Structural Control Enables Catalytic and Electrocatalytic Activity of Porous Tetrametallic Nanorods.

Integrating more than one type of metal into a nanoparticle that has a well-defined morphology and composition expands the functionalities of nanocatalysts. For a metal core/porous multimetallic shell nanoparticle, the availability of catalytically active surface sites and molecular mass transport can be enhanced, and the multielemental synergy can facilitate intraparticle charge transport. In this work, a reliable and robust synthesis of such a functional tetrametallic nanoparticle type is presented, where a micro- and mesoporous PdPtIr shell is grown on Au nanorods. The effect of critical synthesis parameters, namely temperature and the addition of HCl are investigated on the hydrodynamic size of the micellar pore template as well as on the stability of the metal chloride complexes and various elemental analysis techniques prove composition of the porous multimetallic shell. Due to the synergistic properties, the tetrametallic nanorods possess extensive negative surface charge making them a promising catalyst in reduction reactions. Dye degradation as well as the conversion of p-nitrophenol to p-aminophenol is catalyzed by the supportless nanorods without light illumination. By depositing the particles onto conductive substrates, the nanostructured electrodes show promising electrocatalytic activity in ethanol oxidation reaction. The nanocatalyst presents excellent morphological stability during all the catalytic test reactions.

Amorphous, Carbonated Calcium Phosphate and Biopolymer-Composite-Coated Si3N4/MWCNTs as Potential Novel Implant Materials.

A biodegradable amorphous carbonated calcium phosphate (caCP)-incorporated polycaprolactone (PCL) composite layer was successfully deposited by a spin coater. In this specific coating, the PCL acts as a bioadhesive, since it provides a better adherence of the coatings to the substrate compared to powder coatings. The caCP-PCL coatings were deposited and formed thin layers on the surface of a Si3N4-3 wt% MWCNT (multiwalled carbon nanotube) substrate, which is an emerging type of implant material in the biomedical field. The composite coatings were examined regarding their morphology, structure and biological performance. The biocompatibility of the samples was tested in vitro with MC3T3-E1 preosteoblast cells. Owing to the caCP-PCL thin layer, the cell viability values were considerably increased compared to the substrate material. The ALP and LDH tests showed numerous living cells on the investrigated coatings. The morphology of the MC3T3-E1 cells was examined by fluorescent staining (calcein and DAPI) and scanning electron microscopy, both of which revealed a well-spread, adhered and confluent monolayer of cells. All performed biocompatibility tests were positive and indicated the applicability of the deposited thin composite layers as possible candidates for orthopaedic implants for an extended period.

Biominerals Added Bioresorbable Calcium Phosphate Loaded Biopolymer Composites.

Nanocrystalline calcium phosphate (CP) bioceramic coatings and their combination with biopolymers are innovative types of resorbable coatings for load-bearing implants that can promote the integration of metallic implants into human bodies. The nanocrystalline, amorphous CP particles are an advantageous form of the various calcium phosphate phases since they have a faster dissolution rate than that of crystalline hydroxyapatite. Owing to the biomineral additions (Mg, Zn, Sr) in optimized concentrations, the base CP particles became more similar to the mineral phase in human bones (dCP). The effect of biomineral addition into the CaP phases was thoroughly studied. The results showed that the shape, morphology, and amorphous characteristic slightly changed in the case of biomineral addition in low concentrations. The optimized dCP particles were then incorporated into a chosen polycaprolactone (PCL) biopolymer matrix. Very thin, non-continuous, rough layers were formed on the surface of implant substrates via the spin coating method. The SEM elemental mapping proved the perfect incorporation and distribution of dCP particles into the polymer matrix. The bioresorption rate of thin films was followed by corrosion measurements over a long period of time. The corrosion results indicated a faster dissolution rate for the dCP-PCL composite compared to the dCP and CP powder layers.

Comparison of the Morphological and Structural Characteristic of Bioresorbable and Biocompatible Hydroxyapatite-Loaded Biopolymer Composites.

Calcium phosphate (CaP)-based ceramic-biopolymer composites can be regarded as innovative bioresorbable coatings for load-bearing implants that can promote the osseointegration process. The carbonated hydroxyapatite (cHAp) phase is the most suitable CaP form, since it has the highest similarity to the mineral phase in human bones. In this paper, we investigated the effect of wet chemical preparation parameters on the formation of different CaP phases and compared their morphological and structural characteristics. The results revealed that the shape and crystallinity of CaP particles were strongly dependent on the post-treatment methods, such as heat or alkaline treatment of as-precipitated powders. In the next step, the optimised cHAp particles have been embedded into two types of biopolymers, such as polyvinyl pyrrolidone (PVP) and cellulose acetate (CA). The pure polymer fibres and the cHAp-biopolymer composites were produced using a novel electrospinning technique. The SEM images showed the differences between the morphology and network of CA and PVP fibres as well as proved the successful attachment of cHAp particles. In both cases, the fibres were partially covered with cHAp clusters. The SEM measurements on samples after one week of immersion in PBS solution evidenced the biodegradability of the cHAp-biopolymer composites.

Scale granules and colours: Sexual dimorphism in Trichonis (Lepidoptera: Lycaenidae, Theclinae).

A large fraction of dorsal wing surface ground scales show an unusual granulated nature, composed of material apparently extruded from the scale lumen in male individuals of both Trichonis Hewitson, 1865 species in the tribe Eumaeini, a rare Guyanian-Amazonian genus. Only a few not-granulated male specimens are known, females are not granulated. The granulated scales are investigated by various microscopic (optical, scanning and transmission electron microscopy, focused ion beam lamella cutting) and spectroscopic (optical reflectance, energy-dispersive X-ray (EDS), Raman) techniques. The characteristic blue colour unique in the South American representatives of the tribe is documented and analysed. EDS spectra show that the granules contain additional calcium and oxygen as compared with the un-granulated regions of the same scale. Electron diffraction (inside the TEM) did not reveal any crystalline component in the granules. The granulated wing surfaces of the males exhibit a UV absorption band at 280 nm, characteristic for biogenic CaCO3; therefore, the material of the granules is tentatively identified as CaCO3. It is shown that the granules influence the optical properties of the dorsal wing surface resulting in a characteristic spectrum.

Reversible control of magnetism in FeRh thin films.

The multilayer of approximate structure MgO(100)/[nFe51Rh49(63 Å)/57Fe51Rh49(46 Å)]10 deposited at 200 °C is primarily of paramagnetic A1 phase and is fully converted to the magnetic B2 phase by annealing at 300 °C for 60 min. Subsequent irradiation by 120 keV Ne+ ions turns the thin film completely to the paramagnetic A1 phase. Repeated annealing at 300 °C for 60 min results in 100% magnetic B2 phase, i.e. a process that appears to be reversible at least twice. The A1 → B2 transformation takes place without any plane-perpendicular diffusion while Ne+ irradiation results in significant interlayer mixing.

Signature of Large-Gap Quantum Spin Hall State in the Layered Mineral Jacutingaite.

Quantum spin Hall (QSH) insulators host edge states, where the helical locking of spin and momentum suppresses backscattering of charge carriers, promising applications from low-power electronics to quantum computing. A major challenge for applications is the identification of large gap QSH materials, which would enable room temperature dissipationless transport in their edge states. Here we show that the layered mineral jacutingaite (Pt2HgSe3) is a candidate QSH material, realizing the long sought-after Kane-Mele insulator. Using scanning tunneling microscopy, we measure a band gap in excess of 100 meV and identify the hallmark edge states. By calculating the [Formula: see text] invariant, we confirm the topological nature of the gap. Jacutingaite is stable in air, and we demonstrate exfoliation down to at least two layers and show that it can be integrated into heterostructures with other two-dimensional materials. This adds a topological insulator to the 2D quantum material library.