Ol·4MoO₃) solvent at 702 C. The energetics of surface hydration has been measured using a Calvet microcalorimeter coupled with a gas dosing system. The surface enthalpies of hydrated surfaces for anatase TiO₂ nanoparticles, nanowires and sea-urchin-like assemblies are 0.51 ± 0.05, 1.07 ± 0.28, and 1.29 ± 0.16 J m^-2, respectively, whereas those of anhydrous surfaces are 0.74 ± 0.04, 1.24 ± 0.28, and 1.41 ± 0.16 J m^-2, respectively. The trend in TiO₂, which shows higher surface enthalpies for more complex nanostructures, is consistent with that reported in ZnO. The shape-dependent surface enthalpy at the nanoscale level is discussed in terms of exposed surface structures. The enthalpies of hydration appear to be similar for all morphologies.

[en] A 3D porous architecture of Si/graphene nanocomposite has been rationally designed and constructed through a series of controlled chemical processes. In contrast to random mixture of Si nanoparticles and graphene nanosheets, the porous nanoarchitectured composite has superior electrochemical stability because the Si nanoparticles are firmly riveted on the graphene nanosheets through a thin SiO_x layer. The 3D graphene network enhances electrical conductivity, and improves rate performance, demonstrating a superior rate capability over the 2D nanostructure. This 3D porous architecture can deliver a reversible capacity of ∼900 mA h g^-1 with very little fading when the charge rates change from 100 mA g^-1 to 1 A g^-1. Furthermore, the 3D nanoarchitechture of Si/graphene can be cycled at extremely high Li⁺ extraction rates, such as 5 A g^-1 and 10 A g^-1, for over than 100 times. Both the highly conductive graphene network and porous architecture are considered to contribute to the remarkable rate capability and cycling stability, thereby pointing to a new synthesis route to improving the electrochemical performances of the Si-based anode materials for advanced Li-ion batteries.