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This study reports on the aqueous-phase synthesis of rhodium-silver (RhAg) bimetallic composite nanoparticles with a controllable Rh/Ag ratio. Due to the high cost of Rh compared with Ag, the RhAg nanoparticles were synthesized in two steps: the synthesis of Ag nanoparticles and the formation of a Rh-rich RhAg area on the surface of the Ag nanoparticles. Transmission electron microscopy and corresponding elemental mapping analyses exhibited that the synthesized 20 nm-sized quasi-spherical RhAg nanoparticles were composed of Ag-rich and Rh-rich area, respectively. Considering the amount of Rh used and productivity, the RhAg nanoparticles with a Rh content of 0.8% exhibited the best catalytic performance for the direct H2O2 generation reaction.

Today, multimetallic nanoparticles (NPs) are extensively studied to search for high-performance catalysts. Unfortunately, a huge material space of NPs composed of immiscible elements has been gener...

We report a facile one-pot aqueous-phase synthesis of PdAu bimetallic nanoparticles with different Pd/Au ratio. The synthesis was conducted by co-reduction of Pd and Au precursor using ascorbic acid as a reducing agent and in the presence of polyallylamine hydrochloride (PAH). By high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectrometry (EDS) analyses, we found that the synthesized nanoparticles had an onion-like core/shell/shell/shell structure with Au-rich core, Pd-rich shell, Au-rich shell, and Pd shell, respectively. We also investigated the catalytic performance of the synthesized PdAu nanoparticles toward hydrogen peroxide generation reaction.

We investigated the conduction characteristics of plasma-doped Si nanowires (NWs) after various rapid thermal annealing (RTA) times. The plasma doping (PD) process developed a highly-deposited B layer at the NW surface. RTA process controls electrical conductivity by mediating the dopant diffusion from the surface layer. The surface chemical and substitutional states of the B plasma-doped Si NWs were analyzed by x-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. To elucidate the detailed structure of the NWs, we analyzed the change in the optical phonon mode caused by the incorporated B atoms. For this purpose, we examined Fano resonance by the investigation of the asymmetry, line-width, and phonon wavenumber in Raman spectra. The changes in symmetry level of the Raman peak, phonon lifetime, and internal strain were closely related to the number of electrically activated borons, which was drastically increased with RTA time. The change in electrical and optical characterizations related to the doping characteristics of the NWs was investigated using a 4-point probe and terahertz time-domain spectroscopy (THz–TDS). The resistivity of the NWs was 3000 times lower after the annealing process compared to that before the annealing process, which is well consistent with the optical conductivity data. The data provide the potential utility of PD in conformal doping for three-dimensional nanodevices.

In this study, a novel process was developed to produce Al/AlN composites by infiltrating molten Al ingot into a mixture of Al and lamp carbon powders. The findings revealed that, during the process, Al2O3 on the surface of Al powder reacted with nitrogen gas and was transformed to AlN. The degree of nitridation was greatly enhanced by adding only less than 3 wt.% lamp carbon, because lamp carbon could act as a dispersion agent as well as a reduction agent. The Al-based composites containing in situ AlN phases showed coefficient of thermal expansion values of ∼11 × 10−6/℃, which were comparable to those of composites containing 60% ex situ AlN particles.

Pd@Pt core–shell nanocubes with a partially covered Pt shell on the Pd nanocubes were synthesized by a direct seed-mediated growth method without a washing process. The FAO activity of Pd@Pt 0.4 at% was 4.3 times and 2.2 times higher than that of Pd cubes and commercial Pt/C, respectively.

In recent years, methylammonium lead halide (MAPbX3, where X = Cl, Br, and I) perovskites have attracted tremendous interest caused by their outstanding photovoltaic performance. Mixed halides have been frequently used as the active layer of solar cells, as a result of their superior physical properties as compared to those of traditionally used pure iodide. Herein, we report a remarkable finding of reversible halide-exchange reactions of MAPbX3, which facilitates the synthesis of a series of mixed halide perovskites. We synthesized MAPbBr3 plate-type nanocrystals (NCs) as a starting material by a novel solution reaction using octylamine as the capping ligand. The synthesis of MAPbBr(3-x)Clx and MAPbBr(3-x)Ix NCs was achieved by the halide exchange reaction of MAPbBr3 with MACl and MAI, respectively, in an isopropyl alcohol solution, demonstrating full-range band gap tuning over a wide range (1.6-3 eV). Moreover, photodetectors were fabricated using these composition-tuned NCs; a strong correlation was observed between the photocurrent and photoluminescence decay time. Among the two mixed halide perovskite series, those with I-rich composition (x = 2), where a sole tetragonal phase exists without the incorporation of a cubic phase, exhibited the highest photoconversion efficiency. To understand the composition-dependent photoconversion efficiency, first-principles density-functional theory calculations were carried out, which predicted many plausible configurations for cubic and tetragonal phase mixed halides.

We demonstrate a prototype thermal evolution path for liquid thermal conductivity in solids. Thermal evolution of β -Cu2Se shows large interstitial displacement of constituent atoms marked by glass-like transitions and an asymptotic liquid thermal transport. Using ab initio molecular dynamics (AIMD), we identify these transitions, and confirm them with in situ transmission electron microscopy and electron energy loss spectroscopy. The thermal disorder of the Cu+ ions forms homopolar Cu–Cu bonds under a rigid Se framework, and at yet higher temperatures the Se framework undergoes thermal distortion. The non-equilibrium AIMD prediction of lattice thermal conductivity shows significant suppression of the phonon transport, in agreement with experiments and molecular behavior.

In this study, the surface modification of biodegradable pure Magnesium and Mg-5wt%Ca-1wt%Zn alloy was performed through immersion in HBSS, inorganic salt solution and cell media to reduce initial hydrogen evolution and improve cell adhesion. The formation of different CaP-like coatings from immersion of pure Mg and Mg alloy were observed using Cryo FIB analysis and their performances were measured through cell adhesion, quantification of released Mg ions, and cell cytotoxicity assays. The coating layers displayed significant reduction of initial corrosion rate, and cell adhesion for both pure Mg and Mg alloy appeared to be influenced by the amino acids and proteins in the cell media. In general, Mg alloy showed a denser coating layer with higher Ca contents, resulting in greater reduction of initial corrosion rate and improved cell adhesion, when compared to pure Mg. This is due to saturation of Ca around the corrosion site that provided much favorable environmental condition to produce denser calcium phosphate coating mixture. The result from this study suggests that the surface modification of biodegradable Mg alloy by immersion in alkaline solutions can be utilized to obtain ideal biodegradable orthopedic implant material with reduced initial hydrogen evolution rate and improved cell adhesion.

The generation of planar defects in silicon nanowires (SiNWs) synthesized by means of a vapor–liquid–solid (VLS) procedure using Au as a catalyst in an ultra-high vacuum chemical vapor deposition (UHV-CVD) system was investigated. Faceting, the formation of planar defects and the diffusion of Au in SiNWs occurred simultaneously, proportional to the growth temperature and the ratio of the H 2 precursor gas. The planes located on the sidewalls of the wire after Au diffusion were faceted (1 1 1) and (1 0 0) surfaces, which represent equilibrium configurations of Si due to surface energy minimization during rapid wire growth under unstable conditions. Moreover, {1 1 1} twin defects were formed on the sidewalls of the faceted boundaries where the Au clusters were mainly located, due to the surface tension of the Au atoms, resulting in clusters at the liquid/solid interfaces in SiNWs with a 〈1 1 1〉 growth direction.

We have synthesized Cu nanowires via a simple process using both thermal evaporation and CuCl powders. In this method, complicated processes and special instruments are not required to synthesize Cu nanostructures. In addition, we have used commercial CuCl powders as a precursor. There have been no reports on the preparation of Cu nanostructures using simple instruments together with a commercial source material as in this study. Cu nanostructures of various morphologies were formed at relatively low temperature. The microstructure of the Cu nanostructures was investigated using HRTEM images and SAD pattern analysis.

In this study, we investigated the thermal oxidation of silicon nanowires (SiNWs) grown via the vapor-liquid-solid (VLS) method with an Au catalyst. We systematically analyzed the oxidation mechanism of the SiNWs in both the radial and axial directions and mapped the behavior of the Au atoms on the sidewall and at top of the wire as a function of oxidation time. After thermal oxidation at a temperature of 900 °C, two kinds of oxidation behavior in SiNWs were observed: one was conventional radial oxidation and the other was axial oxidation. In particular, the axial oxidation rate at the Si/Au interface increased dramatically compared with the radial oxidation rate, which can be explained by the reaction between the Si atoms precipitated from the Au tip and the O2 gas injected in the area surrounding the Au tip. Additionally, we observed that the oxidation rate in the axial direction was inversely proportional to the wire diameter, which is related to the SiO2 surrounding the Si wire. Moreover, the Au shape changed with respect to the wire diameter, suggesting that both the stress in the Au-Si alloy and the SiO2 shell thickness of the wire critically affect the growth of SiO2 on Au. Open image in new window

In-plane magnetic anisotropy and the corresponding morphology of Fe epitaxial layers have been investigated with respect to underlying MgO growth temperature when epitaxial Fe/MgO layers are grown on InAs (001) substrates. Coexistence of three-dimensional Fe islands with strong in-plane textures along110and (100) is observed on 4 nm thick MgO layers grown on 200 degrees C, leading to the absence of magnetic anisotropy. Meanwhile, the partially relaxed MgO layers grown above 300 degrees C give rise to two-dimensional Fe layers with cubic magnetic anisotropy. The higher MgO growth temperature accelerates the two-dimensional layer formation of the subsequent Fe as well as the advent of cubic anisotropy by reducing underlying strain within the MgO layer.

We investigate the role of hydrogen solubility and diffusivity on the activation energy for hydrogen permeability and the relationship between the hydrogen permeability and resistance to hydrogen embrittlement in amorphous membranes, Cu 50 Zr 50 and Cu 65 Zr 35 . The membrane with the lower activation energy for permeation showed higher hydrogen permeability, but it showed lower durability under hydrogen atmosphere. This relationship between the two properties is discussed on the basis of the nature of the short-range ordered (SRO) structures constituting amorphous membranes under hydrogen ambient.

The microstructural evolution and the effect on in-plane magnetic properties of epitaxial Fe/MgO layers grown on InAs(001) substrates have been investigated as a function of MgO growth temperature. The Fe grows three-dimensional islands with two different in-plane textures along [010] and [110] directions on the MgO layers grown below 200 °C in remarkable contrast to two-dimensional Fe layers on the MgO layers grown above 300 °C. As the MgO growth temperature increases, both tensile-strained MgO and the subsequent Fe are simultaneously relaxed, and the distribution of 45°-rotated Fe lattices with [010] texture becomes dominant. The experimental results imply that the microstructural evolution of the Fe is strongly influenced by the underlying misfit strain within the MgO layers grown at different temperatures. The two different epitaxial relationships of the Fe islands lead to no magnetic anisotropy, while the Fe layer with the single epitaxial relationship of Fe[010]//MgO[110]//InAs[110] shows cubic m...

Silicon nanowires (SiNWs) were synthesized by means of a Vapor–Liquid–Solid (VLS) procedure using Au as a catalyst in a UHV-CVD system. The growth of the SiNWs was critically dependent on the flow rate of H2. In our system, the nanowires showed novel features such as faceting phenomenon and the migration of Au atoms on the lateral surface, which were dependent on the flow rate of H2. In particular, Au that diffused from the catalyst tip to the facet edge was transformed into Au clusters, resulting in the formation of numerous Au stripes that entirely surrounded the pillar during the growth process. A one step synthesis of branched SiNWs can be achieved via the presence of Au clusters at the lateral surface under conditions of a high flow rate of H2. The growth kinetics of SiNWs as a function of H2 flow rate lead to the conclusion that the influence of the effect of hydrogen is a major factor in controlling the growth of SiNWs under conditions of a low partial pressure of silane.

An original two-step procedure, based on the miscibility gap between two elements, produced an in-situ bulk metallic glass matrix composite. The Zr-Ta binary alloy, which exhibits a large immiscible region in solid state, formed a two-phase mixture of Zr- and Ta-rich solid solution by phase separation. When the Zr-Ta binary alloy was remelted with Cu, Zr, and Ti, the Ta-rich solid solution, which has a high melting temperature, did not melt, while the remaining melt containing Zr-rich solid solution mixed with the other elements and solidified into an amorphous phase at lower temperatures. The improvement of strength in the composite indicates that the interfaces between the Ta-rich particles and the BMG matrix formed by phase separation are strong enough to hold a high interfacial cohesion strength.

There have been developments and applications of osteogenic biomaterial substitutes in dentistry to replace missing dentition or to reinforce existing dentitions. The dentistry in practice has evolved into new treatment modality with the development and application of novel biocompatible materials. The examples are dental implants, bone graft materials, surgical plates, and any modification to increase biocompatibility and stability in dentition. These materials cover everything from replacing the missing teeth and/or degenerated supporting structures to the induction of new bone formation. Also, the osseointegrated materials further allowed orthopedic force application on these materials as skeletal anchorage to control tooth movements. Currently, modifications of the surface treatment or combination of osseoinductive materials to improve potential osseointegration are continuously endeavored. This special issue delivers original research on different aspects, studies on the application of the novel biomaterials to fill bone defect rapidly with new bone, improvement of osseointegration through variety of surface treatment, and the possibility of alumina toughened zirconia for the new implant material, and also covers clinical research on a modified dental implant as a gateway to the human body: implant mediated drug delivery system. First, we discuss the studies of novel biomaterial application for new bone formation in bony defect. Rapid bone defect filling with normal bone is a challenge in orthopaedics and dentistry. A study by S. Ansari et al. developed a strategy for bone tissue engineering that entails application of immobilized anti-BMP-2 monoclonal antibodies (mAbs) to capture endogenous BMPs in vivo and promote antibody-mediated osseous regeneration (AMOR). These data have potential implications for the mechanism of action of AMOR, suggesting that anti-BMP-2 may capture endogenous osteogenic BMPs, which may in turn mediate de novo bone formation. Strontium ranelate (SrRan) has been shown to in vitro decrease bone resorption and increase bone formation and represents a potential agent with the capacity to accelerate bone defect filling. G. Zacchetti et al.'s study demonstrates that Sr is integrated both in cortical and in trabecular bone healing of the defect in SrRan-treated rats and improves the bone material level properties of the healing bone mainly after 4 weeks of treatment. These results open up new perspectives for the use of SrRan in clinical studies as a pharmacologic agent with a potential beneficial effect on bone defect repair. A. Monje et al.'s comprehensive systematic review aimed at assessing the feasibility of allogeneic block grafts by means of survival rate, histologic analysis, and causes of failure, for augmentation of the atrophic maxilla, provides a current state of the art about this treatment modality. Therefore, this study can be of a very meaningful importance for clinicians in the decision making of selecting the ideal source for bone block grafting. This special issue illuminates the clinical evaluation of the bone graft materials that have been used conventionally and introduces the histological identification of changes in tissue adjacent to the biomaterials through three original research articles. Particularly, clinical experiment on the management of the thin alveolus which has been considered as tooth movement limitation in orthodontics and the scientific analysis of the methods have been discussed in depth. Alveolar augmented corticotomy is effective in accelerating orthodontic tooth movement, but the effect only lasts for a relatively short time. A study by D.-Y. Lee et al. demonstrated the stable results in a long-term (12 weeks) experiment using xenograft materials in beagle experiment. Absorbable collagen membrane could control the texture of bone surface. K.-B. Lee et al. researched the different types of bone graft materials on the treatment effect of augmented corticotomy. The remarkable thing is that not only allograft or xenograft but also synthetic graft material showed comparable new bone formation. Augmented corticotomy showed stable results regardless of the graft material types, and in particular synthetic bone material showed dramatic new bone formation. The study of H.-J. Choi et al. was to investigate the underlying biology of the immediate periodontal response to orthodontic tooth movement after the augmented corticotomy with alloplastic bone grafts. The results demonstrated that measurable tooth movement began as early as 3 days after the intervention in beagle dogs. Based on the results and histological findings, augmented corticotomy-facilitated orthodontic tooth movement might enhance the condition of the periodontal tissue and the stability of the outcomes of orthodontic treatment. There has been increased interest in search of the new biomaterial for dental implant. We would like to examine the possibility of alumina toughened zirconia for the new implant material through several articles. S. Y. Kim et al.'s study classified the influence of different topographies and hydrophilicities of Ti surfaces on the expression of various functional factors in PDLSCs involved in osteogenesis in the absence of osteogenic supplements and evaluated biomarkers of cellular activity, including the expression of transcription factors and signaling molecules of PDLSCs on the Ti surfaces. The relevance of J. Markhoff et al.'s research was to develop a glass solder matrix for coating zirconia ceramics to improve osseointegration of ceramic dental implants with adequate mechanical properties at once. Thereby, the existing advantages in esthetic appearance and hypersensitivity of ceramic dental implants in contrast to metallic implants may become effective in clinical application in the near future. The results of R. Olivares-Navarrete et al.'s study indicate that effects of the complex SLA topography are greater than the effect of acid etching or grit blasted on regulation of osteogenesis, osteoclastogenesis, and angiogenesis on multipotent BMCs and committed osteoblasts. 1α,25(OH)2D3 had a major role in enhancing these effects that was sex depended. Alumina-zirconia composites have attracted significant interest in the past few years for orthopedic and dental use. Although yttria stabilized zirconia is the only ceramic currently employed for dental implant fabrication, several reasons suggest that alumina-zirconia composites may conveniently substitute this monolithic material. Here, F. Mussano et al. report the results of the experiments performed in vitro and in vivo to assess the behavior of alumina toughened zirconia (ATZ) dental implants. It is important to underline that ATZ is different from zirconia-toughened alumina (ZTA) due to the relative percentage of the two materials and the consequent mechanical and possibly biological properties. Another topic enlightened in this special issue is dental implant. It is about neither improving osseointegration potential nor improving functional occlusion of implant, but it is a preliminary study on the prospect of dental implant as a drug delivery system. In an article by Y.-S. Park et al., they developed and proposed a new implant mediated drug delivery system (IMDDS) through a modified titanium implant. In the nearest future, the IMDDS may provide a novel approach to treat patients with chronic diseases. In conclusion, we debated about the current status of osteogenic biomaterials in contemporary dentistry, the osteogenic biomaterial types, the application of the material, and the future study. We would like to suggest a right direction of osteogenic biomaterial in this special issue because comprehension of recent advances in biomaterial of dentistry would lead to appropriate applications of these biomaterials and successful strategies to improve treatment outcomes to better serve patients. Seong-Hun Kim Jae-Pyung Ahn Homayoun H. Zadeh Eric J. W. Liou

Multiwalled boron carbonitride (BCN) nanotubes with two different structures were synthesized via thermal chemical vapor deposition; one has 10% C atoms homogeneously doped into BN nanotubes (B0.45C0.1N0.45 NTs), and the other has BN layers sheathed with 5-nm-thick C outerlayers (BN-C NTs). The electronic structures of the B, C, and N atoms were thoroughly probed by synchrotron X-ray photoelectron spectroscopy and the X-ray absorption near-edge structure method. The B0.45C0.1N0.45 NTs contain a significant amount of B-C and C-N bonding with a pyridine-like structure (hole structure), which reduces the pi bonding states of the B and N atoms. From the XPS valence band spectrum, the band gap was estimated to be about 2.8 eV. In the BN-C NTs, the C and BN domains are separated without forming the pyridine-like structure. Using the first principles method, we investigated the relative stabilities and electronic structures of the various isomers of the double-walled (12,0)@(20,0) BCN NTs. The C-outerlayer BN nanotube structure is the most stable isomer, when there exist no defects in the tubes with B/N = 1.0 (i.e., graphite-like structure). In addition, a reasonable model, which is characterized by the motives consisted of three pyridine-like rings around a hollow site, is presented for the local structure of C atoms in the B0.45N0.45C0.1 NTs. A considerable decrease of the band gap due to the 10% C doping was predicted, which was consistent with the experimental results.

We report vapor-phase synthesis of single-crystalline free-standing Ag nanowires and polarized surface-enhanced Raman scattering (SERS) of a single nanowire, as a first step toward fabrication of well-controlled nanobiosensors employing the SERS technique.

Si1−xGexnanowires (NWs) were prepared by a Vapor–Liquid–Solid (VLS) procedure using Au as the catalyst at a fixed growth temperature of 400 °C. The alloy composition was adjusted and the growth rate of the Si1−xGex NWs was achieved by varying the inlet gas ratio and the H2 flow rate. The growth of Si1−xGex NWs can be explained by two mechanisms that are related to growth kinetics; first, collisional activation is a dominant factor at flow rates of H2 100 sccm and second, in the case of a H2 flow rate of 200 sccm, the reaction is unimolecular. In addition, a Ge concentration (0.56 < x < 0.91) in Si1−xGex NWs is observed at a relatively high growth temperature of 400 °C as compared with data reported in the literature. The findings herein indicate that the high Ge concentration (x) can be attributed to the presence of interstitial Ge atoms in the Si1−xGex NWs, when they are grown under non-equilibrium conditions. This was confirmed by comparing the measured Ge concentration between EDX and XRD, Raman and strongly demonstrated by XPS results indicating the development of Ge interstitial states at lower binding energy, rather than bulk-like bonding.

Commercially pure Al alloy sheets were processed using high-strain-rate, dissimilar-channel angular pressing (DCAP) for as many as 100 passages through a channel with φ=120 deg, to investigate the work hardening caused by a low strain level (ɛ