共查询到20条相似文献,搜索用时 750 毫秒
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1995年,德国科学家布斯塔尼通过理论计算提出了硼团簇的构造法则——“Aufbau原则”,为硼烯的理论模型研究奠定了基础。在新的理论和计算方法不断提出的背景下,硼烯的理论模型得到了进一步的完善,2014年,美国布朗大学的王来生正式提出“硼烯”这一概念,至此二维硼烯的概念得到了广泛的确信。2015年,研究者首次报道在Ag(111)衬底上生成二维硼烯薄膜。随后,科学家们通过实验探究发现硼烯在超导材料、电池电极材料、催化剂、储氢等领域有巨大的应用前景。硼烯的发展史揭示了理论和实验交互验证的新型科学发展模式,促进了二维材料发展观的演进。 相似文献
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一八七六年的诺贝尔化学奖已经授予纯无机化学的研究,特别是硼烷的领域。我非常高兴并表示深切的感谢。我在这个领域中的方向,如同我的全部研究工作一样,是分子的化学行为与它的三维空间结构和电子结构之间的相互关系。用X-射线衍射的方法对硼烷分子结构的早期研究工作,给化学键的理论——区别于由原来的碳化学的典型理论而发展起来的化学键理论——奠定了一个可靠的基础,并对这类化合物多面体的性质,提供了一个满意的理解。这个原理被合成化学家采用,并帮助建立了一大片迄今还陌生的硼烷化学领域。由此证实了在周期表中位于与碳邻近的那个硼原子确实具有复杂的化学。 相似文献
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《有机化学》2017,(10)
有机硼化合物在合成化学、材料科学、生命健康等领域都有广泛应用,因此有机硼化合物的合成一直是研究热点.目前,催化C—B键形成反应通常使用联硼酸频哪醇酯(B2Pin2)、频哪醇硼烷(HBPin)、儿茶酚硼烷(HBCat)等作为硼试剂.相比于传统的硼试剂,硼烷与胺、膦或N-杂环卡宾等强Lewis碱的加合物(统称为稳定硼烷加合物)具有易于合成、稳定性高、易操作等特点,其作为硼试剂参与的有机硼化合物的合成最近受到越来越多的关注,已被成功用于烯(炔)烃的硼氢化、C—H键硼化、卡宾对B—H键的插入、硼自由基串联环化、取代等反应中,为有机硼化合物的合成提供了新的思路和方法.以反应类型为线索,系统综述了稳定硼烷加合物在有机硼化物合成中的应用研究进展. 相似文献
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过渡金属催化不对称C—H硼化反应是构建手性有机硼化合物最为有效的策略之一,具有原子和步骤经济性,在合成化学、药物化学和材料学等领域受到广泛关注.新型手性配体的设计与合成是过渡金属催化不对称C—H硼化反应成功的关键,根据手性配体的设计和发展过程,对近年来实现的过渡金属催化不对称C(sp2)—H和C(sp3)—H硼化反应的研究进展进行综述. 相似文献
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Yi Sun Xiuyun Zhang Jingyi Tang Tianxia Guo Min Zhou Xiaojing Yao Lili Liu Yongjun Liu Feng Ding 《Chemphyschem》2021,22(9):894-903
Unlike graphene and other 2D materials, borophene is 2D polymorphic with diverse hexagonal holes (HHs)-triangles ratios and the concentrations of HHs are highly substrate dependent. Here, we systematically explored the evolution of boron cluster on Ag(111) surface, BN@Ag(111) (N=1∼36), to understand the nucleation of 2D boron sheet on metal surface. Our calculation showed that, with the size increasing, the structures of most stable BN clusters undergo an evolution from compact triangular lattice, such as double-chains or triple-chains, to the ones with mixed triangular-hexagonal lattices. The first single-HH appears at N=12 and the first double-HH appears at N=27. The stability of large BN clusters with mixed structures is derived from the charge transfer between triangular lattice and the HHs, as well as between the substrates and the BN clusters. Our results provide a deep understanding on the formation of small boron clusters in the initial nucleation stage of borophene growth. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(34):10227-10231
An electron‐counting strategy starting from magnesium boride was used to show the inevitability of hexagonal holes in 2D borophene. The number (hole density, HD) and distribution of the hexagonal holes determine the binding energy per boron atom in monolayer borophenes. The relationship between binding energy and HD changes dramatically when the borophene is placed on a Ag(111) surface. The distribution of holes in borophenes on Ag(111) surfaces depends on the temperature. DFT calculations show that aside from the previously reported S1 and S2 borophene phases, other polymorphs may also be competitive. Plots of the electron density distribution of the boron sheets suggest that the observed STM image of an S2 phase corresponds to a sheet with a HD of 2/15 instead of a sheet with a HD of 1/5. The hole density and the hole distribution echo the distribution of vacancies and extra occupancies in complex β‐rhombohedral boron. 相似文献
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《Progress in Surface Science》2023,98(2):100704
Borophene, a two-dimensional (2D) planar boron sheet, has attracted dramatic attention for its unique physical properties that are theoretically predicted to be different from those of bulk boron, such as polymorphism, superconductivity, Dirac fermions, mechanical flexibility and anisotropic metallicity. Nevertheless, it has long been difficult to obtain borophene experimentally due to its susceptibility to oxidation and the strong covalent bonds in bulk forms. With the development of growth technology in ultra-high vacuum (UHV), borophene has been successfully synthesized by molecular beam epitaxy (MBE) supported by substrates in recent years. Due to the intrinsic polymorphism of borophene, the choice of substrates in the synthesis of borophene is pivotal to the atomic structure of borophene. The different interactions and commensuration of borophene on various substrates can induce various allotropes of borophene with distinct atomic structures, which suggests a potential approach to explore and manipulate the structure of borophene and benefits the realization of novel physical and chemical properties in borophene due to the structure–property correspondence. In this review, we summarize the recent research progress in the synthesis of monolayer (ML) borophene on various substrates, including Ag(1 1 1), Ag(1 1 0), Ag(1 0 0), Cu(1 1 1), Cu(1 0 0), Au(1 1 1), Al(1 1 1) and Ir(1 1 1), in which the polymorphism of borophene is present. Moreover, we introduce the realization of bilayer (BL) borophene on Ag(1 1 1), Cu(1 1 1) and Ru(0 0 0 1) surfaces, which possess richer electronic properties, including better thermal stability and oxidation resistance. Then, the stabilization mechanism of polymorphic borophene on their substrates is discussed. In addition, experimental investigations on the unique physical properties of borophene are also introduced, including metallicity, topology, superconductivity, optical and mechanical properties. Finally, we present an outlook on the challenges and prospects for the synthesis and potential applications of borophene. 相似文献
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Dr. Zhuhua Zhang Yang Yang Guoying Gao Prof. Boris I. Yakobson 《Angewandte Chemie (International ed. in English)》2015,54(44):13022-13026
Two‐dimensional (2D) materials, such as graphene and boron nitride, have specific lattice structures independent of external conditions. In contrast, the structure of 2D boron sensitively depends on metal substrate, as we show herein using the cluster expansion method and a newly developed surface structure‐search method, both based on first‐principles calculations. The preferred 2D boron on weaker interacting Au is nonplanar with significant buckling and numerous polymorphs as in vacuum, whereas on more reactive Ag, Cu, and Ni, the polymorphic energy degeneracy is lifted and a particular planar structure is found to be most stable. We also show that a layer composed of icosahedral B12 is unfavorable on Cu and Ni but unexpectedly becomes a possible minimum on Au and Ag. The substrate‐dependent 2D boron choices originate from a competition between the strain energy of buckling and chemical energy of electronic hybridization between boron and metal. 相似文献
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T. Götz W. Hoheisel M. Vollmer F. Träger 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1995,33(2):133-141
Small sodium and silver particles were generated on dielectric substrates like LiF, quartz and sapphire under ultrahigh vacuum conditions. The optical transmission spectra of the clusters were measured as a function of cluster size and shape, for low and high substrate temperatures as well as for s- and p- polarization of the incident light. Excitation of dipolar surface plasmon oscillations in the directions normal and parallel to the substrate surface could be identified. Furthermore, optical spectra for Na and Ag clusters were calculated with the classical Mie theory. The measured spectra vary strongly if the experimental conditions are changed and can be exploited, for example, to characterize the particles with regard to their size and shape. In particular, the axial ratio of the spheroidal clusters could be determined. Its value is considerably different for the two investigated metals and depends on the substrate material. Furthermore, the temperature of the substrate has a pronounced influence on the shape of the particles. At low temperature of T=100 K two-dimensional island growth is predominant. The particles extend only little in the direction perpendicular to the surface and coalesce readily at small coverage of metal atoms. In contrast, the clusters are truly three-dimensional at T=300 K. At this stage, sodium particles still exhibit a rather small axial ratio whereas silver clusters appear almost spherical. Thus, measurements of the optical spectra permit direct in situ monitoring of cluster growth during the nucleation of adsorbed atoms and of temperature induced shape variations. In addition to investigations of the shape of the particles, the quadrupolar surface plasmon mode was observed for Ag clusters. 相似文献
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Atomic-Scale Insights into the Interlayer Characteristics and Oxygen Reactivity of Bilayer Borophene
Dr. Linfei Li Dr. Jeremy F. Schultz Dr. Sayantan Mahapatra Prof. Xiaolong Liu Prof. Xu Zhang Prof. Mark C. Hersam Prof. Nan Jiang 《Angewandte Chemie (International ed. in English)》2023,62(32):e202306590
Bilayer (BL) two-dimensional boron (i.e., borophene) has recently been synthesized and computationally predicted to have promising physical properties for a variety of electronic and energy technologies. However, the fundamental chemical properties of BL borophene that form the foundation of practical applications remain unexplored. Here, we present atomic-level chemical characterization of BL borophene using ultrahigh vacuum tip-enhanced Raman spectroscopy (UHV-TERS). UHV-TERS identifies the vibrational fingerprint of BL borophene with angstrom-scale spatial resolution. The observed Raman spectra are directly correlated with the vibrations of interlayer boron–boron bonds, validating the three-dimensional lattice geometry of BL borophene. By virtue of the single-bond sensitivity of UHV-TERS to oxygen adatoms, we demonstrate the enhanced chemical stability of BL borophene compared to its monolayer counterpart by exposure to controlled oxidizing atmospheres in UHV. In addition to providing fundamental chemical insight into BL borophene, this work establishes UHV-TERS as a powerful tool to probe interlayer bonding and surface reactivity of low-dimensional materials at the atomic scale. 相似文献
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A brief review of our laboratory's recent scanning tunneling microscopy (STM) studies on nanoclusters supported on TiO2(110) is presented. Particular emphasis is placed on the system Au/TiO2(110). The nucleation and growth of the clusters, which were vapor-deposited on TiO2(110) under ultra high vacuum (UHV) conditions, were investigated using STM. It was found that Au, Pd, and Ag clusters all grow in a three-dimensional (3D) (Volmer-Weber) fashion on TiO2(110), but that at low coverages, quasi-two dimensional (quasi-2D) Au and Pd clusters were observed. These quasi-2D clusters are characterized by heights of 1–2 atomic layers. Annealing studies show that Au and Pd clusters form large microcrystals with well-defined hexagonal shapes. Al clusters, which have a strong interaction with the substrate, are oxidized upon deposition, “wetting” the surface and forming small clusters. In addition to the topographic studies, the local electronic properties of these clusters have been studied using scanning tunneling spectroscopy (STS) to measure the cluster band gaps. The electronic structure was found to be cluster size-dependent, as seen by the appearance of a band gap as the cluster size decreased. More specifically, the onset of cluster metallic properties correlates with the transition from quasi-2D to 3D cluster growth. 相似文献
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We report an extensive first-principles study of the structure and electronic properties of Ag(n) (n = 1-8) clusters isolated in gas phase and deposited on the α-Al(2)O(3) surface. We have used the plane wave based pseudopotential method within the framework of density functional theory. The electron ion interaction has been described using projector augmented wave (PAW), and the spin-polarized GGA scheme was used for the exchange correlation energy. The results reveal that, albeit interacting with support alumina, the Ag atoms prefers to remain bonded together suggesting an island growth motif is preferred over wetting the surface. When compared the equilibrium structures of Ag clusters between free and on alumina substrate, a significant difference was observed starting from n = 7 onward. While Ag(7) forms a three-dimensional (3D) pentagonal bipyramid in the isolated gas phase, on alumina support it forms a planar hexagonal structure parallel to the surface plane. Moreover, the spin moment of the Ag(7) cluster was found to be fully quenched. This has been attributed to higher delocalization of electron density as the size of the cluster increases. Furthermore, a comparison of chemical bonding analysis through electronic density of state (EDOS) shows that the EDOS of the deposited Ag(n) cluster is significantly broader, which has been ascribed to the enhanced spd hybridization. On the basis of the energetics, it is found that the adsorption energy of Ag clusters on the α-Al(2)O(3) surface decreases with cluster size. 相似文献
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Zhang WJ Meng XM Chan CY Chan KM Wu Y Bello I Lee ST 《The journal of physical chemistry. B》2005,109(33):16005-16010
We have studied the nucleation and growth of cubic boron nitride (cBN) films deposited on silicon and diamond-coated silicon substrates using fluorine-assisted chemical vapor deposition (CVD). These comparative studies substantiate that the incubation amorphous/turbostratic BN layers, essential for the cBN nucleation on silicon, are not vital precursors for cBN nucleation on diamond, and they are inherently eliminated. At vastly reduced critical bias voltage, down to -10 V, cBN growth is still maintained on diamond surfaces, and cBN and underlying diamond crystallites exhibit an epitaxial relationship. However, the epitaxial growth is associated with stress in the cBN-diamond interfacial region. In addition, some twinning of crystallites and small-angle grain boundaries are observed between the cBN and diamond crystallites because of the slight lattice mismatch of 1.36%. The small-angle grain boundaries could be eliminated by imposing a little higher bias voltage during the initial growth stage. The heteroepitaxial growth of cBN films on different substrate materials are discussed in the view of lattice matching, surface-energy compatibility, and stability of the substrate against ion irradiation. 相似文献
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Jin Zhang Jia Zhang Dr. Liujiang Zhou Cai Cheng Dr. Chao Lian Jian Liu Prof. Sergei Tretiak Dr. Johannes Lischner Prof. Feliciano Giustino Prof. Sheng Meng 《Angewandte Chemie (International ed. in English)》2018,57(17):4585-4589
Two‐dimensional boron sheets (borophenes) have been successfully synthesized in experiments and are expected to exhibit intriguing transport properties. A comprehensive first‐principles study is reported of the intrinsic electrical resistivity of emerging borophene structures. The resistivity is highly dependent on different polymorphs and electron densities of borophene. Interestingly, a universal behavior of the intrinsic resistivity is well‐described using the Bloch–Grüneisen model. In contrast to graphene and conventional metals, the intrinsic resistivity of borophenes can be easily tuned by adjusting carrier densities, while the Bloch–Grüneisen temperature is nearly fixed at 100 K. This work suggests that monolayer boron can serve as intriguing platform for realizing tunable two‐dimensional electronic devices. 相似文献