| 1. |
- Wang, Yang, et al.
(författare)
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Role of point defects on the reactivity of reconstructed anatase titanium dioxide (001) surface
- 2013
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 4, s. 2214-
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Tidskriftsartikel (refereegranskat)abstract
- The chemical reactivity of different surfaces of titanium dioxide (TiO2) has been the subject of extensive studies in recent decades. The anatase TiO2(001) and its (1 x 4) reconstructed surfaces were theoretically considered to be the most reactive and have been heavily pursued by synthetic chemists. However, the lack of direct experimental verification or determination of the active sites on these surfaces has caused controversy and debate. Here we report a systematic study on an anatase TiO2(001)-(1 x 4) surface by means of microscopic and spectroscopic techniques in combination with first-principles calculations. Two types of intrinsic point defects are identified, among which only the Ti3+ defect site on the reduced surface demonstrates considerable chemical activity. The perfect surface itself can be fully oxidized, but shows no obvious activity. Our findings suggest that the reactivity of the anatase TiO2(001) surface should depend on its reduction status, similar to that of rutile TiO2 surfaces.
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| 2. |
- Cao, Lina, et al.
(författare)
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Atomically dispersed iron hydroxide anchored on Pt for preferential oxidation of CO in H-2
- 2019
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Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 565:7741, s. 631-635
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Tidskriftsartikel (refereegranskat)abstract
- Proton-exchange-membrane fuel cells (PEMFCs) are attractive next-generation power sources for use in vehicles and other applications(1), with development efforts focusing on improving the catalyst system of the fuel cell. One problem is catalyst poisoning by impurity gases such as carbon monoxide (CO), which typically comprises about one per cent of hydrogen fuel(2-4). A possible solution is on-board hydrogen purification, which involves preferential oxidation of CO in hydrogen (PROX)(3-7). However, this approach is challenging(8-15) because the catalyst needs to be active and selective towards CO oxidation over a broad range of low temperatures so that CO is efficiently removed (to below 50 parts per million) during continuous PEMFC operation (at about 353 kelvin) and, in the case of automotive fuel cells, during frequent cold-start periods. Here we show that atomically dispersed iron hydroxide, selectively deposited on silica-supported platinum (Pt) nanoparticles, enables complete and 100 per cent selective CO removal through the PROX reaction over the broad temperature range of 198 to 380 kelvin. We find that the mass-specific activity of this system is about 30 times higher than that of more conventional catalysts consisting of Pt on iron oxide supports. In situ X-ray absorption fine-structure measurements reveal that most of the iron hydroxide exists as Fe-1(OH)(x) clusters anchored on the Pt nanoparticles, with density functional theory calculations indicating that Fe-1(OH)(x)-Pt single interfacial sites can readily react with CO and facilitate oxygen activation. These findings suggest that in addition to strategies that target oxide-supported precious-metal nanoparticles or isolated metal atoms, the deposition of isolated transition-metal complexes offers new ways of designing highly active metal catalysts.
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| 3. |
- Chen, Lan, et al.
(författare)
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Mechanism for negative differential resistance in molecular electronic devices : Local orbital symmetry matching
- 2007
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:14
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Tidskriftsartikel (refereegranskat)abstract
- A new mechanism for negative differential resistance (NDR) originating from local orbital symmetry matching between an electrode and a molecule in a single molecular electronic device is proposed and demonstrated by a joint experimental and theoretical scanning tunneling microscope study of a cobalt phthalocyanines (CoPc) molecule on a gold substrate. For two different metal tips used, Ni and W, NDR occurs only with Ni tips and shows no dependence on the geometrical shape of the tip. Calculations reveal that such a behavior is a result of local orbital symmetry matching between the Ni tip and Co atom.
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| 4. |
- Feng, Feng, et al.
(författare)
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Room-temperature large magnetic-dielectric coupling in new phase anatase VTiO4
- 2013
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 49:89, s. 10462-10464
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Tidskriftsartikel (refereegranskat)abstract
- The synthetic new-phase VTiO4, as a new solid solution structure of anatase type, brings a large magnetodielectric ratio (Delta epsilon/epsilon(0)) of 7.2% at 300 K, representing a new simple-oxide structural catalogue exhibiting a room-temperature large magnetic-dielectric effect.
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| 5. |
- Feng, Jun, et al.
(författare)
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Giant Moisture Responsiveness of VS2 Ultrathin Nanosheets for Novel Touchless Positioning Interface
- 2012
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 24:15, s. 1969-1974
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Tidskriftsartikel (refereegranskat)abstract
- Utilizing a thin film of VS2 ultrathin nanosheets with giant and fast moisture responsiveness, a brand-new model of moisture-based positioning interface is put forward here, by which not only the 2D position information of finger tips can be acquired, but also the relative height can be detected as the third dimensionality, representing a promising platform for advanced man-machine interactive systems.
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| 6. |
- Fu, Qiang, et al.
(författare)
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First-principles calculations of adsorption and dehydrogenation of trans-2-butene molecule on Pd(110) surface
- 2009
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 131:15
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Tidskriftsartikel (refereegranskat)abstract
- Adsorption and dehydrogenation processes of trans-2-butene molecule on the Pd(110) surface have been studied by density functional theory calculations. Different adsorption configurations of the reactant, the dehydrogenated product, and the most favorable reaction pathway have been determined. The calculated energy barrier agrees well with the value deduced from experiments. It is found that the reactant molecule must undergo a rotation before the C-H bond cleavage, and surface Pd atoms are involved in the dehydrogenation reaction through the formation of the Pd-C-H three-membered metallacycle. Our calculations have not only provided reliable interpretation for various experimental observations but also shed more light on the dynamics of the reaction processes.
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| 7. |
- Fu, Qiang, et al.
(författare)
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Mechanism for tautomerization induced conductance switching of naphthalocyanin molecule
- 2009
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 95:18
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Tidskriftsartikel (refereegranskat)abstract
- Reaction mechanism for tautomerization process of a single naphthalocyanin molecule has been studied using density functional theory. It is found that tautomerization of the naphthalocyanin molecule is not a concerted reaction, but a step-wise process in that one hydrogen atom transfers after another. A stable intermediate state and the possible transition state of the reaction processes have been located. The occurrence of the intermediate state suggests that the tautomerization induced conductance switching involves four conductance states with different conductances, and the earlier proposed two-state system model is not valid.
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| 8. |
- Fu, Qiang, et al.
(författare)
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Understanding the concept of randomness in inelastic electron tunneling excitations
- 2010
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 12:38, s. 12012-12023
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Tidskriftsartikel (refereegranskat)abstract
- Inelastic electron tunneling excitation has been realized in the last decade as an effective way to probe reliably detailed atomic structures and control precisely behaviors of surface adsorbates at a single molecule level. A good understanding of rich and complex processes on the surface under inelastic electron excitations is of great importance, not only from a fundamental scientific point of view but also for potential practical applications. In this perspective paper, we give an overview of recent developments on excitations and characterizations of inelastic electron tunneling processes in surface adsorbates and molecular junctions. Special attention has been paid to the understanding of the randomness of the processes. A recently proposed general statistical model is introduced which has resolved a long-standing puzzle concerning the experimentally observed non-integer power law relationship between the rate of molecular conformation changes and the tunneling current. The success of the new model is highlighted by its applications for molecular switches.
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| 9. |
- Hao, Ren, et al.
(författare)
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Simulation of inelastic electronic tunneling spectra of adsorbates from first principles
- 2009
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 130:134707
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Tidskriftsartikel (refereegranskat)abstract
- We present first-principles simulations for inelastic electron tunneling spectra of molecules adsorbed on metal surface as measured in scanning tunneling microscopy experiments. Both elastic and inelastic tunneling processes are modeled in terms of Tersoff-Hamann approximation with a full vibration analysis at density functional theory levels. The calculated spectra of carbon oxide and acetylene molecules adsorbed on Cu(100) surface have well reproduced their experimental counterparts. The inelastic electron tunneling images of the observable vibration modes have been provided. The performance of gradient-corrected density functional is compared with that of local density functional.
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| 10. |
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| 11. |
- Jiang, Jun, et al.
(författare)
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Structure dependent quantum confinement effect in hydrogen-terminated nanodiamond clusters
- 2010
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 108:9, s. 094303-
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Tidskriftsartikel (refereegranskat)abstract
- Size-dependent quantum confinement effect on electronic structure of hydrogen-terminated carbon nanodiamond (ND) cluster has been investigated at the hybrid density functional theory level. Large scale all-electron calculations have been carried out for ND clusters of 0.76 nm (29 carbons) to 7.3 nm (20 959 carbons) in diameter. It is demonstrated that the quantum confinement effect in these clusters shows strong structural dependence. An important structural factor, describing the ratio between the number of atoms within the inner core and outer shell of the cluster, is identified which dictates the size-dependent behavior of the electronic states. For ND clusters with diameter smaller than 1.5 nm, the core-shell ratio changes fast with the increase in cluster size, and the evolution of electronic properties does not follow conventional quantum confinement models. For ND clusters exceeding the threshold of 1.5 nm in diameter, the change in the core-shell ratio saturates and quantum confinement effect becomes visible. Electronic states within the inner core and surface show different size dependence, but a general formula is proposed and describes their structure dependent quantum confinement effects. This formula provides useful insights into quantum confinement behavior in ND clusters, and thereby leads to important physical property information. The calculated electron effective masses for core and surface states of ND clusters are in very good agreement with the experiments.
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| 12. |
- Li, Xiaofei, et al.
(författare)
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Important structural factors controlling the conductance of DNA pairs in molecular junctions
- 2010
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:33, s. 14240-14242
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Tidskriftsartikel (refereegranskat)abstract
- It has been demonstrated experimentally that DNA base pairs and sequences can be identified by measuring their current changes in metal junctions. We report here a first principles study on electron transport properties of DNA base pairs in gold metal junctions. It is found that the experimentally observed electrode-separation-width-dependent current changes of DNA base pairs are not due to the difference in number of hydrogen bonds involved in different base pairs as proposed in earlier experimental studies but caused by the difference in their stacking structures. It reveals that such an electronic read-out technique is not exact, but practically useful since the statistically favorable misaligned junctions do show distinct dependence on the character of the base pair.
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| 13. |
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| 14. |
- Li, Zhenyu, et al.
(författare)
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How Graphene is Cut upon Oxidation?
- 2009
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 131:18, s. 6320-6321
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Tidskriftsartikel (refereegranskat)abstract
- Our first principles calculations reveal that an oxidative cut of graphene is realized by forming epoxy and then carbonyl pairs. Direct formation of a carbonyl pair to tear graphene up from an edge position is not favorable in energy. This atomic picture is valuable for developing effective means of graphene manipulation. The proposed epoxy pairs may be related to some long puzzling experimental observations on graphene oxide.
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| 15. |
- Lin, Chenwen, et al.
(författare)
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Hydrogen-Incorporated TiS2 Ultrathin Nanosheets with Ultrahigh Conductivity for Stamp-Transferrable Electrodes
- 2013
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 135:13, s. 5144-5151
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Tidskriftsartikel (refereegranskat)abstract
- As a conceptually new class of two-dimensional (2D) materials, the ultrathin nanosheets as inorganic graphene analogues (IGAs) play an increasingly vital role in the new-generation electronics. However, the relatively low electrical conductivity of inorganic ultrathin nanosheets in current stage significantly hampered their conducting electrode applications in constructing nanodevices. We developed the unprecedentedly high electrical conductivity in inorganic ultrathin nanosheets. The hydric titanium disulfide (HTS) ultrathin nanosheets, as a new IGAs, exhibit the exclusively high electrical conductivity of 6.76 x 10(4) S/m at room temperature, which is superior to indium tin oxide (1.9 x 10(4) S/m), recording the best value in the solution assembled 2D thin films of both graphene (5.5 x 10(4) S/m) and inorganic graphene analogues (5.0 x 10(2) S/m). The modified hydrogen on S-Ti-S layers contributes additional electrons to the TiS2 layered frameworks, rendering the controllable electrical conductivity as well as the electron concentrations. Together with synergic advantages of the excellent mechanical flexibility, high stability, and stamp-transferrable properties, the HTS thin films show promising capability for being the next generation conducting electrode material in the nanodevice fields.
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| 16. |
- Monti, Susanna, et al.
(författare)
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Effects due to interadsorbate interactions on the dipeptide/TiO2 surface binding mechanism investigated by molecular dynamics simulations
- 2007
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 111:21, s. 7765-7771
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Tidskriftsartikel (refereegranskat)abstract
- Classical molecular dynamics simulations, supported by ab initio periodic calculations, were carried out to investigate peptide adsorption mechanisms onto a rutile (110) TiO2 layer in the presence of water molecules. Different binding modes, comprising multiple coordination to the titanium atoms, of several conformers, simultaneously adsorbed upon the surface, were analyzed in detail. In agreement with experimental and theoretical findings, peptide carbonyl oxygens and nitrogens were found to be possible coordination atoms. Local effects were responsible of adsorption and desorption events and intermolecular interactions induced conformational changes and reorientations of the molecules with respect to the surface that produced both strongly and weakly adsorbed species.
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| 17. |
- Pan, Shuan, et al.
(författare)
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Design and control of electron transport properties of single molecules
- 2009
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 106:36, s. 15259-15263
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 18. |
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| 19. |
- Qiang, Fu, et al.
(författare)
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A first principles study on the dissociation and rotation processes of a single O2 molecule on the Pt(111) surface
- 2011
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society. - 1932-7447 .- 1932-7455. ; 115:14, s. 6864-6869
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Tidskriftsartikel (refereegranskat)abstract
- Through density functional theory calculations, a detailed description on the dissociation and rotation processes of a single oxygen molecule adsorbed on the Pt(111) surface has been provided. Both dissociation and rotation reaction pathways have been identified, and some interesting phenomena related to the scanning tunneling microscopy experiments are finally explained. It is found that the prior occupation of oxygen atom on the metastable hcp-hollow site after O2 dissociation is originated from the particular structure of the intermediate state, and the low energy barrier of the O2 rotation can be attributed to an effective pathway. The experimentally observed noninteger power-law dependence of the rotation rate as a function of the current has been accurately determined by a newly developed statistical model for the inelastic electron tunneling. By considering the randomness of multielectron inelastic tunneling processes, it is found that the noninteger exponent comes from a statistical contribution of various n-electron events.
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| 20. |
- Ren, Hao, et al.
(författare)
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Identifying configuration and orientation of adsorbed molecules by inelastic electron tunneling spectra
- 2010
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 133:6, s. 064702-
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Tidskriftsartikel (refereegranskat)abstract
- Scanning tunneling microscopy (STM) topographical images and inelastic electron tunneling spectra (IETS) of a cis-2-butene molecule adsorbed on a Pd(110) surface have been simulated by first-principles calculations. Calculations have eliminated the ambiguity between the STM image and the adsorption orientation caused by the symmetry of the system and local chemical environment. A combination of STM images and IETS spectra has been shown to be particularly useful in determining the configuration of the molecule on the surface. (C) 2010 American Institute of Physics. [doi:10.1063/1.3474807]
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| 21. |
- Sen, Partha, et al.
(författare)
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Novel FOXF1 Mutations in Sporadic and Familial Cases of Alveolar Capillary Dysplasia with Misaligned Pulmonary Veins Imply a Role for its DNA Binding Domain
- 2013
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Ingår i: Human Mutation. - : Hindawi Limited. - 1059-7794. ; 34:6, s. 801-811
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Tidskriftsartikel (refereegranskat)abstract
- Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare and lethal developmental disorder of the lung defined by a constellation of characteristic histopathological features. Nonpulmonary anomalies involving organs of gastrointestinal, cardiovascular, and genitourinary systems have been identified in approximately 80% of patients with ACD/MPV. We have collected DNA and pathological samples from more than 90 infants with ACD/MPV and their family members. Since the publication of our initial report of four point mutations and 10 deletions, we have identified an additional 38 novel nonsynonymous mutations of FOXF1 (nine nonsense, seven frameshift, one inframe deletion, 20 missense, and one no stop). This report represents an up to date list of all known FOXF1 mutations to the best of our knowledge. Majority of the cases are sporadic. We report four familial cases of which three show maternal inheritance, consistent with paternal imprinting of the gene. Twenty five mutations (60%) are located within the putative DNA-binding domain, indicating its plausible role in FOXF1 function. Five mutations map to the second exon. We identified two additional genic and eight genomic deletions upstream to FOXF1. These results corroborate and extend our previous observations and further establish involvement of FOXF1 in ACD/MPV and lung organogenesis.
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| 22. |
- Tan, Shijing, et al.
(författare)
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Visualizing Elementary Reactions of Methanol by Electrons and Holes on TiO2(110) Surface
- 2018
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 122:50, s. 28805-28814
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Tidskriftsartikel (refereegranskat)abstract
- Direct visualization and comparison of the elementary reactions induced by electrons and holes are of importance for finding a way to conduct chemical reactions and reaction sequences in a controllable manner. As a semiconductor, TiO2 provides a playground to perform the measurements, and moreover, the information can be useful for design of high-performance TiO2-based catalysts and photocatalysts. Here, we present our investigation on the elementary reactions of CH3OH on TiO2 surface through visualization of specific elementary steps by highly controllable electron and hole injection using scanning tunneling microscopy. The distinct sequential routes and their kinetics, namely, breaking C-O and O-H bonds by electrons and breaking O-H and C-H bonds by holes, respectively, have been experimentally identified and well elucidated by density functional theory calculations. Our nonlocal h-injection experimental and theoretical results suggest that the delocalized holes in the TiO2 substrate should be responsible for the temperature-dependent h-route reactions. The locally triggered e-route reaction is associated with the fact that the location of the unoccupied hybridization states is much higher than that of the conduction band onset. Our findings resolve the long-standing debate about the intermediate species and reaction mechanism in photocatalytic oxidation of CH3OH. Our proposed protocol offers a powerful means to study elementary reactions induced by electrons and holes on a semiconductor surface in general.
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| 23. |
- Xu, Kun, et al.
(författare)
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Highly entangled K0.5V2O5 superlong nanobelt membranes for flexible nonvolatile memory devices
- 2012
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 22:35, s. 18214-18220
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Tidskriftsartikel (refereegranskat)abstract
- Flexible electronics has been an intensively pursued hot topic in recent years, and flexible nonvolatile memory devices (NVMs) are also an important concept in modern electronics due to the advantages of retaining stored information even when not powered, with great portability and high deformability. In this study, we report that delta-K0.5V2O5 bronze with sandwiched potassium atoms in the V-O framework has been found to be a new promising material platform for intriguing nonvolatile memory applications. The bronze structure with the sandwiched alkali metal atoms between the two V2O5 layers ensures the promising NVM effect by changing the electronic properties under an applied electric field. The delta-K0.5V2O5 bronze entangled superlong nanobelt networks, which are established via the "solid-solution-solid" (SSS) mechanism and a hydrogen-bond-assisted entangling process, bring the synergic advantages of excellent mechanical and electrical properties. Spin polarized GGA+U density functional theory calculations elucidate well the nature of bronze-based NVM, in which the overall effect of applying an electric field is to reduce the energy gap, no matter what the direction of the electric field is; the effects of electric field and ion shift would follow the same trend, the non-linear band gap changes would lead to resistance changes of this material. The NVMs based on the entangled superlong nanobelt membrane possess the advantages of not only low cost and very simple device structure, but also a reversible and noticeable nonlinear hysteresis, low consumption, stable WRER cycles, and a long retention time over 1000 s, showing promise for next-generation flexible NVMs.
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| 24. |
- You, Sifan, et al.
(författare)
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Quantifying the conductivity of a single polyene chain by lifting with an STM tip
- 2024
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Ingår i: Nature Communications. - : NATURE PORTFOLIO. - 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Conjugated polymers are promising candidates for molecular wires in nanoelectronics, with flexibility in mechanics, stability in chemistry and variety in electrical conductivity. Polyene, as a segment of polyacetylene, is a typical conjugated polymer with straightforward structure and wide-range adjustable conductance. To obtain atomic scale understanding of charge transfer in polyene, we have measured the conductance of a single polyene-based molecular chain via lifting it up with scanning tunneling microscopy tip. Different from semiconducting characters in pristine polyene (polyacetylene), high conductance and low decay constant are obtained, along with an electronic state around Fermi level and characteristic vibrational mode. These observed phenomena result from pinned molecular orbital owing to molecule-electrode coupling at the interface, and weakened bond length alternation due to electron-phonon coupling inside single molecular chain. Our findings emphasize the interfacial characteristics in molecular junctions and promising properties of polyene, with single molecular conductance as a vital tool for bringing insights into the design and construction of nanodevices. Polyene is a segment of polyacetylene, a conductive polymer. Here, the authors measured the conductance of single molecular chain of trans-polyene and found a high conductivity and low decay constant, attributed to the alignment of the energy levels.
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| 25. |
- Zhang, Wenhua, et al.
(författare)
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Electronic structure of [121]tetramantane-6-thiol on gold and silver surfaces
- 2009
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 130:054705
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism for electron photoemission of [121]tetramantane and its functionalized compound [121]tetramantane-6-thiol adsorbed on different noble metal surfaces has been investigated by density functional theory calculations. It is found that good chemical bonding between molecules and metal surfaces is a helpful but not a necessary condition for electron photoemission. A lower work function and weaker hybridization between the molecule and the metal could lead to much more efficient electron photoemission. It is observed that, neglecting final state effect, a simple ground state picture cannot result in negative electron affinity for the systems under investigation. Calculations have shown that by exciting an electron in the lowest unoccupied molecular orbital, the highest singly occupied molecular orbital of the molecule can be shifted above the vacuum level, resulting in negative electron affinity and emission of the accumulated electrons.
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| 26. |
- Zhang, Wenhua, et al.
(författare)
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First Principles Study on the Geometric and Electronic Structures of the FeO/Pt(111) Surface
- 2009
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:19, s. 8302-8305
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Tidskriftsartikel (refereegranskat)abstract
- 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 fee 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.
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| 27. |
- Zhang, Wenhua, et al.
(författare)
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Oxidation states of graphene : Insights from computational spectroscopy
- 2009
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 131:24
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Tidskriftsartikel (refereegranskat)abstract
- When it is oxidized, graphite can be easily exfoliated forming graphene oxide (GO). GO is a critical intermediate for massive production of graphene, and it is also an important material with various application potentials. With many different oxidation species randomly distributed on the basal plane, GO has a complicated nonstoichiometric atomic structure that is still not well understood in spite of intensive studies involving many experimental techniques. Controversies often exist in experimental data interpretation. We report here a first principles study on binding energy of carbon 1s orbital in GO. The calculated results can be well used to interpret experimental x-ray photoelectron spectroscopy (XPS) data and provide a unified spectral assignment. Based on the first principles understanding of XPS, a GO structure model containing new oxidation species epoxy pair and epoxy-hydroxy pair is proposed. Our results demonstrate that first principles computational spectroscopy provides a powerful means to investigate GO structure.
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| 28. |
- Zhang, Wenhua, et al.
(författare)
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Quantum molecular dynamics study of water onTiO2(110) surface
- 2009
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 129:064703
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of water on perfect TiO2(110) surface is studied by quantum molecular dynamics simulation adopting a periodic model formed by five water molecules on a (5 x 1) surface unit cell of a five layer slab of TiO2. The total simulation time is 3.2 ps. At about 1.3 ps, one water molecule dissociates with the help of other adsorbed waters and surface bridging oxygens. During the remaining 1.9 ps, the waters and OH groups vibrate, but no more dissociation or recombination is observed. By comparing recent experimental O1s photoemission (x-ray photoelectron spectroscopy) spectra of H2O/TiO2(110) to the computed spectrum of the adsorbate in the configurations supplied by the molecular dynamics simulation, the observed peaks can be attributed to different oxygen species. The proposed assignment of the main spectral features supports the occurrence of partial water dissociation (similar to 20%) also on a perfect TiO2 surface.
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