Improving the activity of electrochemical reduction of CO_(2) to C_(1) products by oxidation derived copper catalyst

Cu-based electrocatalysts have become the focus in the field of electrochemical CO_(2) reduction reaction(ECO_(2) RR)due to their ability to produce multicarbon products.However,the research on generating single carbon products with higher economic feasibility via ECO_(2) RR based on Cu-based electrocatalysts is rather rare,and the roles of the surface architecture and oxides of the electrocatalysts have not been explained exactly.In this work,a two-step method including thermal oxidation and electroreduction is proposed to introduce Cuþinto pure Cu foil to form Cu_(2)O/Cu electrocatalyst.By regulating the surface composition and morphology of the electrocatalyst in this way,the activity of ECO 2 RR to C_(1) products has been greatly improved.The Faradaic efficiency of carbon products of the Cu_(2)O/Cu electrode reaches 84%at?0.7 V vs.RHE with good selectivity for HCOOH and CO.The current density of Cu_(2)O/Cu electrode reaches-12.21 mA cm^(2) at-0.8 V vs.RHE,which is much higher than that of the Cu foil electrode(?0.09 mA cm?2).In-situ Raman characterization shows that Cuþin Cu_(2)O/Cu electrode could inhibit hydrogen generation and promote ECO_(2) RR by stabilizing the adsorption of CO_(2).

Efficient Nanostructuring of Isotropic Gas-Atomized MnAl Powder by Rapid Milling(30s)

An unprecedentedly short milling time of 30 s was applied to gas-atomized MnAl powder in order to develop permanent magnet properties and,in particular,coercivity.It is shown that such a short processing time followed by annealing results in efficient nanostructuring and controlled phase transformation.The defects resulting from the microstrain induced during milling,together with the creation of the bphase during post-annealing,act as pinning centers resulting in an enhanced coercivity.This study shows the importance of finding a balance between the formation of the ferromagnetic s-MnAl phase and the bphase in order to establish a compromise between magnetization and coercivity.A coercivity as high as 4.2 kOe(1 Oe=79.6 A·m^-1)was obtained after milling(30 s)and annealing,which is comparable to values previously reported in the literature for milling times exceeding 20 h.This reduction of the postannealing temperature by 75℃ for the as-milled powder and a 2.5-fold increase in coercivity,while maintaining practically unchanged the remanence of the annealed gas-atomized material,opens a new path for the synthesis of isotropic MnAl-based powder.

通过超宽139La固体核磁共振波谱研究层状La（OH）2NO3

层状稀土氢氧化物是一类新型的稀土功能材料,本文采用固体核磁共振(SSNMR)方法研究了同时具备离子交换能力和非线性光学特性的层状La(OH)2NO3化合物,探讨了通过四极核CPMG(QCPMG)脉冲序列和变频谱图采集获取超宽^139La SSNMR谱图的方法,并描述了适用于此类实验的滤波方程和谱图重建方法.重建谱图同时包含四极核中心跃迁和卫星跃迁信息,本文使用QUEST软件对超宽^139La NMR谱图进行了模拟,获取的四极耦合常数CQ和非对称因子ηQ均与CASTEP密度泛函理论计算值高度吻合.SSNMR实验结果证实层状La(OH)2NO3化合物属于非中心对称结构(P21),解决了对其结构长期以来存在的争论.

Electrostatic interactions in twisted bilayer graphene

The effects of the long range electrostatic interaction in twisted bilayer graphene are described using the HartreeFock approximation. The results show a significant dependence of the band widths and shapes on electron filling,and the existence of broken symmetry phases at many densities, either valley/spin polarized, with broken sublattice symmetry, or both.

Spatial Raman mapping investigation of SERS performance related to localized surface plasmons

In this research,it reported a novel three-dimensional(3D)metallic hybrid system by introducing single-layer graphene(SLG)between silver nanoparticles(NPs)and silver nano-discs(NDs)arrays(Ag NPs/SLG/Ag NDs).By combining the plasmonic metallic nanostructures and the unique physical/chemical properties of graphene,Ag NPs/SLG/Ag NDs hybrid substrate was fabricated,and it exhibited extremely high surface-enhanced Raman scattering(SERS)performance.By tuning the diameter of Ag NDs,the SERS performance of Ag NPs/SLG/Ag NDs hybrid substrate has been systematically studied.The detection limit for rhodamine 6g(R6G)could reach the concentrations as low as 1×10^−12 mol/L,and the average enhancement factor(EF)of the Ag NPs/SLG/Ag NDs substrate could reach 5.65×10^8.These advantages indicated that the Ag NPs/SLG/Ag NDs hybrid substrate could be regarded as a candidate for organic molecules detection under extremely low concentration.Besides,spatial Raman mapping of Ag NPs/SLG/Ag NDs with 2.5μm diameter NDs showed the larger SERE signal existed around the rim of Ag NDs which was related to the localized surface plasmons.This phenomenon was contributed by a larger electromagnetic field which was tuned by Ag NPs and the edge of Ag NDs.This mechanism also has been confirmed by the electromagnetic simulation result.

Large-scale highly ordered periodic Au nano-discs/graphene and graphene/Au nanoholes plasmonic substrates for surface-enhanced Raman scattering

In this paper,the study of using masks to directly generate large area,highly ordered and periodical nanostructure has been exhibited.Periodic Au nano-discs(NDs)arrays have been fabricated on top of graphene by using holey SigN4 mask which is directly fixed on top of graphene and Au metal is deposited through the holes in mask by thermal evaporation method under vacuum condition.This fabrication method provides an easy,fast and cost efficiency way to generate periodical nanostructure.Also,Au nanoholes(NHs)structure has been studied by using holey SigN4 as a template.The surface-enhanced Raman scattering(SERS)sensitvities of periodical Au NDs/graphene and graphene/Au NHs hybrid structures have been systematically studied.The internal mechanisms could be explained by chemical mechanism effect of graphene and electromagnetic mechanism effect of metallic nano-structures.The enhancement factors have been systematically investigated by varying the diameter and the thickness of Au discs and Au NHs.Raman mappings of Au NDs with 2.5 um diameter ilustrate that the larger SERS enhancements exist in the rim of NDs which has good agreement with the electric field simulation result.The SERE enhancement factors of fluorescein obtained from Au NDs/graphene substrates shows an improvement factor of 500%in comparison of graphene substrate.The calculated SERS enhancement factors of graphene/Au NHs achieve 1,200%in comparison of graphene/planar Au film substrate.

氧化铈纳米粒子的抗菌机理及应用（英文）

纳米材料因其特殊的抗菌机理,在抗菌领域得到了广泛应用.氧化铈纳米粒子是重要的抗菌材料之一,具有对正常细胞毒性低,且抗菌机理基于可逆价态转化的优势.目前已有许多关于氧化铈纳米粒子抗菌活性的研究报道,但系统性探究其抗菌机理的文章则极为少见.本文首先系统性地探究了氧化铈纳米粒子可能的抗菌机理,即静电相互作用在抗菌过程中发挥重要作用,此外抗菌过程还伴随活性氧物种的产生和纳米粒子对细菌的机械损伤.其次,本文分析了氧化铈纳米粒子抗菌效果的影响因素,并总结了不同研究中氧化铈纳米粒子对大肠杆菌和金黄葡萄球菌的抗菌效果.最后提出了氧化铈纳米粒子可能的应用前景.本文将有利于对氧化铈纳米粒子抗菌机理的深入理解,并为该类材料在未来的设计和应用提供借鉴.

CeO_(2)with diverse morphologies-supported IrOx nanocatalysts for efficient oxygen evolution reaction—Commemorating the 100th anniversary of the birth of Academician Guangxian Xu

IrOx-based catalysts are considered the most promising candidates for oxygen evolution reaction(OER)due to their high efficiency.However,improving their intrinsic catalytic activity is essential for practical application.In this work,CeO_(2)with three different morphologies(rod,cube,octahedron)and supported IrOx nanoparticles were fabricated,and they display morphology-dependent OER activity.The IrOx/CeO_(2)-rod shows the highest activity;the catalysts have a catalytic activity sequence of rod>cube>octahedron.A plausible mechanism was proposed:the CeO_(2)support with different morphologies modulates the electronic structure of IrOx by the synergistic interaction promoted by oxygen vacancies between the active component and the support,thereby altering the catalytic activity of the IrOx/CeO_(2)catalyst.

一种通过电子束曝光制备高性能纳米结构Ce-Fe-B磁性材料的新方法

Ce_(2)Fe_(14)B作为一种基于广泛而廉价的稀土(铈)的新型永磁体,低矫顽力和低最大磁能积严重限制了其在永磁领域中的应用.在这项工作中,我们报道了一种将熔融纺丝技术和电子束曝光(EBE)技术结合的新方法,旨在制造高性能Ce-Fe-B磁体.值得注意的是,该方法可以在不使用任何其他重稀土元素的情况下调控出合适的晶界构型.在最佳EBE条件下,纯Ce-Fe-B合金的最大磁能积为6.5 MGOe,比常规快速热处理方法制备的合金的最大磁能积高四倍左右.这说明,使用EBE制备的Ce Fe B材料作为前驱体,经过进一步加工之后,如热变形或烧结,有望填补六角铁氧体与Nd-Fe-B磁体之间的市场空白.

Rare-earth-incorporated low-dimensional chalcogenides: Dry-method syntheses and applications

Chalcogenide thin films incorporating rare-earth (RE) elements with applicationsin optics, electronics, and magnetics have received considerable attention.Aiming at growing pure chalcogenides, dry-method syntheses have beendeveloped. In this review, we summarize the progress thus far on lowdimensionalRE-based chalcogenides (RECs), covering fabrication methods,structures, and applications. This review also provides the summary and perspectivesof the challenges of fabrication and opportunities on the applicationof RECs in the future.

On-surface activation of benzylic C-H bonds for the synthesis of pentagon-fused graphene nanoribbons

Graphene nanoribbons (GNRs) have potential for applications in electronic devices. A key issue, thereby, is the fine-tuning of their electronic characteristics, which can be achieved through subtle structural modifications. These are not limited to the conventional armchair, zigzag, and cove edges, but also possible through incorporation of non-hexagonal rings. On-surface synthesis enables the fabrication and visualization of GNRs with atomically precise chemical structures, but strategies for the incorporation of non-hexagonal rings have been underexplored. Herein, we describe the on-surface synthesis of armchair-edged GNRs with incorporated five-membered rings through the C-H activation and cyclization of benzylic methyl groups. Ortho-Tolyl-substituted dibromobianthryl was employed as the precursor monomer, and visualization of the resulting structures after annealing at 300 °C on a gold surface by high-resolution noncontact atomic force microscopy clearly revealed the formation of methylene-bridged pentagons at the GNR edges. These persisted after annealing at 340 °C, along with a few fully conjugated pentagons having singly-hydrogenated apexes. The benzylic methyl groups could also migrate or cleave-off, resulting in defects lacking the five-membered rings. Moreover, unexpected and unique structural rearrangements, including the formation of embedded heptagons, were observed. Despite the coexistence of different reaction pathways that hamper selective synthesis of a uniform structure, our results provide novel insights into on-surface reactions en route to functional, non-benzenoid carbon nanomaterials.

Stepwise magnetization reversal of geometrically tuned in diameter Ni and FeCo bi-segmented nanowire arrays

Magnetization reversal processes of hexagonal dense arrays of bi-segmented Ni and Fe50Co50 nanowires consisting of two well defined diameters (45 and 80 nm) have been studied.The nanowires were grown inside of tailored pores of anodic alumina templates by combined anodization,atomic layer deposition (ALD) and electrodeposition techniques.The experiments have allowed to identify their two-step magnetization reversal process ascribed to the respective segments of different diameter.This is concluded from the differential susceptibility observed in the hysteresis loops,contrary to those for nanowires with homogeneous diameter.These results are also confirmed by the first-order reversal curve (FORC) distribution diagrams,where an elongation parallel to the interaction axis around two coercive field values is obtained,which is correlated to the difference in diameter of the two segments.This well-defined two-step magnetization reversal process through the nanowire diameter design is thought to be very useful for the advanced control of the remagnetization in arrays of magnetic multidomain systems.

An atomistic approach for the structural and electronic properties of twisted bilayer graphene-boron nitride heterostructures

Twisted bilayer graphene(TBG)has taken the spotlight in the condensed matter community since the discovery of correlated phases.In this work,we study heterostructures of TBG and hexagonal boron nitride(hBN)using an atomistic tight-binding model together with semi-classical molecular dynamics to consider relaxation effects.The hBN substrate has significant effects on the band structure of TBG even in the case where TBG and hBN are not aligned.Specifically,the substrate induces a large mass gap and strong pseudo-magnetic fields that break the layer degeneracy.Interestingly,such degeneracy can be recovered with a second hBN layer.Finally,we develop a continuum model that describes the tight-binding band structure.Our results show that a real-space tight-binding model in combination with semi-classical molecular dynamics is a powerful tool to study the electronic properties of moiréheterostructures,and to explain experimental results in which the effect of the substrate plays an important role.