Eutectoid decompositions in Ce-containing ABO perovskites: Part II, the case of divorced growth in CeCrO.

A eutectoid phase transformation was exhibited by the perovskite CeCrO when heated in air. The kinetics of the reaction, microstructure of the product, and mechanisms of the transformation were studied using thermogravimetric analysis, X-ray and Raman spectroscopy, X-ray diffraction, and electron microscopy. Fluorite CeO and corundum CrO were formed from the decomposition of CeCrO.

Strongly Interacting Nanoferrites for Magnetic Particle Imaging and Spatially Resolved Thermometry.

High-crystal-quality nanoferrites with short surface ligands (oleic acid) were recently shown to exhibit enhanced sensitivity and spatial resolution, likely due to chain formation (uniaxial assemblies of particles) for magnetic particle imaging (MPI). Here, we develop a simple one-pot thermal decomposition approach to produce ferrite (iron oxide) magnetic nano-objects (MNOs) that strongly interact magnetically and have good synthetic reproducibility. The ferrite MNOs were physically characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and dynamic light scattering.

Solution Synthesis of NdTe Magnetic Nanosheets.

Neodymium tritelluride is a layered van der Waals material, with correlated electronic properties including high electronic mobility, charge density waves, and antiferromagnetism. We developed a solution synthesis method to form free-standing nanosheets of NdTe, with nanosheet lateral dimensions of 200-400 nm. The morphology of the nanosheet was influenced by the neodymium precursor.

Spin-Phonon Coupling and Magnetic Transition in an Organic Molecule Intercalated CrGeTe.

The manipulation of spin-phonon coupling in both formations and explorations of magnetism in two-dimensional van der Waals ferromagnetic semiconductors facilitates unprecedented prospects for spintronic devices. The interlayer engineering with spin-phonon coupling promises controllable magnetism via organic cation intercalation. Here, spectroscopic evidence reveals the intercalation effect on the intrinsic magnetic and electronic transitions in quasi-two-dimensional CrGeTe using tetrabutyl ammonium (TBA) as the intercalant.

Reproducible graphene synthesis by oxygen-free chemical vapour deposition.

Chemical vapour deposition (CVD) synthesis of graphene on copper has been broadly adopted since the first demonstration of this process. However, widespread use of CVD-grown graphene for basic science and applications has been hindered by challenges with reproducibility and quality. Here we identify trace oxygen as a key factor determining the growth trajectory and quality for graphene grown by low-pressure CVD.

Thermosensitivity through Exchange Coupling in Ferrimagnetic/Antiferromagnetic Nano-Objects for Magnetic-Based Thermometry.

Temperature is a fundamental physical quantity important to the physical and biological sciences. Measurement of temperature within an optically inaccessible three-dimensional (3D) volume at microscale resolution is currently limited. Thermal magnetic particle imaging (T-MPI), a temperature variant of magnetic particle imaging (MPI), hopes to solve this deficiency.

Thermal and Electronic Properties of BaMnSe.

The structural, thermal, and electronic properties of BaMnSe were investigated. Analysis of the low-temperature heat capacity revealed a low Debye temperature and a low average speed of sound that, together with the bonding in this material, result in a low thermal conductivity over a relatively large temperature range. Density functional theory and calculated electron localization were employed to investigate the electronic structure and bonding.

High-Throughput DFT-Based Discovery of Next Generation Two-Dimensional (2D) Superconductors.

High-throughput density functional theory (DFT) calculations allow for a systematic search for conventional superconductors. With the recent interest in two-dimensional (2D) superconductors, we used a high-throughput workflow to screen over 1000 2D materials in the JARVIS-DFT database and performed electron-phonon coupling calculations, using the McMillan-Allen-Dynes formula to calculate the superconducting transition temperature () for 165 of them. Of these 165 materials, we identify 34 dynamically stable structures with transition temperatures above 5 K, including materials such as WN, NbO, ZrBrO, TiClO, NaSnS, MgBC, and the previously unreported MgBN ( = 21.

Advanced characterization of magnetization dynamics in iron oxide magnetic nanoparticle tracers.

Characterization of the magnetization dynamics of single-domain magnetic nanoparticles (MNPs) is important for magnetic particle imaging (MPI), magnetic resonance imaging (MRI), and emerging medical diagnostic/therapeutic technologies. Depending on particle size and temperature, nanoparticle magnetization relaxation time constants span from nanoseconds to seconds. In solution, relaxation occurs via coupled Brownian and Néel relaxation mechanisms.

Dependence of Single-Wall Carbon Nanotube Alignment on the Filter Membrane Interface in Slow Vacuum Filtration.

The recent introduction of slow vacuum filtration (SVF) technology has shown great promise for reproducibly creating high-quality, large-area aligned films of single-wall carbon nanotubes (SWCNTs) from solution-based dispersions. Despite clear advantages over other SWCNT alignment techniques, SVF remains in the developmental stages due to a lack of an agreed-upon alignment mechanism, a hurdle which hinders SVF optimization. In this work, the filter membrane surface is modified to show how the resulting SWCNT nematic order can be significantly enhanced.

Synthesis of Mixed-Valent Lanthanide Sulfide Nanoparticles.

In targeting reduced valent lanthanide chalcogenides, we report the first nanoparticle synthesis of the mixed-valent ferromagnets Eu S and EuSm S . Using divalent lanthanide halides with bis(trimethylsilyl)sulfide and oleylamine, we prepared nanoparticles of EuS, Eu S , EuSm S , SmS , and Sm S . All nanoparticle phases were identified using powder X-ray diffraction, transmission electron microscopy was used to confirm morphology and nanoparticle size, and magnetic susceptibility measurements for determining the ordering temperatures and valence.

High-throughput Density Functional Perturbation Theory and Machine Learning Predictions of Infrared, Piezoelectric and Dielectric Responses.

Many technological applications depend on the response of materials to electric fields, but available databases of such responses are limited. Here, we explore the infrared, piezoelectric and dielectric properties of inorganic materials by combining high-throughput density functional perturbation theory and machine learning approaches. We compute Γ-point phonons, infrared intensities, Born-effective charges, piezoelectric, and dielectric tensors for 5015 non-metallic materials in the JARVIS-DFT database.

Global Alignment of Solution-Based Single-Wall Carbon Nanotube Films via Machine-Vision Controlled Filtration.

Over the past decade, substantial progress has been made in the chemical control (chiral enrichment, length sorting, handedness selectivity, and filling substance) of single-wall carbon nanotubes (SWCNTs). Recently, it was shown that large, horizontally aligned films can be created out of postprocessed SWCNT solutions. Here, we use machine-vision automation and parallelization to simultaneously produce globally aligned SWCNT films using pressure-driven filtration.

Electrical Detection of Singlet Fission in Single Crystal Tetracene Transistors.

We present the electrical detection of singlet fission in tetracene by using a field-effect transistor (FET). Singlet fission is a photoinduced spin-dependent process, yielding two triplet excitons from the absorption of a single photon. In this study, we engineered a more deterministic platform composed of an organic single crystal FET rather than amorphous or polycrystalline FETs to elucidate spin-dependent processes under magnetic fields.

Contact and Noncontact Measurement of Electronic Transport in Individual 2D SnS Colloidal Semiconductor Nanocrystals.

Colloidal-based solution syntheses offer a scalable and cost-efficient means of producing 2D nanomaterials in high yield. While much progress has been made toward the controlled and tailorable synthesis of semiconductor nanocrystals in solution, it remains a substantial challenge to fully characterize the products' inherent electronic transport properties. This is often due to their irregular morphology or small dimensions, which demand the formation of colloidal assemblies or films as a prerequisite to performing electrical measurements.

High-throughput assessment of vacancy formation and surface energies of materials using classical force-fields.

In this work, we present an open access database for surface and vacancy-formation energies using classical force-fields (FFs). These quantities are essential in understanding diffusion behavior, nanoparticle formation and catalytic activities. FFs are often designed for a specific application, hence, this database allows the user to understand whether a FF is suitable for investigating particular defect and surface-related material properties.

Contacts to solution-synthesized SnS nanoribbons: dependence of barrier height on metal work function.

Tin(ii) monosulfide (SnS) is a layered, anisotropic material that is of interest as a two-dimensional semiconductor for opto-electronic, thermoelectric, and piezoelectric applications. In this study, the effect of work function on contact behavior was investigated. Ni/Au, Pd/Au, Cr/Au, and Ti/Au contacts were fabricated onto individual, solution-synthesized, p-type SnS nanoribbons.

Charge Carrier Dynamics and Mobility Determined by Time-Resolved Terahertz Spectroscopy on Films of Nano-to-Micrometer-Sized Colloidal Tin(II) Monosulfide.

Tin(II) monosulfide (SnS) is a semiconductor material with an intermediate band gap, high absorption coefficient in the visible range, and earth abundant, non-toxic constituent elements. For these reasons, SnS has generated much interest for incorporation into optoelectronic devices, but little is known concerning the charge carrier dynamics, especially as measured by optical techniques. Here, as opposed to prior studies of vapor deposited films, phase-pure colloidal SnS was synthesized by solution chemistry in three size regimes, ranging from nanometer- to micron-scale (SnS small nanoparticles, SnS medium 2D nanosheets, and SnS large 2D μm-sheets), and evaluated by time-resolved terahertz spectroscopy (TRTS); an optical, non-contact probe of the photoconductivity.

Ligand-induced fate of embryonic species in the shape-controlled synthesis of rhodium nanoparticles.

The shapes of noble metal nanoparticles directly impact their properties and applications, including in catalysis and plasmonics, and it is therefore important to understand how multiple distinct morphologies can be controllably synthesized. Solution routes offer powerful capabilities for shape-controlled nanoparticle synthesis, but the earliest stages of the reaction are difficult to interrogate experimentally and much remains unknown about how metal nanoparticle morphologies emerge and evolve. Here, we use a well-established polyol process to synthesize uniform rhodium nanoparticle cubes, icosahedra, and triangular plates using bromide, trifluoroacetate, and chloride ligands, respectively.

Electrocatalytic and photocatalytic hydrogen production from acidic and neutral-pH aqueous solutions using iron phosphide nanoparticles.

Nanostructured transition-metal phosphides have recently emerged as Earth-abundant alternatives to platinum for catalyzing the hydrogen-evolution reaction (HER), which is central to several clean energy technologies because it produces molecular hydrogen through the electrochemical reduction of water. Iron-based catalysts are very attractive targets because iron is the most abundant and least expensive transition metal. We report herein that iron phosphide (FeP), synthesized as nanoparticles having a uniform, hollow morphology, exhibits among the highest HER activities reported to date in both acidic and neutral-pH aqueous solutions.

Ternary hybrid nanoparticle isomers: directing the nucleation of Ag on Pt-Fe(3)O(4) using a solid-state protecting group.

Colloidal hybrid nanoparticles are an important class of materials that incorporate multiple nanoparticles into a single system through solid-state interfaces, which can result in multifunctionality and the emergence of synergistic properties not found in the individual components. These hybrid structures are typically produced using seeded-growth methods, where preformed nanoparticles serve as seeds onto which additional domains are added through subsequent reactions. For hybrid nanoparticles that contain more than two domains, multiple configurations with distinct connectivities and functionalities are possible, and these can be considered as nanoparticle analogues of molecular isomers.

Synthesis and crystallographic analysis of shape-controlled SnS nanocrystal photocatalysts: evidence for a pseudotetragonal structural modification.

Tin sulfide, SnS, is a narrow band gap semiconductor comprised of inexpensive, earth abundant, and environmentally benign elements that is emerging as an important material for a diverse range of applications in solar energy conversion, energy storage, and electronics. Relative to many comparable systems, much less is known about the factors that influence the synthesis or morphology-dependent properties of SnS nanostructures. Here, we report the synthesis of colloidal SnS cubes, spherical polyhedra, and sheets and demonstrate their activity for the photocatalytic degradation of methylene blue.

Nanostructured nickel phosphide as an electrocatalyst for the hydrogen evolution reaction.

Nanoparticles of nickel phosphide (Ni2P) have been investigated for electrocatalytic activity and stability for the hydrogen evolution reaction (HER) in acidic solutions, under which proton exchange membrane-based electrolysis is operational. The catalytically active Ni2P nanoparticles were hollow and faceted to expose a high density of the Ni2P(001) surface, which has previously been predicted based on theory to be an active HER catalyst. The Ni2P nanoparticles had among the highest HER activity of any non-noble metal electrocatalyst reported to date, producing H2(g) with nearly quantitative faradaic yield, while also affording stability in aqueous acidic media.

The solvent matters: kinetic versus thermodynamic shape control in the polyol synthesis of rhodium nanoparticles.

The polyol process is one of the most common methods for synthesizing metal nanoparticles with controlled shapes and sizes due to its wide applicability and ease of use. These nanostructures often have unique morphology-dependent properties that are useful in a range of applications, including catalysis, plasmonics, and medical diagnostics and therapeutics. While many variations of the polyol process have been developed to produce shape-controlled nanoparticles, there has been no systematic investigation that defines the influence of the solvent on the shape and uniformity of the product.

Nitrogen gas purging for the deoxygenation of polyaromatic hydrocarbon solutions in cyclohexane for routine fluorescence analysis.

During routine fluorescence analysis, the presence of dissolved oxygen in solutions can result in the dynamic quenching of a fluorophore's emission through collisional deexcitation of the fluorophore's excited state. In order to avoid this type of fluorescence quenching, dissolved oxygen is often removed from solutions by an inert gas purging procedure. However, the details and quantification of this purging process are often limited in fluorescence studies.