Structure, morphology and magnetic properties of flowerlike gamma-Fe2O3@NiO core/shell nanocomposites synthesized from different precursor concentrations

The flowerlike gamma-Fe2O3@NiO core/shell nanocomposites are synthesized by the two-step method. Their structure and morphology can be controlled by tuning the precursor concentration. Microstructural analysis reveals that all the samples have distinct core/shell structure without impurities, and the NiO shells are built of many irregular nanosheets which enclose the surface of gamma-Fe2O3 core. As the precursor concentration decreases (i.e., more NiO content), the NiO grain grows significantly, and the thickness of NiO shells increases. Magnetic experiments are performed to analyze the influences of different microstructures on magnetic properties of samples and we have the following two results. First, at 5 K, along with increasing thickness of NiO shell, the saturation magnetization increases, while the residual magnetization decreases slightly. Second, the hysteresis loops under cooling field demonstrate that the value of exchange bias effect fluctuates between 13 Oe and 17 Oe. This is mainly because of the NiO shell that (i) is composed of irregular nanosheets with disordered orientations, and (ii) does not form a complete coating around gamma-Fe2O3 core

Topological Superfluid in one-dimensional Ultracold Atomic System with Spin-Orbit Coupling

We propose a one-dimensional Hamiltonian $H_{1D}$ which supports Majorana fermions when $d_{x^{2}-y^{2}}$-wave superfluid appears in the ultracold atomic system and obtain the phase-separation diagrams both for the time-reversal-invariant case and time-reversal-symmetry-breaking case. From the phase-separation diagrams, we find that the single Majorana fermions exist in the topological superfluid region, and we can reach this region by tuning the chemical potential $\mu$ and spin-orbit coupling $\alpha_{R}$. Importantly, the spin-orbit coupling has realized in ultracold atoms by the recent experimental achievement of synthetic gauge field, therefore, our one-dimensional ultra-cold atomic system described by $H_{1D}$ is a promising platform to find the mysterious Majorana fermions.Comment: 5 papers, 2 figure

Understanding the geometric and electronic factors of PtNi bimetallic surfaces for efficient and selective catalytic hydrogenation of biomass-derived oxygenates

Ni-base catalysts are promising candidate for the hydrogenation of furfural (FAL) to high-value chemicals. However, slow intermediate desorption and low selectivity limit its implementation. Identifying the catalytic performance of each active sites is vital to design hydrogenation catalyst, and tuning the geometrical sites at molecule level in PtNi could lead to the modification of electronic structure, and thus the selectity for the hydrogenation of FAL was modulated. Herein, PtNi hollow nanoframes (PtNi HNFs) with three dimensional (3D) molecular accessibility were synthesized, EDX results suggested that Ni was evenly distributed inside of the hollow nanoframes, whereas Pt was relatively concentrated at the edges. DFT calculation demonstrated that PtNi significant decrease the desorption energy of the intermediates. This strategy could not only enhance the desorption of intermediates to improve the catalytic performance, but also transfer the adsorption mode of FAL on catalyst surface to selective hydrogenation of FAL to FOL or THFA. The PtNi HNFs catalyst afforded excellent catalytic performance for selective hydrogenation of a broad range of biomass-derived platform chemicals under mild conditions, especially of FAL to furfuryl alcohol (FOL), in quantitative FOL yields (99%) with a high TOF of 2.56 h(-1). It is found that the superior performance of PtNi HNFs is attributed to its 3D hierarchical structure and synergistic electronic effects between Pt and Ni. Besides, the kinetic study demonstrated that the activation energy for hydrogenation of FAL was as low as 54.95 kJ mol(-1). (C) 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved

Hydrophobicity graded gas diffusion electrode with enhanced CO intermediate coverage for high-performance electroreduction of CO2 to ethylene

Electroreduction using a gas diffusion electrode (GDE) provides an efficient method for high rate conversion of CO2 to value-added chemicals. However, long term production with high yields remains challenging due to rapid electrolyte flooding through the hydrophobic gas diffusion layer (GDL). Here, we report a universal strategy to convert a commercial GDL into a hydrophobicity graded GDL (HGGDL) that resists electrolyte flooding. The CO2 electroreduction performance of a family of tandem catalysts consisting of a nickel-single-atom catalyst and Cu nanoparticles immobilized on GDLs and HGGDLs is compared with respect to ethylene production. In situ Raman studies reveal that the HGGDL increases the CO intermediate coverage as a result of the higher differential pressure across the electrodes. Lower carbonate formation also is observed. Enhanced ethylene production efficiency and an order of magnitude improvement in long term stability is achieved in a membrane electrode assembly electrolyzer

Systemic antibiotics increase microbiota pathogenicity and oral bone loss

Abstract Periodontitis is the most widespread oral disease and is closely related to the oral microbiota. The oral microbiota is adversely affected by some pharmacologic treatments. Systemic antibiotics are widely used for infectious diseases but can lead to gut dysbiosis, causing negative effects on the human body. Whether systemic antibiotic-induced gut dysbiosis can affect the oral microbiota or even periodontitis has not yet been addressed. In this research, mice were exposed to drinking water containing a cocktail of four antibiotics to explore how systemic antibiotics affect microbiota pathogenicity and oral bone loss. The results demonstrated, for the first time, that gut dysbiosis caused by long-term use of antibiotics can disturb the oral microbiota and aggravate periodontitis. Moreover, the expression of cytokines related to Th17 was increased while transcription factors and cytokines related to Treg were decreased in the periodontal tissue. Fecal microbiota transplantation with normal mice feces restored the gut microbiota and barrier, decreased the pathogenicity of the oral microbiota, reversed the Th17/Treg imbalance in periodontal tissue, and alleviated alveolar bone loss. This study highlights the potential adverse effects of long-term systemic antibiotics-induced gut dysbiosis on the oral microbiota and periodontitis. A Th17/Treg imbalance might be related to this relationship. Importantly, these results reveal that the periodontal condition of patients should be assessed regularly when using systemic antibiotics in clinical practice

Two-Dimensional Boron Sheets as Metal-Free Catalysts for Hydrogen Evolution Reaction

Current metal-free catalysts for hydrogen evolution reaction (HER) are mainly carbon-based. In this work, HER catalytic activity on two-dimensional (2D) boron sheets (α and β₁₂) are explored using periodic density functional theory. Using the binding free energy of H (Δ<i>G</i>_H*) as the descriptor, we found that both α and β₁₂ sheets present superior activity, with Δ<i>G</i>_H* being close to zero. It is expected that 2D boron sheets would be a promising metal-free catalyst in the electrolysis of water and may offer novel thoughts for the design of new catalysts for other reactions

Atomic nickel cluster decorated defect-rich copper for enhanced C\u3csub\u3e2\u3c/sub\u3e product selectivity in electrocatalytic CO\u3csub\u3e2\u3c/sub\u3e reduction

This work describes a coordination enabled galvanic replacement method to decorate atomic Ni clusters on defect-rich Cu surface to provide the first Ni/Cu bimetallic system that significantly enhances the production of C products from electrocatalytic CO reduction. Specifically, with a surface Ni/Cu ratio of 0.82 %, a 7-fold increase in the selectivity for C products was found in comparison with pristine Cu. Density functional theory calculations reveal that the rate determining step for *CO formation changes from the formation of *COOH on copper to the chemisorption of CO on Ni decorated surfaces. An alteration of binding sites from Ni-Ni bridge for *CO and *COOH to Ni-Cu bridge for *CO is discovered and is proposed to favor the key C–C coupling step. The catalytic mechanism demonstrated in the Cu-Ni system points to the new directions for the development of advanced bimetallic electrocatalysts for producing multi-carbon materials from CO reduction. 2 2 2 2 2