| 21. |
- Nisar, Jawad, et al.
(författare)
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Mo- and N-doped BiNbO(4) for photocatalysis applications
- 2011
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 99:5, s. 051909-
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of pure BiNbO(4) has been calculated and their electronic band positions have been aligned with respect to the water oxidation/reduction potential. The effect of cationic (Mo), anionic (N), and co-doping (Mo-N) on BiNbO(4) has been studied and discussed with respect to the standard redox potential levels. Our results show that co-doping of Mo and N in BiNbO(4) reduces the band gap up to 31.8%, thus making it a potential candidate for the photocatalysis of water for hydrogen production. The relative stability between the mono-and co-doped BiNbO(4) materials show that co-doped material is more stable and feasible in comparison to the mono-doped materials.
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| 22. |
- Nisar, Jawad, et al.
(författare)
-
Screened hybrid density functional study on Sr2Nb2O7 for visible light photocatalysis
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:18, s. 181903-
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of pure Sr2Nb2O7 and its electronic band position are being aligned with respect to the water oxidation/reduction potential level using hybrid functional (HSE06) theory. The experimental band gap (3.90 eV) of pure Sr2Nb2O7 can be reproduced (3.92 eV) using this level of theory. The cationic-anionic co-doping (Mo-N) in layered perovskite Sr2Nb2O7 structure reduces the band gap significantly, and its electronic band position is excellent for the visible-light photocatalysis. The respective cationic and anionic mono-doped systems create an occupied or unoccupied impurity states in the band gap, which can reduce the efficiency of the photocatalysis.
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| 23. |
- Nisar, Jawad, et al.
(författare)
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Semiconducting allotrope of graphene
- 2012
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 23:38, s. 385704-
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Tidskriftsartikel (refereegranskat)abstract
- From first-principles calculations, we predict a planar stable graphene allotrope composed of a periodic array of tetragonal and octagonal (4, 8) carbon rings. The stability of this sheet is predicted from the room-temperature molecular dynamics study and the electronic structure is studied using state-of-the-art calculations such as the hybrid density functional and the GW approach. Moreover, the mechanical properties of (4, 8) carbon sheet are evaluated from the Youngs modulus and intrinsic strength calculations. We find this is a stable planar semiconducting carbon sheet with a bandgap between 0.43 and 1.01eV and whose mechanical properties are as good as graphenes.
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| 24. |
- Pathak, Biswarup, et al.
(författare)
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Borane Derivatives : A New Class of Super- and Hyperhalogens
- 2011
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Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 12:13, s. 2422-2427
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Tidskriftsartikel (refereegranskat)abstract
- Super- and hyperhalogens are a class of highly electronegative species whose electron affinities far exceed those of halogen atoms and are important to the chemical industry as oxidizing agents, biocatalysts, and building blocks of salts. Using the well-known Wade-Mingos rule for describing the stability of closo-boranes B(n)H(n)(2-) and state-of-the-art theoretical methods, we show that a new class of super-and hyperhalogens, guided by this rule, can be formed by tailoring the size and composition of borane derivatives. Unlike conventional superhalogens, in which a central metal atom is surrounded by halogen atoms, the superhalogens formed according to the Wade-Mingos rule do not have to have either halogen or metal atoms. We demonstrate this by using B(12)H(13) and its isoelectronic cluster CB(11)H(12) as examples. We also show that while conventional superhalogens containing alkali atoms require at least two halogen atoms, a single borane-like moiety is sufficient to give M(B(12)H(12)) clusters (M = Li, Na, K, Rb, Cs) superhalogen properties. In addition, hyperhalogens can be formed by using the above superhalogens as building blocks. Examples include M(B(12)H(13))(2) and M(CB(11)H(12))(2) (M = Li-Cs). This finding opens the door to an untapped source of superhalogens and weakly coordinating anions with potential applications.
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| 25. |
- Pathak, Biswarup, et al.
(författare)
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Double-functionalized nanopore-embedded gold electrodes for rapid DNA sequencing
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:2, s. 023701-
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the effect of double-functionalization on gold electrodes for improving nanopore-based DNA sequencing. The functionalizing molecular probes are, respectively, capable of temporarily forming hydrogen bonds with both the nucleobase part and the phosphate group of the target DNA, thus potentially minimizing the structural fluctuations of a single-stranded DNA molecule passing between the gold electrodes. The results of our first-principles study indicate that the proposed setup yields current signals that differ by at least 1 order of magnitude for the four different nucleic acid bases, thus offering the possibility to electrically distinguish them.
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| 26. |
- Pathak, Biswarup, et al.
(författare)
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Functionalized Boranes for Hydrogen Storage
- 2012
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Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 13:1, s. 300-304
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Tidskriftsartikel (refereegranskat)abstract
- Using density functional theory, the generalized gradient approximation for the exchange-correlation potential and MollerPlesset perturbation theory we study the hydrogen uptake of Li- and Mg-doped boranes. Specifically, we calculate the structures and binding energies of hydrogen molecules sequentially attached to LiB6H7, LiB12H13, Li2B6H6, Li2B12H12, MgB6H6, and MgB12H12. Up to three H2 molecules can be bound quasi-molecularly to each of the metal cations with binding energies per H2 molecule ranging between 0.07 eV and 0.27 eV. The corresponding gravimetric densities lie in the range of 3.49 to 12 wt %, not counting the H atoms bound chemically to the B atoms.
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| 27. |
- Prasongkit, Jariyanee, et al.
(författare)
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Theoretical Study of Electronic Transport through DNA Nucleotides in a Double-Functionalized Graphene Nanogap
- 2013
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:29, s. 15421-15428
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Tidskriftsartikel (refereegranskat)abstract
- Graphene nanogaps and nanopores show potential for the purpose of electrical DNA sequencing, in particular because single-base resolution appears to be readily achievable. Here, we evaluated from first principles the advantages of a nanogap setup with functionalized graphene edges. To this end, we employed density functional theory and the non-equilibrium Green's function method to investigate the transverse conductance properties of the four nucleotides occurring in DNA when located between opposing functionalized graphene electrodes. In particular, we determined the electrical tunneling current variation as a function of the applied bias and analyzed the associated differential conductance at a voltage which appears suitable to distinguish between the four nucleotides. Intriguingly, we predict for one of the nucleotides (deoxyguanosine monophosphate) a negative differential resistance effect.
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| 28. |
- Prasongkit, Jariyanee, et al.
(författare)
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Transverse Conductance of DNA Nucleotides in a Graphene Nanogap from First Principles
- 2011
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 11:5, s. 1941-1945
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Tidskriftsartikel (refereegranskat)abstract
- The fabrication of nanopores in atomically thin graphene has recently been achieved, and translocation of DNA has been demonstrated. Taken together with an earlier proposal to use graphene nanogaps for the purpose of DNA sequencing, this approach can resolve the technical problem of achieving single-base resolution in electronic nucleobase detection. We have theoretically evaluated the performance of a graphene nanogap setup for the purpose of whole-genome sequencing, by employing density functional theory and the nonequilibrium Green's function method to investigate the transverse conductance properties of nucleotides inside the gap. In particular, we determined the electrical tunneling current variation at finite bias due to changes in the nucleotides orientation and lateral position. Although the resulting tunneling current is found to fluctuate over several orders of magnitude, a distinction between the four DNA bases appears possible, thus ranking the approach promising for rapid whole-genome sequencing applications.
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| 29. |
- Qian, Zhao, et al.
(författare)
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C-60-mediated hydrogen desorption in Li-N-H systems
- 2012
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 23:48, s. 485406-
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen desorption from a LiH + NH3 mixture is very difficult due to the formation of the stable LiNH4 compound. Using cluster models and first-principles theory, we demonstrate that the C-60 molecule can in fact significantly improve the thermodynamics of ammonia-mediated hydrogen desorption from LiH due to the stabilization of the intermediate state, LiNH4. The hydrogen desorption following the path of LiNH4-C-60 -> LiNH3-C-60 + 1/2H(2) is exothermic. Molecular dynamic simulations show that this reaction can take place even at room temperature (300 K). In contrast, the stable LiNH4 compound cannot desorb hydrogen at room temperature in the absence of C-60. The introduction of C-60 also helps to restrain the NH3 gas which is poisonous in proton exchange membrane fuel cell applications.
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| 30. |
- Qian, Zhao, et al.
(författare)
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Energetic and structural analysis of N2H4BH3 inorganic solid and its modified material for hydrogen storage
- 2013
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Ingår i: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 38:16, s. 6718-6725
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Tidskriftsartikel (refereegranskat)abstract
- Here we have exposed the electronic structure, chemical bonding of the light-weight N2H4BH3 inorganic material for hydrogen storage applications and analyzed its hydrogen removal energetics using state-of-the-art first-principles method. The mechanism for the H-host bond weakening in this kind of solid has also been explored. It is shown that the electronic density of states of N(2)H(4)BH(3)d solid near the Fermi level is mainly contributed by the B p-states, H (B) s-states, and the end N p-states. The calculated smallest hydrogen removal energy of N2H4BH3 solid is 4.16 eV. One Li-modified structure has been obtained through ab initio relaxations and its hydrogen removal energies are found dramatically decreased by as much as 50% compared with those of pristine N2H4BH3 solid. The B-H bond weakening is attributed to the elongation of the bond length; for the N H bonds, the weakening is found to be due to the destabilization of N-H bonds before hydrogen removal and the stabilization of residual N-H bond after hydrogen removal. The weakening of these bonds is of great significance for the improvement of hydrogen desorption kinetics of the material. We propose this study should help to deepen understanding of properties of N2H4BH3 inorganic solid and its related materials for hydrogen storage applications and guide experimentalists and engineers to develop better candidate materials for the advance of the field.
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