Pt 3 Co Concave Nanocubes: Synthesis, Formation Understanding, and Enhanced Catalytic Activity toward Hydrogenation of Styrene

We report a facile synthesis route to prepare high‐quality Pt 3 Co nanocubes with a concave structure, and further demonstrate that these concave Pt 3 Co nanocubes are terminated with high‐index crystal facets. The success of this preparation is highly dependent on an appropriate nucleation process with a successively anisotropic overgrowth and a preservation of the resultant high‐index planes by control binding of oleyl‐amine/oleic acid with a fine‐tuned composition. Using a hydrogenation of styrene as a model reaction, these Pt 3 Co concave nanocubes as a new class of nanocatalysts with more open structure and active atomic sites located on their high‐index crystallographic planes exhibit an enhanced catalytic activity in comparison with low‐indexed surface terminated Pt 3 Co nanocubes in similar size. Anisotropic overgrowth : Pt 3 Co concave nanocubes bounded by high‐index facets were prepared with a facile wet‐chemical method. The formation process for such concave nanostructures was systematically studied, and a plausible mechanism was proposed. These nanocrystals can be used as advanced nanocatalysts, showing high activity and reusability toward hydrogenation of styrene (see figure).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102689/1/chem_201301724_sm_miscellaneous_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/102689/2/1753_ftp.pd

Timing Matters: the Underappreciated Role of Temperature Ramp Rate for Shape Control and Reproducibility of Quantum Dot Synthesis

Understanding the coupled kinetic and thermodynamics factors governing colloidal nanocrystals nucleation and growth are critical factors in the predictable and reproducible synthesis of advanced nanomaterials. We show that the temporal temperature profile is decisive in tuning the particle shape from pseudo-spherical to monodisperse cubes. The shape of the nanocrystals was characterized by transmission electron microscopy and X-ray diffraction.We introduce a mechanism for the shape controlled synthesis in the context of temperature-dependent nucleation and growth and provide experimental evidence to support it.The authors would like to thank Richard Robinson for helpful discussions. This publication was based on work supported by Award No. KUS-C1-018-02, made by King Abdullah University of Science and Technology (KAUST). We also acknowledge the Cornell Center for Materials Science (NSF DMR-0520404)

Sub-Fiber Scale Precision Dicing of Aramid Fiber-Reinforced Plastic Composites

Aramid fiber-reinforced plastic (AFRP) composites are widely used in aerospace, rail transit, marine and military industries, due to their high specific strength, high impact resistance, fatigue resistance and excellent designable properties. In order to meet different application requirements, cutting processes need to be carried out, such as window opening, edge cutting and slit cutting. However, the characteristics of high tensile strength and toughness, low interlaminar strength, non-uniformity and anisotropy make AFRP composites a difficult-to-machine material. They are prone to produce rough cutting surfaces and cutting damages including burr, wire drawing, delamination, resin burn, material flanging, etc. To solve this problem, the ultra-thin diamond dicing blade was used for high-speed cutting of AFRP composites in sub-fiber scale in this research. The influence of process parameters on cutting force, cutting temperature, maximum spindle current, tool wear and cutting surface quality were investigated by establishing the cutting force model, L16(45) orthogonal experiment, single factor experiment, range analysis and variance analysis. The theoretical and experimental results show that cutting AFRP composites with ultra-thin diamond dicing blade can obtain smooth surfaces without common cutting damages. When the cutting speed is 91.11 m/s (spindle speed n = 30,000 r/min), the cutting depth is 0.2 mm and the feed speed is 5 mm/s, the surface roughness Ra can be as low as 32 nm, which realize the precision cutting of AFRP composites

In vitro digestion analysis of soft candy containing peptide-zinc chelates derived from low-fluoride protein hydrolysates of Antarctic krill (Euphausia superba) powder

This study developed a soft candy with peptide-zinc chelates using low-fluorine protein hydrolysates derived from Antarctic krill powder. To achieve this, the enzymatic hydrolysis conditions of the protein isolates were optimized through single-factor experiments. Protein hydrolysates were used to produce Antarctic krill peptides (AKP) through ceramic membrane microfiltration at various pressure levels. AKP-zinc chelates (AKP-Zn) were prepared by mixing AKP and zinc sulfate, subsequent to characterized the resulting complex. Finally, we examined the tolerance of AKP-Zn and soft candy containing AKP-Zn (SC-AKP-Zn) to simulated gastrointestinal digestion in vitro. The optimal enzyme mix was a 1:1 ratio of alkaline and flavored protease, with 4000 U/g enzymes, pH 7.5 and 3 h, and the ceramic membrane microfiltration increased the protein content in AKP by approximately 85.34 ± 3.54 %. Characterization showed that AKP effectively interacts zinc ions through bonding with oxygen and nitrogen atoms, helps the strength of AKP-Zn in various pH levels and simulated digestive systems. AKP-Zn and SC-AKP-Zn showed higher bioavailability compared to zinc sulfate and zinc gluconate. These results provide a solid theoretical foundation for creating ready-to-eat food products with AKP-Zn and offer new insights into the potential applications of Antarctic krill proteins

Process research on ultrasonic vibration assisted lapping of single crystal silicon carbide

Aimming at the problems such as low material removal rate and abrasive agglomeration when polishing single crystal silicon carbide wafers with traditional methods, this study proposed a ultrasonic vibration assisted lapping method. It studied the influence of different process parameters including speeds, abrasive concentrations, pressures and abrasive grain sizes on the lapping efficiency and lapping quality of single crystal silicon carbide wafers. The experimental results and theoretical analysis show that ultrasonic vibration effectively improves the material removal rate of single crystal silicon carbide wafer polishing. When the lapping disc speed is 50 r/min, the lapping fluid concentration is 2.5%, the pressure is 0.015 MPa and the abrasive grain size is 0.5 μm, the effect of improving the material removal rate is the most obvious, thus increased by 23.4%, 33.8%, 72.3% and 184.2% respectively. At the same time, by tracking and testing the surface roughness during the lapping process, the best time for ultrasonic vibration-assisted grinding of abrasives with different particle sizes was determined

A New Slurry for Photocatalysis-Assisted Chemical Mechanical Polishing of Monocrystal Diamond

Diamond needs to have a perfectly smooth surface due to the growing requirements in the fields of electronic semiconductors, optical windows and high-fidelity loudspeakers. However, the polishing of diamonds is highly challenging due to their exceptional hardness and chemical stability. In this study, a new polishing slurry is prepared for the proposed photocatalysis-assisted chemical mechanical polishing (PCMP) approach to obtain an ultra-smooth surface for large-area diamond. The analyses and experimental findings revealed the significance of the photocatalyst, abrasive, electron capture agent and pH regulator as essential components of the PCMP slurry. TiO2 with a 5 nm pore size and P25 TiO2 possess improved photocatalysis efficiency. Moreover, diamond removal is smooth under the acidic environment of H3PO4 due to the high oxidation–reduction potential (ORP) of the slurry, and, during the methyl orange test, P25 TiO2 exhibits reasonable photocatalytic effects. Moreover, in 8 h, a smooth surface free of mechanical scratches can be obtained by reducing the surface roughness from Ra 33.6 nm to Ra 2.6 nm

Distinct Excitonic Emissions in 2D (C7H7N2)2PbX4 (X = Cl, Br) under Compression

Abstract Two dimensional (2D) hybrid metal halides (HMHs) usually exhibit free excitonic (FE) emission, and self‐trapped excitonic (STE) emission can also be achieved by adopting appropriate halogens and organic cations. Recently, significant efforts have been made to modulate and then clarify the transformation and connection between these two types of excitonic emissions in 2D HMHs. In this study, intriguing pressure‐tuned transitions between FE emission and STE emission are observed in 2D (C7H7N2)2PbCl4. In contrast, only FE emissions with tunable emission energies are observed in 2D (C7H7N2)2PbBr4 which possesses a similar structure with (C7H7N2)2PbCl4 under compression. Such distinct halide‐dependent optical responses under pressure are experimentally revealed to arise from the intricate interplay among several factors in these HMHs, including the stiffness of the structure, the Coulomb force between the organic cations and the inorganic octahedra, and the magnitude of inorganic octahedral distortion. These high‐pressure optical explorations can unravel the underlying interrelationship between the crystal structure and excitonic emission in 2D HMHs

Screening of immunogenic proteins and evaluation of vaccine candidates against Mycoplasma synoviae

Abstract Mycoplasma synoviae (M. synoviae) is a serious avian pathogen that causes significant economic losses to chicken and turkey producers worldwide. The currently available live attenuated and inactivated vaccines provide limited protection. The objective of this study was to identify potential subunit vaccine candidates using immunoproteomics and reverse vaccinology analyses and to evaluate their preliminary protection. Twenty-four candidate antigens were identified, and five of them, namely RS01790 (a putative sugar ABC transporter lipoprotein), BMP (a substrate-binding protein of the BMP family ABC transporter), GrpE (a nucleotide exchange factor), RS00900 (a putative nuclease), and RS00275 (an uncharacterized protein), were selected to evaluate their immunogenicity and preliminary protection. The results showed that all five antigens had good immunogenicity, and they were localized on the M. synoviae cell membrane. The antigens induced specific humoral and cellular immune responses, and the vaccinated chickens exhibited significantly greater body weight gain and lower air sac lesion scores and tracheal mucosal thicknesses. Additionally, the vaccinated chickens had lower M. synoviae loads in throat swabs than non-vaccinated chickens. The protective effect of the RS01790, BMP, GrpE, and RS00900 vaccines was better than that of the RS00275 vaccine. In conclusion, our study demonstrates the potential of subunit vaccines as a new approach to developing M. synoviae vaccines, providing new ideas for controlling the spread of M. synoviae worldwide