Co-reporter:Ruiqi Zhang, Zhenyu Li, and Jinlong Yang
The Journal of Physical Chemistry Letters September 21, 2017 Volume 8(Issue 18) pp:4347-4347
Publication Date(Web):August 25, 2017
DOI:10.1021/acs.jpclett.7b01721
Oxides of two-dimensional (2D) atomic crystals have been widely studied due to their unique properties. In most 2D oxides, oxygen acts as a functional group, which makes it difficult to control the degree of oxidation. Because borophene is an electron-deficient system, it is expected that oxygen will be intrinsically incorporated into the basal plane of borophene, forming stoichiometric 2D boron oxide (BO) structures. By using first-principles global optimization, we systematically explore structures and properties of 2D BO systems with well-defined degrees of oxidation. Stable B–O–B and OB3 tetrahedron structure motifs are identified in these structures. Interesting properties, such as strong linear dichroism, Dirac node-line (DNL) semimetallicity, and negative differential resistance, have been predicted for these systems. Our results demonstrate that 2D BO represents a versatile platform for electronic structure engineering via tuning the stoichiometric degree of oxidation, which leads to various technological applications.
Co-reporter:Haoqi Chen, Bin Li, and Jinlong Yang
ACS Applied Materials & Interfaces November 8, 2017 Volume 9(Issue 44) pp:38999-38999
Publication Date(Web):October 16, 2017
DOI:10.1021/acsami.7b11454
Black phosphorus is a promising candidate for future nanoelectronics with a moderate electronic band gap and a high carrier mobility. Introducing the magnetism into black phosphorus will widely expand its application scope and may present a bright prospect in spintronic nanodevices. Here, we report our first-principles calculations of spin-polarized electronic structure of monolayer black phosphorus (phosphorene) adsorbed on a magnetic europium oxide (EuO) substrate. Effective spin injection into the phosphorene is realized by means of interaction with the nearby EuO(111) surface, i.e., proximity effect, which results in spin-polarized electrons in the 3p orbitals of phosphorene, with the spin polarization at Fermi level beyond 30%, together with an exchange-splitting energy of ∼0.184 eV for conduction-band minimum of the adsorbed phosphorene corresponding to an energy region where only one spin channel is conductive. The energy region of these exchange-splitting and spin-polarized band gaps of the adsorbed phosphorene can be effectively modulated by in-plane strain. Intrinsically high and anisotropic carrier mobilities at the conduction-band minimum of the phosphorene also become spin-polarized mainly due to spin polarization of deformation potentials and are not depressed significantly after the adsorption. These extraordinary properties would endow black phosphorus with great potentials in the future spintronic nanodevices.Keywords: black phosphorus; carrier mobility; magnetic substrate; proximity effect; spin injection;
Co-reporter:Wei Hu, Lin Lin, Ruiqi Zhang, Chao Yang, and Jinlong Yang
Journal of the American Chemical Society November 1, 2017 Volume 139(Issue 43) pp:15429-15429
Publication Date(Web):October 13, 2017
DOI:10.1021/jacs.7b08474
Two-dimensional phosphorene with desirable optoelectronic properties (ideal band gap, high carrier mobility, and strong visible light absorption) is a promising metal-free photocatalyst for water splitting. However, the band edge positions of the valence band maximum (VBM) and conduction band maximum (CBM) of phosphorene are higher than the redox potentials in photocatalytic water splitting reactions. Thus, phosphorene can only be used as the photocathode for hydrogen evolution reaction as a low-efficiency visible-light-driven photocatalyst for hydrogen production in solar water splitting cells. Here, we propose a new mechanism to improve the photocatalytic efficiency of phosphorene nanoribbons (PNRs) by modifying their edges for full reactions in photocatalytic water splitting. By employing first-principles density functional theory calculations, we find that pseudohalogen (CN and OCN) passivated PNRs not only show desired VBM and CBM band edge positions induced by edge electric dipole layer, but also possess intrinsic optoelectronic properties of phosphorene, for both water oxidation and hydrogen reduction in photocatalytic water splitting without using extra energy. Furthermore, our calculations also predict that the maximum energy conversion efficiency of heterojunction solar cells consisting of different edge-modified PNRs can be as high as 20% for photocatalytic water splitting.
Co-reporter:Wenhua Zhang;Zhenyu Li;Yi Luo
The Journal of Physical Chemistry C May 14, 2009 Volume 113(Issue 19) pp:8302-8305
Publication Date(Web):2017-2-22
DOI:10.1021/jp810751j
The geometric, electronic, and magnetic properties of the FeO monolayer on a Pt(111) surface are investigated by first principles calculations. Generally, antiferromagnetic (AFM) structures are more stable than that of the ferromagnetic one. On the basis of a specific AFM structure, the long puzzling scanning tunneling microscopy (STM) experimental observations can be well explained. In this AFM model, the Fe−O layer distance at the fcc region is larger than the hcp region, in contrast to previous theoretical results. The STM images at the field-emission regime are explained by local surface potential.
Co-reporter:Xu Liu, Jinyun Yuan, Chuanhao Yao, Jishi Chen, Lingling Li, Xiaoli Bao, Jinlong Yang, and Zhikun Wu
The Journal of Physical Chemistry C June 29, 2017 Volume 121(Issue 25) pp:13848-13848
Publication Date(Web):June 7, 2017
DOI:10.1021/acs.jpcc.7b01730
We prepare a series of MAg24(SR)18 (M = Ag/Pd/Pt/Au) nanoclusters (NCs) with similar core–inner shell–outer shell structures and investigate their crystal and solution photoluminescence. The core silver atom replacement by the Pd/Pt/Au atom obviously tunes the geometric and electronic structures of Ag25(SR)18 NC. The crystal photoluminescence intensities sequence hints a core-atom-directing charge transfer from the ligands to the metal kernels. Both the calculated NPA charge and the measured Aginner shell–Sterminal bond length support the proposed mechanism. Further experiments show the solvent influence on the NCs photoluminescence supported by the blue-shift of emissions of MAg24(SR)18 NCs and the solvent-dependent photoluminescence intensity sequences. Especially, for PtAg24(SR)18, the quantum yield is almost 100-fold greater in CH3CN (18.6%) than in CH2Cl2 (0.2%). However, the emission wavelengths of the series of NCs are barely influenced by the solvent type. This work indicates the importance of the core atom and the solvent to the photoluminescence of core–inner shell–outer shell silver NCs, having important implications for the photoluminescence mechanisms and tuning of noble metal nanoparticles.
Co-reporter:Junxiang Zhang, Wei Hu, Jun Zhang, Shengjun Liu, Jing Tong, Xudong Hou, Wenlong Liu, Jinlong Yang, and Bo Liu
The Journal of Physical Chemistry C August 31, 2017 Volume 121(Issue 34) pp:18326-18326
Publication Date(Web):August 7, 2017
DOI:10.1021/acs.jpcc.7b04064
We report a stable and semiconductive heteropolyoxotitanate of [Ti12Cr6O18(OOCC6H5)30] (denoted as POTi12Cr6), which exhibits a pronounced photocatalytic hydrogen evolution rate, photothermal effect, and photocurrent under full solar spectrum, including near-infrared (NIR) irradiation, moreover, with high stability in both acid and base aqueous solution. Crystallinity and photocatalytic activity of POTi12Cr6 remain unchanged under cycling photocatalysis tests. This work demonstrates an approach to overcome the common restriction of low stability and limited solar absorption capability in polyoxotitanate- and TiO2-based materials. The result will open up heteropolyoxotitanate as a novel type of semiconductor material for the full solar spectrum, especially NIR energy utilization including photothermal transformation, photocurrent response, and photocatalytic H2 evolution.
Co-reporter:Haidi Wang, Bin LiJinlong Yang
The Journal of Physical Chemistry C 2017 Volume 121(Issue 6) pp:
Publication Date(Web):January 18, 2017
DOI:10.1021/acs.jpcc.6b12864
In recent years, carbon-based complex nanostructures have been explored due to many of their unique properties and related applications. Here we employ theoretical simulation based on density functional theory to investigate electronic, optical, and mechanical properties of a new type of the carbon-based complex nanostructure, i.e., experimentally fabricated one-dimensional complex material of hydrogenated diamond nanowires encapsulated in carbon nanotubes (CNW@CNT). The complex structure CNW@CNT is found to possess metallicity for the outer CNT and wide band gap nature for the inner CNW simultaneously. Under uniaxial strain a specific insulator-to-metal transition occurs for the inner CNW in the complex structure, with threshold value much smaller than that for the individual insulator. This effect is interpreted as that the strain induces relative shifting of bands of CNW and CNT and even charge transfer between them, making the valence band of CNW become not fully occupied. The inner CNW in the complex structure has optical absorption only in the ultraviolet waveband. The further examinations on the conductive bands reveal existences of nearly free-electron states which entirely dominate the conductive bands of the inner CNW and suggest that the electron–hole separation will happen in the CNW@CNT upon the ultraviolet illumination. The simulation results also reveal higher Young’s modulus of the CNW@CNT and the individual CNW even larger than those of CNT and graphene. We propose a simple parallel spring model to establish the relationship between the Young’s modulus of the complex structure and the one of its component which should be helpful to future predictions for other complex structures. The potential applications of this new type of carbon-based complex structure as a multifunctional integrated nanomaterial in future nanoelectronics, nano-optoelectronics, and nanoelectromechanics are discussed.
Co-reporter:Shengjun Liu;Wei Hu;Jayanta Kr. Nath;Jing Tong;Xudong Hou;Wenlong Liu;Bo Liu
Dalton Transactions 2017 vol. 46(Issue 3) pp:678-684
Publication Date(Web):2017/01/17
DOI:10.1039/C6DT04261A
We present a novel strategy to improve the stability and optical absorption of polyoxotitanates (POTs) via concurrently fully carboxylate-coordinating and hetero-metal-doping, and illustrate the strategy by an indium doped hetero-polyoxotitanate (h-POT) of a [Ti12In6O18(OOCC6H5)30] (POTi12In6) nanocluster, which possesses ultrahigh stability in both acid and base aqueous solutions. The nanocluster structurally features a core–shell double wheel structure and a polar cavity. Both experiments and theoretical calculations confirm the semiconductive properties of the nanocluster. Under visible irradiation the POTi12In6 nanocluster can produce pronounced photocurrent, and reactive oxygen species for pollutant degradation. Without using any cocatalyst, POTi12In6 exhibits important visible-light-driven photocatalytic activity for H2 evolution in an aqueous system. This work could render a polyoxotitanate as a new type of visible-photoactive photocatalyst.
Co-reporter:Wei Hu
Journal of Materials Chemistry C 2017 vol. 5(Issue 47) pp:12289-12297
Publication Date(Web):2017/12/07
DOI:10.1039/C7TC04697A
Two-dimensional (2D) materials, such as graphene, phosphorene, graphitic carbon nitride (g-C3N4), graphitic zinc oxide (g-ZnO) and transition metal dichalcogenides (TMDs, e.g., MoS2), have already attracted extensive attention due to their outstanding properties and wide range of applications in electronic and optoelectronic devices. In particular, 2D van der Waals heterojunctions combining the electronic structures of such 2D materials have also been predicted theoretically and synthesized experimentally to expect more new properties (e.g., bandgap opening in graphene, semiconductor band alignment, charge transfer and new optical absorption) and potential applications (e.g., solar cells, field-effect transistors (FFTs), PN junctions, PN diodes and photodetectors) far beyond corresponding 2D materials. This review focuses on recent theoretical works about 2D van der Waals heterojunctions especially for functional materials and devices such as photovoltaic solar cells (phosphorene/MoS2 and edge-modified phosphorene nanoflake based heterojunctions), Schottky and Ohmic contacts (graphene/MoS2 based heterojunctions), PN junctions (graphene/g-ZnO based heterojunctions) and supercapacitors (graphene/h-BN based heterojunctions). These theoretical simulations and designs of 2D van der Waals heterojunctions provide a promising direction for high-performance electronic and optoelectronic devices in experiments.
Co-reporter:Ang Bian;Yafei Dai
Nanoscale (2009-Present) 2017 vol. 9(Issue 44) pp:17505-17512
Publication Date(Web):2017/11/16
DOI:10.1039/C7NR05805E
Using a gas separation membrane as a simple gas separation device has an obvious advantage because of the low energy consumption and pollution-free manufacturing. The first-principles calculations used in this work show that germanene with its divacancy is an excellent material for use as a hydrogen (H2) and helium (He) separation membrane, and that it displays an even better competitive advantage than porous graphene and porous silicene. Porous germanene with its divacancy is chemically inert to gas molecules, because it lacks additional atoms to protect the edged dangling germanium atoms in defects, and thus shows great advantages for gas separation over previously prepared graphene. The energy barriers to H2 and He penetrating porous germanene are quite low, and the permeabilities to H2 and He are high. Furthermore, the selectivities of porous germanene for H2 and He relative to other gas molecules are high, up to 1031 and 1027, respectively, which are superior to those of porous graphene (1023) and porous silicene (1013); thus the separation efficiency of porous germanene is much higher than that of porous graphene and porous silicene. Therefore, germanene is a favorable candidate as a gas separation membrane material. At the same time, the successful synthesis of germanene in the laboratory means that it is possible to use it in real applications.
Co-reporter:Ang Bian;Yafei Dai
Nanoscale (2009-Present) 2017 vol. 9(Issue 44) pp:17505-17512
Publication Date(Web):2017/11/16
DOI:10.1039/C7NR05805E
Using a gas separation membrane as a simple gas separation device has an obvious advantage because of the low energy consumption and pollution-free manufacturing. The first-principles calculations used in this work show that germanene with its divacancy is an excellent material for use as a hydrogen (H2) and helium (He) separation membrane, and that it displays an even better competitive advantage than porous graphene and porous silicene. Porous germanene with its divacancy is chemically inert to gas molecules, because it lacks additional atoms to protect the edged dangling germanium atoms in defects, and thus shows great advantages for gas separation over previously prepared graphene. The energy barriers to H2 and He penetrating porous germanene are quite low, and the permeabilities to H2 and He are high. Furthermore, the selectivities of porous germanene for H2 and He relative to other gas molecules are high, up to 1031 and 1027, respectively, which are superior to those of porous graphene (1023) and porous silicene (1013); thus the separation efficiency of porous germanene is much higher than that of porous graphene and porous silicene. Therefore, germanene is a favorable candidate as a gas separation membrane material. At the same time, the successful synthesis of germanene in the laboratory means that it is possible to use it in real applications.
Co-reporter:Liren Liu;Jinyun Yuan;Longjiu Cheng
Nanoscale (2009-Present) 2017 vol. 9(Issue 2) pp:856-861
Publication Date(Web):2017/01/05
DOI:10.1039/C6NR07878H
Revealing the stability and structural patterns is important for precisely synthesizing or assembling ligand protected nanoclusters, and even their applications as functional nanomaterials. Investigations on structural evolutional patterns and structural stability are very challenging, because structures change with the nanocluster size and the structural stability depends on both the electron structures of cores and ligand type. Herein, we propose a hybrid superatom network (hSAN) model to understand the stability of some gold nanoclusters with different kinds of ligands. In this model, 4c-2e superatom Au4 can form conjugated superatom networks by vertex sharing, and ligands further connect the conjugated superatom networks together to form a bigger complex network, i.e. a hSAN. The stability of the clusters, including [Au24(CCPh)14(PPh3)4]2+, Au28(S-c-C6H11)20, Au36(SCH2Ph-tBu)8Cl20, Au40(O-MBT)24 and Au52(TBBT)32 can be explained uniformly by the hSAN model. Beyond that, a new heuristic structural pattern named the Au13 topological rule is proposed. In the light of this heuristic rule, every Au7 bi-tetrahedral kernel is included in an Au13 structure with quasi-Oh symmetry, i.e. as long as the Au7 bi-tetrahedral kernel is formed, it will be surrounded by six Au atoms to form an Au13 structure topologically. According to this understanding, a new nanocluster [Au44(CCH3)26(PCH3)4]2+ and a new nanowire with the structural evolutional formula [Au(20n+4)(CCH3)(12n+2)(PCH3)4]2+ (n = 1, 2, 3, 4, …) are predicted. Both the understanding of the stability and the structure rule are free from the type of ligand, and will be useful for the structural predictions and determinations of ligand protected gold nanoclusters.
Co-reporter:Huanjun Song;Cenfeng Fu;Na Li;Hao Zhu;Zhantao Peng;Wenhui Zhao;Jingxin Dai;Lingbo Xing;Zhichao Huang;Wei Chen;Yongfeng Wang;Kai Wu
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 33) pp:22401-22405
Publication Date(Web):2017/08/23
DOI:10.1039/C7CP03153J
An intermediate shuttling structure of a chloroaluminum phthalocyanine(ClAlPc)-based molecular switch is transiently created and analyzed by combined scanning tunneling microcopy/spectroscopy and density-functional theory calculations, which suggests that the Cl atom is squeezed into the space between the central Al atom and the inner N-containing ring in ClAlPc.
Co-reporter:Haidi Wang;Xingxing Li;Zhao Liu
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 3) pp:2402-2408
Publication Date(Web):2017/01/18
DOI:10.1039/C6CP07944J
Based on the crystal structure prediction, we propose a new allotrope of phosphorene, ψ-phosphorene (ψ-P), with a porous structure, which is both thermally and dynamically stable in comparison with the previously reported allotropes. Due to its unique atom configuration, ψ-P has highly orientation-dependent mechanical properties and excellent flexibility. Calculations using the HSE functional predict that ψ-P is semiconducting with an indirect band gap of 1.57 eV and possesses anisotropic transport properties. Particularly, the electron mobility along the x-direction is up to 1.3 × 104 cm2 V−1 s−1, which is comparable with that of black phosphorene. Considering its intrinsic porous structure, the performance of monolayer ψ-P as a gas purification membrane was investigated. The calculation demonstrates that ψ-P could be used for hydrogen purification from the mixture of CH4, CO2, N2, CO, and H2 with high selectivity. Furthermore, combining a suitable band gap with high carrier mobility, a MoSe2/ψ-P van der Waals heterojunction is predicted to be a good solar cell material, whose power conversion efficiency is estimated up to 20.26%. Finally, we demonstrated that the Au(110) surface could be a suitable substrate for the synthesis of ψ-P.
Co-reporter:Haidi Wang;Xingxing Li;Pai Li
Nanoscale (2009-Present) 2017 vol. 9(Issue 2) pp:850-855
Publication Date(Web):2017/01/05
DOI:10.1039/C6NR08550D
As a basic mechanical parameter, Poisson's ratio (ν) measures the mechanical responses of solids against external loads. In rare cases, materials have a negative Poisson's ratio (NPR), and present an interesting auxetic effect. That is, when a material is stretched in one direction, it will expand in the perpendicular direction. To design modern nanoscale electromechanical devices with special functions, two dimensional (2D) auxetic materials are highly desirable. In this work, based on first principles calculations, we rediscover the previously proposed δ-phosphorene (δ-P) nanosheets [Jie Guan, et al., Phys. Rev. Lett., 2014, 113, 046804] which are good auxetic materials with a high NPR. The results show that the Young's modulus and Poisson's ratio of δ-P are all anisotropic. The NPR value along the grooved direction is up to −0.267, which is much higher than the recently reported 2D auxetic materials. The auxetic effect of δ-P originating from its puckered structure is robust and insensitive to the number of layers due to weak interlayer interactions. Moreover, δ-P possesses good flexibility because of its relatively small Young's modulus and high critical crack strain. If δ-P can be synthesized, these extraordinary properties would endow it with great potential in designing low dimensional electromechanical devices.
Co-reporter:Cen-Feng Fu;Xingxing Li;Qiquan Luo
Journal of Materials Chemistry A 2017 vol. 5(Issue 47) pp:24972-24980
Publication Date(Web):2017/12/05
DOI:10.1039/C7TA08812D
Currently, various two-dimensional (2D) monolayer materials have been predicted to be photocatalysts for water splitting. In the present work, the structural and electronic properties of 2D multilayer Zr2CO2, Hf2CO2 and Sc2CO2 are explored by density functional theory calculations. We found that the band gap of multilayer Zr2CO2 and Hf2CO2 becomes smaller with increasing layer number and the band edge positions demonstrate to be not suitable for driving the oxygen evolution reaction. However, applying an appropriate strain to multilayer Zr2CO2 and Hf2CO2 could make them into available photocatalysts for water splitting. For Sc2CO2, due to the built-in perpendicular electric field in monolayer Sc2CO2, there are more feasible stacking configurations of multilayer Sc2CO2, yet some of the multilayer Sc2CO2 are also proved to be potential photocatalysts for water splitting.
Co-reporter:Jinyun Yuan, Guowei Li, Jinlong Yang
Computational and Theoretical Chemistry 2017 Volume 1099(Volume 1099) pp:
Publication Date(Web):1 January 2017
DOI:10.1016/j.comptc.2016.11.013
•The most stable structures of AlConC2H0/− (n = 1–5) clusters were identified.•C2H interacts with AlCon0/− via its π orbital with 3d orbitals of Co atoms.•C2H is preferentially to be adsorbed on Co atoms instead of Al atom.•The CC triple bond of C2H is activated to double bond.The geometric and electronic structures of AlConC2H0/− (n = 1–5) clusters were investigated using density functional theory calculations. The most stable structures of AlConC2H0/− (n = 1–5) clusters were identified, in which ethynyl (C2H) interacts with AlCon0/− (n = 1–5) clusters via π orbital of C2H with 3d orbitals of Co clusters. The C2H binds preferentially to Co atoms. Doping with single atom Al only leads into an additional adsorption site, and has nearly no effect on the binding mode of C2H to Con clusters. The adsorption energies, adiabatic and vertical detachment energies of AlConC2H− (n = 1–5) have been predicted.Download high-res image (103KB)Download full-size image
Co-reporter:Wei Hu, Lin Lin, Chao Yang, Jun Dai, and Jinlong Yang
Nano Letters 2016 Volume 16(Issue 3) pp:1675-1682
Publication Date(Web):February 5, 2016
DOI:10.1021/acs.nanolett.5b04593
We propose to use edge-modified phosphorene nanoflakes (PNFs) as donor and acceptor materials for heterojunction solar cells. By using density functional theory based calculations, we show that heterojunctions consisting of hydrogen- and fluorine-passivated PNFs have a number of desired optoelectronic properties that are suitable for use in a solar cell. We explain why these properties hold for these types of heterojunctions. Our calculations also predict that the maximum energy conversion efficiency of these type of heterojunctions, which can be easily fabricated, can be as high as 20%, making them extremely competitive with other types of two-dimensional heterojunctions.
Co-reporter:Nan Yan, Lingwen Liao, Jinyun Yuan, Yue-jian Lin, Lin-hong Weng, Jinlong Yang, and Zhikun Wu
Chemistry of Materials 2016 Volume 28(Issue 22) pp:8240
Publication Date(Web):October 23, 2016
DOI:10.1021/acs.chemmater.6b03132
Doped nanoparticles (especially bimetal doped nanoparticles) have attracted extensive interest not only for fundamental scientific research but also for application purposes. However, their indefinite composition (structure) and broad distribution hinder an insightful understanding of the interaction between these invasive metals in bimetal doped nanoparticles. Fortunately, atom-precise bimetal doped ultrasmall nanoparticles (nanoclusters) provide opportunities to obtain such insights. However, atom-precise trimetal nanoclusters and their structures have rarely been reported. Here, we successfully dope thiolated Au25 nanoclusters with Hg and Ag successively by using a biantigalvanic reduction method. We then fully characterize the as-obtained trimetal nanoclusters using multiple techniques (including single-crystal X-ray crystallography), and we demonstrate that the mercury and silver dopings exhibit not only a synergistic but also a counteractive influence on some of the physicochemical properties of Au25.
Co-reporter:Lin Hu, Xiaojun Wu and Jinlong Yang
Nanoscale 2016 vol. 8(Issue 26) pp:12939-12945
Publication Date(Web):27 May 2016
DOI:10.1039/C6NR02417C
To realize antiferromagnetic spintronics in the nanoscale, it is highly desirable to identify new nanometer-scale antiferromagnetic metals with both high Néel temperature and large spin–orbit coupling. In this work, on the basis of first-principles calculation and particle swarm optimization (PSO) global structure search, we demonstrate that a two-dimensional Mn2C monolayer is an antiferromagnetic metal with a Mn magnetic moment of ∼3μB. Mn2C monolayer has an anti-site structure of MoS2 sheet with carbon atoms hexagonally coordinated by neighboring Mn atoms. Remarkably, the in-plane carrier mobility of 2D Mn2C is highly anisotropic, amounting to about 47000 cm2 V−1 s−1 in the a′ direction, which is much higher than that of MoS2 monolayer. The Néel temperature of Mn2C monolayer is high up to 720 K. Due to strong spin–orbit coupling in plane, the magnetic anisotropy energy of Mn2C monolayer is larger than those of pure metals, such as Fe, Co, and Ni. These advantages render 2D Mn2C sheet with great potential applications in nanometer-scale antiferromagnetic spintronics.
Co-reporter:Wei Hu, Tian Wang, Ruiqi Zhang and Jinlong Yang
Journal of Materials Chemistry A 2016 vol. 4(Issue 9) pp:1776-1781
Publication Date(Web):02 Feb 2016
DOI:10.1039/C6TC00207B
Combining the electronic structures of graphene and molybdenum disulphide (MoS2) monolayers in two-dimensional (2D) ultrathin graphene and MoS2 heterostructures has been realized experimentally for novel nanoelectronic devices. Here, first-principles calculations are performed to investigate the effects of interlayer coupling and the electric field on the electronic structures of graphene and MoS2 heterobilayers (G/MoS2 HBLs). We find that an n-type Schottky contact is formed at the G/MoS2 interface with a small Schottky barrier of 0.23 eV, because the work function of graphene is close to the electron affinity of MoS2. Furthermore, increasing the interfacial distances between graphene and MoS2 can reduce the n-type Schottky barriers at the G/MoS2 interface. But applying the electric field perpendicular to the G/MoS2 HBL can not only control the Schottky barriers but also the Schottky contacts (n-type and p-type) and Ohmic contacts (n-type) at the G/MoS2 interface. Tunable p-type doping in graphene is easily achieved at negative electric fields because electrons can easily transfer from the Dirac point of graphene to the conduction band of MoS2.
Co-reporter:Liren Liu, Pai Li, Lan-Feng Yuan, Longjiu Cheng and Jinlong Yang
Nanoscale 2016 vol. 8(Issue 25) pp:12787-12792
Publication Date(Web):31 May 2016
DOI:10.1039/C6NR01998F
As an extension of the superatom concept, a new concept “isosuperatom” is proposed, reflecting the physical phenomenon that a superatom cluster can take multiple geometrical structures with their electronic structures topologically invariant. The icosahedral and cuboctahedral Au135+ units in the Au25(SCH2CH2Ph)18−, Au23(SC6H11)16− and Au24(SAdm)16 nanoclusters are found to be examples of this concept. Furthermore, two isosuperatoms can combine to form a supermolecule. For example, the structure of the {Ag32(DPPE)5(SC6H4CF3)24}2− nanocluster can be understood well in terms of a Ag2212+ supermolecule formed by two Ag138+ isosuperatoms. On the next level of complexity, various combinations of isosuperatoms can lead to supermolecules with different geometrical structures but similar electronic structures, i.e., “isosupermolecules”. We take two synthesized nanoclusters Au20(PPhpy2)10Cl42+ and Au30S(StBu)18 to illustrate two Au206+ isosupermolecules. The proposed concepts of isosuperatom and isosupermolecule significantly enrich the superatom concept, give a new framework for understanding a wide range of nanoclusters, and open a new door for designing assembled materials.
Co-reporter:Ruiqi Zhang, Xiaojun Wu and Jinlong Yang
Nanoscale 2016 vol. 8(Issue 7) pp:4001-4006
Publication Date(Web):08 Jan 2016
DOI:10.1039/C5NR06856H
The diffusion of Li in electrode materials is a key factor for the charging/discharging rate capacity of a Li-ion battery (LIB). Recently, two-dimensional phosphorene has been proposed as a very promising electrode material due to its ultrafast and directional lithium diffusion, as well as large energy capacity. Herein, on the basis of density functional theory, we report that intrinsic point defects, including vacancy and stone–wales defects, will block the directional ultrafast diffusion of lithium in phosphorene. On the defect-free phosphorene, diffusion of Li along the zig-zag lattice direction is 1.6 billion times faster than along the armchair lattice direction, and 260 times faster than that in graphite. After introducing intrinsic vacancy and stone–wales defect, the diffusion energy barrier of Li along the zig-zag lattice direction increases sharply to the range of 0.17–0.49 eV, which blocks the ultrafast migration of lithium along the zig-zag lattice direction. Moreover, the open circuit voltage increases with the emergence of defects, which is not suitable for anode materials. In addition, the formation energies of the defects in phosphorene are considerably lower than those in graphene and silicene sheet; therefore, it is highly important to generate defect-free phosphorene for LIB applications.
Co-reporter:Xinxing Wu, Ruiqi Zhang and Jinlong Yang
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 28) pp:19412-19419
Publication Date(Web):23 Jun 2016
DOI:10.1039/C6CP03183H
In this article, we studied the thermodynamic and electronic properties of Mg and MgH2 nanowires with different diameters, and elucidated why MgH2 nanowires are good hydrogen storage materials through first-principles calculations. Previous experiments have shown that the orientation relationship between Mg and MgH2 nanowires is the Mg[0001] direction parallel to the MgH2[110] direction. In our calculations, Mg nanowires oriented along the [0001] direction and MgH2 nanowires oriented along the [110] direction were built from bulk Mg and MgH2 crystals, respectively. We found that as the diameters of Mg and MgH2 nanowires decrease, Mg and MgH2 nanowires become more unstable, and the hydrogen desorption energies and temperatures of MgH2 nanowires decrease. That is, the thinner the MgH2 nanowires get, the more dramatically hydrogen desorption temperatures (Td) will decrease. Meanwhile, we also found that when the diameters of MgH2 nanowires are larger than 1.94 nm, the Td almost maintain the same value at about 440 K, only about 40 K lower than that of bulk MgH2 crystal; if the diameters are less than 1.94 nm, the Td reduce very quickly. In particular, compared with bulk MgH2 crystal, the Td of the thinnest MgH2 nanowire with a diameter of 0.63 nm can be reduced by 164 K. In addition, the electronic structure calculations showed that Mg nanowires are metals, while MgH2 nanowires are semiconductors. In particular, our results showed that the electronic structures of MgH2 nanowires are influenced by the surface effect and quantum size effect. That is to say, the band gaps of MgH2 nanowires are controlled by surface electronic states and the size of MgH2 nanowires.
Co-reporter:Wei Hu, Jinlong Yang
Computational Materials Science 2016 Volume 112(Part B) pp:518-526
Publication Date(Web):1 February 2016
DOI:10.1016/j.commatsci.2015.06.033
•2D materials have outstanding properties and wide applications.•2D van der Waals heterojunctions show new properties beyond single components.Research on graphene and other two-dimensional (2D) materials, such as silicene, germanene, phosphorene, hexagonal boron nitride (h-BN), graphitic carbon nitride (g-C3N4), graphitic zinc oxide (g-ZnO) and molybdenum disulfide (MoS2), has recently received considerable interest owing to their outstanding properties and wide applications. Looking beyond this field, combining the electronic structures of 2D materials in ultrathin van der Waals heterojunctions has also emerged to widely study theoretically and experimentally to explore some new properties and potential applications beyond their single components. Here, this article reviews our recent theoretical studies on the structural, electronic, electrical and optical properties of 2D van der Waals heterojunctions using density functional theory calculations, including the Graphene/Silicene, Graphene/Phosphorene, Graphene/g-ZnO, Graphene/MoS2 and g-C3N4/MoS2 heterojunctions. Our theoretical simulations, designs and calculations show that novel 2D van der Waals heterojunctions provide a promising future for electronic, electrochemical, photovoltaic, photoresponsive and memory devices in the experiments.
Co-reporter:Huimin Wang;Dr. Xingxing Li; Jinlong Yang
ChemPhysChem 2016 Volume 17( Issue 13) pp:2100-2104
Publication Date(Web):
DOI:10.1002/cphc.201600209
Abstract
Water-splitting photocatalysts with good energy efficiency are highly desirable, among which metal-free graphitic carbon nitride (g-C3N4) is considered to be very promising and has been intensively studied in recent years. However, its practical application is hindered by the relatively low efficiencies of visible-light absorption and electron–hole separation. Herein, based on first-principles calculations, it is predicted that, by forming nanocomposites with another carbon nitride (C2N), the energy efficiency of g-C3N4 can be significantly improved. On one hand, C2N has a wide, strong optical absorption in the visible-light region, which acts as a photosensitizer and enhances the photoabsorption efficiency of the composite photocatalyst. On the other hand, C2N forms a type II heterojunction with g-C3N4, which leads to efficient separation of photogenerated electron–hole pairs through the chemical potential difference between the two components. These results provide a potential route to achieve highly efficient metal-free photocatalysts for water splitting.
Co-reporter:Dr. Jian-Wei Liu;Jie Xu;Dr. Wei Hu;Dr. Jin-Long Yang;Dr. Shu-Hong Yu
ChemNanoMat 2016 Volume 2( Issue 3) pp:167-170
Publication Date(Web):
DOI:10.1002/cnma.201500206
Abstract
In the past two decades, tremendous efforts have been made towards the development of synthetic strategies for nanostructured materials with well-controlled size, shape, composition, and spatial arrangement. Herein, we report a systematic study on the synthesis of tellurium nanostructures, which can evolve from nanoparticles to nanorods, nanowires, and nanotubes by a simple solution-based process. The size- and diameter-dependent optical properties of Te nanowires have been explained based on the modeling calculations using the joint density of states (JDOS).
Co-reporter:Dr. Jian-Wei Liu;Jie Xu;Dr. Wei Hu;Dr. Jin-Long Yang;Dr. Shu-Hong Yu
ChemNanoMat 2016 Volume 2( Issue 3) pp:
Publication Date(Web):
DOI:10.1002/cnma.201600051
Co-reporter:Jinyun Yuan, Peng Wang, Gao-Lei Hou, Gang Feng, Wen-Jing Zhang, Xi-Ling Xu, Hong-Guang Xu, Jinlong Yang, and Wei-Jun Zheng
The Journal of Physical Chemistry A 2016 Volume 120(Issue 9) pp:1520-1528
Publication Date(Web):February 12, 2016
DOI:10.1021/acs.jpca.6b00241
The structural evolution and electronic properties of VnC2–/0 and VnC4–/0 (n = 1–6) clusters were investigated using photoelectron spectroscopy and density functional theory calculations. The adiabatic and vertical detachment energies of VnC2– and VnC4– (n = 1–6) clusters were obtained from their photoelectron spectra. The most stable structures were identified by comparing the results of our calculations with the experimental data. We found that the carbon atoms of VnC2–/0 and VnC4–/0 (n = 1–6) clusters were separated gradually with increasing number of vanadium atoms. For VnC2–/0 (n = 3–6) and VnC4–/0 (n = 4–6) clusters, the carbon atoms are separated by the vanadium atoms. The geometry of V4C4 is a cubic structure and the geometries of V5C4 and V6C4 are formed by one and two vanadium atoms capping the cubic V4C4 structure, respectively.
Co-reporter:Lingwen Liao; Shiming Zhou; Yafei Dai; Liren Liu; Chuanhao Yao; Cenfeng Fu; Jinlong Yang;Zhikun Wu
Journal of the American Chemical Society 2015 Volume 137(Issue 30) pp:9511-9514
Publication Date(Web):July 21, 2015
DOI:10.1021/jacs.5b03483
Controlling the bimetal nanoparticle with atomic monodispersity is still challenging. Herein, a monodisperse bimetal nanoparticle is synthesized in 25% yield (on gold atom basis) by an unusual replacement method. The formula of the nanoparticle is determined to be Au24Hg1(PET)18 (PET: phenylethanethiolate) by high-resolution ESI-MS spectrometry in conjunction with multiple analyses including X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). X-ray single-crystal diffraction reveals that the structure of Au24Hg1(PET)18 remains the structural framework of Au25(PET)18 with one of the outer-shell gold atoms replaced by one Hg atom, which is further supported by theoretical calculations and experimental results as well. Importantly, differential pulse voltammetry (DPV) is first employed to estimate the highest occupied molecular orbit (HOMO) and the lowest unoccupied molecular orbit (LUMO) energies of Au24Hg1(PET)18 based on previous calculations.
Co-reporter:Chuanhao Yao; Yue-jian Lin; Jinyun Yuan; Lingwen Liao; Min Zhu; Lin-hong Weng; Jinlong Yang;Zhikun Wu
Journal of the American Chemical Society 2015 Volume 137(Issue 49) pp:15350-15353
Publication Date(Web):November 23, 2015
DOI:10.1021/jacs.5b09627
Controlling the dopant type, number, and position in doped metal nanoclusters (nanoparticles) is crucial but challenging. In the work described herein, we successfully achieved the mono-cadmium doping of Au25 nanoclusters, and revealed using X-ray crystallography in combination with theoretical calculations that one of the inner-shell gold atoms of Au25 was replaced by a Cd atom. The doping mode is distinctly different from that of mono-mercury doping, where one of the outer-shell Au atoms was replaced by a Hg atom. Au24Cd is readily transformed to Au24Hg, while the reverse (transformation from Au24Hg to Au24Cd) is forbidden under the investigated conditions.
Co-reporter:Ruiqi Zhang, Bin Li and Jinlong Yang
Nanoscale 2015 vol. 7(Issue 33) pp:14062-14070
Publication Date(Web):22 Jul 2015
DOI:10.1039/C5NR03895B
Recently, a new type of two-dimensional layered material, i.e. a nitrogenated holey two-dimensional structure C2N-h2D, has been synthesized using a simple wet-chemical reaction and used to fabricate a field-effect transistor device (Nat. Commun., 2015, 6, 6486). Here we have performed a first-principles study of the electronic properties of few-layer C2N-h2D with different stacking orders and layer numbers. Because of the interlayer coupling mainly in terms of the orbital interaction, band structure of this system, especially splitting of the bands and band gap, depends on its stacking order between the layers, and the band gap exhibits monotonically decreasing behavior as the layer number increases. All the few-layer C2N-h2D materials have characteristics of direct band gap, irrespective of the stacking order and layer number examined in our calculations. And bulk C2N-h2D has an indirect or direct band gap, depending on the stacking order. Besides, when we apply an out-of-plane electric field on few-layer C2N-h2D, its band gap will decrease as the electric field increases due to a giant Stark effect except for the monolayer case, and even a semiconductor-to-metal transition may occur for few-layer C2N-h2D with more layers under an appropriate electric field. Owing to their tunable band gaps in a wide range, the layered C2N-h2D materials will have tremendous opportunities to be applied in nanoscale electronic and optoelectronic devices.
Co-reporter:Lin Hu, Jin Zhao and Jinlong Yang
Nanoscale 2015 vol. 7(Issue 19) pp:8962-8967
Publication Date(Web):10 Apr 2015
DOI:10.1039/C5NR00023H
We propose that a nano-scale displacement sensor with high resolution in weak-force systems can be realized based on vertically stacked two-dimensional (2D) atomic corrugated layer materials bound through van der Waals (vdW) interactions. Using first-principles calculations, we found that the electronic structures of bi-layer blue phosphorus (BLBP) vary appreciably with lateral and vertical interlayer displacements. The variation of the electronic structure is attributed to the change of the interlayer distance dz for both the lateral and vertical displacement. For lateral displacement, the change of dz is induced by atomic layer corrugation. Despite the different stacking configurations of BLBP, we find that the change of the indirect band gap is proportional to dz−2. Furthermore, this dz−2 dependence is found to be applicable to other graphene-like corrugated bi-layer materials such as MoS2. BLBP represents a large family of bi-layer 2D atomic corrugated materials for which the electronic structure is sensitive to the interlayer vertical and lateral displacement, and thus could be used for a nano-scale displacement sensor. This can be done by monitoring the tunable electronic structure using absorption spectroscopy. Because this type of sensor is established on atomic layers coupled through vdW interactions, it provides unique applications in the measurements of nano-scale displacement induced by tiny external forces.
Co-reporter:Wei Hu, Tian Wang and Jinlong Yang
Journal of Materials Chemistry A 2015 vol. 3(Issue 18) pp:4756-4761
Publication Date(Web):07 Apr 2015
DOI:10.1039/C5TC00759C
Combining the electronic structures of two-dimensional monolayers in ultrathin hybrid nanocomposites is expected to display new properties beyond their single components. Here, first-principles calculations are performed to study the structural and electronic properties of hybrid graphene and phosphorene nanocomposites. Our calculations show that weak van der Waals interactions dominate between graphene and phosphorene with their intrinsic electronic properties preserved. Furthermore, we found that as the interfacial distance decreases, the Dirac point of graphene moves from the conduction band to the valence band of phosphorene in hybrid graphene and phosphorene nanocomposites, inducing a transition from an n-type Schottky contact to a p-type Schottky contact at the graphene/phosphorene interface.
Co-reporter:Jiahui Zhang, Xingxing Li and Jinlong Yang
Journal of Materials Chemistry A 2015 vol. 3(Issue 11) pp:2563-2567
Publication Date(Web):27 Jan 2015
DOI:10.1039/C4TC02587C
The direct control of carrier spin by an electric field at room temperature is one of the most important challenges in the field of spintronics. For this purpose, we here propose a quaternary Heusler alloy FeVTiSi. Based on first principles calculations, the FeVTiSi alloy is found to be an intrinsic bipolar magnetic semiconductor in which the valence band and conduction band approach the Fermi level through opposite spin channels. Thus the FeVTiSi alloy can conduct completely spin-polarized currents with a tunable spin-polarization direction simply by applying a gate voltage. Furthermore, by Monte Carlo simulations based on the classical Heisenberg Hamiltonian, the Curie temperature of the FeVTiSi alloy is predicted to be well above the room temperature. The bipolar magnetic semiconducting character and the room temperature magnetic ordering endow the FeVTiSi alloy with great potential for developing electrically controllable spintronic devices working at room temperature.
Co-reporter:Zhongjun Li, Xingxing Li, and Jinlong Yang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 23) pp:12981
Publication Date(Web):May 27, 2015
DOI:10.1021/acsami.5b02782
Understanding the nature of the contacts in devices based on MoS2 with metal electrodes is vital to enhancing carrier injection efficiency. In this work, geometric and electronic structures of Sc and Ti contacts with MoS2 have been comparatively studied by first-principles calculations. The analyses of geometric parameters, charge density distributions, and density of states for the Sc and Ti top contacts with monolayer MoS2 (mMoS2) indicate that the interface bonding results in the localization of 4d states of Mo atoms and the consequent metallization of mMoS2. Therefore, the Sc and Ti top contacts with mMoS2 are Ohmic, and electron injections via these contacts are efficient. Because of the formations of the metalized Sc–mMoS2 and Ti–mMoS2 complexes, in the Sc and Ti top contacts with multilayer MoS2, Schottky interfaces may be formed in two contact regions. One is in the edge contacts of the Sc–mMoS2 and Ti–mMoS2 complexes with mMoS2 in the channel region in which Schottky barrier heights of 0.11 and 0.39 eV are extracted, respectively. The other is in the top contacts of these two complexes with mMoS2 under the contacts in which Schottky barrier heights of 0.15 and 0.34 eV are obtained, respectively. Moreover, as the layer number of MoS2 increases in the top contacts, the Schottky barrier heights show decreasing trends. These trends can be understood on the basis of the changes of electron affinity of multilayer MoS2. According to the present results, the device based on MoS2 with Sc electrodes should have better electron injection efficiency and stronger back-gated manipulation of current than the one with Ti electrodes. Furthermore, the electron injection efficiency can be enhanced by using multilayer MoS2. These predictions are generally consistent with recent experimental observations and provide a delicate understanding of the contacts in these devices.Keywords: metallization; MoS2; Ohmic contact; Sc; Schottky contact;
Co-reporter:Yingdi Jin, Xingxing Li and Jinlong Yang
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 28) pp:18665-18669
Publication Date(Web):16 Jun 2015
DOI:10.1039/C5CP02813B
A serial of two-dimensional titanium and zirconium trichalcogenides nanosheets MX3 (M = Ti, Zr; X = S, Se, Te) were investigated based on first-principles calculations. The evaluated low cleavage energy indicates that stable two-dimensional monolayers can be exfoliated from their bulk crystals in the experiment. Electronic studies reveal the very rich electronic properties in these monolayers, including metallic TiTe3 and ZrTe3, direct band gap semiconductor, TiS3, and indirect band gap semiconductors, TiSe3, ZrS3 and ZrSe3. The band gaps of all the semiconductors are between 0.57 and 1.90 eV, which implies their potential applications in nano-electronics. In addition, the calculated effective masses demonstrate the highly anisotropic conduction properties for all the semiconductors. Optically, TiS3 and TiSe3 monolayers exhibit good light absorption in the visible and near-infrared region, respectively, indicating their potential applications in optical devices. In particular, the highly anisotropic optical absorption of the TiS3 monolayer suggests it could be used in designing nano-optical waveguide polarizers.
Co-reporter:Lijuan Yan
The Journal of Physical Chemistry C 2015 Volume 119(Issue 40) pp:23274-23278
Publication Date(Web):September 24, 2015
DOI:10.1021/acs.jpcc.5b07917
A unique tetrahedral structure of Au17+ (Td) is found by using first-principles global optimization, which lies 0.40 eV lower in energy than the previously known structure and has a fairly large HOMO–LUMO gap (1.46 eV) at the TPSS/def2-TZVP level. For neutral Au17, this tetrahedral structure is distorted to D2d symmetry but is also 0.18 eV lower in energy than the previous flat cage structure. Au17+ (Td) has a FCC Au13 octahedral core, and the other four gold atoms are above its four triangular faces. Magic electronic stability of the cluster is explained by the super valence bond model, of which it can be seen as a superatomic molecule in the electronic structure. Moreover, the cluster can also be viewed as a network of eight 2e-superatoms. This Au17+ cluster mimics the behavior of the Au20 pyramid, known as a unique one among the family of gold clusters since its discovery in 2003, in electronic structures.
Co-reporter:Dr. Yafei Dai; Dr. Zhenyu Li; Dr. Jinlong Yang
ChemPhysChem 2015 Volume 16( Issue 13) pp:2783-2788
Publication Date(Web):
DOI:10.1002/cphc.201500400
Abstract
The atomically precise edge chlorination of nanographenes has recently been reported as a crucial technology of functionalization through which the planar structure and optical properties of nanographenes can be significantly changed. To check the effects of molecular size, geometrical symmetry and edge functionalization of nanographenes on their optical properties, a series of nanographenes is studied in the framework of density functional theory with the B3LYP functional. Our results indicate that edge functionalization remarkably changes the nonlinear optical properties and increases the anisotropy of nanographenes compared to the effects of the molecular size and system geometric symmetry. Furthermore, the nonlinear optical properties of nanographenes can be tuned by precise edge functionalization, which opens a new avenue for using nanographenes as nonlinear optical materials.
Co-reporter:Wenhua Zhang;Weixin Huang
Science China Chemistry 2015 Volume 58( Issue 4) pp:565-573
Publication Date(Web):2015 April
DOI:10.1007/s11426-015-5337-6
With potential applications in various fields, gold related catalysts have received intensive attentions. In the past decade, mechanisms of gold catalysis for low-temperature CO oxidation, NOx oxidation/reduction, selective oxidation of alcohols have been investigated both experimentally and theoretically based on model catalysts using free or supported gold nanoparticles and single crystal gold surfaces. In this short review, we summarize recent theoretical studies on molecular oxygen activation process, water or hydroxyl involved oxidation reaction, and also the effect of local structure on the reactivity and selectivity.
Co-reporter:Wei Hu
The Journal of Physical Chemistry C 2015 Volume 119(Issue 35) pp:20474-20480
Publication Date(Web):August 18, 2015
DOI:10.1021/acs.jpcc.5b06077
Defects are inevitably present in materials and always can affect their properties. Here we perform first-principles calculations to systematically investigate the stability and electronic structures of 10 kinds of point defects in 2D semiconducting phosphorene, including the Stone–Wales (SW-1 and SW-2) defect, and single (SV-(5|9) and SV-(55|66)) and double (DV-(5|8|5)-1, DV-(5|8|5)-2, DV-(555|777)-1, DV-(555|777)-2, DV-(555|777)-3, and DV-(4|10|4)) vacancy defects. We find that these defects are all created quite easily in phosphorene with higher areal density compared with graphene and silicene. Most of them are easy to distinguish from each other and correlate with their defective atomic structures with simulated scanning tunneling microscopy images at positive bias. The SW, DV-(5|8|5)-1, DV-(555|777), and DV-(4|10|4) defects have little effect on phosphorene’s electronic properties, and defective phosphorene monolayers still show semiconducting with similar band gap values to perfect phosphorene. The SV-(5|9) and DV-(5|8|5)-2 defects can introduce unoccupied localized states into phosphorene’s fundamental band gap. Specifically, the SV-(5|9) and SV-(55|66) defects can induce hole doping in phosphorene, and the SV-(5|9) defect can result in local magnetic moments in phosphorene different from all other defects.
Co-reporter:Ruiqi Zhang
The Journal of Physical Chemistry C 2015 Volume 119(Issue 5) pp:2871-2878
Publication Date(Web):January 14, 2015
DOI:10.1021/jp5116564
Density functional theory calculations have been carried out to investigate single-layer phosphorene functionalized with two kinds of organic molecules, i.e., an electrophilic molecule tetracyano-p-quinodimethane (TCNQ) as electron acceptor and a nucleophilic molecule tetrathiafulvalene (TTF) as electron donor. The TCNQ molecule introduces shallow acceptor states in the gap of phosphorene close to the valence band edge, which makes the doped system become a p-type semiconductor. However, when the TTF molecule is adsorbed on the phosphorene, the occupied molecular states introduced into the gap are of deep donor states so that effective n-doping for transport cannot be realized. This disadvantageous situation can be amended by applying an external out-of-plane electric field with direction from phosphorene to TTF, or an in-plane tensile strain, or their combination, under which the conduction band edge of the phosphorene moves closer to the TTF-derived donor states, and then the TTF-adsorbed phosphorene system becomes an n-type semiconductor. It is also noted that the out-of-plane electric field and in-plane strain can modulate the band gap of the TTF-adsorbed phosphorene markedly. The effective bipolar doping of single-layer phosphorene via molecular adsorption, especially n-doping against its native p-doping propensity, and the good response of band gap in the infrared waveband of the TTF-adsorbed phosphorene to the out-of-plane electric field and in-plane strain would broaden the way to the application of this new type of two-dimensional material in nanoelectronic and optoelectronic devices.
Co-reporter:Songtao Zhao ; Zhenyu Li
Journal of the American Chemical Society 2014 Volume 136(Issue 38) pp:13313-13318
Publication Date(Web):September 4, 2014
DOI:10.1021/ja5065125
Nearly free electron (NFE) states are widely existed on atomically smooth surfaces in two-dimensional materials. Since they are mainly distributed in free space, these states can in principle provide ideal electron transport channels without nuclear scattering. Unfortunately, NFE states are typically unoccupied, and electron doping is required to shift them toward the Fermi level and, thus, to be involved in electron transport. Instead of occupying these NFE states, it is more desirable to have intrinsic nucleus-free two-dimensional electron gas in free space (2DEG-FS) at the Fermi level without relying on doping. Inspired by a recently identified electride material, we suggest that Ca2N monolayer should possess such a 2DEG-FS state, which is then confirmed by our first-principles calculations. Phonon dispersion in Ca2N monolayer shows no imagery frequency indicating that the monolayer structure is stable. A mechanical analysis demonstrates that Ca2N bulk exfoliation is feasible to produce a freestanding monolayer. However, in real applications, the strong chemical activity of 2DEG-FS may become a practical issue. It is found that some ambient molecules can dissociatively adsorb on the Ca2N monolayer, accompanying with a significant charge transfer from the 2DEG-FS state to adsorbates. To protect the 2DEG-FS state from molecule adsorption, we predict that graphane can be used as an effective encapsulating material. A well-encapsulated intrinsic 2DEG-FS state is expected to play an important role in low-dimensional electronics by realizing nuclear scattering free transport.
Co-reporter:Xingxing Li ; Xiaojun Wu
Journal of the American Chemical Society 2014 Volume 136(Issue 31) pp:11065-11069
Publication Date(Web):July 18, 2014
DOI:10.1021/ja505097m
Searching two-dimensional (2D) half-metallic crystals that are feasible in experiment is essential to develop next-generation nanospintronic devices. Here, a 2D exfoliated MnPSe3 nanosheet with novel magnetism is first proposed based on first-principles calculations. In particular, the evaluated low cleavage energy and high in-plane stiffness indicate that the free-standing MnPSe3 nanosheet can be exfoliated from its bulk structure in experiment. The MnPSe3 nanosheet is an antiferromagnetic semiconductor at its ground state, whereas both electron and hole doping induce its transition from antiferromagnetic semiconductor to ferromagnetic half-metal. Moreover, the spin-polarization directions of 2D half-metallic MnPSe3 are opposite for electron and hole doping, which can be controlled by applying an external voltage gate. The Monte Carlo simulation based on the Ising model suggests the Curie temperature of the doped 2D MnPSe3 crystal is up to 206 K. These advantages render the 2D MnPSe3 crystal with great potentials for application in electric-field controlled spintronic devices.
Co-reporter:Xingxing Li ; Xiaojun Wu
Journal of the American Chemical Society 2014 Volume 136(Issue 15) pp:5664-5669
Publication Date(Web):March 27, 2014
DOI:10.1021/ja412317s
Exploring half-metallic materials with high Curie temperature, wide half-metallic gap, and large magnetic anisotropy energy is one of the effective solutions to develop high-performance spintronic devices. Using first-principles calculations, we design a practicable half-metal based on a layered La(Mn0.5Zn0.5)AsO alloy via element substitutions. At its ground state, the pristine La(Mn0.5Zn0.5)AsO alloy is an antiferromagnetic semiconductor. Either hole doping via (Ca2+/Sr2+,La3+) substitutions or electron doping via (H–/F–,O2–) substitutions in the [LaO]+ layer induce half-metallicity in the La(Mn0.5Zn0.5)AsO alloy. The half-metallic gap is as large as 0.74 eV. Monte Carlo simulations based on the Ising model predict a Curie temperature of 475 K for 25% Ca doping and 600 K for 50% H doping, respectively. Moreover, the quasi two-dimensional structure endows the doped La(Mn,Zn)AsO alloy a sizable magnetic anisotropy energy with the magnitude of at least one order larger than those of Fe, Co, and Ni bulks.
Co-reporter:Xingxing Li and Jinlong Yang
Journal of Materials Chemistry A 2014 vol. 2(Issue 34) pp:7071-7076
Publication Date(Web):04 Jul 2014
DOI:10.1039/C4TC01193G
Two-dimensional (2D) ferromagnetic semiconductors hold a great potential for nano-electronic and spintronic devices. Nevertheless, their experimental realization remains a big challenge. Through first-principles calculations, we here demonstrate the possibility of realizing 2D ferromagnetic semiconductors simply by exfoliating layered crystals of CrXTe3 (X = Si, Ge). The exfoliation of CrXTe3 is feasible due to its small cleavage energy, and CrXTe3 nanosheets can form free-standing membranes. Interestingly, upon exfoliation, the ferromagnetism and semiconducting character are well preserved from bulk to the nanosheet form. Long-range ferromagnetic order with a magnetization of 3 μB per Cr atom is confirmed in 2D CrXTe3 from classical Heisenberg model Monte Carlo simulations. Both bulk and 2D CrXTe3 are indirect-gap semiconductors with their valence and conduction bands fully spin-polarized in the same direction, which is promising for spin-polarized carrier injection and detection. We further demonstrate the tunability and enrichment of the properties of CrXTe3 nanosheets via external operations. Under moderate tensile strain, the 2D ferromagnetism can be largely enhanced. By pure electron doping or adsorbing nucleophilic molecules, CrXTe3 nanosheets become 2D half metals.
Co-reporter:Longjiu Cheng, Xiuzhen Zhang, Baokang Jin and Jinlong Yang
Nanoscale 2014 vol. 6(Issue 21) pp:12440-12444
Publication Date(Web):11 Sep 2014
DOI:10.1039/C4NR03550J
Using the super valence bond model, a generalized chemical picture for the electronic shells of an Au20 pyramid is given. It is found that Au20 can be viewed to be a superatomic molecule, of which its superatomic 16c–16e core (T) is in D3S hybridization bonded with four vertical Au atoms for the molecule-like (TAu4) electronic shell-closure. Based on such a superatom–atom bonding model, TX4 (X = F, Cl, or Br) are predicted to be very stable. Such a superatom–atom T–Au/T–X bonding enriches the scope of chemistry.
Co-reporter:Wenqi Xia, Wei Hu, Zhenyu Li and Jinlong Yang
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 41) pp:22495-22498
Publication Date(Web):29 Aug 2014
DOI:10.1039/C4CP03292F
The adsorption of common gas molecules (N2, CO, CO2, H2O, NH3, NO, NO2, and O2) on germanene is studied with density functional theory. The results show that N2, CO, CO2, and H2O are physisorbed on germanene via van der Waals interactions, while NH3, NO, NO2, and O2 are chemisorbed on germanene via strong covalent (Ge–N or Ge–O) bonds. The chemisorption of gas molecules on germanene opens a band gap at the Dirac point of germanene. NO2 chemisorption on germanene shows strong hole doping in germanene. O2 is easily dissociated on germanene at room temperature. Different adsorption behaviors of common gas molecules on germanene provide a feasible way to exploit chemically modified germanene.
Co-reporter:Wei Hu, Nan Xia, Xiaojun Wu, Zhenyu Li and Jinlong Yang
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 15) pp:6957-6962
Publication Date(Web):23 Jan 2014
DOI:10.1039/C3CP55250K
On the basis of first-principles calculations, we demonstrate the potential application of silicene as a highly sensitive molecule sensor for NH3, NO, and NO2 molecules. NH3, NO and NO2 molecules chemically adsorb on silicene via strong chemical bonds. With distinct charge transfer from silicene to molecules, silicene and chemisorbed molecules form charge-transfer complexes. The adsorption energy and charge transfer in NO2-adsorbed silicene are larger than those of NH3- and NO-adsorbed silicones. Depending on the adsorbate types and concentrations, the silicene-based charge-transfer complexes exhibit versatile electronic properties with tunable band gap opening at the Dirac point of silicene. The calculated charge carrier concentrations of NO2-chemisorbed silicene are 3 orders of magnitude larger than intrinsic charge carrier concentration of graphene at room temperature. The results present a great potential of silicene for application as a highly sensitive molecule sensor.
Co-reporter:Lei Wang, Qiquan Luo, Wenhua Zhang, Jinlong Yang
International Journal of Hydrogen Energy 2014 Volume 39(Issue 35) pp:20190-20196
Publication Date(Web):3 December 2014
DOI:10.1016/j.ijhydene.2014.10.034
•H2 and CO adsorption on metal embedded graphene has been study using DFT.•At standard conditions, Fe and Co embedded graphene can capture CO efficiently with H2 free.•Fe-G and Co-G can be used as a filter membrane for removing CO efficiently in the feed gas of hydrogen fuel cells.The adsorption of CO and H2 on single-metal-atom (Fe, Co, Ni and Cu) embedded graphene (M-G) has been studied using density functional theory calculations. Fe-G and Co-G can capture up to three CO molecules per metal atom strongly, but tend to weakly or not adsorb H2 molecules. Under standard conditions (298.15 K and 1 bar), they show a high adsorption selectivity ratio for CO over H2. The density of states analysis reveals that the strong adsorption between CO and Fe(Co)-G results from the hybridization between d states of Fe (Co) and sp states of CO. Our findings suggest that Fe-G and Co-G can be used as a filter membrane for removing CO efficiently in the feed gas of hydrogen fuel cells.
Co-reporter:Yafei Dai ; Zhenyu Li
The Journal of Physical Chemistry C 2014 Volume 118(Issue 6) pp:3313-3318
Publication Date(Web):January 23, 2014
DOI:10.1021/jp409899n
Recently, a grossly warped nanographene C80H30 has been synthesized experimentally. Its optical properties are studied and compared with bucky ball C60, C70, and a flat nanographene C78H30 in the framework of density functional theory (DFT) with the B3LYP functional. The static polarizability α, first-order hyperpolarizability β, and second-order hyperpolarizability γ are calculated using the finite field approach. The average values of ⟨α⟩ and ⟨γ⟩ for C80H30 are 151.7 Å3 and 54.5 × 10–35 esu, respectively, much higher than those of C60 and C70. Both ⟨α⟩ and ⟨γ⟩ of planar C78H30 are higher than those of C80H30, which is consistent with the fact that the energy gap of C78H30 is smaller than that of C80H30. However, the diagonal component of α along the z axis of C80H30 is 86.2 Å3, much higher than 30.7 Å3 of C78H30. Furthermore, the values of the hyperpolarizability in the z direction (γxxzz, γyyzz, and γzzzz) of C80H30 are almost 1 order of magnitude higher than those of C78H30. The relationship between optical properties and electron delocalization in molecules indicated by aromaticity is also discussed. Our results indicate that C80H30 can be used as a promising optical material.
Co-reporter:Lei Wang ; Chaozheng He ; Wenhua Zhang ; Zhenyu Li
The Journal of Physical Chemistry C 2014 Volume 118(Issue 31) pp:17511-17520
Publication Date(Web):July 11, 2014
DOI:10.1021/jp501620h
With density functional theory, all elementary steps of methanol (CH3OH) dehydrogenation and oxidation on atomic-oxygen-covered or OH-covered Au (111) surfaces are systematically studied. Our results suggest that on low oxygen coverage Au (111) surface the production of CH2O and CO start from α-H elimination and β-H elimination, respectively. The selective oxidation pathway is controlled by thermodynamics of the first step rather than kinetics. The overall energy barrier to produce CO is 0.39 eV corresponding to gas-phase methanol, which indicates that the reaction can proceed at low temperature. On high oxygen coverage Au (111) surface, the elimination of α-H and one β-H can take place simultaneously to form CH2O for the cooperative interaction of two nearby atomic oxygen. The missing observation of CH2O may come from the fact that the newly formed CH2O is ready to react with surface atomic oxygen and hydroxyl to form CH2OO(H) rather than desorption from the surface. The rate-limiting step of the oxidation of CH2OO(H) is the dehydrogenation of CHO2 with an energy barrier of 0.95 eV. Also, the newly formed CH2O can be dehydrogenated by surface atomic oxygen to form CO and then to CO2 with low energy barrier. Our results give good explanation for experimental observations and make up the discrepancy between experimental observation and previous theoretical work.
Co-reporter:Ruiqi Zhang, Zhenpeng Hu, Bin Li, and Jinlong Yang
The Journal of Physical Chemistry A 2014 Volume 118(Issue 39) pp:8953-8959
Publication Date(Web):April 7, 2014
DOI:10.1021/jp5018218
On the basis of Bardeen’s perturbation theory on electron tunneling and inspired by Paz et al.’s study, a new expression for the tunneling current between the scanning tunneling microscopy (STM) tip and sample has been obtained, and it provides us with an efficient method to simulate STM images. The method can be implemented in any code of first-principles computing software, which offers the wave functions of the tip and sample, calculated independently at the same footing, as input. By calculating the integral with fast Fourier transform (FFT), simulating the STM image of a given sample surface by a database of different tips on a PC turns out to be not a time-consuming work. Compared with Paz et al.’s method, our method abandons the application of the vacuum Green function and possesses better computing efficiency, fewer parameters, and more reasonable simulated results especially at lower computing cost. Simple tip–sample systems, such as H–H and Pd2–Ag2, are taken as benchmarks to test our method. The topographic images of a CO molecule adsorbed on a Cu(111) surface obtained by using a tungsten tip and a CO-terminated tip are also simulated, and the simulated results are in good agreement with the experimental ones.
Co-reporter:Jin Zhao, Qijing Zheng, Hrvoje Petek, and Jinlong Yang
The Journal of Physical Chemistry A 2014 Volume 118(Issue 35) pp:7255-7260
Publication Date(Web):January 3, 2014
DOI:10.1021/jp410460m
Nearly free electron (NFE) states with density maxima in nonnuclear (NN) voids may have remarkable electron transport properties ranging from suppressed electron–phonon interaction to Wigner crystallization. Such NFE states, however, usually exist near the vacuum level, which makes them unsuitable for transport. Through first principles calculations on nanocomposites consisting of carbon nanotube (CNT) arrays sandwiched between boron nitride (BN) sheets, we describe a stratagem for stabilizing the NN-NFE states to below the Fermi level. By doping the CNTs with negative charge, we establish Coulomb barriers at CNTs walls that, together with the insulating BN sheets, define the transverse potentials of one-dimensional (1D) transport channels, which support the NN-NFE states.
Co-reporter:Jian-Qiang Zhong, Xinming Qin, Jia-Lin Zhang, Satoshi Kera, Nobuo Ueno, Andrew Thye Shen Wee, Jinlong Yang, and Wei Chen
ACS Nano 2014 Volume 8(Issue 2) pp:1699
Publication Date(Web):January 16, 2014
DOI:10.1021/nn406050e
Understanding the effect of intermolecular and molecule–substrate interactions on molecular electronic states is key to revealing the energy level alignment mechanism at organic–organic heterojunctions or organic–inorganic interfaces. In this paper, we investigate the energy level alignment mechanism in weakly interacting donor–acceptor binary molecular superstructures, comprising copper hexadecafluorophthalocyanine (F16CuPc) intermixed with copper phthalocyanine (CuPc), or manganese phthalocynine (MnPc) on graphite. The molecular electronic structures have been systematically studied by in situ ultraviolet photoelectron spectroscopy (UPS) and low-temperature scanning tunneling microscopy/spectroscopy (LT-STM/STS) experiments and corroborated by density functional theory (DFT) calculations. As demonstrated by the UPS and LT-STM/STS measurements, the observed unusual energy level realignment (i.e., a large downward shift in donor HOMO level and a corresponding small upward shift in acceptor HOMO level) in the CuPc–F16CuPc binary superstructures originates from the balance between intermolecular and molecule–substrate interactions. The enhanced intermolecular interactions through the hydrogen bonding between neighboring CuPc and F16CuPc can stabilize the binary superstructures and modify the local molecular electronic states. The obvious molecular energy level shift was explained by gap-state-mediated interfacial charge transfer.Keywords: binary molecular superstructures; energy level alignment; gap states; scanning tunneling microscopy; self-assembly; ultraviolet photoelectron spectroscopy; weak intermolecular interactions
Co-reporter:Wei Hu, Xiaojun Wu, Zhenyu Li and Jinlong Yang
Nanoscale 2013 vol. 5(Issue 19) pp:9062-9066
Publication Date(Web):11 Jul 2013
DOI:10.1039/C3NR02326E
Helium purification has become more important for increasing demands in scientific and industrial applications. In this work, we demonstrated that the porous silicene can be used as an effective ultimate membrane for helium purification on the basis of first-principles calculations. Prinstine silicene monolayer is impermeable to helium gas with a high penetration energy barrier (1.66 eV). However, porous silicene with either Stone–Wales (SW) or divacancy (555777 or 585) defect presents a surmountable barrier for helium (0.33 to 0.78 eV) but formidable for Ne, Ar, and other gas molecules. In particular, the porous silicene with divacancy defects shows high selectivity for He/Ne and He/Ar, superior to graphene, polyphenylene, and traditional membranes.
Co-reporter:Longjiu Cheng, Changda Ren, Xiuzhen Zhang and Jinlong Yang
Nanoscale 2013 vol. 5(Issue 4) pp:1475-1478
Publication Date(Web):04 Jan 2013
DOI:10.1039/C2NR32888G
Based on the recently proposed super valence bond model, in which superatoms can compose superatomic molecules by sharing valence pairs and nuclei for shell closure, the 23c-14e bi-icosahedral Au23(+9) core of Au38(SR)24 is proved to be a superatomic molecule. Molecular orbital analysis reveals that the Au23(+9) core is an exact analogue of the F2 molecule in electronic configuration. Chemical bonding analysis by the adaptive natural density partitioning method confirms the superatomic molecule bonding framework of Au38(SR)24 in a straightforward manner.
Co-reporter:Xingxing Li, Xiaojun Wu and Jinlong Yang
Journal of Materials Chemistry A 2013 vol. 1(Issue 43) pp:7197-7201
Publication Date(Web):12 Sep 2013
DOI:10.1039/C3TC31514B
The control of spin without magnetic field is one of the challenges in developing spintronic devices. In an attempt to solve this problem, we proposed a novel hypothetical La(Mn0.5Zn0.5)AsO alloy from two experimentally synthesized rare earth element transition metal arsenide oxides, i.e. LaMnAsO and LaZnAsO. On the basis of the first-principles calculations with strong-correlated correction, we found that the La(Mn0.5Zn0.5)AsO alloy is an antiferromagnetic semiconductor at the ground state, and a bipolar magnetic semiconductor at the ferromagnetic state. Both electron and hole doping in the La(Mn0.5Zn0.5)AsO alloy induce the transition from antiferromagnetic to ferromagnetic, as well as semiconductor to half metal. In particular, the spin-polarization direction is switchable depending on the doped carrier type. As carrier doping can be realized easily in experiment by applying a gate voltage, the La(Mn0.5Zn0.5)AsO alloy stands as a promising spintronic material to generate and control the spin-polarized carriers with an electric field.
Co-reporter:Xingxing Li and Jinlong Yang
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 38) pp:15793-15801
Publication Date(Web):07 Aug 2013
DOI:10.1039/C3CP52623B
In spintronics, both the charge and spin of the electrons are exploited for information processing. Developing simple methods to manipulate and detect the carriers' spin orientation is among the key issues for spintronics applications. Electrical field has the advantage that it can be easily applied locally in contrast with a conventionally used magnetic field, thus it is more convenient and efficient. Bipolar magnetic materials, characterized by a unique electronic structure where the valence band and conduction band possess opposite spin polarization around the Fermi level, serve as a new class of materials for spintronics through which electrical control of spin-polarization direction can be realized simply by applying a gate voltage. This article reviews a range of materials that have bipolar spin polarization, including bipolar half metals and bipolar magnetic semiconductors, and their potential applications for creating, manipulating, and detecting spin-polarized carriers. These materials provide a promising future for electrically controllable spintronics devices.
Co-reporter:Long Yuan, Zhenyu Li and Jinlong Yang
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 2) pp:497-503
Publication Date(Web):02 Nov 2012
DOI:10.1039/C2CP43129G
Recently, a new kind of spintronics material, bipolar magnetic semiconductors (BMS), has been proposed. The spin polarization of BMS can be conveniently controlled by a gate voltage, which makes it very attractive in device engineering. Now, the main challenge is finding more BMS materials. In this article, we propose that hydrogenated wurtzite SiC nanofilm is a two-dimensional BMS material. Its BMS character is very robust under the effect of strain, substrate or even a strong electric field. The proposed two-dimensional BMS material paves the way to use this promising new material in an integrated circuit.
Co-reporter:Yuan Yuan, Longjiu Cheng, and Jinlong Yang
The Journal of Physical Chemistry C 2013 Volume 117(Issue 25) pp:13276-13282
Publication Date(Web):June 3, 2013
DOI:10.1021/jp402816b
A recent experiment reported that a newly crystallized phosphine-protected Au20 nanocluster [Au20(PPhy2)10Cl4]Cl2 [PPhpy2 = bis(2-pyridyl)phenylphosphine] owns a very stable Au20 core, but the number of valence electrons of the Au20 core is 14e, which is not predicted by the superatom model. So we apply the density functional theory to further study this cluster from its molecular orbital and chemical bonding. The results suggest that the Au20(+6) core is an analogue of the F2 molecule based on the super valence bond model, and the 20-center–14-electron Au20(+6) core can be taken as a superatomic molecule bonded by two 11-center–7-electron superatoms, where the two 11c superatoms share two Au atoms and two electrons to meet an 8-electron closed shell for each. The electronic shell closure enhances the stability of the Au20 core, besides the PN bridges. Exceptionally, the theoretical HOMO–LUMO gap (1.03 eV) disagrees with the experimental value (2.24 eV), and some possible reasons for this big difference are analyzed in this paper.
Co-reporter:Erjun Kan ; Wei Hu ; Chuanyun Xiao ; Ruifeng Lu ; Kaiming Deng ; Jinlong Yang ;Haibin Su
Journal of the American Chemical Society 2012 Volume 134(Issue 13) pp:5718-5721
Publication Date(Web):March 22, 2012
DOI:10.1021/ja210822c
The unprecedented applications of two-dimensional (2D) atomic sheets in spintronics are formidably hindered by the lack of ordered spin structures. Here we present first-principles calculations demonstrating that the recently synthesized dimethylmethylene-bridged triphenylamine (DTPA) porous sheet is a ferromagnetic half-metal and that the size of the band gap in the semiconducting channel is roughly 1 eV, which makes the DTPA sheet an ideal candidate for a spin-selective conductor. In addition, the robust half-metallicity of the 2D DTPA sheet under external strain increases the possibility of applications in nanoelectric devices. In view of the most recent experimental progress on controlled synthesis, organic porous sheets pave a practical way to achieve new spintronics.
Co-reporter:Chong Xiao ; Xinming Qin ; Jie Zhang ; Ran An ; Jie Xu ; Kun Li ; Boxiao Cao ; Jinlong Yang ; Bangjiao Ye ;Yi Xie
Journal of the American Chemical Society 2012 Volume 134(Issue 44) pp:18460-18466
Publication Date(Web):October 15, 2012
DOI:10.1021/ja308936b
The subject of the involved phase transition in solid materials has formed not only the basis of materials technology but also the central issue of solid-state chemistry for centuries. The ability to design and control the required changes in physical properties within phase transition becomes key prerequisite for the modern functionalized materials. Herein, we have experimentally achieved the high thermoelectric performance (ZT value reaches 1.5 at 700 K) and reversible p-n-p semiconducting switching integrated in a dimetal chalcogenide, AgBiSe2 during the continuous hexagonal–rhombohedral–cubic phase transition. The clear-cut evidences in temperature-dependent positron annihilation and Raman spectra confirmed that the p-n-p switching is derived from the bimetal atoms exchange within phase transition, whereas the full disordering of bimetal atoms after the bimetal exchange results in the high thermoelectric performance. The combination of p-n-p switching and high thermoelectric performance enables the dimetal chalcogenides perfect candidates for novel multifunctional electronic devices. The discovery of bimetal atoms exchange during the phase transition brings novel phenomena with unusual properties which definitely enrich solid-state chemistry and materials science.
Co-reporter:Xingxing Li, Xiaojun Wu, Zhenyu Li, Jinlong Yang and J. G. Hou
Nanoscale 2012 vol. 4(Issue 18) pp:5680-5685
Publication Date(Web):20 Jul 2012
DOI:10.1039/C2NR31743E
Electrical control of spin polarization is very desirable in spintronics, since electric fields can be easily applied locally, in contrast to magnetic fields. Here, we propose a new concept of bipolar magnetic semiconductors (BMS) in which completely spin-polarized currents with reversible spin polarization can be created and controlled simply by applying a gate voltage. This is a result of the unique electronic structure of BMS, where the valence and conduction bands possess opposite spin polarization when approaching the Fermi level. BMS is thus expected to have potential for various applications. Our band structure and spin-polarized electronic transport calculations on semi-hydrogenated single-walled carbon nanotubes confirm the existence of BMS materials and demonstrate the electrical control of spin-polarization in them.
Co-reporter:Jun Dai, Zhenyu Li, Jinlong Yang and Jianguo Hou
Nanoscale 2012 vol. 4(Issue 10) pp:3032-3035
Publication Date(Web):29 Mar 2012
DOI:10.1039/C2NR12018F
Based on first-principles lattice dynamics and electron–phonon coupling calculations, B2C sheets are predicted to be a two-dimensional (2D) phonon-mediated superconductors with a relatively high transition temperature (Tc). The electron–phonon coupling parameter was calculated to be 0.92 and it is mainly contributed by low frequency out-of-plane phonon modes and electronic states with a π character. When the Coulomb pseudopotential, μ*, is set to 0.10, the estimated temperature, Tc, is 19.2 K. To the best of our knowledge, B2C is the first pristine 2D superconductor with a Tc higher than the boiling point of liquid helium.
Co-reporter:Shuang Ni, Zhenyu Li and Jinlong Yang
Nanoscale 2012 vol. 4(Issue 4) pp:1184-1189
Publication Date(Web):07 Dec 2011
DOI:10.1039/C1NR11086A
The energy barrier of oxygen molecule dissociation on carbon nanotubes or graphene with different types of nitrogen doping is investigated using density functional theory. The results show that the energy barriers can be reduced efficiently by all types of nitrogen doping in both carbon nanotubes and graphene. Graphite-like nitrogen and Stone–Wales defect nitrogen decrease the energy barrier more efficiently than pyridine-like nitrogen, and a dissociation barrier lower than 0.2 eV can be obtained. Higher nitrogen concentration reduces the energy barrier much more efficiently for graphite-like nitrogen. These observations are closely related to partial occupation of π* orbitals and change of work functions. Our results thus provide useful insights into the oxygen reduction reactions.
Co-reporter:Long Yuan, Zhenyu Li, Jinlong Yang and Jian Guo Hou
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 22) pp:8179-8184
Publication Date(Web):16 Apr 2012
DOI:10.1039/C2CP40635G
In this article, based on first-principles calculations, we systematically study functionalization induced diamondization of graphene bilayer and graphene–BN hybrid bilayer. With single-side functionalization, the diamondized structures are magnetic semiconductors. Interestingly, if both sides of the bilayer are functionalized, diamondization becomes spontaneous without a barrier. On the other hand, when the bottom layer of the bilayer graphene is replaced by a single hexagonal BN layer, the diamondized structure becomes a nonmagnetic metal. The tunable electronic and magnetic properties pave new avenues to construct graphene-based electronics and spintronics devices.
Co-reporter:Yu Zhao, Xiaojun Wu, Jinlong Yang and Xiao Cheng Zeng
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 16) pp:5545-5550
Publication Date(Web):17 Feb 2012
DOI:10.1039/C2CP40081B
Two-dimensional (2D) hexagonal boron-nitride oxide (h-BNO) is a structural analogue of graphene oxide. Motivated by recent experimental studies of graphene oxide, we have investigated the chemical oxidation of 2D h-BN sheet and the associated electronic properties of h-BNO. Particular emphasis has been placed on the most favorable site(s) for chemisorption of atomic oxygen, and on the migration barrier for an oxygen atom hopping to the top, bridge, or hollow site on the h-BN surface, as well as the most likely pathway for the dissociation of an oxygen molecule on the h-BN surface. We find that when an oxygen atom migrates on the h-BN surface, it is most likely to be over an N atom, but confined by three neighbor B atoms (forming a triangle ring). In general, chemisorption of an oxygen atom will stretch the B–N bond, and under certain conditions may even break the B–N bond. Depending on the initial location of the first chemisorbed O atom, subsequent oxidation tends to form an O domain or O chain on the h-BN sheet. The latter may lead to a synthetic strategy for the unzipping of the h-BN sheet along a zigzag direction. A better understanding of the oxidation of h-BN sheet has important implications for tailoring the properties of the h-BN sheet for applications.
Co-reporter:Yan Zhang ; Xiaojun Wu ; Qunxiang Li
The Journal of Physical Chemistry C 2012 Volume 116(Issue 16) pp:9356-9359
Publication Date(Web):April 10, 2012
DOI:10.1021/jp301691z
The band-gap modulation of graphane nanoribbons under uniaxial elastic strain is investigated with the density functional theory method. Our results predict that the band gap of graphane nanoribbons can be tuned linearly with strain regardless of their widths or edge structures. The band gap increases remarkably from 2.49 to 4.11 eV and 2.04 to 4.21 eV for 13-armchair and 6-zigzag graphane nanoribbons when the strain changes from −10.0% to 10.0%, respectively. Moreover, the band gap of the graphane nanoribbon is more sensitive to the compressive than tensile deformation, which mainly originates from the shift of its valence band edge under strain. Our results imply the great potential of graphane nanoribbons in the pressure sensor and optical electronics applications at nanoscale.
Co-reporter:Xiuling Li, Xiaojun Wu, Xiao Cheng Zeng, and Jinlong Yang
ACS Nano 2012 Volume 6(Issue 5) pp:4104
Publication Date(Web):April 8, 2012
DOI:10.1021/nn300495t
We perform a comprehensive study of the effects of line defects on electronic and magnetic properties of monolayer boron-nitride (BN) sheets, nanoribbons, and single-walled BN nanotubes using first-principles calculations and Born–Oppenheimer quantum molecular dynamic simulation. Although line defects divide the BN sheet (or nanotube) into domains, we show that certain line defects can lead to tailor-made edges on BN sheets (or imperfect nanotube) that can significantly reduce the band gap of the BN sheet or nanotube. In particular, we find that the line-defect-embedded zigzag BN nanoribbons (LD-zBNNRs) with chemically homogeneous edges such as B- or N-terminated edges can be realized by introducing a B2, N2, or C2 pentagon–octagon–pentagon (5–8–5) line defect or through the creation of the antisite line defect. The LD-zBNNRs with only B-terminated edges are predicted to be antiferromagnetic semiconductors at the ground state, whereas the LD-zBNNRs with only N-terminated edges are metallic with degenerated antiferromagnetic and ferromagnetic states. In addition, we find that the hydrogen-passivated LD-zBNNRs as well as line-defect-embedded BN sheets (and nanotubes) are nonmagnetic semiconductors with markedly reduced band gap. The band gap reduction is attributed to the line-defect-induced impurity states. Potential applications of line-defect-embedded BN nanomaterials include nanoelectronic and spintronic devices.Keywords: band gap reduction; h-BN sheet; line defect; nanoribbon; nanotube
Co-reporter:Yuling Liu ; Xiaojun Wu ; Yu Zhao ; Xiao Cheng Zeng
The Journal of Physical Chemistry C 2011 Volume 115(Issue 19) pp:9442-9450
Publication Date(Web):April 28, 2011
DOI:10.1021/jp201350e
Motivated by successful fabrication of monolayer materials consisting of hybrid graphene and boron nitride domains (Ci, L.; et al. Nat. Mater. 2010, 9, 430–435), we report a first-principles study of hybrid graphene/boron nitride (C-BN) nanoribbons with dihydrogenated edge(s). The first-principles study suggests that hybrid C-BN nanoribbons can possess half-metallicity with a certain range of widths for the graphene and BN sections. In general, the hybrid C-BN nanoribbons, either in HC1HB2–(C2)m(BN)n or HC2HB2–(C2)m(BN)n form, can undergo the semiconductor-to-half-metal-to-metal transitions as the width of both graphene and BN nanoribbons increases. The calculated electronic structures of the hybrid C-BN nanoribbons suggest that dihydrogenation of the boron edge can induce localized edge states around the Fermi level, and the interaction among the localized edge states can lead to the semiconductor-to-half-metal-to-metal transitions.
Co-reporter:Lingshun Xu ; Wenhua Zhang ; Yulin Zhang ; Zongfang Wu ; Bohao Chen ; Zhiquan Jiang ; Yunsheng Ma ; Jinlong Yang ;Weixin Huang
The Journal of Physical Chemistry C 2011 Volume 115(Issue 14) pp:6815-6824
Publication Date(Web):March 14, 2011
DOI:10.1021/jp200423j
The reactivity of surface hydroxyls on FeO(111) monolayer films on Pt(111) with different oxygen vacancy concentrations has been investigated by means of X-ray photoelectron spectroscopy, thermal desorption spectroscopy, low energy electron diffraction, and density functional theory calculations. Surface hydroxyls on the FeO(111) monolayer films undergo two types of surface reactions: one type is surface reactions to form H2O and create oxygen vacancies; the other is surface reactions to form H2. Surface reactions to form H2O and create oxygen vacancies are preferred for surface hydroxyls on the stoichiometric FeO(111) monolayer film but get suppressed with the increasing of the oxygen vacancy concentration on the FeO(111) monolayer film. On the FeO0.67(111) monolayer film, surface hydroxyls prefer surface reactions to form H2. The accompanying DFT calculation results demonstrate that the thermodynamically favorable reaction between two OH(a) switches from the surface reaction to form H2O and oxygen vacancies on the stoichiometric FeO(111) monolayer film to the surface reaction to form H2 on the FeO0.75(111) monolayer film. These results reveal a novel concept of oxygen vacancy-controlled reactivity of surface hydroxyls in which the thermodynamically favorable reactions switch from reactions to form H2O and oxygen vacancies on the stoichiometric FeO(111) monolayer film to those to form H2 on the partially reduced FeO0.75(111) monolayer film. The interplay between oxygen vacancies and surface hydroxyls that both exert great influence on the physical chemistry and reactivity of oxide surface will greatly deepen the fundamental understanding of the relevant heterogeneous catalytic reaction systems involving transitional metal oxides.
Co-reporter:Jing Zhou ; Haiming Li ; Linjuan Zhang ; Jie Cheng ; Haifeng Zhao ; Wangsheng Chu ; Jinlong Yang ; Yi Luo ;Ziyu Wu
The Journal of Physical Chemistry C 2011 Volume 115(Issue 1) pp:253-256
Publication Date(Web):December 13, 2010
DOI:10.1021/jp105121y
Structural and magnetic properties of 3d transition-metal-doped silicon carbide in cubic (3C) polytype have been systematically studied from first principles to reconcile conflicting experimental findings. The most energetically favorable structures fall in two distinct sets depending on the character of the 3d transition metal and the Si atomic chemical potential. The structure of substitutional TMSi is the most stable one for early transition metals like Ti, V, Cr, and Mn, while the clustering of TMSi−TMI dimers formed by the neighboring substitutional TMSi and interstitial TMI is energetically favored for late transition metals such as Co, Ni, and Cu. For Fe, the most stable structure is the substitutional configuration under C-rich conditions, while under Si-rich conditions the clustering of the FeSi−FeI dimer is energetically favored. It is found in the doped silicon carbide that the Co dimer is nonmagnetic, while both Ni and Cu atoms interact ferromagnetically and make the whole doped system half metallic. Fe atoms show a ferrimagnetic order with a local magnetic moment of 2.0 and −0.34 μB at substitutional and interstitial sites, respectively. Such intrinsically tunable magnetic properties of 3d transition-metal-doped silicon carbide could find many exciting potential applications in spintronics.
Co-reporter:Huizhi Bao;Dr. Wenhua Zhang;Qing Hua;Dr. Zhiquan Jiang;Dr. Jinlong Yang;Dr. Weixin Huang
Angewandte Chemie 2011 Volume 123( Issue 51) pp:12502-12506
Publication Date(Web):
DOI:10.1002/ange.201103698
Co-reporter:Qiang Fu, Jinlong Yang, and Xue-Bin Wang
The Journal of Physical Chemistry A 2011 Volume 115(Issue 15) pp:3201-3207
Publication Date(Web):March 30, 2011
DOI:10.1021/jp1120542
Electron affinity (EA) is an important molecular property relevant to the electronic structure, chemical reactivity, and stability of a molecule. A detailed understanding of the electronic structures and EAs of benzoquinone (BQ) molecules can help rationalize their critical roles in a wide range of applications, from biological photosynthesis to energy conversion processes. In this Article, we report a systematic spectroscopic probe on the electronic structures and EAs of all three isomers—o-, m-, and p-BQ—employing photodetachment photoelectron spectroscopy (PES) and ab initio electronic structure calculations. The PES spectra of the three BQ●− radical anions were taken at several photon energies under low-temperature conditions. Similar spectral patterns were observed for both o- and p-BQ●−, each revealing a broad ground-state feature and a large band gap followed by well-resolved excited states peaks. The EAs of o- and p-BQ were determined to be 1.90 and 1.85 eV with singlet−triplet band gaps of 1.68 and 2.32 eV, respectively. In contrast, the spectrum of m-BQ●− is distinctly different from its two congeners with no clear band gap and a much higher EA (2.89 eV). Accompanied theoretical study confirms the experimental EAs and band gaps. The calculations further unravel a triplet ground state for m-BQ in contrast to the singlet ground states for both o- and p-BQ. The diradical nature of m-BQ, which is consistent with its non-Kekulé structure, is primarily responsible for the observed high EA and helps explain its nonexistence in bulk materials.
Co-reporter:Huizhi Bao;Dr. Wenhua Zhang;Qing Hua;Dr. Zhiquan Jiang;Dr. Jinlong Yang;Dr. Weixin Huang
Angewandte Chemie International Edition 2011 Volume 50( Issue 51) pp:12294-12298
Publication Date(Web):
DOI:10.1002/anie.201103698
Co-reporter:Shuang Ni ; Wei He ; Zhenyu Li
The Journal of Physical Chemistry C 2011 Volume 115(Issue 26) pp:12760-12762
Publication Date(Web):June 2, 2011
DOI:10.1021/jp2017874
There is a controversy in the literature about the transport behavior of azafullerene encapsulated single-walled carbon nanotubes (SWCNTs). Both n-type and p-type semiconducting behaviors have been suggested experimentally. To clarify this issue, we study the electronic structure of C59N nanopeapods with density functional theory. It turns out that C59N doping in pristine SWCNTs does not change the carrier type, although it is possible to change the transport behavior from p-type to n-type for SWCNTs with defects via a new mechanism.
Co-reporter:Zhenyu Li, Bin Li, Jinlong Yang and Jian Guo Hou
Accounts of Chemical Research 2010 Volume 43(Issue 7) pp:954
Publication Date(Web):April 1, 2010
DOI:10.1021/ar9001558
To develop new functional materials and nanoscale electronics, researchers would like to accurately describe and precisely control the quantum state of a single molecule on a surface. Scanning tunneling microscopy (STM), combined with first-principles simulations, provides a powerful technique for acquiring this level of understanding. Traditionally, metal phthalocyanine (MPc) molecules, composed of a metal atom surrounded by a ligand ring, have been used as dyes and pigments. Recently, MPc molecules have shown great promise as components of light-emitting diodes, field-effect transistors, photovoltaic cells, and single-molecule devices. In this Account, we describe recent research on the characterization and control of adsorption and electronic states of a single MPc molecule on noble metal surfaces. In general, the electronic and magnetic properties of a MPc molecule largely depend on the type of metal ion within the phthalocyanine ligand and the type of surface on which the molecule is adsorbed. However, with the STM technique, we can use on-site molecular “surgery” to manipulate the structure and the properties of the molecule. For example, STM can induce a dehydrogenation reaction of the MPc, which allows us to control the Kondo effect, which describes the spin polarization of the molecule and its interaction with the complex environment. A specially designed STM tip can allow researchers to detect certain molecule−surface hybrid states that are not accessible by other techniques. By matching the local orbital symmetry of the STM tip and the molecule, we can generate the negative differential resistance effect in the formed molecular junction. This orbital symmetry based mechanism is extremely robust and does not critically depend on the geometry of the STM tip. In summary, this simple model system, a MPc molecule absorbed on a noble metal surface, demonstrates the power of STM for quantum characterization and manipulation of single molecules, highlighting the potential of this technique in a variety of applications.
Co-reporter:Shuanglin Hu, Jin Zhao, Yingdi Jin, Jinlong Yang, Hrvoje Petek, and J. G. Hou
Nano Letters 2010 Volume 10(Issue 12) pp:4830-4838
Publication Date(Web):November 4, 2010
DOI:10.1021/nl1023854
By first-principles theory we study the nearly free electron (NFE) states of carbon and boron nitride nanotubes. In addition to the well-known π* bands, we found a series of one-dimensional (1D) NFE bands with on-axis spatial distributions, which resemble atomic orbitals projected onto a plane. These bands are 1D counterparts of the recently discovered superatom orbitals of 0D fullerenes. In addition to the previously reported lowest energy NFE state with the angular quantum number l = 0 corresponding to s atomic orbital character, we find higher energy NFE bands with l > 0 corresponding to the p, d, etc., orbitals. We show that these atom-like states of nanotubes originate from the many-body screening, which is responsible for the image potential of the parent two-dimensional (2D) graphene or BN sheets. With a model potential that combines the short-range exchange-correlation and the long-range Coulomb interactions, we reproduce the energies and radial wave function profiles of the NFE states from the density functional theory calculations. When the nanotube radius exceeds the radial extent on NFE states, the NFE state energies converge to those of image potential states of the parent 2D molecular sheets. To explore possible applications in molecular electronics that take advantage of the NFE properties of nanotube building blocks, we investigate the modification of NFE states by transverse electric fields, alkali metal encapsulation, and lateral and concentric nanotube dimerization.
Co-reporter:Jun Dai, Zhenyu Li and Jinlong Yang
Physical Chemistry Chemical Physics 2010 vol. 12(Issue 39) pp:12420-12422
Publication Date(Web):31 Aug 2010
DOI:10.1039/C0CP00735H
Based on first-principles equation-of-state and lattice dynamics calculations, a new boron allotrope with K4 structure is proposed, which gives the first example of a three-dimensional all sp2 network.
Co-reporter:Haiqing Liang, Zhenyu Li and Jinlong Yang
Physical Chemistry Chemical Physics 2010 vol. 12(Issue 17) pp:4431-4434
Publication Date(Web):24 Feb 2010
DOI:10.1039/B923012B
All-atomistic molecular dynamics simulations with explicit water solution are performed to investigate the interaction between single-stranded DNA (ssDNA) molecules and chiral N-isobutyryl-cysteine (NIBC) molecule coated Au surfaces. Different contributions to the force exerted on ssDNA are analyzed. It turns out that the experimentally observed stereospecific adsorption behavior of ssDNA on D/L-NIBC self-assembled monolayer surface mainly originates from the interaction between the dipole moment of NIBC and the negative charge carried by ssDNA.
Co-reporter:Xue-Bin Wang, Qiang Fu and Jinlong Yang
The Journal of Physical Chemistry A 2010 Volume 114(Issue 34) pp:9083-9089
Publication Date(Web):July 29, 2010
DOI:10.1021/jp103752t
Hydroxyl substituted phenoxides, o-, m-, p-HO(C6H4)O−, and the corresponding neutral radicals are important species; in particular, the p-isomer pair, i.e., p-HO(C6H4)O− and p-HO(C6H4)O•, is directly involved in the proton-coupled electron transfer in biological photosynthetic centers. Here we report the first spectroscopic study of these species in the gas phase by means of low-temperature photoelectron spectroscopy (PES) and ab initio calculations. Vibrationally resolved PES spectra were obtained at 70 K and at several photon energies for each anion, directly yielding electron affinity (EA) and electronic structure information for the corresponding hydroxyphenoxyl radical. The EAs are found to vary with OH positions, from 1.990 ± 0.010 (p) to 2.315 ± 0.010 (o) and 2.330 ± 0.010 (m) eV. Theoretical calculations were carried out to identify the optimized molecular structures for both anions and neutral radicals. The electron binding energies and excited state energies were also calculated to compare with experimental data. Excellent agreement is found between calculations and experiments. Molecular orbital analyses indicate a strong OH antibonding interaction with the phenoxide moiety for the o- as well as the p-isomer, whereas such an interaction is largely missing for the m-anion. The variance of EAs among three isomers is interpreted primarily due to the interplay between two competing factors: the OH antibonding interaction and the H-bonding stabilization (existed only in the o-anion).
Co-reporter:Honghui Shang, Zhenyu Li and Jinlong Yang
The Journal of Physical Chemistry A 2010 Volume 114(Issue 2) pp:1039-1043
Publication Date(Web):November 23, 2009
DOI:10.1021/jp908836z
A method to calculate Hartree-Fock-type exact exchange has been implemented in the electronic structure code SIESTA based on a localized numerical atomic orbital basis set. In our implementation, the electron repulsion integrals are calculated by solving Poisson’s equation using the interpolating scaling function method and then doing numerical integration in real-space. Test calculations for both isolated and periodic systems are performed, and good agreement with results calculated by Gaussian03 or Crystal06 packages is obtained.
Co-reporter:Zhuo Wang ; Yan Zhao ; Xuefeng Cui ; Shijing Tan ; Aidi Zhao ; Bing Wang ; Jinlong Yang ;J. G. Hou
The Journal of Physical Chemistry C 2010 Volume 114(Issue 42) pp:18222-18227
Publication Date(Web):September 30, 2010
DOI:10.1021/jp1059165
We report the investigation on the adsorption behaviors of CO on the rutile TiO2(110)-1 × 1 surface with preadsorbed O adatoms using scanning tunneling microscopy (STM) joint with density functional theory (DFT) calculations. The STM experimental results show that the diffusive CO molecules tend to adsorb at the site close to the O adatoms, forming CO−O and CO−O−CO complexes. These complexes are quite stable against the high bias voltages and UV illumination. DFT calculations give an activation energy barrier of 0.56 eV for CO oxidation through the CO−O complex to produce CO2. Our experimental and theoretical results both indicate that the dissociative O2, that is, the O adatoms on Ti4+, may not be directly responsible for the catalytic oxidation at low temperature.
Co-reporter:Huizhi Bao, Wenhua Zhang, Daili Shang, Qing Hua, Yunsheng Ma, Zhiquan Jiang, Jinlong Yang and Weixin Huang
The Journal of Physical Chemistry C 2010 Volume 114(Issue 14) pp:6676-6680
Publication Date(Web):March 11, 2010
DOI:10.1021/jp101617z
In this paper the reducibility of octahedral and cubic Cu2O nanocrystals that respectively expose the (111) and (100) crystal planes has been investigated both experimentally and theoretically. Reduced either by H2 or CO, the reduction temperature of octahedral Cu2O nanocrystals is lower than that of cubic Cu2O nanocrystals by more than 120 °C, which provides the unambiguous experimental results that the Cu2O(111) crystal plane is much more facile to be reduced than the Cu2O(100) crystal plane. The DFT calculation results reveal that the different reducibilities of octahedral and cubic Cu2O nanocrystals arise from their different surface structures, in which the Cu2O(111) surface has coordination unsaturated Cu but the Cu2O(100) surface does not. The chemisorption and activation of CO and H2 are stronger on the Cu2O(111) surface than on the Cu2O(100) surface. These results provide the convincing evidence for the shape-dependent surface reactivity of oxide nanocrystals.
Co-reporter:Haiming Li, Jun Dai, Jiong Li, Shuo Zhang, Jing Zhou, Linjuan Zhang, Wangsheng Chu, Dongliang Chen, Haifeng Zhao, Jinlong Yang and Ziyu Wu
The Journal of Physical Chemistry C 2010 Volume 114(Issue 26) pp:11390-11394
Publication Date(Web):June 10, 2010
DOI:10.1021/jp1024558
First principles calculations were performed to study the electronic structures of gallium nitride (GaN) sheets and nanoribbons (NRs) in order to understand the influence of defects or edge states on magnetic properties. It is shown that the Ga-defective GaN sheet may be a good candidate for spintronics due to its half-metal property under certain conditions, even if a perfect GaN sheet is a nonmagnetic semiconductor. We investigated both zigzag and armchair GaN NRs with and without edge atoms passivated by H. The H-passivated GaN NRs and bare armchair NRs can be classified as nonmagnetic semiconductors. Band gap gradually decreases with the increase of the width of NRs. A ferromagnetic character occurs in bare zigzag GaN NRs with width of about 1.7 nm (mainly determined by edge Ga and N). Furthermore, we have shown that thin layer GaN NRs could also be ferromagnetic. Magnetic moment does not decrease to zero even up to six layers. Results offer a deeper understanding of the influence of both defects and edge states of GaN sheets and monolayer and multilayer NRs, particularly in terms of their structural and magnetic properties.
Co-reporter:Shuan Pan;Qiang Fu;Tian Huang;Aidi Zhao;Bing Wang;Yi Luo;Jianguo Hou
PNAS 2009 Volume 106 (Issue 36 ) pp:15259-15263
Publication Date(Web):2009-09-08
DOI:10.1073/pnas.0903131106
We demonstrate in this joint experimental and theoretical study how one can alter electron transport behavior of a single
melamine molecule adsorbed on a Cu (100) surface by performing a sequence of elegantly devised and well-controlled single
molecular chemical processes. It is found that with a dehydrogenation reaction, the melamine molecule becomes firmly bonded
onto the Cu surface and acts as a normal conductor controlled by elastic electron tunneling. A current-induced hydrogen tautomerization
process results in an asymmetric melamine tautomer, which in turn leads to a significant rectifying effect. Furthermore, by
switching on inelastic multielectron scattering processes, mechanical oscillations of an N-H bond between two configurations
of the asymmetric tautomer can be triggered with tuneable frequency. Collectively, this designed molecule exhibits rectifying
and switching functions simultaneously over a wide range of external voltage.
Co-reporter:X. Y. Feng, Zhenyu Li and Jinlong Yang
The Journal of Physical Chemistry C 2009 Volume 113(Issue 52) pp:21911-21914
Publication Date(Web):December 7, 2009
DOI:10.1021/jp908347s
Using butane molecular wire as an example, based on density functional theory and the nonequilibrium Green’s function technique, we study the effect of anchoring groups on the transport properties of the corresponding molecular junctions. Consistent with available experimental data, we observe a conductance increase from amine to sulfide and phosphide anchoring groups. This behavior can be understood with the tunneling barrier model, where the p orbital energy of N, S, or P determines the energy of the highest occupied molecular orbital and thus the barrier height. Our results demonstrate the critical role of anchoring group chemistry in molecular electronics.
Co-reporter:ZhenYu Li;Jing Huang;QunXiang Li
Science China Chemistry 2008 Volume 51( Issue 12) pp:1159-1165
Publication Date(Web):2008 December
DOI:10.1007/s11426-008-0134-0
Diblock oligomers are widely used in molecular electronics. Based on fully self-consistent nonequilibrium Green’s function method and density functional theory, we study the electron transport properties of the molecular junction with a dipyrimidinyl-diphenyl (PMPH) diblock molecule sandwiched between two gold electrodes. Effects of different kinds of molecule-electrode anchoring geometry and protonation of the PMPH molecule are studied. Protonation leads to both conductance and rectification enhancements. However, the experimentally observed rectifying direction inversion is not found in our calculation. The preferential current direction is always from the pyrimidinyl to the phenyl side. Our calculations indicate that the protonation of the molecular wire is not the only reason of the rectification inversion.
Co-reporter:Zhenpeng Hu, Lan Chen, Aidi Zhao, Zhenyu Li, Bing Wang, Jinlong Yang and J. G. Hou
The Journal of Physical Chemistry C 2008 Volume 112(Issue 40) pp:15603-15606
Publication Date(Web):2017-2-22
DOI:10.1021/jp8065508
A tungsten tip and an iron-coated tungsten tip were used to investigate cobalt phthalocyanine molecules absorbed on a Au(111) surface. Similar STM images but different STS curves were obtained above the central part of the molecules. Theoretical analysis points out that the delocalized orbital of ligands hybridized with the Au surface at 0.4 eV below Fermi level can be detected and enhanced with an iron-coated tungsten tip due to the extended spatial distribution of the frontier orbital in the tip. As the spatial distribution of the frontier orbital in the tungsten tip is localized, the hybrid state cannot be detected above the central part of the molecule. These results indicate that the appropriateness of selection and preparation of the STM tip can probe richer chemistry and physics on surfaces.
Co-reporter:Xiurong Zhang, Xunlei Ding, Qiang Fu, Jinlong Yang
Journal of Molecular Structure: THEOCHEM 2008 Volume 867(1–3) pp:17-21
Publication Date(Web):30 October 2008
DOI:10.1016/j.theochem.2008.07.010
The adsorption properties of N2 molecules on anionic, cationic, and neutral Wn clusters (n = 1 – 5) are studied using the density functional theory with the generalized gradient approximation and with the hybrid functional. Adsorption energies accompanying charge population and vibrational analysis are used to characterize the adsorption properties of N2 on Wn clusters with different sizes and charge states. Our calculations show that all the W clusters can adsorb one N2 molecule with adsorption energy about 0.29–1.72 eV at B3LYP level, and 0.35–2.05 eV at PW91 level, by forming a linear or quasi-linear structure W–N–N.
Co-reporter:Zhenpeng Hu, Bin Li, Aidi Zhao, Jinlong Yang and J. G. Hou
The Journal of Physical Chemistry C 2008 Volume 112(Issue 35) pp:13650-13655
Publication Date(Web):2017-2-22
DOI:10.1021/jp8043048
A first-principles study is performed to explore the electronic and magnetic properties of several 3d transition metal phthalocyanines (including MnPc, FePc, NiPc, and CuPc) adsorbed on a Au(111) surface. Our results show that the most favorite adsorption site is the top site for MnPc molecule whereas it is the hcp site for other molecules. The electronic structures of MnPc and FePc change obviously when they are adsorbed onto the Au(111) surface, while those of NiPc and CuPc change slightly near the Fermi level due to the weak molecule−surface interactions. By analyzing the properties of d orbitals at the spatial and energy scales, we have discussed the possible Kondo effect related to these metal phthalocyanines adsorbed on the Au(111) surface.
Co-reporter:Shuanglin Hu ; Zhenyu Li ; X. C. Zeng
The Journal of Physical Chemistry C 2008 Volume 112(Issue 22) pp:8424-8428
Publication Date(Web):May 8, 2008
DOI:10.1021/jp800096s
We investigate the electronic structures of some defective boron nitride nanotubes (BNNTs) under transverse electric fields within density-functional theory. (16,0) BNNTs with antisite, carbon substitution, single vacancy, and Stone-Wales 5775 defects are studied. Under transverse electric fields, the band gaps of the defective BNNTs are reduced, similar to the pristine ones. The energy levels of the defect states vary with the transverse electric field directions, due to the different electrostatic potential shift at the defect sites induced by the electric fields. Therefore, besides electronic structure and optical property engineering, the transverse electric field can be used to identify the defect positions in BNNTs.
Co-reporter:Aidi Zhao;Qunxiang Li;Lan Chen;Hongjun Xiang;Weihua Wang;Shuan Pan;Bing Wang;Xudong Xiao;J. G. Hou;Qingshi Zhu
Science 2005 Vol 309(5740) pp:1542-1544
Publication Date(Web):02 Sep 2005
DOI:10.1126/science.1113449
Abstract
We report that the Kondo effect exerted by a magnetic ion depends on its chemical environment. A cobalt phthalocyanine molecule adsorbed on an Au(111) surface exhibited no Kondo effect. Cutting away eight hydrogen atoms from the molecule with voltage pulses from a scanning tunneling microscope tip allowed the four orbitals of this molecule to chemically bond to the gold substrate. The localized spin was recovered in this artificial molecular structure, and a clear Kondo resonance was observed near the Fermi surface. We attribute the high Kondo temperature (more than 200 kelvin) to the small on-site Coulomb repulsion and the large half-width of the hybridized d-level.
Co-reporter:Qunxiang Li, Xiaojun Wu, Jing Huang, Jinlong Yang
Ultramicroscopy 2005 Volume 105(1–4) pp:293-298
Publication Date(Web):November 2005
DOI:10.1016/j.ultramic.2005.06.052
The electronic transport properties of a single 4,4′-bipyridine molecule sandwiched between two gold electrodes are studied by using first-principles non-equilibrium Green's function method. The theoretical results show that the relative position of the lowest unoccupied molecular orbital lies close to the Fermi level, and shifts away by applying voltage bias. The transmission of the molecular junction is almost contributed by a single conductance channel at small bias. The conductance behavior of the 4,4′-bipyridine junction is metallic. The current does not change significantly by varying the distance of Au–N slightly and is found to be linear at small bias. Theoretical results reproduce the main features of the experimental current–voltage characteristics.
Co-reporter:Xiurong Zhang, Xunlei Ding, Bing Dai, Jinlong Yang
Journal of Molecular Structure: THEOCHEM 2005 Volume 757(1–3) pp:113-118
Publication Date(Web):30 December 2005
DOI:10.1016/j.theochem.2005.09.021
Density functional theory (DFT) calculations are performed to study small Wn (n=2–4) clusters in their neutral and anionic states. Equilibrium geometries, electronic structures, total atomization energies, dissociation energies and detachment energies are determined at B3LYP level. Time-dependent DFT is used to calculate the low-lying excited states of Wn (n=2–4). Theoretical assignments for the features in the experimental photoelectron spectra are given. All results obtained are in good agreement with available experimental data.
Co-reporter:Zhenyu Li Dr.;J. G. Hou Dr.;Qingshi Zhu
Chemistry - A European Journal 2004 Volume 10(Issue 7) pp:
Publication Date(Web):29 JAN 2004
DOI:10.1002/chem.200305315
Inorganic electrides are a novel kind of ionic compounds in which the anions are electrons confined in a complex array of cavities or channels and the cations are nanoscale arrays of alkali metal ions that provide charge balance. In electrides the donated electron behaves like a low-density correlated electron gas, whereby the dimensionality of the electron gas and its electronic and magnetic properties are determined by the topology of the cavities in the host matrix. Unlike traditional electrides, in which alkali cations are encapsulated within an organic cage, inorganic electrides are thermally stable. The current inorganic electrides based on alkali metal loaded zeolites can be designed as useful reduced-dimensionality materials. Inorganic electrides are powerful reducing agents, and they are able to reduce small aromatic molecules to the radical anions within the channels of the zeolite.
Co-reporter:Zhenyu Li Dr. Dr.;J. G. Hou Dr.;Qingshi Zhu Dr.
Angewandte Chemie International Edition 2004 Volume 43(Issue 47) pp:
Publication Date(Web):1 DEC 2004
DOI:10.1002/anie.200461200
Yes or no? Mayenite without the clathrated oxygen can be classified as an inorganic electride based on combined charge-density (see picture, A) and electron-localization-function (ELF) analysis (B). Ionic chemical bonds are found to form between extra electrons and the positively charged crystal framework in this material.
Co-reporter:Zhenyu Li Dr. Dr.;J. G. Hou Dr.;Qingshi Zhu Dr.
Angewandte Chemie 2004 Volume 116(Issue 47) pp:
Publication Date(Web):1 DEC 2004
DOI:10.1002/ange.200461200
Ja oder Nein? Mayenit ohne eingeschlossenen Sauerstoff kann auf der Grundlage einer Kombination aus Ladungsdichte- (A im Bild) und Elektronenlokalisierungsfunktion(ELF)-Analyse (B) als anorganisches Elektrid klassifiziert werden. Zwischen den zusätzlichen Elektronen und dem positiv geladenen Kristallgerüst dieses Materials ließen sich ionische chemische Bindungen nachweisen.
Co-reporter:Bing Dai, Kaiming Deng, Jinlong Yang
Chemical Physics Letters 2002 Volume 364(1–2) pp:188-195
Publication Date(Web):23 September 2002
DOI:10.1016/S0009-2614(02)01330-1
Density functional theory (DFT) calculations are performed to study the Y4O molecule in its neutral, anionic, and cationic states. The equilibrium geometries of Y4O, Y4O−, and Y4O+ are trigonal bi-pyramids. The ground states of Y4O, Y4O−, and Y4O+ are triplet (), doublet (), and doublet (), respectively. Time-dependent DFT is used to calculate the excited states. A theoretical assignment for the features in the experimental photoelectron spectrum is given. All results obtained are in good agreement with the available experimental data.
Co-reporter:Kun Qian, Wenhua Zhang, Huaxing Sun, Jun Fang, Bo He, Yunsheng Ma, Zhiquan Jiang, Shiqiang Wei, Jinlong Yang, Weixin Huang
Journal of Catalysis (3 January 2011) Volume 277(Issue 1) pp:95-103
Publication Date(Web):3 January 2011
DOI:10.1016/j.jcat.2010.10.016
The NaOH additive substantially enhances the catalytic activity of Au/SiO2 catalyst inert in catalyzing CO oxidation at temperatures below 150 °C, and Au/NaOH/SiO2 catalyst with a NaOH:Au atomic ratio of 6 is active at room temperature. Both the particle size distribution and the electronic structure of Au nanoparticles were found to be similar in Au/SiO2 and Au/NaOH/SiO2 catalysts, unambiguously proving that hydroxyls on “inert” Au nanoparticles can induce the activation of O2 for CO oxidation at room temperature. The accompanying density functional theory (DFT) calculation results reveal the determining role of COOH(a) in hydroxyls-induced activation of O2 on the Au(1 1 1) surface. Our results successfully elucidate the influence of hydroxyls on the intrinsic activity of Au nanoparticles in CO oxidation, providing novel insights into the role of hydroxyls in the catalytic activity of Au catalysts and advancing the fundamental understanding of oxidation reactions catalyzed by Au catalysts.Graphical abstractHydroxyls can induce the activation of molecular oxygen on “inert” Au nanoparticles for low-temperature CO oxidation.Download high-res image (138KB)Download full-size imageResearch highlights► Hydroxyls on “inert” Au nanoparticles induce the activation of O2 to catalyze CO oxidation at room temperature. ► Chemisorbed COOH species plays the determining role in the hydroxyls-induced activation of O2 on the “inert” Au surface. ► Chemisorbed di-CO3H species on the Au surface is the poison in low-temperature CO oxidation. ► The accumulation of chemisorbed di-CO3H species on the Au surface is thermodynamically controlled.
Co-reporter:Shengjun Liu, Wei Hu, Jayanta Kr. Nath, Jing Tong, Xudong Hou, Wenlong Liu, Jinlong Yang and Bo Liu
Dalton Transactions 2017 - vol. 46(Issue 3) pp:NaN684-684
Publication Date(Web):2016/11/28
DOI:10.1039/C6DT04261A
We present a novel strategy to improve the stability and optical absorption of polyoxotitanates (POTs) via concurrently fully carboxylate-coordinating and hetero-metal-doping, and illustrate the strategy by an indium doped hetero-polyoxotitanate (h-POT) of a [Ti12In6O18(OOCC6H5)30] (POTi12In6) nanocluster, which possesses ultrahigh stability in both acid and base aqueous solutions. The nanocluster structurally features a core–shell double wheel structure and a polar cavity. Both experiments and theoretical calculations confirm the semiconductive properties of the nanocluster. Under visible irradiation the POTi12In6 nanocluster can produce pronounced photocurrent, and reactive oxygen species for pollutant degradation. Without using any cocatalyst, POTi12In6 exhibits important visible-light-driven photocatalytic activity for H2 evolution in an aqueous system. This work could render a polyoxotitanate as a new type of visible-photoactive photocatalyst.
Co-reporter:Jun Dai, Zhenyu Li and Jinlong Yang
Physical Chemistry Chemical Physics 2010 - vol. 12(Issue 39) pp:NaN12422-12422
Publication Date(Web):2010/08/31
DOI:10.1039/C0CP00735H
Based on first-principles equation-of-state and lattice dynamics calculations, a new boron allotrope with K4 structure is proposed, which gives the first example of a three-dimensional all sp2 network.
Co-reporter:Haiqing Liang, Zhenyu Li and Jinlong Yang
Physical Chemistry Chemical Physics 2010 - vol. 12(Issue 17) pp:NaN4434-4434
Publication Date(Web):2010/02/24
DOI:10.1039/B923012B
All-atomistic molecular dynamics simulations with explicit water solution are performed to investigate the interaction between single-stranded DNA (ssDNA) molecules and chiral N-isobutyryl-cysteine (NIBC) molecule coated Au surfaces. Different contributions to the force exerted on ssDNA are analyzed. It turns out that the experimentally observed stereospecific adsorption behavior of ssDNA on D/L-NIBC self-assembled monolayer surface mainly originates from the interaction between the dipole moment of NIBC and the negative charge carried by ssDNA.
Co-reporter:Xingxing Li and Jinlong Yang
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 38) pp:NaN15801-15801
Publication Date(Web):2013/08/07
DOI:10.1039/C3CP52623B
In spintronics, both the charge and spin of the electrons are exploited for information processing. Developing simple methods to manipulate and detect the carriers' spin orientation is among the key issues for spintronics applications. Electrical field has the advantage that it can be easily applied locally in contrast with a conventionally used magnetic field, thus it is more convenient and efficient. Bipolar magnetic materials, characterized by a unique electronic structure where the valence band and conduction band possess opposite spin polarization around the Fermi level, serve as a new class of materials for spintronics through which electrical control of spin-polarization direction can be realized simply by applying a gate voltage. This article reviews a range of materials that have bipolar spin polarization, including bipolar half metals and bipolar magnetic semiconductors, and their potential applications for creating, manipulating, and detecting spin-polarized carriers. These materials provide a promising future for electrically controllable spintronics devices.
Co-reporter:Yingdi Jin, Xingxing Li and Jinlong Yang
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 28) pp:NaN18669-18669
Publication Date(Web):2015/06/16
DOI:10.1039/C5CP02813B
A serial of two-dimensional titanium and zirconium trichalcogenides nanosheets MX3 (M = Ti, Zr; X = S, Se, Te) were investigated based on first-principles calculations. The evaluated low cleavage energy indicates that stable two-dimensional monolayers can be exfoliated from their bulk crystals in the experiment. Electronic studies reveal the very rich electronic properties in these monolayers, including metallic TiTe3 and ZrTe3, direct band gap semiconductor, TiS3, and indirect band gap semiconductors, TiSe3, ZrS3 and ZrSe3. The band gaps of all the semiconductors are between 0.57 and 1.90 eV, which implies their potential applications in nano-electronics. In addition, the calculated effective masses demonstrate the highly anisotropic conduction properties for all the semiconductors. Optically, TiS3 and TiSe3 monolayers exhibit good light absorption in the visible and near-infrared region, respectively, indicating their potential applications in optical devices. In particular, the highly anisotropic optical absorption of the TiS3 monolayer suggests it could be used in designing nano-optical waveguide polarizers.
Co-reporter:Xinxing Wu, Ruiqi Zhang and Jinlong Yang
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 28) pp:NaN19419-19419
Publication Date(Web):2016/06/23
DOI:10.1039/C6CP03183H
In this article, we studied the thermodynamic and electronic properties of Mg and MgH2 nanowires with different diameters, and elucidated why MgH2 nanowires are good hydrogen storage materials through first-principles calculations. Previous experiments have shown that the orientation relationship between Mg and MgH2 nanowires is the Mg[0001] direction parallel to the MgH2[110] direction. In our calculations, Mg nanowires oriented along the [0001] direction and MgH2 nanowires oriented along the [110] direction were built from bulk Mg and MgH2 crystals, respectively. We found that as the diameters of Mg and MgH2 nanowires decrease, Mg and MgH2 nanowires become more unstable, and the hydrogen desorption energies and temperatures of MgH2 nanowires decrease. That is, the thinner the MgH2 nanowires get, the more dramatically hydrogen desorption temperatures (Td) will decrease. Meanwhile, we also found that when the diameters of MgH2 nanowires are larger than 1.94 nm, the Td almost maintain the same value at about 440 K, only about 40 K lower than that of bulk MgH2 crystal; if the diameters are less than 1.94 nm, the Td reduce very quickly. In particular, compared with bulk MgH2 crystal, the Td of the thinnest MgH2 nanowire with a diameter of 0.63 nm can be reduced by 164 K. In addition, the electronic structure calculations showed that Mg nanowires are metals, while MgH2 nanowires are semiconductors. In particular, our results showed that the electronic structures of MgH2 nanowires are influenced by the surface effect and quantum size effect. That is to say, the band gaps of MgH2 nanowires are controlled by surface electronic states and the size of MgH2 nanowires.
Co-reporter:Xingxing Li, Xiaojun Wu and Jinlong Yang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 43) pp:NaN7201-7201
Publication Date(Web):2013/09/12
DOI:10.1039/C3TC31514B
The control of spin without magnetic field is one of the challenges in developing spintronic devices. In an attempt to solve this problem, we proposed a novel hypothetical La(Mn0.5Zn0.5)AsO alloy from two experimentally synthesized rare earth element transition metal arsenide oxides, i.e. LaMnAsO and LaZnAsO. On the basis of the first-principles calculations with strong-correlated correction, we found that the La(Mn0.5Zn0.5)AsO alloy is an antiferromagnetic semiconductor at the ground state, and a bipolar magnetic semiconductor at the ferromagnetic state. Both electron and hole doping in the La(Mn0.5Zn0.5)AsO alloy induce the transition from antiferromagnetic to ferromagnetic, as well as semiconductor to half metal. In particular, the spin-polarization direction is switchable depending on the doped carrier type. As carrier doping can be realized easily in experiment by applying a gate voltage, the La(Mn0.5Zn0.5)AsO alloy stands as a promising spintronic material to generate and control the spin-polarized carriers with an electric field.
Co-reporter:Xingxing Li and Jinlong Yang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 34) pp:NaN7076-7076
Publication Date(Web):2014/07/04
DOI:10.1039/C4TC01193G
Two-dimensional (2D) ferromagnetic semiconductors hold a great potential for nano-electronic and spintronic devices. Nevertheless, their experimental realization remains a big challenge. Through first-principles calculations, we here demonstrate the possibility of realizing 2D ferromagnetic semiconductors simply by exfoliating layered crystals of CrXTe3 (X = Si, Ge). The exfoliation of CrXTe3 is feasible due to its small cleavage energy, and CrXTe3 nanosheets can form free-standing membranes. Interestingly, upon exfoliation, the ferromagnetism and semiconducting character are well preserved from bulk to the nanosheet form. Long-range ferromagnetic order with a magnetization of 3 μB per Cr atom is confirmed in 2D CrXTe3 from classical Heisenberg model Monte Carlo simulations. Both bulk and 2D CrXTe3 are indirect-gap semiconductors with their valence and conduction bands fully spin-polarized in the same direction, which is promising for spin-polarized carrier injection and detection. We further demonstrate the tunability and enrichment of the properties of CrXTe3 nanosheets via external operations. Under moderate tensile strain, the 2D ferromagnetism can be largely enhanced. By pure electron doping or adsorbing nucleophilic molecules, CrXTe3 nanosheets become 2D half metals.
Co-reporter:Haidi Wang, Xingxing Li, Zhao Liu and Jinlong Yang
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 3) pp:NaN2408-2408
Publication Date(Web):2016/12/19
DOI:10.1039/C6CP07944J
Based on the crystal structure prediction, we propose a new allotrope of phosphorene, ψ-phosphorene (ψ-P), with a porous structure, which is both thermally and dynamically stable in comparison with the previously reported allotropes. Due to its unique atom configuration, ψ-P has highly orientation-dependent mechanical properties and excellent flexibility. Calculations using the HSE functional predict that ψ-P is semiconducting with an indirect band gap of 1.57 eV and possesses anisotropic transport properties. Particularly, the electron mobility along the x-direction is up to 1.3 × 104 cm2 V−1 s−1, which is comparable with that of black phosphorene. Considering its intrinsic porous structure, the performance of monolayer ψ-P as a gas purification membrane was investigated. The calculation demonstrates that ψ-P could be used for hydrogen purification from the mixture of CH4, CO2, N2, CO, and H2 with high selectivity. Furthermore, combining a suitable band gap with high carrier mobility, a MoSe2/ψ-P van der Waals heterojunction is predicted to be a good solar cell material, whose power conversion efficiency is estimated up to 20.26%. Finally, we demonstrated that the Au(110) surface could be a suitable substrate for the synthesis of ψ-P.
Co-reporter:Cen-Feng Fu, Qiquan Luo, Xingxing Li and Jinlong Yang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 48) pp:NaN18898-18898
Publication Date(Web):2016/11/14
DOI:10.1039/C6TA08769H
The Z-scheme is an efficient route for hydrogen production from photocatalytic water splitting; however, there is no theoretical design for two-dimensional (2D) systems. In the present work, the 2D van der Waals (vdW) MoSe2/graphene/HfS2 and MoSe2/N-doped graphene/HfS2 nanocomposites are proposed to be promising candidates for Z-scheme photocatalysts and verified by density functional theory calculations. The fine control of the n-type doping on graphene can enhance the efficiency of solar energy utilization. Furthermore, the 2D vdW MoSe2/HfS2 nanocomposite is shown to be a direct Z-scheme system for photocatalytic water splitting without redox mediators, which is more easily synthesized in experiment.
Co-reporter:Jiahui Zhang, Xingxing Li and Jinlong Yang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 11) pp:NaN2567-2567
Publication Date(Web):2015/01/27
DOI:10.1039/C4TC02587C
The direct control of carrier spin by an electric field at room temperature is one of the most important challenges in the field of spintronics. For this purpose, we here propose a quaternary Heusler alloy FeVTiSi. Based on first principles calculations, the FeVTiSi alloy is found to be an intrinsic bipolar magnetic semiconductor in which the valence band and conduction band approach the Fermi level through opposite spin channels. Thus the FeVTiSi alloy can conduct completely spin-polarized currents with a tunable spin-polarization direction simply by applying a gate voltage. Furthermore, by Monte Carlo simulations based on the classical Heisenberg Hamiltonian, the Curie temperature of the FeVTiSi alloy is predicted to be well above the room temperature. The bipolar magnetic semiconducting character and the room temperature magnetic ordering endow the FeVTiSi alloy with great potential for developing electrically controllable spintronic devices working at room temperature.
Co-reporter:Wei Hu, Tian Wang and Jinlong Yang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 18) pp:NaN4761-4761
Publication Date(Web):2015/04/07
DOI:10.1039/C5TC00759C
Combining the electronic structures of two-dimensional monolayers in ultrathin hybrid nanocomposites is expected to display new properties beyond their single components. Here, first-principles calculations are performed to study the structural and electronic properties of hybrid graphene and phosphorene nanocomposites. Our calculations show that weak van der Waals interactions dominate between graphene and phosphorene with their intrinsic electronic properties preserved. Furthermore, we found that as the interfacial distance decreases, the Dirac point of graphene moves from the conduction band to the valence band of phosphorene in hybrid graphene and phosphorene nanocomposites, inducing a transition from an n-type Schottky contact to a p-type Schottky contact at the graphene/phosphorene interface.
Co-reporter:Wei Hu, Tian Wang, Ruiqi Zhang and Jinlong Yang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 9) pp:NaN1781-1781
Publication Date(Web):2016/02/02
DOI:10.1039/C6TC00207B
Combining the electronic structures of graphene and molybdenum disulphide (MoS2) monolayers in two-dimensional (2D) ultrathin graphene and MoS2 heterostructures has been realized experimentally for novel nanoelectronic devices. Here, first-principles calculations are performed to investigate the effects of interlayer coupling and the electric field on the electronic structures of graphene and MoS2 heterobilayers (G/MoS2 HBLs). We find that an n-type Schottky contact is formed at the G/MoS2 interface with a small Schottky barrier of 0.23 eV, because the work function of graphene is close to the electron affinity of MoS2. Furthermore, increasing the interfacial distances between graphene and MoS2 can reduce the n-type Schottky barriers at the G/MoS2 interface. But applying the electric field perpendicular to the G/MoS2 HBL can not only control the Schottky barriers but also the Schottky contacts (n-type and p-type) and Ohmic contacts (n-type) at the G/MoS2 interface. Tunable p-type doping in graphene is easily achieved at negative electric fields because electrons can easily transfer from the Dirac point of graphene to the conduction band of MoS2.
Co-reporter:Wei Hu, Nan Xia, Xiaojun Wu, Zhenyu Li and Jinlong Yang
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 15) pp:NaN6962-6962
Publication Date(Web):2014/01/23
DOI:10.1039/C3CP55250K
On the basis of first-principles calculations, we demonstrate the potential application of silicene as a highly sensitive molecule sensor for NH3, NO, and NO2 molecules. NH3, NO and NO2 molecules chemically adsorb on silicene via strong chemical bonds. With distinct charge transfer from silicene to molecules, silicene and chemisorbed molecules form charge-transfer complexes. The adsorption energy and charge transfer in NO2-adsorbed silicene are larger than those of NH3- and NO-adsorbed silicones. Depending on the adsorbate types and concentrations, the silicene-based charge-transfer complexes exhibit versatile electronic properties with tunable band gap opening at the Dirac point of silicene. The calculated charge carrier concentrations of NO2-chemisorbed silicene are 3 orders of magnitude larger than intrinsic charge carrier concentration of graphene at room temperature. The results present a great potential of silicene for application as a highly sensitive molecule sensor.
Co-reporter:Wenqi Xia, Wei Hu, Zhenyu Li and Jinlong Yang
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 41) pp:NaN22498-22498
Publication Date(Web):2014/08/29
DOI:10.1039/C4CP03292F
The adsorption of common gas molecules (N2, CO, CO2, H2O, NH3, NO, NO2, and O2) on germanene is studied with density functional theory. The results show that N2, CO, CO2, and H2O are physisorbed on germanene via van der Waals interactions, while NH3, NO, NO2, and O2 are chemisorbed on germanene via strong covalent (Ge–N or Ge–O) bonds. The chemisorption of gas molecules on germanene opens a band gap at the Dirac point of germanene. NO2 chemisorption on germanene shows strong hole doping in germanene. O2 is easily dissociated on germanene at room temperature. Different adsorption behaviors of common gas molecules on germanene provide a feasible way to exploit chemically modified germanene.
Co-reporter:Long Yuan, Zhenyu Li and Jinlong Yang
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 2) pp:NaN503-503
Publication Date(Web):2012/11/02
DOI:10.1039/C2CP43129G
Recently, a new kind of spintronics material, bipolar magnetic semiconductors (BMS), has been proposed. The spin polarization of BMS can be conveniently controlled by a gate voltage, which makes it very attractive in device engineering. Now, the main challenge is finding more BMS materials. In this article, we propose that hydrogenated wurtzite SiC nanofilm is a two-dimensional BMS material. Its BMS character is very robust under the effect of strain, substrate or even a strong electric field. The proposed two-dimensional BMS material paves the way to use this promising new material in an integrated circuit.
Co-reporter:Long Yuan, Zhenyu Li, Jinlong Yang and Jian Guo Hou
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 22) pp:NaN8184-8184
Publication Date(Web):2012/04/16
DOI:10.1039/C2CP40635G
In this article, based on first-principles calculations, we systematically study functionalization induced diamondization of graphene bilayer and graphene–BN hybrid bilayer. With single-side functionalization, the diamondized structures are magnetic semiconductors. Interestingly, if both sides of the bilayer are functionalized, diamondization becomes spontaneous without a barrier. On the other hand, when the bottom layer of the bilayer graphene is replaced by a single hexagonal BN layer, the diamondized structure becomes a nonmagnetic metal. The tunable electronic and magnetic properties pave new avenues to construct graphene-based electronics and spintronics devices.
Co-reporter:Yu Zhao, Xiaojun Wu, Jinlong Yang and Xiao Cheng Zeng
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 16) pp:NaN5550-5550
Publication Date(Web):2012/02/17
DOI:10.1039/C2CP40081B
Two-dimensional (2D) hexagonal boron-nitride oxide (h-BNO) is a structural analogue of graphene oxide. Motivated by recent experimental studies of graphene oxide, we have investigated the chemical oxidation of 2D h-BN sheet and the associated electronic properties of h-BNO. Particular emphasis has been placed on the most favorable site(s) for chemisorption of atomic oxygen, and on the migration barrier for an oxygen atom hopping to the top, bridge, or hollow site on the h-BN surface, as well as the most likely pathway for the dissociation of an oxygen molecule on the h-BN surface. We find that when an oxygen atom migrates on the h-BN surface, it is most likely to be over an N atom, but confined by three neighbor B atoms (forming a triangle ring). In general, chemisorption of an oxygen atom will stretch the B–N bond, and under certain conditions may even break the B–N bond. Depending on the initial location of the first chemisorbed O atom, subsequent oxidation tends to form an O domain or O chain on the h-BN sheet. The latter may lead to a synthetic strategy for the unzipping of the h-BN sheet along a zigzag direction. A better understanding of the oxidation of h-BN sheet has important implications for tailoring the properties of the h-BN sheet for applications.
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