| 1. |
- 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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| 2. |
- 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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| 3. |
- Fu, Le, et al.
(författare)
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Ultrastrong translucent glass ceramic with nanocrystalline, biomimetic structure
- 2018
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 18:11, s. 7146-7154
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Tidskriftsartikel (refereegranskat)abstract
- Transparent/translucent glass ceramics (GCs) have broad applications in biomedicine, armor, energy, and constructions. However, GCs with improved optical properties typically suffer from impaired mechanical properties, compared to traditional sintered full-ceramics. We present a method of obtaining high-strength, translucent GCs by preparing ZrO2-SiO2 nanocrystalline glass ceramics (NCGCs), with a microstructure of monocrystalline ZrO2 nanoparticles (NPs), embedded in an amorphous SiO2 matrix. The ZrO2-SiO2 NCGC with a composition of 65%ZrO2-35%SiO2 (molar ratio, 65Zr) achieved an average flexural strength of 1 GPa. This is one of the highest flexural strength values ever reported for GCs. ZrO2 NPs have a core-shell structure, and the shell is a thin (2–3 nm) amorphous Zr/Si interfacial layer that provides strong bonding between the ZrO2 NPs and SiO2 matrix. The diffusion of Si atoms into the ZrO2 NPs forms a Zr-O-Si superlattice. Electron tomography results show that some of the ZrO2 NPs are connected in one direction, forming in situ ZrO2 nanofibers (with length of ~500 nm), and that the ZrO2 nanofibers are stacked in an ordered way in all three dimensions. The nano-architecture of the ZrO2 nanofibers mimics the architecture of mineralized collagen fibril in cortical bone. Strong interface bonding enables efficient load transfer from the SiO2 matrix to the 3D nano-architecture built by ZrO2 nanofibers and NPs, and the 3D nano-architecture carries the majority of the external load. These two factors synergistically contribute to the high strength of the 65Zr NCGC. This study deepens our fundamental understanding of the microstructure-mechanical strength relationship, which could guide the design and manufacture of other high-strength, translucent GCs.
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| 4. |
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| 5. |
- Hu, Shuanglin, et al.
(författare)
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Formic Acid on TiO2-x (110) : Dissociation, Motion, and Vacancy Healing
- 2014
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:27, s. 14876-14887
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption and dissociation of a formic acid molecule (HCOOH) on a partially reduced rutile TiO2-x (110) surface and the subsequent transformations of the adsorbed fragments are studied via quantum-mechanical molecular dynamics simulations and climbing-image nudged elastic band (CI-NEB) calculations. The electronic structure methods used are self-consistent-charge density functional tight binding (SCC-DFTB) and DFT+U calculations. We address the apparent lack of consensus in the literature regarding the formic acid adsorbate species that heal the O vacancies, where different experiments have suggested the occurrence of one, two, or no such species types. From our calculations, we propose that the formic acid molecule quickly dissociates on the surface into a formate ion and a proton. If no mechanism exists by which the dissociation products can migrate away from each other, three formate species will coexist on the partially reduced TiO2 surface: one majority species bound to the Ti rows and two minority species healing the O vacancies. However, if such a diffusion mechanism does exist, our barrier calculations show that one of the minority species will transform into the other, and only two adsorbate types can be expected on the surface. We also identify a new adsorbate configuration (which we denote C'), where the formate is located on the row of two-coordinated oxygen atoms, healing an O vacancy and accepting an H-bond from the detached H atom.
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| 6. |
- Hu, Shuanglin, et al.
(författare)
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Optical properties of Mg-doped VO2 : Absorption measurements and hybrid functional calculations
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:20, s. 201902-
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Tidskriftsartikel (refereegranskat)abstract
- Mg-doped VO2 thin films with thermochromic properties were made by reactive DC magnetron co-sputtering onto heated substrates, and spectral absorption was recorded at room temperature in the 0.5 < <(h)over bar>omega < 3.5 eV energy range. Clear evidence was found for a widening of the main band gap from 1.67 to 2.32 eV as the Mg/(V + Mg) atomic ratio went from zero to 0.19, thereby significantly lowering the luminous absorption. This technologically important effect could be reconciled with spin-polarized density functional theory calculations using the Heyd-Scuseria-Ernzerhof [Heyd et al., J. Chem. Phys. 118, 8207 (2003); ibid. 124, 219906 (2006)] hybrid functional. Specifically, the calculated luminous absorptance decreased when the Mg/(V + Mg) ratio was increased from 0.125 to 0.250.
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| 7. |
- Hu, Shuanglin, et al.
(författare)
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Simulation of IRRAS Spectra for Molecules on Oxide Surfaces : CO on TiO2(110)
- 2015
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:10, s. 5403-5411
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Tidskriftsartikel (refereegranskat)abstract
- We explore a method that cart sirriulate infrared refiection absotption spectroscopy (IRRAS) spectra for molecules adsjorlied on semiconductor surfaces. The method rakes it possible to directly correlate experimental spectra with possible adsorbate structures. Our example in thiS paper is CO adsoihed on rutile TiO2(110). We present simulated IRRAS spectra for coverages in the range from 0.125 to 1.5 Monolayer (ML) An explanation is provided. for the apparent inconsistency in the literature concerning the tilting geometry of 1 ML CO on this surface. We find that a tilted structure (which is also the lowest-energy configuration) generates IRRAS spectra in excellent agreement with the experimental spectra. Furthermore, we predict the adsorption structure for 1.5 ML CO coverage over TiO2 (110), which consists of very weakly bound CO molecules on top of the monolayer. In all cases, our simulation method) which is based On density functioual theory (PFT) vibrational calculations, produces s- and p-polarized IRRAS spectra in excellent agreement with the experimental spectra.
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| 8. |
- Kan, Erjun, et al.
(författare)
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Two-Dimensional Hexagonal Transition-Metal Oxide for Spintronics
- 2013
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Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 4:7, s. 1120-1125
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional materials have been the hot subject of studies due to their great potential in applications. However, their applications in spintronics have been blocked by the difficulty in producing ordered spin structures in 2D structures. Here we demonstrated that the ultrathin films of recently experimentally realized wurtzite MnO can automatically transform into a stable graphitic structure with ordered spin arrangement via density functional calculation, and the stability of graphitic structure can be enhanced by external strain. Moreover, the antiferromagnetic ordering of graphitic MnO single layer can be switched into half-metallic ferromagnetism by small hole-doping, and the estimated Curie temperature is higher than 300 K. Thus, our results highlight a promising way toward 2D magnetic materials.
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| 9. |
- 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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| 10. |
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| 11. |
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| 12. |
- Mattsson, Andreas, et al.
(författare)
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Adsorption of formic acid on rutile TiO2 (110) revisited : An infrared reflection-absorption spectroscopy and density functional theory study
- 2014
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 140:3, s. 034705-
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Tidskriftsartikel (refereegranskat)abstract
- Formic acid (HCOOH) adsorption on rutile TiO2 (110) has been studied by s- and p-polarized infrared reflection-absorption spectroscopy (IRRAS) and spin-polarized density functional theory together with Hubbard U contributions (DFT+U) calculations. To compare with IRRAS spectra, the results from the DFT+U calculations were used to simulate IR spectra by employing a three-layer model, where the adsorbate layer was modelled using Lorentz oscillators with calculated dielectric constants. To account for the experimental observations, four possible formate adsorption geometries were calculated, describing both the perfect (110) surface, and surfaces with defects; either O vacancies or hydroxyls. The majority species seen in IRRAS was confirmed to be the bridging bidentate formate species with associated symmetric and asymmetric frequencies of the nu(OCO) modes measured to be at 1359 cm(-1) and 1534 cm(-1), respectively. The in-plane delta(C-H) wagging mode of this species couples to both the tangential and the normal component of the incident p-polarized light, which results in absorption and emission bands at 1374 cm(-1) and 1388 cm(-1). IRRAS spectra measured on surfaces prepared to be either reduced, stoichiometric, or to contain surplus O adatoms, were found to be very similar. By comparisons with computed spectra, it is proposed that in our experiments, formate binds as a minority species to an in-plane Ti-5c atom and a hydroxyl, rather than to O vacancy sites, the latter to a large extent being healed even at our UHV conditions. Excellent agreement between calculated and experimental IRRAS spectra is obtained. The results emphasize the importance of protonation and reactive surface hydroxyls - even under UHV conditions - as reactive sites in e. g., catalytic applications. (C) 2014 AIP Publishing LLC.
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| 13. |
- Sun, Yongfu, et al.
(författare)
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Fabrication of flexible and freestanding zinc chalcogenide single layers
- 2012
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 3, s. 1057-
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Tidskriftsartikel (refereegranskat)abstract
- Inorganic graphene analogues (IGAs) are a conceptually new class of materials with attractive applications in next-generation flexible and transparent nanodevices. However, their species are only limited to layered compounds, and the difficulty in extension to non-layered compounds hampers their widespread applicability. Here we report the fabrication of large-area freestanding single layers of non-layered ZnSe with four-atomic thickness, using a strategy involving a lamellar hybrid intermediate. Their surface distortion, revealed by means of synchrotron radiation X-ray absorption fine structure spectroscopy, is shown to give rise to a unique electronic structure and an excellent structural stability, thus determining an enhanced solar water splitting efficiency and photostability. The ZnSe single layers exhibit a photocurrent density of 2.14 mA cm(-2) at 0.72 V versus Ag/AgCl under 300 W Xe lamp irradiation, 195 times higher than that of bulk counterpart. This work opens the door for extending atomically thick IGAs to non-layered compounds and holds promise for a wealth of innovative applications.
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| 14. |
- 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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