Freestanding Penta-Twinned Palladium Nanosheets.

Control over the morphology of nanomaterials to have a 2D structure and manipulating the surface strain of nanostructures through defect control have proved to be promising for developing efficient catalysts for sustainable chemical and energy conversion. Here a one-pot aqueous synthesis route of freestanding Pd nanosheets with a penta-twinned structure (PdPT NSs) is presented. The generation of the penta-twinned nanosheet structure can be succeeded by directing the anisotropic growth of Pd under the controlled reduction kinetics of Pd precursors. Experimental and computational investigations showed that the surface atoms of the PdPT NSs are effectively under a compressive environment due to the strain imposed by their twin boundary defects. Due to the twin boundary-induced surface strain as well as the 2D structure of the PdPT NSs, they exhibited highly enhanced electrocatalytic activity for oxygen reduction reaction compared to Pd nanosheets without a twin boundary, 3D Pd nanocrystals, and commercial Pd/C and Pt/C catalysts.

Integrated Metabolomics and Transcriptomics Unravel the Metabolic Pathway Variations for Different Sized Beech Mushrooms.

Beech mushrooms (Hypsizygus marmoreus) are largely relished for their characteristic earthy flavor, chewy-texture, and gustatory and nutritional properties in East Asian societies. Intriguingly, the aforementioned properties of beech mushroom can be subsumed under its elusive metabolome and subtle transcriptome regulating its various stages of growth and development. Herein, we carried out an integrated metabolomic and transcriptomic profiling for different sized beech mushrooms across spatial components (cap and stipe) to delineate their signature pathways. We observed that metabolite profiles and differentially expressed gene (DEGs) displayed marked synergy for specific signature pathways according to mushroom sizes. Notably, the amino acid, nucleotide, and terpenoid metabolism-related metabolites and genes were more abundant in small-sized mushrooms. On the other hand, the relative levels of carbohydrates and TCA intermediate metabolites as well as corresponding genes were linearly increased with mushroom size. However, the composition of flavor-related metabolites was varying in different sized beech mushrooms. Our study explores the signature pathways associated with growth, development, nutritional, functional and organoleptic properties of different sized beech mushrooms.

Core-Shell Nanoparticle Clusters Enable Synergistic Integration of Plasmonic and Catalytic Functions in a Single Platform.

Designing controlled hybrid nanoarchitectures between plasmonic and catalytic materials is of paramount importance to fully exploit each function of constituent materials. This study reports a new synthetic strategy for the realization of colloidal clusters of core-shell nanoparticles with plasmonic cores and catalytically active shells. The Au@M (M = Pd or Pt) nanoparticle clusters (NPCs) with a high density of sub-1 nm interparticle gaps are successfully prepared by the deposition of M shells onto thermally activated Au NPCs. NPCs with other metal, metal sulfide, and metal oxide shells can also be synthesized by using the present approach. The prepared Au@M NPCs show remarkably enhanced plasmonic performance compared to their Au@M nanoparticle counterparts due to the localization of a strong electromagnetic field at the interparticle gaps, while the inherent catalytic function of shells is intact. In situ real-time Raman spectroscopy and plasmon-enhanced electrocatalysis experiments demonstrate that the controlled assembly of core-shell nanoparticles is a very effective route for the synergistic integration of plasmonic and catalytic functions in a single platform.

Ultrathin Free-Standing Ternary-Alloy Nanosheets.

A synthesis strategy for the preparation of ultrathin free-standing ternary-alloy nanosheets is reported. Ultrathin Pd-Pt-Ag nanosheets with a thickness of approximately 3 nm were successfully prepared by co-reduction of the metal precursors in an appropriate molar ratio in the presence of CO. Both the presence of CO and the interplay between the constituent metals provide fine control over the anisotropic two-dimensional growth of the ternary-alloy nanostructure. The prepared Pd-Pt-Ag nanosheets were superior catalysts of ethanol electrooxidation owing to their specific structural and compositional characteristics. This approach will pave the way for the design of multicomponent 2D nanomaterials with unprecedented functions.

Enrichment by supernovae in globular clusters with multiple populations.

The most massive globular cluster in the Milky Way, omega Centauri, is thought to be the remaining core of a disrupted dwarf galaxy, as expected within the model of hierarchical merging. It contains several stellar populations having different heavy elemental abundances supplied by supernovae-a process known as metal enrichment. Although M 22 appears to be similar to omega Cen, other peculiar globular clusters do not. Therefore omega Cen and M 22 are viewed as exceptional, and the presence of chemical inhomogeneities in other clusters is seen as 'pollution' from the intermediate-mass asymptotic-giant-branch stars expected in normal globular clusters. Here we report Ca abundances for seven globular clusters and compare them to omega Cen. Calcium and other heavy elements can only be supplied through numerous supernovae explosions of massive stars in these stellar systems, but the gravitational potentials of the present-day clusters cannot preserve most of the ejecta from such explosions. We conclude that these globular clusters, like omega Cen, are most probably the relics of more massive primeval dwarf galaxies that merged and disrupted to form the proto-Galaxy.

One-pot synthesis and electrocatalytic properties of Pd@Pt core-shell nanocrystals with tailored morphologies.

Pd@Pt core-shell nanocrystals consisting of well-defined Pd nanocube cores and dendritic Pt shells were prepared by a new facile aqueous one-pot synthetic method. The prepared Pd@Pt nanocrystals exhibited efficient catalytic activity and stability toward methanol electrooxidation, and their catalytic function was highly dependent on their Pt shell thickness due to the different synergism between Pt and Pd.

One-pot self-templating synthesis of Pt hollow nanostructures and their catalytic properties for CO oxidation.

Nanoporous Pt hollow nanostructures with octahedral and hexagonal frame-like morphologies were prepared by a novel one-pot self-templating route with no assistance from a preformed template or shape-directing agent. The hexagonal frame-like Pt hollow structures exhibited significantly enhanced catalytic activity toward CO oxidation reaction compared to the octahedral Pt hollow nanostructures due to the higher oxidation state of Pt.

Kinetically controlled growth of polyhedral bimetallic alloy nanocrystals exclusively bound by high-index facets: Au-Pd hexoctahedra.

Au-Pd alloy nanocrystals (NCs) with a hexoctahedral structure, enclosed exclusively by high-index {541} facets, are prepared via the simultaneous reduction of Au and Pd precursors without added seeds or additional metal ions as structure-regulating agents. Manipulating the NC growth kinetics via control of the relative amount of reductant is the key synthetic lever for controlling the morphology of the Au-Pd NCs. The hexoctahedral Au-Pd NCs exhibit higher catalytic performance toward the electro-oxidation of ethanol than low-index-faceted Au-Pd NCs.

One-pot synthesis of CeO2-supported Pd-Cu-alloy nanocubes with high catalytic activity.

Cerium and nanocubes: CeO2-supported Pd-Cu-alloy nanocubes (Pd-Cu NCs/CeO2) with high content and good dispersion of the Pd-Cu NCs were prepared in high yields by heating a solution containing Pd, Cu, and Ce precursors. The prepared Pd-Cu NCs/CeO2 have excellent catalytic activity and stability toward formic acid electro-oxidation due to the synergism between the Pd-Cu-alloy catalysts and the CeO2 support.

Synergistic effect of bimetallic Pd-Pt nanocrystals for highly efficient methanol oxidation electrocatalysts.

Metal nanocrystals (NCs) with controlled compositional and distributional structures have gained increasing attention due to their unique properties and broad applications, particularly in fuel cell systems. However, despite the significant importance of composition in metal NCs and their electrocatalytic behavior, comprehensive investigations into the relationship between atomic distribution and electrocatalytic activity remain scarce. In this study, we present the development of four types of nanocubes with similar sizes and controlled compositions (Pd-Pt alloy, Pd@Pt core-shell, Pd, and Pt) to investigate their influence on electrocatalytic performance for methanol oxidation reaction (MOR). The electrocatalytic activity and stability of these nanocubes exhibited variations based on their compositional structures, potentially affecting the interaction between the surface-active sites of the nanocrystals and reactive molecules. As a result, leveraging the synergistic effect of their alloy nanostructure, the Pd-Pt alloy nanocubes exhibited exceptional performance in MOR, surpassing the catalytic activity of other nanocubes, including Pd@Pt core-shell nanocubes, monometallic Pd and Pt nanocubes, as well as commercial Pd/C and Pt/C catalysts.

Hexoctahedral Au nanocrystals with high-index facets and their optical and surface-enhanced Raman scattering properties.

Au nanocrystals (NCs) with an unprecedented hexoctahedral structure enclosed exclusively by high-index {321} facets have been prepared for the first time. Manipulating the NC growth kinetics by controlling the amount of reductant and the reaction temperature in the presence of a suitable surfactant was the key synthetic lever for controlling the morphology of the Au NCs. The hexoctahedral Au NCs exhibited efficient optical and surface-enhanced Raman scattering activities due to their unique morphological characteristics.

Synthesis and photocatalytic properties of Cu2S-Pd4S hybrid nanoplates.

Hex appeal! Cu(2)S-Pd(4)S hybrid nanocrystals with a novel hexagonal nanoplate structure were prepared in high yield by a simple one-pot synthetic method (see figure). Successful synthesis of this unique structure was achieved through a consecutive thermolysis process. The Cu(2)S-Pd(4)S hybrid nanoplates exhibited substantially higher photocatalytic activities than pure Cu(2)S nanoplates.

Suppression of star formation in early-type galaxies by feedback from supermassive black holes.

Detailed high-resolution observations of the innermost regions of nearby galaxies have revealed the presence of supermassive black holes. These black holes may interact with their host galaxies by means of 'feedback' in the form of energy and material jets; this feedback affects the evolution of the host and gives rise to observed relations between the black hole and the host. Here we report observations of the ultraviolet emissions of massive early-type galaxies. We derive an empirical relation for a critical black-hole mass (as a function of velocity dispersion) above which the outflows from these black holes suppress star formation in their hosts by heating and expelling all available cold gas. Supermassive black holes are negligible in mass compared to their hosts but nevertheless seem to play a critical role in the star formation history of galaxies.

Formation of flower-like Ag colloids using pulsed proton beam.

A new solution phase method is presented for the synthesis of "flower-like" silver nanomaterials using a pulsed proton beam irradiation process at room temperature. It was observed that the morphology of the prepared silver crystals was easily controlled by varying the number of exposures to the pulsed proton beam. The synthesized flower-like silver nanocrystals exhibited excellent surface enhanced Raman scattering (SERS) signals, which were attributed to the rough microstructures on the surface of the synthesized Ag crystals.

Nanogap-tailored Au nanoparticles fabricated by pulsed laser ablation for surface-enhanced Raman scattering.

Herein, gold nanoparticles (Au NPs) were synthesized by pulsed laser ablation (PLA) in a mixed-phase solvent of acetonitrile and water. The size of Au NPs and the number of graphitic carbon (GC) layers were controlled by varying the ratio of the solvent mixture. The surface-enhanced Raman scattering (SERS) of the Au NPs was investigated using 10-3 M 4-aminobenzenethiol and 10-4 M 4-nitrobenzenethiol as probe molecules. The SERS activity strongly depended on the nanogaps between particles owing to the formation of hot spots. In the present work, the nanogaps were controlled by changing the amount of GC layers. No GC layers were produced in water, resulting low SERS intensity. In contrast, Au NPs prepared in 30 vol% of acetonitrile showed significant SERS enhancement, which was attributed to the optimal size of the GC-coated NPs and a reasonable gap between them. The obtained results revealed that Au NPs produced by PLA in liquid could be applied in SERS-based microsensors.

Novel fabrication method of diverse one-dimensional Pt/ZnO hybrid nanostructures and its sensor application.

A novel low-temperature, solution-phase method for the facile fabrication of a variety of one-dimensional (1D) metal/metal oxide hybrid nanostructures has been developed. This method is based on the wet chemical synthesis of metal oxide nanowires, followed by the surface coating of metal nanoparticles on metal oxide nanowire templates via reduction of metal ions along with controlled etching of metal oxide nanowires at the core, all in a low-temperature liquid environment. As a proof-of-concept, we applied this method to the fabrication of various 1D Pt/ZnO hybrid nanostructures including Pt nanoparticle-coated ZnO nanowires/nanotubes and Pt nanotubes on silicon and polymer substrates. The diverse morphology tuning is attributed to the control of pH in the solution with different metal precursor concentrations and amounts of reducing agent. The change of morphology, crystalline structure, and composition of various 1D Pt/ZnO hybrid nanostructures was observed by SEM, TEM (HRTEM), XRD and ICP-AES, respectively. Further, we have demonstrated a highly sensitive strain sensor (gauge factor = 15) with a Pt nanotube film fabricated by the developed method on a flexible polymer substrate.

Shape- and Size-Controlled Palladium Nanocrystals and Their Electrocatalytic Properties in the Oxidation of Ethanol.

Pd nanoparticles (PdNPs) were synthesized in an aqueous environment via the reduction of K2PdCl4 by a surfactant under a high temperature. Highly monodisperse spherical PdNPs and multi-pod PdNPs with a controlled size ranging from 18 to 50 nm were prepared in high yields by varying the concentration of cetyltrimethylammonium chloride. The structural and optical properties of the synthesized Pd NPs were characterized by transmission electron microscopy, X-ray diffraction and UV-vis spectroscopy. The spherical and multi-pod PdNPs exhibited catalytic properties that were unique to their size and shape and presented efficient electrocatalytic activities toward the ethanol oxidation reaction.

One-Pot Synthesis of Ternary Alloy Hollow Nanostructures with Controlled Morphologies for Electrocatalysis.

The rational design and synthesis of multimetallic hollow nanostructures (HNSs) have been attracting great attention due to their structural and compositional advantages for application in electrocatalysis. Herein, the one-pot synthesis of Pd-Pt-Ag ternary alloy HNSs with controllable morphologies through a self-templating approach without any pre-synthesized templates is reported. Simultaneous reduction of multiple metal precursors by ascorbic acid in the presence of cetyltrimethylammonium chloride (CTAC) yielded initially metastable Pd-Ag nanocrystals, which can act as a self-template, and subsequent galvanic replacement and reduction led to the formation of final Pd-Pt-Ag HNSs. The size and hollowness (the ratio of inner cavity diameter to outer diameter) of the HNSs could be tuned through control over the concentration of CTAC. This can be attributed to the manipulated reduction kinetics of multiple metal precursors with the change in the CTAC concentration. The prepared Pd-Pt-Ag HNSs exhibited improved catalytic performance for ethanol electro-oxidation due to their large active surface areas and ternary alloy composition.

One-step synthesis of Au@Pd core-shell nanooctahedron.

Octahedral Au@Pd core-shell nanoparticles have been prepared by a one-step aqueous synthesis method where both metal precursors are present simultaneously with the use of cetyltrimethylammonium chloride as both reductant and stabilizer.

Polyhedral Au nanocrystals exclusively bound by {110} facets: the rhombic dodecahedron.

The rhombic dodecahedral Au nanocrystals enclosed by 12 {110} facets could be readily prepared without the use of any seeds, surfactants, or foreign metal ions but only with N,N-dimethylformamide as both reductant and solvent.