Abstract: A novel potassium-based fluoride-phosphate, KVPO4F, with a KTiOPO4 (KTP) type structure is synthesized and characterized. About 85% of potassium has been electrochemically extracted on oxidation producing a cathode material with attractive performance for Li-ion batteries. The material operates at the electrode potential near 4V vs Li/Li+ exhibiting a sloping voltage profile, extremely low polarization, small volume change of about 2% and excellent rate capability, maintaining more than 75% of the initial capacity at 40C discharge rate without significant fading.

Abstract: Antiferromagnetic(AFM)|ferrimagnetic(FiM) core|shell (CS) nanoparticles (NPs) of formula Co0.3Fe0.7O|Co0.6Fe2.4O4 with mean diameter from 6 to 18 nm have been synthesized through a one-pot thermal decomposition process. The CS structure has been generated by topotaxial oxidation of the core region, leading to the formation of a highly monodisperse single inverted AFM|FiM CS system with variable AFM-core diameter and constant FiM-shell thickness (~2 nm). The sharp interface, the high structural matching between both phases and the good crystallinity of the AFM material have been structurally demonstrated and are corroborated by the robust exchange-coupling between AFM and FiM phases, which gives rise to one among the largest exchange bias (HE) values ever reported for CS NPs (8.6 kOe) and to a strongly enhanced coercive field (HC). In addition, the investigation of the magnetic properties as a function of the AFM-core size (dAFM), revealed a non-monotonous trend of both HC and HE, which display a maximum value for dAFM = 5 nm (19.3 and 8.6 kOe, respectively). These properties induce a huge improvement of the capability of storing energy of the material, a result which suggests that the combination of highly anisotropic AFM|FiM materials can be an efficient strategy towards the realization of novel Rare Earth-free permanent magnets.

Abstract: The recent revival of the Na-ion battery concept has prompted intense activities in the search for new Na-based layered oxide positive electrodes. The largest capacity to date was obtained for a Na-deficient layered oxide that relies on cationic redox processes only. To go beyond this limit, we decided to chemically manipulate these Na-based layered compounds in a way to trigger the participation of the anionic network. We herein report the electrochemical properties of a Na-rich phase Na2IrO3, which can reversibly cycle 1.5 Na+ per formula unit while not suffering from oxygen release nor cationic migrations. Such large capacities, as deduced by complementary XPS, X-ray/neutron diffraction and transmission electron microscopy measurements, arise from cumulative cationic and anionic redox processes occurring simultaneously at potentials as low as 3.0 V. The inability to remove more than 1.5 Na+ is rooted in the formation of an O1-type phase having highly stabilized Na sites as confirmed by DFT calculations, which could rationalize as well the competing metal/oxygen redox processes in Na2IrO3. This work will help to define the most fertile directions in the search for novel high energy Na-rich materials based on more sustainable elements than Ir.

Abstract: Palladium nanoparticles (NPs) have received tremendous attention over the years due to their high catalytic activity for various chemical reactions. However, unlike other noble metal nanoparticles such as Au and Ag NPs, they exhibit poor plasmonic properties with broad extinction spectra and less scattering efficiency, and thus limiting their applications in the field of plasmonics. Therefore, it has been challenging to integrate tunable and strong plasmonic properties into catalytic Pd nanoparticles. Here we show that plasmonic Au@Pd nanorods (NRs) with relatively narrow and remarkably tunable optical responses in the NIR region can be obtained by directional growth of Pd on penta-twinned Au NR seeds. We found the presence of bromide ions facilitates the stabilization of facets for the directional growth of Pd shell to obtain Au@Pd nanorods (NR) with controlled length scales. Interestingly, it turns out the Au NR supported Pd NRs exhibit much narrow extinction compared to pure Pd NRs, which makes them suitable for plasmonic sensing applications. Moreover, these nanostructures display, to the best of our knowledge, one of the highest ensemble refractive index sensitivity values reported to date (1067 nm per refractive index unit, RIU). Additionally, we showed the application of such plasmonic Au@Pd NRs for localized surface plasmon resonance (LSPR)-based sensing of hydrogen both in solution as well as on substrate. Finally, we demonstrate the integration of excellent plasmonic properties in catalytic palladium enables the in situ monitoring of a reaction progress by surface-enhanced Raman scattering. We postulate the proposed approach to boost the plasmonic properties of Pd nanoparticles will ignite the design of complex shaped plasmonic Pd NPs to be used in various plasmonic applications such as sensing and in situ monitoring of various chemical reactions.

Abstract: Using the simplified linear combination of atomic orbitals (LCAO) method in combination with ab initio calculations, we construct a tight-binding (TB) model for two different crystal structures of monolayer gallium: a(100)- and b(010)-Gallenene. The analytical expression for the Hamiltonian and numerical results for the overlap matrix elements between different orbitals of the Ga atoms and for the Slater and Koster (SK) integrals are obtained. We find that the compaction of different structures affects significantly the formation of the orbitals. The results for a(100)-Gallenene can be very well explained with an orthogonal basis set, while for b(010)-Gallenene we have to assume a non-orthogonal basis set in order to construct the TB model. Moreover, the transmission properties of nanoribbons of both monolayers oriented along the AC and ZZ directions are also investigated and it is shown that both AC- and ZZ-b(010)-Gallenene nanoribbons exhibit semiconducting behavior with zero transmission while those of a(100)-Gallenene nanoribbons are metallic.

Abstract: Inspired by the recent successful growth of Ti2C and Ti3C2 monolayers, here, we investigate the structural, electronic, and mechanical properties of functionalized Ti2C and Ti3C2 monolayers by means of density functional theory calculations. The results reveal that monolayers of Ti2C and Ti3C2 are dynamically stable metals. Phonon band dispersion calculations demonstrate that two-surface functionalization of Ti2C and Ti(3)C(2)via chalcogenides (S, Se, and Te), halides (F, Cl, Br, and I), and oxygen atoms results in dynamically stable novel functionalized monolayer materials. Electronic band dispersions and density of states calculations reveal that all functionalized monolayer structures preserve the metallic nature of both Ti2C and Ti3C2 except Ti2C-O-2, which possesses the behavior of an indirect semiconductor via full-surface oxygen passivation. In addition, it is shown that although halide passivated Ti3C2 structures are still metallic, there exist multiple Dirac-like cones around the Fermi energy level, which indicates that semi-metallic behavior can be obtained upon external effects by tuning the energy of the Dirac cones. In addition, the computed linear-elastic parameters prove that functionalization is a powerful tool in tuning the mechanical properties of stiff monolayers of bare Ti2C and Ti3C2. Our study discloses that the electronic and structural properties of Ti2C and Ti3C2 MXene monolayers are suitable for surface modification, which is highly desirable for material property engineering and device integration.

Abstract: The process intensification abilities of gas–solid vortex units (GSVU) are very promising for gas–solid processes. By working in a centrifugal force field, much higher gas–solid slip velocities can be obtained compared to gravitational fluidized beds, resulting in a significant increase in heat and mass transfer rates. In this work, local azimuthal and radial particle velocities for an experimental GSVU are simulated using the Euler–Euler framework in OpenFOAM and compared with particle image velocimetry measurements. With the validated model, the effect of the particle diameter, number of inlet slots and reactor length on the bed hydrodynamics is assessed. Starting from 1g-Geldart-B type particles, increasing the particle diameter or density, increasing the number of inlet slots or increasing the gas injection velocity leads to an increased bed stability and uniformity. However, a trade-off has to be made since increased bed stability and uniformity lead to higher shear stresses and attrition.

Abstract: High quality epitaxial c axis oriented La2NiO4+ä thin films have been prepared by the pulsed injection metal organic chemical vapor deposition technique on different substrates. High-resolution electron microscopy/transmission electron microscopy has been used to confirm the high crystalline quality of the deposited films. The c-parameter evolution has been studied by XRD as a function of time and gas atmosphere. The high temperature transport properties along the basal a−b plane of epitaxial La2NiO4+ä films have been measured, and the total conductivity of the layers has been found to increase as the thickness is reduced. Layers of 50 nm and thinner have shown a maximum conductivity larger than that measured for single-crystals, in particular, the 33 nm thick films with a conductivity of 475 S/cm in oxygen correspond to the highest value measured to date for this material.

Abstract: The nonlinear absorption of Ag atomic clusters and nanoparticles dispersed in a transparent oxyfluoride glass host has been studied. The as-prepared glass, containing 0.15 atom % Ag, shows an absorption band in the UV/violet attributed to the presence of amorphous Ag atomic nanoclusters with an average size of 1.2 nm. Upon heat treatment the Ag nanoclusters coalesce into larger nanoparticles that show a surface plasmon absorption band in the visible. Open aperture z-scan experiments using 480 nm nanosecond laser pulses demonstrated nonsaturated and saturated nonlinear absorption with large nonlinear absorption indices for the Ag nanoclusters and nanoparticles, respectively. These properties are promising, e.g., for applications in optical limiting and objects contrast enhancement.

Abstract: We present a study of the relation between the surface chemistry and nanocrystal shape of PbSe nanocrystals with a variable Pb-to-Se stoichiometry and density of oleate ligands. The oleate ligand density and binding configuration are monitored by nuclear magnetic resonance and Fourier transform infrared absorbance spectroscopy, allowing us to quantify the number of surface-attached ligands per NC and the nature of the surface−Pb−oleate configuration. The three-dimensional shape of the PbSe nanocrystals is obtained from high-angle annular dark field scanning transmission electron microscopy combined with an atom counting method. We show that the enhanced oleate capping results in a stabilization and extension of the {111} facets, and a crystal shape transformation from a truncated nanocube to a truncated octahedron.

Abstract: <script type='text/javascript'>document.write(unpmarked('By depositing ceria on the surface of yttrium stabilized zirconia (YSZ) nanocrystals and further activation under high-temperature reducing conditions, a 13% mol. CeO2/YSZ catalyst structured as subnanometer thick, pyrochlore-type, ceria-zirconia islands has been prepared. This nanostructured catalyst depicts not only high oxygen storage capacity (OSC) values but, more importantly, an outstandingly stable redox response upon oxidation and reduction treatments at very high temperatures, above 1000 degrees C. This behavior largely improves that observed on conventional ceria-zirconia solid solutions, not only of the same composition but also of those with much higher molar cerium contents. Advanced scanning transmission electron microscopy (STEM-XEDS) studies have revealed as key not only to detect the actual state of the lanthanide in this novel nanocatalyst but also to rationalize its unusual resistance to redox deactivation at very high temperatures. In particular, high-resolution X-ray dispersive energy studies have revealed the presence of unique bilayer ceria islands on top of the surface of YSZ nanocrystals, which remain at surface positions upon oxidation and reduction treatments up to 1000 degrees C. Diffusion of ceria into the bulk of these crystallites upon oxidation at 1100 degrees C irreversibly deteriorates both the reducibility and OSC of this nanostructured catalyst.'));

Abstract: Nonequilibrium plasmas offer a pathway for energy-efficient CO2 conversion through vibrationally induced dissociation. However, the efficiency of this pathway is limited by a rise in gas temperature, which increases vibrational−translational (VT) relaxation and quenches the vibrational levels. Therefore, we investigate here the effect of plasma pulsing on the VT nonequilibrium and on the CO2 conversion by means of a zerodimensional chemical kinetics model, with self-consistent gas temperature calculation. Specifically, we show that higher energy efficiencies can be reached by correctly tuning the plasma pulse and interpulse times. The ideal plasma pulse time corresponds to the time needed to reach the highest vibrational temperature. In addition, the highest energy efficiencies are obtained with long interpulse times, that is, ≥0.1 s, in which the gas temperature can entirely drop to room temperature. Furthermore, additional cooling of the reactor walls can give higher energy efficiencies at shorter interpulse times of 1 ms. Finally, our model shows that plasma pulsing can significantly improve the energy efficiency at low reduced electric fields (50 and 100 Td, typical for microwave and gliding arc plasmas) and intermediate ionization degrees (5 × 10−7 and 10−6).

Abstract: A biomimetic sensor for cefquinome (CFQ) was designed at multi-walled carbon nanotubes modified graphite screen-printed electrodes (MWCNTs-G-SPEs) as a proof-of-concept for the creation of a sensors array for beta-lactam antibiotics detection in milk. The sensitive and selective detection of antibiotic residues in food and environment is a fundamental step in the elaboration of prevention strategies to fight the insurgence of antimicrobial resistance (AMR) as recommended by authorities around the world (EU, WHO, FDA). The detection strategy is based on the characteristic electrochemical fingerprint of the target antibiotic cefquinome. A conducive electropolymerized molecularly imprinted polymer (MIP) coupled with MWCNTs was found to be the optimal electrode modifier, able to provide an increased selectivity and sensitivity for CFQ detection. The design of CFQ-MIP was facilitated by the rational selection of the monomer, 4-aminobenzoic acid (4-ABA). The electropolymerization process of 4-ABA have not been fully elucidated yet; for this reason a thorough study and optimization of electropolymerization conditions was performed to obtain a conducive and stable poly(4-ABA) film. The modified electrodes were characterized by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and cyclic voltammetry (CV). CFQ-MIP were synthesized at MWCNT-G-SPEs by electropolyrnerization in pH approximate to 1 (0.1 M sulphuric acid) with a monomer:template ratio of 5:1. Two different analytical protocols were tested (single and double step detection) to minimize unspecific adsorptions and improve the sensitivity. Under optimal conditions, the lowest CFQ concentration detectable by square wave voltammetry (SWV) at the modified sensor was 50 nM in 0.1 M phosphate buffer pH 2.