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Now showing items 1 - 16 of 86

  • Review of borophene and its potential applications

    Wang, Zhi-Qiang   Lu, Tie-Yu   Wang, Hui-Qiong   Feng, Yuan Ping   Zheng, Jin-Cheng  

    Since two-dimensional boron sheet (borophene) synthesized on Ag substrates in 2015, research on borophene has grown fast in the fields of condensed matter physics, chemistry, material science, and nanotechnology. Due to the unique physical and chemical properties, borophene has various potential applications. In this review, we summarize the progress on borophene with a particular emphasis on the recent advances. First, we introduce the phases of borophene by experimental synthesis and theoretical predictions. Then, the physical and chemical properties, such as mechanical, thermal, electronic, optical and superconducting properties are summarized. We also discuss in detail the utilization of the borophene for wide ranges of potential application among the alkali metal ion batteries, Li-S batteries, hydrogen storage, supercapacitor, sensor and catalytic in hydrogen evolution, oxygen reduction, oxygen evolution, and CO2 electroreduction reaction. Finally, the challenges and outlooks in this promising field are featured on the basis of its current development.
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  • Crease -induced targeted cutting and folding of graphene origami

    Wei, Ning   Chen, Yang   Zhang, Yingyan   Zheng, Jin-Cheng   Zhao, Junhua   Mai, Yiu-Wing  

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  • Origin of metallicity in 2D multilayer nickel bis(dithiolene) sheets

    Li, Suchun   Lu, Tie-Yu   Zheng, Jin-Cheng   Yang, Shuo-Wang   Wang, Jian-Sheng   Wu, Gang  

    We systematically studied the electronic structures of two-dimensional (2D) multilayered nickel bis(dithiolene) sheets using first-principles calculations. The monolayer is semiconducting, while all multilayers become good metals. We reveal that the metallicity mainly arises from covalent-like interlayer interaction between the 3pz orbitals of S atoms in adjacent layers. We show that such interlayer orbital hybridization widely exists in many 2D layered materials involving extensively out-of-plane orbitals. This interlayer orbital hybridization greatly enriches the physical properties of this class of 2D layered materials compared to pure van der Waals 2D layered materials. More importantly, we demonstrate that these properties are easily tunable by controlling the interlayer distance or stacking, making them very promising in meeting the desired requirements in practical applications.
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  • Phylogeny and evolution of the cholesterol transporter NPC1 in insects

    Zheng, Jin-Cheng   Sun, Shao-Lei   Yue, Xiao-Rong   Liu, Tong-Xian   Jing, Xiangfeng  

    Sterols are essential nutrients for eukaryotes. Insects are obligate sterol auxotrophs and must acquire this key nutrient from their diets. The digestive tract is the organ for absorbing nutrients as well as sterols from food. In mice, the Niemann-Pick type Cl Like 1 (NPC1L1) gene is highly expressed in the intestine and is critical for cholesterol absorption. In contrast, the molecular mechanisms for the absorption of dietary sterols in insects have not been well studied. We annotated NPC1 genes in 39 insects from 10 orders using available genomic and transcriptomic information and inferred phylogenetic relationships. Insect NPC1 genes were grouped into two sister-clades, NPCla and NPC1b, suggesting a likely duplication in the ancestor of insects. The former exhibited weaker gut-biased expression or a complete lack of tissue-biased expression, depending on the species, while the latter was highly enriched in the gut of three lepidopteran species. This result is similar to previous findings in Drosophila melanogaster. In insects, NPCla accumulated non-synonymous substitutions at a lower rate than NPC1b. This pattern was consistent across orders, indicating that NPCla evolved under stronger molecular constraint than NPCIb.
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  • : The Origin of Second-Order Modulation

    Deng, Shiqing   Wu, Lijun   Cheng, Hao   Zheng, Jin-Cheng   Cheng, Shaobo   Li, Jun   Wang, Wenbin   Shen, Jian   Tao, Jing   Zhu, Jing   Zhu, Yimei  

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  • Review of borophene and its potential applications

    Wang, Zhi-Qiang   Lü, Tie-Yu   Wang, Hui-Qiong   Feng, Yuan Ping   Zheng, Jin-Cheng  

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  • Excited State Biexcitons in Atomically Thin MoSe2

    Pei, Jiajie   Yang, Jiong   Wang, Xibin   Wang, Fan   Mokkapati, Sudha   Lu, Tieyu   Zheng, Jin-Cheng   Qin, Qinghua   Neshev, Dragomir   Tan, Hark Hoe   Jagadish, Chennupati   Lu, Yuerui  

    The tightly bound biexcitons found in atomically thin semiconductors have very promising applications for optoelectronic and quantum devices. However, there is a discrepancy between theory and experiment regarding the fundamental structure of these biexcitons. Therefore, the exploration of a biexciton formation mechanism by further experiments is of great importance. Here, we successfully triggered the emission of biexcitons in atomically thin MoSe2, via the engineering of three critical parameters: dielectric screening, density of trions, and excitation power. The observed binding energy and formation dynamics of these biexcitons strongly support the model that the biexciton consists of a charge attached to a trion (excited state biexciton) instead of four spatially symmetric particles (ground state biexciton). More importantly, we found that the excited state biexcitons not only can exist at cryogenic temperatures but also can be triggered at room temperature in a freestanding bilayer MoSe2. The demonstrated capability of biexciton engineering in atomically thin MoSe2 provides a route for exploring fundamental many-body interactions and enabling device applications, such as bright entangled photon sources operating at room temperature.
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  • A super-stretchable boron nanoribbon network

    Wang, Zhi-Qiang   Cheng, Hao   Lu, Tie-Yu   Wang, Hui-Qiong   Feng, Yuan Ping   Zheng, Jin-Cheng  

    We have studied the mechanical properties of a two-dimensional (2D) boron nanoribbon network (BNRN) subjected to a uniaxial or a biaxial tensile strain using first principles calculations. The results show that the 2D BNRN is super-stretchable. The critical tensile strains of the BNRN in the chi-h1 phase along the a- and b-directions are 0.51 and 0.41, respectively, and that for the biaxial strain reaches an ultrahigh value of 0.84. By analyzing the B-B interatomic distance, coordination number and charge distribution, it is found that with increasing biaxial tensile strain, the chi-h1 BNRN undergoes two structural phase transitions, which are characterized by breaking of the B-B bonds and the partial transformation of the nanoribbon-like structures into chain-like structures. The strain-induced phase transitions significantly reduce the strain energy. We also discuss the elastic constants, Young's modulus, shear modulus, and Poisson's ratios. The super-stretchable and flexible mechanical properties of the BNRNs, together with their superior transport properties, make BNRNs useful in a wide range of applications in nanoscale electronic devices.
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  • Phylogeny and evolution of the cholesterol transporter NPC1 in insects

    Zheng, Jin-Cheng   Sun, Shao-Lei   Yue, Xiao-Rong   Liu, Tong-Xian   Jing, Xiangfeng  

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  • Regulate the polarity of phosphorene's mechanical properties by oxidation

    Lu, Tie-Yu   Feng, Hai   Zhang, Yufeng   Lu, Yuerui   Zheng, Jin-Cheng  

    How to effectively manipulate the mechanical properties of atomically thin materials, is critical and can enable many new types of devices for various applications, such as sensing, actuation, energy harvesting, and so on. Here, we propose and demonstrate a new way to regulate the polarity of phosphorene's mechanical properties by controlling the level of oxidation. Phosphorene and its low-level oxides are treated with ab initio methods in order to evaluate the influence of oxidation on the anisotropic mechanical properties of phosphorene. Our results show that the mechanical properties of phosphorene are anisotropic. For the stable configuration, the anisotropy is gradually reduced with the increase of the oxygen coverage. We have fitted the formulas of Young's (shear) modulus and Poisson's ratio of phosphorene oxide. We also investigated the mechanical properties of metastable configurations. The diagonal configuration increases the anisotropy. The horizontal configuration is very unstable and has no shear moduli. Our results demonstrate that the mechanical properties of phosphorene can be regulated by oxidation, which is useful in design of phosphorene-based mechanical and optoelectronic devices. Our general model for calculating the elastic modulus along arbitrary direction can be applied in any 2D materials. (C) 2017 Elsevier B.V. All rights reserved.
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  • Band structure engineering of borophane by first principles calculations

    Wang, Zhi-Qiang   Lu, Tie-Yu   Wang, Hui-Qiong   Feng, Yuan Ping   Zheng, Jin-Cheng  

    We exploited the band structure engineering in W-borophane, the most stable conformer of the fully hydrogenated borophene in the literature, by first principles calculations. Uniaxial strains along the a and b direction, biaxial strains, shear strains, H vacancy and B-H dimer vacancy defects have been considered. Our results show that uniaxial strains along the a, b directions and biaxial strain can not open the band gap for W-borophane. However, band gap opening can be achieved by applying shear strain. The shear strain induced band gap is 53 meV when the applied shear strain is only 0.01. The band gap increases with the increasing shear strain. When the shear strain reaches 0.12, the band gap can reach up to 538 meV. Two different exchange-correlation potentials have been used to confirm the band gap opening. The excellent dynamical stability of W-borophane under shear strain has been proved by the phonon dispersion, indicating that applying shear strain is an effective and feasible approach to open the band gap for W-borophane. In addition, the Dirac cone of W-borophane is maintained well under the uniaxial and biaxial strains. In free-state, the Dirac fermions of W-borophane possess an ultrahigh Fermi velocity (2.13 x 106 m s(-1)) which is higher than that of graphene. It is very interesting that the Fermi velocities of W-borophane can be tuned in a wide range of values by applying uniaxial and biaxial strain.
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  • High thermal conductivity of hexagonal boron nitride laminates

    Zheng, Jin-Cheng   Zhang, Liang   Kretinin, A V   Morozov, S V   Wang, Yi Bo   Wang, Tun   Li, Xiaojun   Ren, Fei   Zhang, Jingyu   Lu, Ching-Yu   Chen, Jia-Cing   Lu, Miao   Wang, Hui-Qiong   Geim, A K   Novoselov, K S  

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  • Robust Excitons and Trions in Monolayer MoTe2

    Yang, Jiong   Lu, Tieyu   Myint, Ye Win   Pei, Jiajie   Macdonald, Daniel   Zheng, Jin-Cheng   Lu, Yuerui  

    Molybdenum telluride (MoTe2) has emerged as a special member in the family of two-dimensional transition metal dichalcogenide semiconductors, owing to the strong spin orbit coupling and relatively small energy gap, which offers new applications in valleytronic and excitonic devices. Here we successfully demonstrated the electrical modulation of negatively charged (X-), neutral (X-0), and positively charged (X+) excitons in monolayer MoTe2 via photoluminescence spectroscopy. The binding energies of X+ and X- were measured to be similar to 24 and similar to 27 meV, respectively. The exciton binding energy of monolayer MoTe2 was measured to be 0.58 +/- 0.08 eV via photoluminescence excitation spectroscopy, which matches well with our calculated value of 0.64 eV.
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  • Exciton and Trion Dynamics in Bilayer MoS2

    Pei, Jiajie   Yang, Jiong   Xu, Renjing   Zeng, Yong-Hui   Myint, Ye Win   Zhang, Shuang   Zheng, Jin-Cheng   Qin, Qinghua   Wang, Xibin   Jiang, Wugui   Lu, Yuerui  

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  • Interfaces between hexagonal and cubic oxides and their structure alternatives

    Zhou, Hua   Wu, Lijun   Wang, Hui-Qiong   Zheng, Jin-Cheng   Zhang, Lihua   Kisslinger, Kim   Li, Yaping   Wang, Zhiqiang   Cheng, Hao   Ke, Shanming   Li, Yu   Kang, Junyong   Zhu, Yimei  

    Multi-layer structure of functional materials often involves the integration of different crystalline phases. The film growth orientation thus frequently exhibits a transformation, owing to multiple possibilities caused by incompatible in-plane structural symmetry. Nevertheless, the detailed mechanism of the transformation has not yet been fully explored. Here we thoroughly probe the heteroepitaxially grown hexagonal zinc oxide (ZnO) films on cubic (001)-magnesium oxide (MgO) substrates using advanced scanning transition electron microscopy, X-ray diffraction and first principles calculations, revealing two distinct interface models of (001) ZnO/(001) MgO and (100) ZnO/(001) MgO. We have found that the structure alternatives are controlled thermodynamically by the nucleation, while kinetically by the enhanced Zn adsorption and O diffusion upon the phase transformation. This work not only provides a guideline for the interface fabrication with distinct crystalline phases but also shows how polar and non-polar hexagonal ZnO films might be manipulated on the same cubic substrate.
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  • Porous carbon anchored titanium carbonitride for high-performance supercapacitor

    Yan, Hao   Wang, Jianghong   Fang, Yuan   Zhou, Muxuan   Guo, Xiaoya   Wang, Hui-Qiong   Dai, Yang   Li, Wenrong   Zheng, Jin-Cheng  

    Carbon anchored titanium carbonitride for supercapacitor electrode material was prepared by a direct semi-solid-sate carbonitridation method. The prepared sample is highly conductive and mesoporous (250 m(2) g(-1)), enabling fast electron transfer and ion transport. As a result, a high capacitance of 360 F g(-1) at 0.5 A g(-1), and an impressive capacitance retention ratio 100Ag(-1)/1 Ag-1 of 53%, as well as long cyclic capability (>10,000 cycles) can be obtained in 1 MH2SO4. The thick electrode also presents a high area capacitance up to 1.77 F cm(-2). A flexible H2SO4/PVA symmetric supercapacitor was fabricated to demonstrate its practicality. Remarkably, the supercapacitor presents high-rate performance (up to 25 kW kg(-1)) and long cyclic performance (>10,000 cycles), illustrating its potential application in flexible integrated energy storage devices. This work provides a novel insight into designing and preparing carbonitride based materials for high performance supercapacitor. (C) 2019 Elsevier Ltd. All rights reserved.
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