One-step synthesis of vanadium-doped anatase mesocrystals for Li-ion battery anodes.

Here we report a successful one-step synthesis of vanadium-doped anatase mesocrystals by reactive annealing of NH4TiOF3/PEG2000 mesocrystal precursors with NH4VO3. The formation solid solution Ti1-xVxO2with vanadium content up tox = 25 at% inheriting the structure of mesocrystals is observed for the first time. The doping mechanism via vapor phase transport of vanadium is proposed. The Ti1-xVxO2mesocrystals exhibit improved specific capacity of 175 mAh g-1(compared to 150 mAh g-1for pure anatase phase) and decreased potential gap between charge and discharge processes.

Permeability of anodic alumina membranes grown on low-index aluminium surfaces.

Porous anodic aluminium oxide (AAO) membranes have various practical applications in separation and purification technologies. Numerous approaches have been utilized to tailor the transport properties of porous AAO films, but all of them assume an isotropic nature of anodized aluminium. Here, the impact of aluminium crystallography on the permeability of AAO membranes is disclosed. A comparative study of AAO membranes formed on low-index aluminium surfaces by anodizing in a sulphuric acid electrolyte is presented. Small-angle x-ray scattering is used to quantify the out-of-plane pore arrangement. AAO grown on an Al(100) substrate possesses a porous structure with minimal point defects and pore tortuosity, providing the highest permeability of individual gases in a series of AAO membranes. These findings can also be applied for the fabrication of highly permeable AAO membranes on polycrystalline Al foils.

Spontaneous MXene monolayer assembly at the liquid-air interface.

Here we report on the spontaneous assembly of Ti3C2Tx MXene flakes into monolayer films at the liquid-air interface. According to X-ray reflectivity and grazing incidence X-ray fluorescence both the structure of the layers and assembly kinetics depends on the pH value of the solution. At pH > 4 MXene flakes form a single ∼1.5 nm thick layer carrying a negative charge, while in the acidic medium the layer contains coordinated anions with the formation of the Braq-/Ti3C2Tx/subphase interface. The surface layer compression allows the assembling of MXene flakes into a dense monolayer films with the surface coverage of up to 96% and surface pressure exceeding 40 mN m-1 in the case of the acidic subphase. The films can readily be transferred onto solid substrates by the conventional Langmuir-Blodgett approach or modified by surfactants to form MXene/surfactant composite films.

Gas permeation through nanoporous membranes in the transitional flow region.

An experimental study on the permeability of anodic alumina (20-120 nm) and track-etched (30 nm) nanoporous membranes for different gases in the transitional flow regime is reported in the range of Knudsen numbers from 0.1 to 10. A significant variation (up to 30%) of the membrane permeance for different gases at the same Knudsen numbers is reported with certainty. It is established that this discrepancy relates to a molecule's effective collision area, which is poorly described in the frameworks of conventional gas permeation models. Two models are proposed for the description of the effect: self-diffusion of penetrate gases due to intermolecular collisions and enhancement of the slip flow contribution due to tangential momentum accommodation growth with the decrease of a molecule's effective collision area. The best fit parameters for the simultaneous fit of the experimental data with different models for 30 membrane-gas pairs are given.

Synthesis of novel lanthanide acylpyrazolonato ligands with long aliphatic chains and immobilization of the Tb complex on the surface of silica pre-modified via hydrophobic interactions.

Five new complexes Ln(Q(C17))3(H2O)(Solv) (Ln = Y, Solv = H2O, Ln = Tb, Dy, Sm or Eu, Solv = EtOH) were synthesized with the acylpyrazolonato ligand Q(C17) bearing a long aliphatic C17H35 chain in the acyl moiety, and the crystal structure of Y(Q(C17))3(H2O)2 shows the three aliphatic chains from the coordinated ligands positioned in the same direction, affording plane layers built by Y(Q(C17))3(H2O)2 molecules connected through H-bonding interactions. The layers are stitched to each other like in "hook & loop" tapes. Luminescence of complexes was determined and the complex Tb(Q(C17))3(H2O)(EtOH) was immobilized on the surface of silica preprocessed using a C17H35CONH(CH2)3Si(OEt)3 reagent via hydrophobic interactions of long aliphatic chains. Luminescent properties and micromorphology of the obtained hybrid particles and hybrid films were investigated. Intensive green emission of the complex retains after grafting onto the silica surface. Inclusion of the complex on the surface of silica materials occurs as separate molecules, after the disruption of the H-bonding network present in the crystalline phase of the pure terbium sample.

Permeability of anodic alumina membranes with branched channels.

Mass-transport properties of anodic alumina membranes exploited in a number of technological areas are strongly affected by the real pore structure and arrangement of channels that can split or terminate during the anodization process. This paper focuses on the investigation of pore branching and rearrangement caused by voltage variation in the course of the anodic oxidation of aluminum. Gas-transport measurements were utilized for the quantitative determination of an effective through porosity of multilayer anodic alumina membranes with branched channels obtained by variation of anodization voltage. It was shown that on decrease of anodization voltage a branching of pores occurs, while an increase of anodization voltage leads to the termination of some of the pores with an increase in the diameter of others. Gas permeance measurements combined with electron microscopy unambiguously prove dead-end pore formation on voltage increase, while no pore merging appears. This generally affects any mass-transport properties and applications of anodic alumina membranes as the delivery of any species (e.g. ions, gas molecules, etc) through the blocked channels is impossible.