From silicon to silica: a green chemistry approach for hollow sphere nanoparticle formation.

Herein we report on an environmentally friendly and scalable production route for hollow silica spheres (HSSs). The process is based on close to 100% conversion of non-crystalline solid Si nanoparticles ( = 40 ± 9 nm) in mild alkaline solutions (pH ≤ 9.0) at ambient temperature.

(De)sodiation Mechanism of BiMoO in Na-Ion Batteries Probed by Quasi-Simultaneous Operando PDF and XAS.

Operando characterization can reveal degradation processes in battery materials and are essential for the development of battery chemistries. This study reports the first use of quasi-simultaneous operando pair distribution function (PDF) and X-ray absorption spectroscopy (XAS) of a battery cell, providing a detailed, atomic-level understanding of the cycling mechanism of BiMoO as an anode material for Na-ion batteries. This material cycles via a combined conversion-alloying reaction, where electrochemically active, nanocrystalline Na Bi particles embedded in an amorphous Na-Mo-O matrix are formed during the first sodiation.

Unraveling the (De)sodiation Mechanisms of BiFeO at a High Rate with XRD.

Development of new anode materials for Na-ion batteries strongly depends on a detailed understanding of their cycling mechanism. Due to instrumental limitations, the majority of mechanistic studies focus on materials' characterization at low cycling rates. In this work, we evaluate and compare the (de)sodiation mechanisms of BiFeO in Na-ion batteries at different current densities using X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS).

Variable temperature TEM mapping of the thermodynamically stable element distribution in bimetallic Pt-Rh nanoparticles.

We report here the first variable temperature transmission electron microscopy (TEM) study on smaller Pt-Rh nanoparticles (≤24 nm) under vacuum conditions. Well-defined 50 at% Pt/50 at% Rh Pt-Rh solid solution and Rh(core)-Pt(shell) nanoparticles, obtained colloidal synthesis routes, were investigated between room temperature and 650 °C to elucidate the tendency of elemental mixing/segregation. Key findings are that Pt-Rh nanoparticles <13 nm are stable in a solid solution configuration over the entire studied temperature range, whereas nanoparticles >13 nm tend to segregate upon cooling.

Prediction of intermediate band in Ti/V doped γ-InS.

Materials with an intermediate energy band (IB) introduced in the forbidden gap are viable alternatives to tandem configurations of solar cells for increasing the photon-conversion efficiency. One of the aspiring designs proposed for the intermediate band concept is hyperdoped (Ti, V):InS. Being very important in copper indium gallium sulfide (CIGS) solar cells, indium thiospinel (InS) is known for its three different temperature as well as pressure, polymorphs.

Operando XRD studies on BiMoOas anode material for Na-ion batteries.

Based on the same rocking-chair principle as rechargeable Li-ion batteries, Na-ion batteries are promising solutions for energy storage benefiting from low-cost materials comprised of abundant elements. However, despite the mechanistic similarities, Na-ion batteries require a different set of active materials than Li-ion batteries. Bismuth molybdate (BiMoO) is a promising NIB anode material operating through a combined conversion/alloying mechanism.

Efficient Exfoliation of Layered Double Hydroxides; Effect of Cationic Ratio, Hydration State, Anions and Their Orientations.

The exfoliation ability of nitrate based MgAl(OH)(NO)·HO layered double hydroxides (Mg-Al LDH) in formamide into single or multilayer nanosheets depends strongly on nitrate anion orientation and layer charge. Our systematic studies used materials that were likely to disclose differences with respect to anion type and their concentrations in the interlayer gallery. We assured to avoid any carbonate incorporation into the galleries for nitrate, chloride, iodide, and sulfate based Mg-Al LDHs.

One-pot synthesis of cobalt-rhenium nanoparticles taking the unusual β-Mn type structure.

Using a facile one-pot colloidal method, it is now possible to obtain monodisperse Co Re nanoparticles (NPs), with excellent control of Re stoichiometry for < 0.15. Re-incorporation in terms of a solid solution stabilizes the β-Mn polymorph relative to the hcp/ccp variants of cobalt.

Atomic Layer Deposition of GdCoO and GdCaCoO.

Thin films of the catalytically interesting ternary and quaternary perovskites GdCoO and GdCaCoO are fabricated by atomic layer deposition using metal β-diketonates and ozone as precursors. The resulting thin films are amorphous as deposited and become single-oriented crystalline on LaAlO(100) and YAlO(100/010) after post-annealing at 650 °C in air. The crystal orientations of the films are tunable by choice and the orientation of the substrate, mitigated through the interface via solid face epitaxy upon annealing.

Advances in the LiCl salt flux method and the preparation of phase pure LaNdLiHO (0 ≤ x ≤ 2) oxyhydrides.

The LiCl salt flux method is an established aid in oxyhydride synthesis. By operating the flux below its melting point, we have obtained phase pure Nd2LiHO3 for the first time. Further, the suitability of the flux method is shown to be dictated by a delicate balance between the thermal stability of the oxyhydride in question and the ionic mobility of the reactants.

New Insights into Hydride Bonding, Dynamics, and Migration in LaLiHO Oxyhydride.

Hydride anion-conducting oxyhydrides have recently emerged as a brand new class of ionic conductors. Here we shed a first light onto their local vibrations, bonding mechanisms, and anion migration properties using the powerful combination of high-resolution inelastic neutron scattering and a set of rigorously experimentally validated density functional theory calculations. By means of charge-density analysis we establish the bonding to be strongly anisotropic; ionic in the perovskite layer and covalent in the rock salt layer.

Thermal and Structural Aspects of the Hydride-Conducting Oxyhydride LaLiHO Obtained via a Halide Flux Method.

Oxyhydrides, in which oxide and hydride anions share the same anionic lattice, are relatively rare compounds. LaLiHO belongs to this family. We report the synthesis of LaLiHO by means of an alkali halide flux method, which allows the production of larger quantities of material relative to the usually adopted synthesis routes.

From Colloidal Monodisperse Nickel Nanoparticles to Well-Defined Ni/AlO Model Catalysts.

In the past few decades, advances in colloidal nanoparticle synthesis have created new possibilities for the preparation of supported model catalysts. However, effective removal of surfactants is a prerequisite to evaluate the catalytic properties of these catalysts in any reaction of interest. Here we report on the colloidal preparation of surfactant-free Ni/AlO model catalysts.

Engineering Functions into Platinum and Platinum-Rhodium Nanoparticles in a One-Step Microwave Irradiation Synthesis.

Platinum (Pt) and platinum-rhodium (PtRh) nanoparticles (NPs) are active catalysts for a range of important industrial reactions, and their response has been shown to be affected by size, morphology, composition, and architectural configuration. We report herein the engineering of these functionalities into NPs by suitably modifying our single-step fabrication process by using microwave irradiation dielectric heating. NPs with different morphologies are acquired by manipulating the reaction kinetics with the concentration of the capping agent while keeping the reaction time constant.

In situ TEM observation of the Boudouard reaction: multi-layered graphene formation from CO on cobalt nanoparticles at atmospheric pressure.

Using a MEMS nanoreactor in combination with a specially designed in situ Transmission Electron Microscope (TEM) holder and gas supply system, we imaged the formation of multiple layers of graphene encapsulating a cobalt nanoparticle, at 1 bar CO : N (1 : 1) and 500 °C. The cobalt nanoparticle was imaged live in a TEM during the Boudouard reaction. The in situ/operando TEM studies give insight into the behaviour of the catalyst at the nanometer-scale, under industrially relevant conditions.

Stacking Faults and Polytypes for Layered Double Hydroxides: What Can We Learn from Simulated and Experimental X-ray Powder Diffraction Data?

Layered double hydroxides (LDH) are a broad group of widely studied materials. The layered character of those materials and their high flexibility for accommodating different metals and anions make them technologically interesting. The general formula for the LDH compound is [MM(OH)][A]·mHO, where M is a divalent metal cation which can be substituted by M trivalent cation, and A is a charge compensating anion located between positively charged layers.

Electronic and Magnetic Structures of Hole Doped Trilayer LaSrNiO from First-Principles Calculations.

The magnetic and electronic properties of trilayer LaNiO, similar to hole-doped cuprates, are investigated by performing full-potential linearized augmented plane wave method-based spin-polarized calculations with LDA and GGA functionals including Hubbard U parameters to account for strong correlation effects. On the basis of these calculations, we found that LaNiO is a C-type anti-ferromagnetic (C-AFM) Mott insulator in agreement with previous experimental and theoretical observations. Our calculations suggest that the two crystallographically nonequivalent nickel atoms Ni1 and Ni2 are found to be in high-spin state with an average valency of +1.

Theoretical and experimental investigation on structural, electronic and magnetic properties of layered MnO.

We have investigated the crystal, electronic, and magnetic structures of MnO by means of state-of-the-art density functional theory calculations and neutron powder diffraction (NPD) measurements. This compound stabilizes in the monoclinic structure with space group C2/m where the Mn ions are in the distorted octahedral and trigonal prismatic coordinations with oxygen atoms. The calculated structural parameters based on total energy calculations are found to be in excellent agreement with low temperature NPD measurements when we accounted for the correct magnetic structure and Coulomb correlation effect in the computation.

Crystal Structure of LaSr3Fe3O8(OH)2·xH2O.

The crystal structure of the hydrated Ruddlesden-Popper (RP) phase LaSr3Fe3O8(OH)2·xH2O has been investigated with focus on the orientation of the hydroxide groups and intercalated water. Combined powder synchrotron X-ray and neutron diffraction techniques were used. On the basis of Rietveld refinements and Fourier maps, intercalated water was found to form a network within the rock-salt-type layers of the RP phase with a likely dynamic interchange between different orientations.

Burst nucleation by hot injection for size controlled synthesis of ε-cobalt nanoparticles.

Background: Reproducible growth of narrow size distributed ε-Co nanoparticles with a specific size requires full understanding and identification of the role of essential synthesis parameters for the applied synthesis method. For the hot injection methodology, a significant discrepancy with respect to obtained sizes and applied reaction conditions is reported. Currently, a systematic investigation controlling key synthesis parameters as injection-temperature and time, metal to surfactant ratio and reaction holding time in terms of their impact on mean ([Formula: see text]mean) and median ([Formula: see text]median) particle diameter using dichlorobenzene (DCB), Co2(CO)8 and oleic acid (OA) as the reactant matrix is lacking.

Preparation of Nb-substituted titanates by a novel sol-gel assisted solid state reaction.

Single-phase layered Nb-substituted titanates, Na(2)Ti(3-x)Nb(x)O(7) (x = 0-0.06) and Cs(0.7)Ti(1.