Inside Ceramics and Between MgO Grains: Solid-State Synthesis of Intergranular Semiconducting or Magnetic Spinels.

Configurations of composite metal oxide nanoparticles are typically far off their thermodynamic equilibrium state. As such they represent a versatile but so far overlooked source material for the intergranular solid-state chemistry inside ceramics. Here, it is demonstrated how the admixture of Fe and In ions to MgO nanoparticles, as achieved by flame spray pyrolysis, can be used to engage ion exsolution, phase separation, and subsequent spinel formation inside the network of diamagnetic and insulating MgO grains.

High-Performance Lithium-Ion Batteries with High Stability Derived from Titanium-Oxide- and Sulfur-Loaded Carbon Spherogels.

This study presents a novel approach to developing high-performance lithium-ion battery electrodes by loading titania-carbon hybrid spherogels with sulfur. The resulting hybrid materials combine high charge storage capacity, electrical conductivity, and core-shell morphology, enabling the development of next-generation battery electrodes. We obtained homogeneous carbon spheres caging crystalline titania particles and sulfur using a template-assisted sol-gel route and carefully treated the titania-loaded carbon spherogels with hydrogen sulfide.

Water-Mediated Conversion of BaTiO Nanoparticles into BaCO Nanorods in Electrospun Polymer Fibers: Implications for Carbon Capture Applications.

Under ambient conditions and in aqueous environments, transformations of nanoparticle-based ferroelectric components can raise important stability issues that are relevant for applications as multilayer capacitors, flexible piezoelectrics, or biomedical devices. We show that X-ray amorphous BaTiO nanoparticles that were grown by flame spray pyrolysis and which can be incorporated into electrospun polymer fibers undergo incongruent Ba dissolution in the presence of water. At pH > 5 and in contact with air, corresponding Ba solutes spontaneously convert into crystalline BaCO needles to produce characteristic nano- and microstructures.

Conformal Coverage of ZnO Nanowire Arrays by ZnMnO : Room-temperature Photodeposition from Aqueous Solution.

Compositionally and structurally complex semiconductor oxide nanostructures gain importance in many energy-related applications. Simple and robust synthesis routes ideally complying with the principles of modern green chemistry are therefore urgently needed. Here we report on the one-step, room-temperature synthesis of a crystalline-amorphous biphasic ternary metal oxide at the ZnO surface using aqueous precursor solutions.

Synthesis and Structure of the Double-Layered Sillén-Aurivillius Perovskite Oxychloride LaBiTiOCl as a Potential Photocatalyst for Stable Visible Light Solar Water Splitting.

Exploring photocatalysts for solar water splitting is a relevant step toward sustainable hydrogen production. Sillén-Aurivillius-type compounds have proven to be a promising material class for photocatalytic and photoelectrochemical water splitting with the advantage of visible light activity coupled to enhanced stability because of their unique electronic structure. Especially, double- and multilayered Sillén-Aurivillius compounds [ABO][BiO]X, with A and B being cations and X a halogen anion, offer a great variety in material composition and properties.

Conversion of MgO nanocrystal surfaces into ceramic interfaces: Exsolution of BaO as photoluminescent interface probes.

Ion exsolution can be instrumental to engineer intergranular regions inside ceramic microstructures. BaO admixtures that were trapped inside nanometer-sized MgO grains during gas phase synthesis undergo annealing-induced exsolution to generate photoluminescent surface and interface structures. During their segregation from the bulk into the grain interfaces, the BaO admixtures impact grain coarsening and powder densification, effects that were compared for the first time using an integrated characterization approach.

Cubes to Cubes: Organization of MgO Particles into One-Dimensional and Two-Dimensional Nanostructures.

Developing simple, inexpensive, and environmentally benign approaches to integrate morphologically well-defined nanoscale building blocks into larger high surface area materials is a key challenge in materials design and processing. In this work, we investigate the fundamental surface phenomena between MgO and water (both adsorption and desorption) with particles prepared via a vapor-phase process (MgO nanocubes) and a modified aerogel process (MgO(111) nanosheets). Through these studies, we unravel a strategy to assemble individual MgO nanoparticles into extended faceted single-crystalline MgO nanosheets and nanorods with well-defined exposed surfaces and edges.

Cytotoxicity, Accumulation and Translocation of Silver and Silver Sulfide Nanoparticles in contact with Rainbow Trout Intestinal Cells.

Silver nanoparticles (Ag NPs) are widely used in consumer products especially because of their antimicrobial properties. However, this wide usage of Ag NPs is accompanied by their release into the environment where they will be rapidly transformed to other silver species - especially silver sulfide (AgS). In the present study, we synthesized Ag NPs and sulfidized them to obtain a core-shell system Ag@AgS NPs.

Segregation Engineering in MgO Nanoparticle-Derived Ceramics: The Impact of Calcium and Barium Admixtures on the Microstructure and Light Emission Properties.

Nanostructured segregates of alkaline earth oxides exhibit bright photoluminescence emission and great potential as components of earth-abundant inorganic phosphors. We evaluated segregation engineering of Ca- and Ba-admixtures in sintered MgO nanocube-derived compacts. Compaction and sintering transform the nanoparticle agglomerates into ceramics with residual porosities of = 24-28%.

Coherent light emission in cathodoluminescence when using GaAs in a scanning (transmission) electron microscope.

For most materials science oriented applications incoherent cathodoluminescence (CL) is of main interest, for which the recombination of electron-hole pairs yields the emission of light. However, the incoherent signal is superimposed by coherently excited photons, similar to the situation for X-rays in Energy-Dispersive X-ray spectra (EDX). In EDX two very different processes superimpose in each spectrum: Bremsstrahlung and characteristic X-ray radiation.

Modified H V O to Enhance the Electrochemical Performance for Li-ion Insertion: The Influence of Prelithiation and Mo-Substitution.

Nanostructured H V O is a promising high-capacity cathode material, suitable not only for Li but also for Na+, Mg , and Zn insertion. However, the full theoretical capacity for Li insertion has not been demonstrated experimentally so far. In addition, improvement of cycling stability is desirable.

Isolated Cobalt Ions Embedded in Magnesium Oxide Nanostructures: Spectroscopic Properties and Redox Activity.

Atomic dispersion of dopants and control over their defect chemistry are central goals in the development of oxide nanoparticles for functional materials with dedicated electronic, optical or magnetic properties. We produced highly dispersed oxide nanocubes with atomic distribution of cobalt ions in substitutional sites of the MgO host lattice via metal organic chemical vapor synthesis. Vacuum annealing of the nanoparticle powders up to 1173 K has no effect on the shape of the individual particles and only leads to moderate particle coarsening.

Catalytic activity, water formation, and sintering: Methane activation over Co- and Fe-doped MgO nanocrystals.

Microstructure, structure, and compositional homogeneity of metal oxide nanoparticles can change dramatically during catalysis. Considering the different stabilities of cobalt and iron ions in the MgO host lattice [M. Niedermaier et al.

Particle Consolidation and Electron Transport in Anatase TiO Nanocrystal Films.

A sequence of chemical vapor synthesis and thermal annealing in defined gas atmospheres was used to prepare phase-pure anatase TiO nanocrystal powders featuring clean surfaces and a narrow particle size distribution with a median particle diameter of 14.5 ± 0.5 nm.

Impurity Segregation and Nanoparticle Reorganization of Indium Doped MgO Cubes.

Metal oxide nanocomposites are non-equilibrium solids and promising precursors for functional materials. Annealing of such materials can provide control over impurity segregation and, depending on the level of consolidation, represents a versatile approach to engineer free surfaces, particle-particle interfaces and grain boundaries. Starting with indium-magnesium-oxide nanoparticle powders obtained via injection of an indium organic precursor into the magnesium combustion flame and subsequent particle quenching in argon, we investigated the stability of the trivalent In ions in the host lattice of MgO nanoparticles by determining grain growth, morphology evolution and impurity segregation.

Investigation of Mass-Produced Substrates for Reproducible Surface-Enhanced Raman Scattering Measurements over Large Areas.

Surface-enhanced Raman scattering (SERS) is a versatile spectroscopic technique that suffers from reproducibility issues and usually requires complex substrate fabrication processes. In this article, we report the use of a simple mass production technology based on Blu-ray disc manufacturing technology to prepare large area SERS substrates (∼40 mm) with a high degree of homogeneity (±7% variation in Raman signal) and enhancement factor of ∼6 × 10. An industrial high throughput injection molding process was used to generate periodic microstructured polymer substrates coated with a thin Ag film.

Enzyme adsorption-induced activity changes: a quantitative study on TiO model agglomerates.

Background: Activity retention upon enzyme adsorption on inorganic nanostructures depends on different system parameters such as structure and composition of the support, composition of the medium as well as enzyme loading. Qualitative and quantitative characterization work, which aims at an elucidation of the microscopic details governing enzymatic activity, requires well-defined model systems.

Results: Vapor phase-grown and thermally processed anatase TiO nanoparticle powders were transformed into aqueous particle dispersions and characterized by dynamic light scattering and laser Doppler electrophoresis.