[Show abstract][Hide abstract] ABSTRACT: Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application.
[Show abstract][Hide abstract] ABSTRACT: As a stable allotropy of two-dimensional (2D) carbon materials, δ-graphyne has been predicted to be superior to graphene in many aspects. Using first-principles calculations, we investigated the electronic properties of carbon nanoribbons (CNRs) and nanotubes (CNTs) formed by δ-graphyne. It is found that the electronic band structures of CNRs depend on the edge structure and the ribbon width. The CNRs with zigzag edges (Z-CNRs) have spin-polarized edge states with ferromagnetic (FM) ordering along each edge and anti-ferromagnetic (AFM) ordering between two edges. The CNRs with armchair edges (A-CNRs), however, are semiconductors with the band gap oscillating with the ribbon width. For the CNTs built by rolling up δ-graphyne with different chirality, the electronic properties are closely related to the chirality of the CNTs. Armchair (n, n) CNTs are metallic while zigzag (n, 0) CNTs are semiconducting or metallic. These interesting properties are quite crucial for applications in δ-graphyne-based nanoscale devices.
Full-text · Article · Nov 2015 · Physica E Low-dimensional Systems and Nanostructures
[Show abstract][Hide abstract] ABSTRACT: Elucidating the tumorigenic mechanism of R-2-hydroxyglutarate (R-2HG) is critical for determining how NADP(+)-IDH mutations cause cancer. Here we report that R-2HG induces cancerous metabolism and apoptosis resistance through promoting hypersuccinylation. By competitive inhibition of the mitochondrial tricarboxylic acid cycle enzyme succinate dehydrogenase (SDH), R-2HG preferentially induced succinyl-CoA accumulation and hypersuccinylation in the mitochondria. IDH1 mutation-bearing glioma samples and cells were hypersuccinylated in the mitochondria. IDH1 mutation or SDH inactivation resulted in hypersuccinylation, causing respiration inhibition and inducing cancerous metabolism and mitochondrial depolarization. These mitochondrial dysfunctions induced BCL-2 accumulation at the mitochondrial membrane, leading to apoptosis resistance of hypersuccinylated cells. Relief of hypersuccinylation by overexpressing the desuccinylase SIRT5 or supplementing glycine rescued mitochondrial dysfunctions, reversed BCL-2 accumulation, and slowed the oncogenic growth of hypersuccinylated IDH1(R132C)-harboring HT1080 cells. Thus, R-2HG-induced hypersuccinylation contributes to the tumorigenicity of NADP(+)-IDH mutations, suggesting the potential of hypersuccinylation inhibition as an intervention for hypersuccinylation-related tumors.
[Show abstract][Hide abstract] ABSTRACT: An efficient membrane for helium separation from natural gas is quite crucial for cryogenic industries. However, most experimentally available membranes fail in separating helium from small molecules in natural gas, such as H2, as well as in 3He/4He isotopes separation. Using first-principles calculations, we theoretically demonstrated that the already-synthesized graphitic carbon nitride (g-C3N4) has high efficiency in helium separation from the gas molecules (H2, N2, CO and CH4) in natural gas and the noble gas molecules (Ne and Ar). The selectivity of He over H2 molecule at room temperature is calculated to be as high as 107. More interestingly, the g-C3N4 membrane can also serve as a quantum sieving membrane for 3He/4He separation with a predicted transmission ratio of 18 at 49 K, thus offers a combined means of both He and 3He isotope separation.
[Show abstract][Hide abstract] ABSTRACT: We report our first-principle's calculations on the possibility of Ca-decorated silicene sheet and zigzag silicene nanoribbons (ZSiNRs) as hydrogen storage medium. We predict that Ca atoms prefer to disperse on the silicene or at the edges of ZSiNRs without clustering, due to the strong binding between Ca and Si atoms. By adsorbing Ca atoms on the both sides of silicene, the hydrogen storage capacity can reach to 6.17 wt% (gravimetric density) with an average adsorption energy of 0.265 eV H2−1, which are quite optimial for reversible hydrogen adsorption and desorption at ambient conditions. The hydrogen storage capacity can be further improved to 8.43 wt% with the average adsorption energy in the range of 0.182–0.269 eV H2−1 in the Ca-decorated ZSiNRs. The adsorption of H2 on Ca-decorated Si nanostructures is mainly dominated by polarization and the orbital hybridizations. These findings indicate that the Ca-decorated silicene and ZSiNRs have potential application in hydrogen storage.
No preview · Article · May 2015 · physica status solidi (b)
[Show abstract][Hide abstract] ABSTRACT: It is challenging to epitaxially grow germanene on conventional semiconductor substrates. Based on first-principles calculations, we investigate the structural and electronic properties of germanene/germanane heterostructures (HTSs). The results indicate that the Dirac cone with nearly linear band dispersion of germanene is maintained in the band gap of the substrate. Remarkably, the band gaps opened in these HTSs can be effectively modulated by the external electric field and strain, and they also feature very low effective masses and high carrier mobilities. These results provide a route to design high-performance FETs operating at room temperature in nanodevices.
No preview · Article · Apr 2015 · Physical Chemistry Chemical Physics
[Show abstract][Hide abstract] ABSTRACT: Based on first-principles calculations, we study the electronic structure, magnetic properties and optical properties of transition metal (TM) doped SnO2NSs. Computational results indicate that pristine SnO2NSs is a direct gap semiconductor with nonmagnetic states. Cr, Mn, Fe atom doping can induce 2μB, −3μB and 2μB magnetic moment, respectively, while Ni atom doped SnO2NSs keeps the nonmagnetic states. More interestingly, Fe doped SnO2NSs becomes an indirect gap semiconductor, and the Cr, Mn and Ni atom doping maintain the character of direct gap semiconductor. For optical properties, the optical absorption edge shows red shift phenomenon for a TM atom (Cr, Mn, Fe or Ni) doped SnO2NSs. In addition, the tensity of absorption, reflection and refraction coefficient are enhanced significantly in the visible light region, which may be very useful for the design of solar cells, photoelectronic devices and photocatalysts.
[Show abstract][Hide abstract] ABSTRACT: The structural and electronic properties of silicene/silicane and silicene/germanene heterobilayers (HBLs) are investigated by using first-principles methods. The results show that the silicene interacts overall with silicane (germanene) with a binding energy of −50∼−70 meV per Si (Ge) atom, suggesting a weakly van der Waals interaction between silicene and substrate. A relative large bandgap with a linear band dispersion of HBLs is opened due to the sublattice symmetry broken by the intrinsic interface dipole between silicene and substrate. Remarkably, the band gap of all these HBLs can also be continually tuned modulated by adjusting the interlayer spacing and strain, independent on the stacking arrangements. Silicene is thus expected to be useful for building high-performance FET channel, which would extend its applicability to possible future nanoelectronics.
No preview · Article · Feb 2015 · Materials Chemistry and Physics
[Show abstract][Hide abstract] ABSTRACT: We performed extensively density functional theory (DFT) calculations of palladium (Pd) and gold (Au) alloy clusters adsorbed on graphene monolayer, in order to clarify the geometries and charge transfer of Pd-Au bimetal alloy clusters on graphene. It is found that Pd/Au cluster prefers to bind with graphene through Pd atoms, with strong p-d hybridization between graphene and Pd atoms. Although gold atom has an unpaired electron, the magnetic moments are mainly contributed by palladium. Compared with Pd-Au bimetal, the bond between Au atoms are stronger, therefore, gold atoms form a gold cap covering Pd cluster. Further Bader charge analysis demonstrates that Pd in alloy cluster tends to lose electrons, and the number of charge transfer increases with the introduction of graphene monolayer. Gold atoms and graphene have a synergy to to improve the electron loss on Pd atom, weakening the adsorption of anion, which is expected to prevent the poisoning on Pd nanocatalyst and enhance the catalytic reactivity of alloy clusters. However, the Au-Au coupling could weaken their ability to gain electrons from Pd significantly. So it is an important task for experimental researches to find a way to disperse gold atoms as far as possible to improve the catalytic properties of Pd/Au alloy cluster.
[Show abstract][Hide abstract] ABSTRACT: The electronic structure and optical properties of Mn and B, C, N co-doped molybdenum disulfide (MoS2) monolayers have been investigated through first-principles calculations. It is shown that the MoS2 monolayer reflects magnetism with a magnetic moment of 0.87 μB when co-doped with Mn-C. However, the systems co-doped with Mn-B and Mn-N atoms exhibit semiconducting behavior and their energy bandgaps are 1.03 and 0.81 eV, respectively. The bandgaps of the co-doped systems are smaller than those of the corresponding pristine forms, due to effective charge compensation between Mn and B (N) atoms. The optical properties of Mn-B (C, N) co-doped systems all reflect the redshift phenomenon. The absorption edge of the pure molybdenum disulfide monolayer is 0.8 eV, while the absorption edges of the Mn-B, Mn-C, and Mn-N co-doped systems become 0.45, 0.5, and 0 eV, respectively. As a potential material, MoS2 is widely used in many fields such as the production of optoelectronic devices, military devices, and civil devices.
Preview · Article · Oct 2014 · Nanoscale Research Letters
[Show abstract][Hide abstract] ABSTRACT: We perform first-principles calculations to study the geometric, energetics and electronic properties of graphene supported on BC3 monolayer. The results show that graphene interacts overall weakly with BC3 monolayer via van der Waals interaction. The energy gap of graphene can be up to ~ 0.162 eV in graphene/BC3 heterobilayers (G/BC3 HBL), which is large enough for the gap opening at room temperature. We also find that the interlayer spacing and in-plane strain can tune the band gap of G/BC3 HBLs effectively. Interestingly, the characteristics of Dirac cone with nearly linear band dispersion relation of graphene can be preserved, accompanied by a small electron effective mass, and thus the higher carrier mobility is expected yet. These findings provide a possible way to design effective FETs out of graphene on BC3 substrate.
No preview · Article · Sep 2014 · Physical Chemistry Chemical Physics
[Show abstract][Hide abstract] ABSTRACT: Structural, electronic and optical properties have been calculated for Tin dioxide nanoribbons (SnO2 NRs) with both zigzag and armchair shaped edge by first principle spin polarized total energy calculation. We find that both zigzag and armchair SnO2NR have indirect band gaps. The band gap oscillates between the maximum of 3.38eV and the minimum of 1.69eV and eventually levels off to a certain value of 2.09eV for armchair nanoribbons, while for zigzag nanoribbons, the band gap oscillates between the maximum of 2.25eV to the minimum of 2.04eV and eventually levels off to 2.18eV. Our investigation further reveals that the optical absorption capacity enhanced with increasing the ribbon width for both Z-SnO2NRs and A-SnO2NRs. More interesting, when introducing Ag impurities, the optical absorption edge shift to low energy region. These findings can be a useful tool for the design of new generation of materials with improved solar radiation absorption. Key words: Tin dioxide; nanoribbons; Ag-doped; electronic structure; optical properties.
[Show abstract][Hide abstract] ABSTRACT: We performed first-principles calculations to study the adsorption characteristics of alkali, alkali-earth, group III, and 3d transition-metal (TM) adatoms on germanene. We find that the adsorption of alkali or alkali-earth adatoms on germanene has minimal effects on geometry of germanene. The significant charge transfer from alkali adatoms to germanene leads to metallization of germanene, whereas alkali-earth adatom adsorption, whose interaction is a mixture of ionic and covalent, results in semiconducting behavior with an energy gap of 17-29 meV. For group III adatoms, they also bind germanene with mixed covalent and ionic bonding character. Adsorption characteristics of the transition metals (TMs) are rather complicated, though all TM adsorptions on germanene exhibit strong covalent bonding with germanene. The main contributions to the strong bonding are from the hybridization between the TM 3d and Ge pz orbitals. Depending on the induced-TM type, the adsorbed systems can exhibit metallic, half-metallic, or semiconducting behavior. Also, the variation trends of the dipole moment and work function with the adsorption energy across the different adatoms are discussed. These findings may provide a potential avenue to design new germanene-based devices in nanoelectronics.
No preview · Article · Jun 2014 · Physical Chemistry Chemical Physics
[Show abstract][Hide abstract] ABSTRACT: The geometric, energetic, and magnetic properties of nonmagnetic carbon (C)-doped cadmium sulfur (CdS) nanowires (NWs) are investigated based on first-principles calculations. We find that the two C dopants are most stable when they are close to each other in the surface sites, exhibiting half-metallic (HM) behavior with a net magnetic moment of 2.0 μB C−1. The magnetic interaction between the nearest and next-nearest C dopants results in a strong ferromagnetic (FM) coupling. However, the ground state of the system tends to be paramagnetic when the distance between the C dopants is larger than 6.2 Å. The HMFM order in C-doped CdS NWs, which is sensitive to the confinement of electrons in the radial direction and the curvature of the NW's surface, can be attributed to hole-mediated double exchange through the strong p-p interaction between carbon dopants. These predicted results endow CdS NWs potential applications in spintronics.
[Show abstract][Hide abstract] ABSTRACT: First-principles calculations are performed to study the structural, electronic and magnetic properties of Co-doped SnO2 nanosheets (NSs), using the generalized gradient approximation (GGA) plus Hubbard U method. We find that two Co atoms have a clustering tendency and the magnetic interactions between them exhibit a ferromagnetic (FM) coupling, while the appearance of an oxygen vacancy (VO) turns it into an antiferromagnetic (AFM) order. When the Li atom is codoped into Co-doped SnO2NS, the interactions between Co atoms are rehabilitated to FM coupling with a high Curie temperature (TC) of 850 K. The electronic structure analysis reveals that this is mainly attributed to the hole-induced double-exchange mechanism from s-d hybridizations between Li and Co, which finally activates a long-range FM coupling between two Co atoms. These findings could be very useful in nano-material design for spintronics.
[Show abstract][Hide abstract] ABSTRACT: Based on first-principles calculations, we study the effects of the chlorine atoms on electronic and magnetic properties of AlN nanosheets (NS). We find that both the bare and fully-chlorinated AlNNRs demonstrate semiconducting behavior, while the half-chlorination on surface Al sites leads to the semiconductor-ferromagnetism transition. More interestingly, the chlorination on surface Al sites in monolayer and bilayer AlNNSs demonstrates the half-metallic ferromagnetic (FM) behavior with 100% spin-polarized currents at the Fermi level, suitable for applications in spintronics at the nanoscale.
[Show abstract][Hide abstract] ABSTRACT: Motivated by experimental developments on silicene, we perform first-principles density functional study on the possibility of hydrogen storage on the Li-decorated silicene. The calculated Li-binding energy on silicene is significantly higher than the Li bulk’s cohesive energy, ruling out any possibility of cluster formations in the Li-doped silicene, which facilitate the reversible hydrogen adsorption and desorption. For one Li atom adsorbing on silicene, each Li could adsorb up to five hydrogen molecules. By adsorbing Li atoms on both sides of silicene, the hydrogen capacity can reach as high as 6.35 wt%, and the average binding energy of H2 molecules falls within the range of 0.32–0.17 eV, which is favorable for developing high-capacity hydrogen storage at room temperature. These findings may provide a potential avenue to design new hydrogen storage materials in silicene-based nanoelectronics.
No preview · Article · Oct 2013 · Journal of Nanoparticle Research
[Show abstract][Hide abstract] ABSTRACT: We performed first-principles calculations within density-functional theory to study the magnetic and optical properties of Cu-doped ZnO nanosheet (NS). We found that Cu atom prefers to substitute for Zn site and can induce a local magnetic moment of 1.00 μB per unit in ZnO NS. When two Zn atoms are substituted by two Cu dopants, they tend to form a cluster and ferromagnetic (FM) ordering becomes energetically more favorable. In addition, localized states appear within the band gap due to the introduction of Cu dopant to ZnO NS. With increasing Cu concentrations, both the imaginary part of dielectric function and the absorption spectrum exhibit a red-shift behavior, which are in good agreement with the recent experimental results. The ferromagnetic coupling can be attributed to the p–d hybridization mechanism. The intriguing properties of Cu-doped ZnO NS may be promising for designing novel multifunctional nanodevice.
No preview · Article · Sep 2013 · Physica E Low-dimensional Systems and Nanostructures
[Show abstract][Hide abstract] ABSTRACT: Mounting evidence suggests that cellular metabolites, in addition to being sources of fuel and macromolecular substrates, are actively involved in signaling and epigenetic regulation. Many metabolites, such as cyclic AMP, which regulates phosphorylation/dephosphorylation, have been identified to modulate DNA and histone methylation and protein stability. Metabolite-driven cellular regulation occurs through two distinct mechanisms: proteins allosterically bind or serve as substrates for protein signaling pathways, and metabolites covalently modify proteins to regulate their functions. Such novel protein metabolites include fumarate, succinyl-CoA, propionyl-CoA, butyryl-CoA and crontonyl-CoA. Other metabolites, including α-ketoglutarate, succinate and fumarate, regulate epigenetic processes and cell signaling via protein binding. Here, we summarize recent progress in metabolite-derived post-translational protein modification and metabolite-binding associated signaling regulation. Uncovering metabolites upstream of cell signaling and epigenetic networks permits the linkage of metabolic disorders and human diseases, and suggests that metabolite modulation may be a strategy for innovative therapeutics and disease prevention techniques.
No preview · Article · Jul 2013 · Journal of Genetics and Genomics
[Show abstract][Hide abstract] ABSTRACT: Based on first-principles simulations, the electronic and magnetic properties of bare and hydrogenated CdS nanowires (NWs) are investigated. We find that surface relaxation plays an important role for the hydrogenated CdS NWs and therefore leads to drastic changes of electronic properties. The magnetic properties can be tuned by controlling passivation on surface sites with hydrogen. While hydrogenated NWs on surface S atoms are nonmagnetic, hydrogenation on surface Cd atoms, and especially a monolayer of H on the surface, results in half-metallic properties, due to the redistributions of surface electrons in the sulfur p orbital.
No preview · Article · Jul 2013 · physica status solidi (b)