206 results on '"Wei-Quan Tian"'
Search Results
2. BN-Doped Carbon Nanotubes and Nanoribbons as Nonlinear-Optical Functional Materials for Application in Second-Order Nonlinear Optics
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Cui-Cui Yang, Xu Duan, Li Li, Xue-Lian Zheng, Jiu Chen, Wei Quan Tian, Wei-Qi Li, and Ling Yang
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General Materials Science - Published
- 2023
3. Transport properties of GNR-C60 single-molecule devices
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Xiaohui Liu, Yangyang Hu, Danting Li, Guiling Zhang, and Wei Quan Tian
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Materials Chemistry ,General Chemistry - Abstract
The transport properties of a series of double-layered GNR-C60 devices are investigated, revealing deep insights into experimental discoveries, and provides theoretical guidance for optimizing the transport properties of GNR-C60 devices.
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- 2023
4. Bending Effect on the Electronic Properties and Nonlinear Optical Responses of Linear Porphyrin Oligomer
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Yangyang Hu, Lu Han, Danting Li, Hong Yu, Guiling Zhang, Weiqi Li, and Wei Quan Tian
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Statistics and Probability ,Numerical Analysis ,Multidisciplinary ,Modeling and Simulation - Published
- 2023
5. Electronic Structures and NLO Properties of a Series of TMDs Lateral‐Core–Shell Heterostructures Quantum Dots
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Danting Li, Yadong Wei, Yangyang Hu, Guiling Zhang, Weiqi Li, JianQun Yang, XingJi Li, and Wei Quan Tian
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Statistics and Probability ,Numerical Analysis ,Multidisciplinary ,Modeling and Simulation - Published
- 2023
6. Spin engineering of triangulenes and application for nano nonlinear optical materials design
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Cui-Cui Yang, Xue-Lian Zheng, Jiu Chen, Wei Quan Tian, Wei-Qi Li, and Ling Yang
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General Physics and Astronomy ,Physical and Theoretical Chemistry - Abstract
The recently synthesized triangulenes with non-bonding edge states could have broad potential applications in magnetics, spintronics and electro-optics if they have appropriate electronic structure modulation. In the present work, strategies based on molecular orbital theory through heteroatom doping are proposed to redistribute, reduce or eliminate the spin of triangulenes for novel functional materials design, and the role of B, N, NBN, and BNB in such intended electronic structure manipulation is scrutinized. π-Extended triangulenes with tunable electronic properties could be potential nonlinear optical (NLO) materials with appropriate inhibition of their polyradical nature. The elimination of spin is achieved by B, N, NBN, and BNB doping with the intended geometric arrangement for enhanced polarity. Intended doping of BNB results in an optimal structure with large static first hyperpolarizability (〈
- Published
- 2022
7. Tuning the edge states in X-type carbon based molecules for applications in nonlinear optics
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Wei Quan Tian, Xue-Lian Zheng, Weiqi Li, Cui-Cui Yang, and Ling Yang
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Materials science ,business.industry ,Nanophotonics ,General Physics and Astronomy ,Hyperpolarizability ,Nonlinear optics ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Pockels effect ,0104 chemical sciences ,Nanomaterials ,Optical rectification ,Zigzag ,Optoelectronics ,Physical and Theoretical Chemistry ,0210 nano-technology ,business ,Graphene nanoribbons - Abstract
Novel carbon based “X-type” graphene nanoribbons (GNRs) with azulenes were designed for applications in nonlinear optics in the present work, and the second order nonlinear optical (NLO) properties of those X-type GNRs were predicted using the sum-over-states (SOS) model. The GNRs with edge states are feasibly polarized. The effects of zigzag edges on the NLO properties of GNRs are scrutinized by passivation, and the electronic structures of GNRs are modulated with heteroatoms at the zigzag edges for improved stability and NLO properties. Those nanomaterials were further functionalized with electron-donating and electron-withdrawing groups (NH2/NO2) to enhance the NLO responses, and the connection of those functional groups at the azulene ends play a determinant role in the enhancement of the NLO properties of those X-type nanoribbons, e.g., the static first hyperpolarizability (〈β0〉) changes from −783.23 × 10−30 esu to −1421.98 × 10−30 esu. The mechanism of such an enhancement has been investigated. Through two-dimensional second order NLO spectra simulations, particularly besides the strong electro-optical Pockels effect and optical rectification responses, strong electronic sum frequency generations and difference frequency generations are observed in those GNRs. The strong second order NLO responses of those GNRs in the visible light region bring about potential applications of these carbon nanomaterials in nonlinear nanophotonic devices and biological nonlinear optics.
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- 2022
8. Strong second order nonlinear optical properties of azulene-based porphyrin derivatives
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Cui-Cui Yang, Li Li, Wei Quan Tian, Wei-Qi Li, and Ling Yang
- Subjects
Porphyrins ,General Physics and Astronomy ,Physical and Theoretical Chemistry ,Azulenes - Abstract
The high stability, feasible modification, and good π-conjugation of porphyrin derivatives render these porphyrin-based nanomaterials suitable as potential third order nonlinear optical (NLO) materials. Introducing an azulene in pristine porphyrins can significantly improve the second order NLO properties of the system, and this is studied in the present work using density functional theory based methods and the sum-over-states model. The relative orientation of azulene plays a determinant role in the enhancement of the static first hyperpolarizability (〈
- Published
- 2022
9. Modulation of the Second Order Nonlinear Optical Properties of Helical Graphene Nanoribbons Through Introducing Azulene Defects or/and BN Units
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Ling Liu, Cui-Cui Yang, Xue-Lian Zheng, Yuan-Yuan He, Jiu Chen, and Wei Quan Tian
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chemistry.chemical_compound ,Materials science ,chemistry ,Hyperpolarizability ,Density functional theory ,General Chemistry ,Electron ,Azulene ,Kinetic energy ,Molecular physics ,Order of magnitude ,Spectral line ,Graphene nanoribbons - Abstract
The current study has obtained excellent potential nonlinear optical(NLO) materials by combining density functional theory methods with sum-over-states model to predict the second order NLO properties of helical graphene nanoribbons(HGNs) through introducing azulene defects or/and BN units. The introduction of these functional groups deforms the pristine HGN (compression or tension) and enhances obviously the static first hyperpolarizability(〈β0〉) of system by up to two orders of magnitude. The tensor components along the helical axis of HGNs play a dominant role in the total 〈β0〉. The azulene defects and the BN units polarize the pristine HGN to different degrees, and the azulenes and contiguous benzenes are involved in the major electron excitations with significant contributions to 〈β0〉 but the BN units are not. The BN-doped chiral HGNs have good kinetic stability and strong second order NLO properties(6.84 × 105 × 10−30 esu), and can be a potential candidate of high-performance second order NLO materials. The predicted two-dimensional second order NLO spectra provide useful information for further exploration of those helicenes for electro-optic applications.
- Published
- 2021
10. Giant Out-of-Plane Second Harmonic Generation Susceptibility in Janus Group III Chalcogenide Monolayers
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Wei Quan Tian, Jianqun Yang, Xingji Li, Kaijuan Pang, Xiaodong Xu, Yongyuan Jiang, Yadong Wei, Tao Ying, and Weiqi Li
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Materials science ,Condensed matter physics ,Chalcogenide ,Second-harmonic generation ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Out of plane ,chemistry.chemical_compound ,General Energy ,chemistry ,Group (periodic table) ,Monolayer ,Janus ,Physical and Theoretical Chemistry - Published
- 2021
11. Colossal In-Plane and Out-of-Plane Shift Photocurrents in Single-Layer Two-Dimensional α-Antimonide Phosphorus
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Ngeywo Tolbert Kaner, Yadong Wei, Ali Raza, Weiqi Li, YongYuan Jiang, and Wei Quan Tian
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General Materials Science - Abstract
For materials lacking inversion symmetries, an interband transition induced by a photon may result in excited electrons (holes) experiencing a spatial shift leading to generation of directional photocurrents. This phenomenon known as bulk photovoltaic effect (BPVE) shift photocurrent (SPC) has recently attracted immense attention owing to its potential in generating photovoltages that are not restricted by Shockley-Queisser limitations imposed by materials' electronic band gaps. The BPVE was recently reformulated in a quantum mechanics viewpoint as the change in the geometrical phase upon photoexcitation and can now be promptly calculated from Bloch wave functions generated by first-principles calculations. The SPC of an electron (hole) is robust against crystal defects and impurities both in the interior and the surface and can be less dissipative and ultrafast. Herein, an emergence of colossal SPC in a pristine two-dimensional (2D) single-layer α-SbP crystal is predicted from first-principles calculations. An external electric field is further applied on the 2D crystal, and a large SPC enhancement is achieved. The locations of the SPC peaks due to both in-plane and out-of-plane responses suggest that α-SbP can generate a large photocurrent both in visible-light and ultraviolet regions. Single-layer 2D α-SbP is thus an excellent material for strong SPC. This finding is thus expected to open a pathway to exploring efficient photovoltaic devices based on monolayer α-SbP and similar materials.
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- 2022
12. Giant and anisotropic second harmonic generation of V–V binary phosphorene derivative with permanent dipole
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Weiqi Li, Songsong Wang, Xingji Li, Jianqun Yang, Kaijuan Pang, Yongyuan Jiang, Yadong Wei, Tao Ying, Tolbert Kaner Ngeywo, Xiaodong Xu, and Wei Quan Tian
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Materials science ,Valence (chemistry) ,Condensed matter physics ,Band gap ,Second-harmonic generation ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Ferroelectricity ,0104 chemical sciences ,Phosphorene ,chemistry.chemical_compound ,Dipole ,chemistry ,Orders of magnitude (time) ,Monolayer ,Materials Chemistry ,0210 nano-technology - Abstract
Optical nonlinearity of two-dimensional (2D) materials with a permanent dipole is a subject of intense research in the fields ranging from all-optical signal processing to laser nanotechnology due to the potential outstanding performance of 2D materials in nonlinear optical processes, and the feasibility for extensive integration into optoelectronic devices. In the present work, the group-VA binary monolayers are predicted to have giant and broadband second harmonic generation (SHG) properties superior to some of the most popular NLO materials by first-principles calculations. The SHG susceptibility of the α-PAs reaches up to 8.0 × 106 pm2 V−1, which is nearly 1–2 orders of magnitude higher than that of honeycomb monolayer MoS2 and h-BN, and twice larger than the record-high SHG susceptibility of a 2D ferroelectric GeSe monolayer. This intriguing peak is formed by intraband two photon transition ascribed to the relatively small bandgap and large transition matrix elements between valence and conduction band edges. A high-performance nonlinear optical device can be developed using those 2D group-VA monolayer materials with puckled structure and in-plane polarizabilities for multifunctional and integrated optoelectronic applications.
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- 2021
13. Modeling nonlinear optics of nanosystems with sum-over-states model.
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Wei-Quan Tian
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- 2012
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14. First Principles Calculations of Charge Shift Photocurrent in Vdws Slide Double Layered 2d H-Bn and Β-Ges Homostructures
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Kaner, Ngeywo Tolbert, primary, Wei, Yadong, additional, Raza, Ali, additional, Yang, Jianqun, additional, Li, Xingji, additional, Li, Weiqi, additional, Jiang, Yongyuan, additional, and Wei Quan, Tian, additional
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- 2022
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15. High Performance Nonlinear Optical Materials with Simple Aromatic Hydrocarbons
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Yang, Cui-Cui, primary, Ma, Jia-Ying, additional, Su, Xiao, additional, Zheng, Xue-Lian, additional, Chen, Jiu, additional, He, Yuan-Yuan, additional, Wei Quan, Tian, additional, Li, Weiqi, additional, and Yang, Ling, additional
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- 2022
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16. Enhanced Shift Currents in Monolayer 2D GeS and SnS by Strain-Induced Band Gap Engineering
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Yadong Wei, Kaijuan Pang, Wei Quan Tian, Xiaodong Xu, Ngeywo Tolbert Kaner, Yingjie Jiang, Jianqun Yang, Weiqi Li, Guiling Zhang, Yongyuan Jiang, and Xingji Li
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Phase transition ,Materials science ,Condensed matter physics ,Band gap ,business.industry ,General Chemical Engineering ,General Chemistry ,Ferroelectricity ,Article ,Chemistry ,Semiconductor ,Strain engineering ,Monolayer ,Ultimate tensile strength ,business ,Electronic band structure ,QD1-999 - Abstract
Group IV monochalcogenides exhibit spontaneous polarization and ferroelectricity, which are important in photovoltaic materials. Since strain engineering plays an important role in ferroelectricity, in the present work, the effect of equibiaxial strain on the band structure and shift currents in monolayer two-dimensional (2D) GeS and SnS has systematically been investigated using the first-principles calculations. The conduction bands of those materials are more responsive to strain than the valence bands. Increased equibiaxial compressive strain leads to a drastic reduction in the band gap and finally the occurrence of phase transition from semiconductor to metal at strains of -15 and -14% for GeS and SnS, respectively. On the other hand, tensile equibiaxial strain increases the band gap slightly. Similarly, increased equibiaxial compressive strain leads to a steady almost four times increase in the shift currents at a strain of -12% with direction change occurring at -8% strain. However, at phase transition from semiconductor to metal, the shift currents of the two materials completely vanish. Equibiaxial tensile strain also leads to increased shift currents. For SnS, shift currents do not change direction, just as the case of GeS at low strain; however, at a strain of +8% and beyond, direction reversal of shift currents beyond the band gap in GeS occur.
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- 2020
17. Long Radiation Lifetime and Quasi-Isotropic Excitons in Antioxidant V–V Binary Phosphorene Allotropes with Intrinsic Dipole
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Xiaodong Xu, Xingji Li, Ngeywo Tolbert Kaner, Guiling Zhang, Yongyuan Jiang, Wei Quan Tian, Weiqi Li, Kaijuan Pang, Yingjie Jiang, Jianqun Yang, and Yadong Wei
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Electron mobility ,Materials science ,Exciton ,Physics::Optics ,Binary number ,02 engineering and technology ,Radiation ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Dipole ,Phosphorene ,chemistry.chemical_compound ,General Energy ,chemistry ,Sensitivity (control systems) ,Physical and Theoretical Chemistry ,0210 nano-technology ,Excitation - Abstract
Two-dimensional (2D) V–V binary materials are gaining extensive attention because of high carrier mobility, largely tunable optical exciton properties, and high sensitivity to optical excitation. H...
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- 2020
18. Two-dimensional two-photon absorptions and third-order nonlinear optical properties of Ih fullerenes and fullerene onions
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Ling Yang, Wei Quan Tian, Xue-Lian Zheng, Yingli Niu, Bo Shang, Ming-Qian Wang, and Weiqi Li
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Fullerene ,Materials science ,Absorption spectroscopy ,General Physics and Astronomy ,Hyperpolarizability ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Symmetry (physics) ,0104 chemical sciences ,Third order ,Wavelength ,Two-photon excitation microscopy ,Physics::Space Physics ,Physics::Atomic and Molecular Clusters ,ZINDO ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The third order static and dynamic nonlinear optical (NLO) responses of Ih symmetry fullerenes (C60, C240, and C540) and fullerene onions (C60@C240 and C60@C240@C540) are predicted using the ZINDO method and the sum-over-states model. The static second hyperpolarizability of Ih symmetry fullerenes increases exponentially with fullerene size [from 10.00 × 10−34 esu in C60 to 3266.74 × 10−34 esu ≈ γ0(C60) × 92.63 in C540]. The external fields of strong third order NLO responses of Ih symmetry fullerenes change from ultra-violet (C60) to the visible region (C540) as the fullerene size increases. The outer layer fullerene in the fullerene onions has dominant contributions to the third order NLO properties of the fullerene onions, and the inter-shell charge-transfer excitations have conspicuous contributions to the third order NLO properties. The two-dimensional two-photon absorption spectra of C60 and C240 show that those fullerenes have strong two-photon absorptions in the visible region with short wavelength and in the ultra-violet region.
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- 2020
19. Carbon based Y-type molecules for application in nonlinear optics
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Ling Yang, Jiu Chen, Yuan-Yuan He, Cui-Cui Yang, Weiqi Li, Wei Quan Tian, and Xue-Lian Zheng
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chemistry.chemical_classification ,Materials science ,Nonlinear optics ,Hyperpolarizability ,chemistry.chemical_element ,General Chemistry ,Electron acceptor ,Azulene ,Molecular physics ,chemistry.chemical_compound ,chemistry ,Atom ,Materials Chemistry ,Molecule ,Thermal stability ,Carbon - Abstract
Inducing new nonlinear optical (NLO) properties while maintaining the thermal stability of carbon based nanomaterials broadens the application of carbon nanomaterials in opto-electronics. In the present work, polar azulene defects are introduced in Y-type carbon based molecules to induce polarity thus enhancing the second order NLO properties (for example, the static first hyperpolarizability of Y-type carbon based molecules with azulene defects reaches 4.18 × 10−30 esu per heavy atom while that of p-nitroaniline is 2.97 × 10−30 esu per heavy atom). The addition of an electron acceptor at the heptagon end modifies the π electron distribution of Y-type carbon based molecules and significantly enhances the static first hyperpolarizability from 1.73 × 10−30 esu per heavy atom to 8.87 × 10−30 esu per heavy atom, much larger than that of similarly synthesized NLO compounds. The cause of such enhancement by introduction of electron acceptors has been scrutinized.
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- 2020
20. Structures, stabilities, electronic, and optical properties of C64 fullerene isomers, anions (C642- and C644-), metallofullerene Sc2@C64, and Sc2C2@C64.
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Yan-Hong Cui, Wei-Quan Tian, Ji-Kang Feng, and De-Li Chen
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- 2008
- Full Text
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21. First principles calculations of charge shift photocurrent in vdWs slide double layered 2D h-BN and β-GeS homostructures
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Ngeywo Tolbert Kaner, Yadong Wei, Ali Raza, Jianqun Yang, Xingji Li, Weiqi Li, YongYuan Jiang, and Wei Quan Tian
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History ,Polymers and Plastics ,General Materials Science ,General Chemistry ,Business and International Management ,Condensed Matter Physics ,Industrial and Manufacturing Engineering - Published
- 2022
22. Electronic properties of tricoordinated phosphorus in hexagonal phosphininium compounds and molecular aromaticity.
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Wei-Qi Li, Wei-Quan Tian, Ji-Kang Feng, Zi-Zhong Liu, Ai-Min Ren, Chia-Chung Sun, and Yuriko Aoki
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- 2007
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23. Synergetic interaction between copper and carbon impurity induces low temperature growth of highly-defective graphene for enhanced electrochemical performance
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Yi Xi, Wenbin Zhao, Jing Li, Wei Quan Tian, Zegao Wang, Yan Jin, Xuesong Li, Baoshan Hu, and Qian Yang
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Materials science ,Graphene ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,Chemical vapor deposition ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Copper ,0104 chemical sciences ,Catalysis ,law.invention ,Crystallinity ,chemistry ,Chemical engineering ,Impurity ,law ,Cluster (physics) ,General Materials Science ,0210 nano-technology - Abstract
Defect-engineering of few-layer graphene, by modulating local electronic structure and forming highly-active reaction sites, benefits the charge storage and electrochemical reactions. To control defect morphology of graphene, herein, we devise a CH4- chemical vapor deposition (CVD) approach to directly synthesize graphene film with extremely high defect density of 5.9 × 1011 cm−2 and relatively high crystallinity at a low temperature of 700 °C. The C atoms involved in Cu bulk are induced to segregate onto the Cu surface to establish synergetic C–Cu complex catalyst. Theoretical evidence verifies that the interaction between the Cu and C atoms in form of C cluster atop the Cu plane lowers energy barriers for stepwise decomposition of CH4. The 13CH4 isotope data demonstrate that the C clusters are integrated sequentially into the graphene lattice, unraveling the dual roles of carbon impurities. The defective graphene film exhibits a specific capacitance of 10.6 μF/cm2 and excellent electro-catalytic performance. Such a self-induced synergetic catalyst can innovate the methodology of catalysis engineering for controllable synthesis of graphene and other 2D materials.
- Published
- 2019
24. The influence of coupling between chains on the conductivity of atomic carbon chains
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Qiang Wang, Xiaodong Xu, Weiqi Li, Wei Quan Tian, Guiling Zhang, Yongyuan Jiang, Yingjie Jiang, and Zhewen Liang
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inorganic chemicals ,Physics ,Electron density ,Spin polarization ,Spintronics ,General Physics and Astronomy ,Conductance ,Electron ,01 natural sciences ,Band offset ,010305 fluids & plasmas ,chemistry.chemical_compound ,chemistry ,Chemical physics ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,Density functional theory ,Physics::Atomic Physics ,Atomic carbon ,010306 general physics - Abstract
This work presents a theoretical investigation on the electronic properties of double atomic carbon chains bridging graphene electrodes with density functional theory in combination with non-equilibrium Green's function. The influence of strain on the conductance of atomic carbon chains is significant. However, the coupling effect between adjacent chains dominates the intrinsic transport of double atomic carbon chains. For the coupled double atomic chains, the electron conductance of even-numbered atomic chains is significantly enhanced, while the electron conductance of odd-numbered atomic chains decreases to a certain degree, and the dependence of the conductance of double atomic chains on electrode configuration is stronger than the corresponding single atomic chain. More intriguingly, the coupled double atomic chains exhibit excellent spin-filtering properties with antiparallel spins on two electrodes. The current spin polarization stems from the coupling-induced changes of electron density and band offset reaches 100%. The coupled double atomic carbon chains have great potential application in spintronic devices and carbon-based field-effect transistors.
- Published
- 2019
25. UV photolysis of tetrachloro-p-benzoquinone (TCBQ) in aqueous solution: Mechanistic insight from quantum chemical calculations
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Haoran Song, Ling Yang, Jia Gu, Yang Song, Wei Quan Tian, Jun Ma, and Jin Jiang
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Aqueous solution ,Nucleophilic addition ,Chemistry ,General Chemical Engineering ,Photodissociation ,02 engineering and technology ,General Chemistry ,Conjugated system ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Benzoquinone ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,Intersystem crossing ,Environmental Chemistry ,Irradiation ,Triplet state ,0210 nano-technology - Abstract
In this work, a systematical investigation on the transformation of tetrachloro-p-benzoquinone (TCBQ) under UV irradiation (at 253.7 nm) in aqueous solution has been conducted through quantum chemical calculations. The UV irradiation at 253.7 nm could induce the excitation of TCBQ to its first excited singlet state, followed by the intersystem crossing to its first triplet state. In aqueous solution, the first triplet state of TCBQ was thermodynamically and kinetically feasible to react with H2O via 1,4-addition, where the addition of OH− to the α–β conjugated system was the dominant step. Interestingly, with the addition of hydroxyl to TCBQ, the dechlorination of TCBQ occurred with the formation of the monohydroxylated product of TCBQ (OH-TriCBQ). The UV photolysis pathway of OH-TriCBQ was similar to that of TCBQ, and the 1,4-addition of OH− to the ortho-position of the hydroxyl was the most efficient pathway. The dechlorination by 1,4-addition of OH− was also observed for OH-TriCBQ. With much larger forward energy barriers, the nucleophilic addition of carbonyl by OH− (i.e., 1,2-addition) might be less important for the UV photolysis of TCBQ and OH-TriCBQ. The findings in the present study may help to understand the transformation of TCBQ in aqueous solution.
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- 2019
26. NimMon (m + n = 5) Clusters for Hydrogen Electric Reduction: Synergistic Effect of Ni and Mo on the Adsorption and OH Breaking of H2O
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Peng Xiao, Di Gao, Xue-Lian Zheng, Wei Quan Tian, Yuan-Yuan He, Yunhuai Zhang, and Jiu Chen
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Hydrogen ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Catalysis ,Reduction (complexity) ,General Energy ,Adsorption ,chemistry ,Hydrogen evolution ,Physical and Theoretical Chemistry ,0210 nano-technology ,Hydrogen production - Abstract
High efficient catalysts for hydrogen evolution reaction are crucial for hydrogen production. As potential catalysts for hydrogen evolution reaction, NimMon (m + n = 5) clusters have been studied i...
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- 2019
27. Spiral Graphene Nanoribbons with Azulene Defects as Potential Nonlinear Optical Materials
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Xue-Lian Zheng, Weiqi Li, Yuan-Yuan He, Wei Quan Tian, Ling Yang, Xiaodong Xu, and Jiu Chen
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Quantitative Biology::Biomolecules ,Physics::Biological Physics ,Materials science ,Physics::Medical Physics ,Physics::Optics ,Hyperpolarizability ,Nonlinear optics ,chemistry.chemical_element ,Nanotechnology ,Azulene ,Nanomaterials ,chemistry.chemical_compound ,chemistry ,General Materials Science ,Thermal stability ,Spiral (railway) ,Carbon ,Graphene nanoribbons - Abstract
Inducing new nonlinear optical (NLO) properties while keeping the thermal stability of carbon-based nanomaterials paves a new path for the application of carbon nanomaterials in optoelectronics. In...
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- 2019
28. Chiral heteronanotubes: arrangement-dominated chiral interface states and conductivities
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Linhua Liu, Xiaodong Xu, Yadong Wei, Weiqi Li, Wei Quan Tian, Bingyi Liu, Guiling Zhang, and Yongyuan Jiang
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Work (thermodynamics) ,Nanostructure ,Materials science ,Fabrication ,High Energy Physics::Lattice ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Antiparallel (biochemistry) ,01 natural sciences ,0104 chemical sciences ,Magnetic field ,chemistry.chemical_compound ,chemistry ,Boron nitride ,Chemical physics ,Monolayer ,General Materials Science ,0210 nano-technology ,Stoichiometry - Abstract
Structural analogue between pure carbonic nanostructures and their boron nitride counterparts provides possibilities for the fabrication of BCN hetero-nanomaterials, which have attracted widespread interest and been synthesized with stacked-layer, monolayer and tubular morphologies. In this work, the arrangement-dominated chiral interface states and conductivities of BCN heteronanotubes are investigated in detail by first principles calculations. The π-conjugated states can be driven by the high potential barrier of insulating BN domains to form chiral transport states along the interfaces. The emerging antiparallel and parallel chiral interface states play a dominant role for resonant transport and provide possibilities for the formation of chiral currents. Moreover, the unidirectional chiral currents have advantages to induce a magnetic field which can reach over 0.1 T. In contrast to the parallel-arranged chiral heteronanotubes, the antiparallel-arranged chiral heteronanotubes with the same stoichiometry have narrower band-gaps and stronger chiral conductivities. Such arrangement-dominated chiral transport interface states endow CHNTs with potential application in magneto-electronics.
- Published
- 2019
29. Hydrogen storage of dual-Ti-doped single-walled carbon nanotubes
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Wei Quan Tian, Hong Wei Wei, Ling Yang, Li Li Yu, Wei Qi Li, and Xin Zhou
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Materials science ,Hydrogen ,Renewable Energy, Sustainability and the Environment ,Doping ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,Carbon nanotube ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,law.invention ,Hydrogen storage ,Fuel Technology ,Adsorption ,Chemical engineering ,Physisorption ,chemistry ,law ,Atom ,Molecule ,0210 nano-technology - Abstract
The hydrogen adsorption capacity of dual-Ti-doped (7, 7) single-walled carbon nanotube (Ti-SWCNTs) has been studied by the first principles calculations. Ti atoms show different characters at different locations due to local doping environment and patterns. The dual-Ti-doped SWCNTs can stably adsorb up to six H2 molecules through Kubas interaction at the Ti2 active center. The intrinsic curvature and the different doping pattern of Ti-SWCNTs induce charge discrepancy between these two Ti atoms, and result in different hydrogen adsorption capacity. Particularly, eight H2 molecules can be adsorbed on both sides of the dual-Ti decorated SWCNT with ideal adsorption energy of 0.198 eV/H2, and the physisorption H2 on the inside Ti atom has desirable adsorption energy of 0.107 eV/H2, ideal for efficient reversible storage of hydrogen. The synergistic effect of Ti atoms with different doping patterns enhances the hydrogen adsorption capacity 4.5H2s/Ti of the Ti-doped SWCNT (VIII), and this awaits experimental trial.
- Published
- 2019
30. Tuning azulene defects and doping of N atoms in graphene nanosheets: Improving nonlinear optical properties of carbon-based nano materials
- Author
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Ling Yang, Cui-Cui Yang, Weiqi Li, Xue-Lian Zheng, and Wei Quan Tian
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Materials science ,business.industry ,Graphene ,Doping ,Hyperpolarizability ,Nonlinear optics ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,Nanomaterials ,GNSS applications ,law ,Atom ,Optoelectronics ,Thermal stability ,business - Abstract
Recent successful syntheses of azulene-defect graphene nanosheets (GNSs) pave a path for the applications of those GNSs in nonlinear optics , since azulene-defect GNSs maintains the thermal stability of carbon-based nanomaterials and possesses potential large nonlinear optical (NLO) responses. In the present work, azulene-defect GNSs with different relative position and orientation are designed for applications in optoelectronics and nonlinear optics. The all-carbon azulene-defect GNS Paral-2 with parallel orientated azulenes has good electronic kinetic stability as well as a large static first hyperpolarizability ( 0>) of 1032.28 × 10−30 esu (18.43 × 10−30 esu per heavy atom). The Paral-0-4N, formed by replacing four edge C atoms with N atoms in the GNS Paral-0, has the largest (1247.68 × 10−30 esu, 22.28 × 10−30 esu per heavy atom) due to the charge transfer based electron excitations and the polar structure while with enhanced electronic kinetic stability. The two-dimensional second order NLO spectra of those azulene-defect GNSs provide vital information for further experimental exploration and applications. The introduction of polar azulene in GNSs to improve the NLO responses and doping of nitrogen atoms to enhance the electronic kinetic stability of GNSs provide a practical strategy and useful information for future NLO materials design.
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- 2022
31. Giant Shift Photovoltaic Current in Group V‐V Binary Nanosheets
- Author
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Ngeywo Tolbert Kaner, Yadong Wei, Tao Ying, Xiaodong Xu, Weiqi Li, Ali Raza, Xingji Li, Jianqun Yang, YongYuan Jiang, and Wei Quan Tian
- Subjects
Statistics and Probability ,Numerical Analysis ,Multidisciplinary ,Modeling and Simulation - Published
- 2022
32. Two-dimensional two-photon absorptions and third-order nonlinear optical properties of I
- Author
-
Xue-Lian, Zheng, Ling, Yang, Bo, Shang, Ming-Qian, Wang, Yingli, Niu, Wei-Qi, Li, and Wei Quan, Tian
- Abstract
The third order static and dynamic nonlinear optical (NLO) responses of Ih symmetry fullerenes (C60, C240, and C540) and fullerene onions (C60@C240 and C60@C240@C540) are predicted using the ZINDO method and the sum-over-states model. The static second hyperpolarizability of Ih symmetry fullerenes increases exponentially with fullerene size [from 10.00 × 10-34 esu in C60 to 3266.74 × 10-34 esu ≈ γ0(C60) × 92.63 in C540]. The external fields of strong third order NLO responses of Ih symmetry fullerenes change from ultra-violet (C60) to the visible region (C540) as the fullerene size increases. The outer layer fullerene in the fullerene onions has dominant contributions to the third order NLO properties of the fullerene onions, and the inter-shell charge-transfer excitations have conspicuous contributions to the third order NLO properties. The two-dimensional two-photon absorption spectra of C60 and C240 show that those fullerenes have strong two-photon absorptions in the visible region with short wavelength and in the ultra-violet region.
- Published
- 2020
33. Search for more stable [C.sub.58][X.sub.18] isomers: Stabilities and electronic properties of seven-membered ring [Csub.58][X.sub.18] fullerene derivatives (X = H, F, and Cl)
- Author
-
De-Li Chen, Wei Quan Tian, Ji-Kang Feng, and Chia-Chung Sun
- Subjects
Chlorine compounds -- Chemical properties ,Chlorine compounds -- Structure ,Density functionals -- Usage ,Fluorine compounds -- Chemical properties ,Fluorine compounds -- Structure ,Chemicals, plastics and rubber industries - Abstract
A systematic density functional theory (DFT) calculations is performed on the stabilities and electronic properties of two different structures [Csub.58][X.sub.18] and [C.sub.58][X.sub.1], where X = H, F, and Cl. It is seen that the large energy gaps between the highest occupied molecular orbitals and the lowest unoccupied molecular orbital and the aromatic character possess high stabilities.
- Published
- 2007
34. Evolution of phosphotriesterase activities of the metallo-β-lactamase family: A theoretical study
- Author
-
Rong-Zhen Liao, Ling Yang, Long-Fei Yan, Hao Zhang, and Wei-Quan Tian
- Subjects
Models, Molecular ,0301 basic medicine ,Phylogenetic tree ,Chemistry ,Stereochemistry ,Hydrolysis ,Phosphotriesterase activity ,Zinc ion ,SUPERFAMILY ,Biochemistry ,beta-Lactamases ,Metallo β lactamase ,Inorganic Chemistry ,03 medical and health sciences ,Phosphoric Triester Hydrolases ,030104 developmental biology - Abstract
Metallo-β-lactamase (MβL) is a eubacterial zinc metallo-hydrolase superfamily. Despite their well-known lactamase activities, MβL family members also have the ability to catalyze phosphotriester hydrolysis with different phosphotriesterase activities. In the present study, based on crystal structure comparisons of the related MβL members, a series of models was constructed and calculated using the density functional theory (DFT) method to explore the relationship between active-site changes and phosphotriesterase activities. These calculations show that the energetic barriers for phosphotriesterase activity are considerably reduced due to active-site differences, which describes an evolutionary trend for the development of phosphotriesterase activity in the MβL superfamily. The key event is the appearance of a specialized and negatively charged residue bridging both zinc ions, which plays the two important roles of maintaining charge balance and stabilizing the binuclear active-site structure. This pathway is also consistent with the evolutionary relationships determined by phylogenetic tree analysis using complete residue sequences. Our studies provide the first methodology to explore the development of a new enzyme activity within a superfamily, and to shed new light on understanding the catalytic mechanism from an evolutionary perspective.
- Published
- 2018
35. Insights into the effects of alcohols on hydrated electron (eaq−) generation from the p-benzoquinone/UV process
- Author
-
Jin Jiang, Wei Qiu, Yang Song, Ling Yang, Jia Gu, Jingxin Yang, Jun Ma, and Wei Quan Tian
- Subjects
Semiquinone ,Chemistry ,Process Chemistry and Technology ,Radical ,Butanol ,Photodissociation ,02 engineering and technology ,010501 environmental sciences ,021001 nanoscience & nanotechnology ,Solvated electron ,Photochemistry ,01 natural sciences ,Benzoquinone ,Catalysis ,chemistry.chemical_compound ,Hydroxymethyl ,Triplet state ,0210 nano-technology ,0105 earth and related environmental sciences ,General Environmental Science - Abstract
In this work, the effect of alcohols as hydrogen donors on hydrated electron (e aq − ) generation from p -benzoquinone ( p -BQ) photolysis was investigated by quantum chemical calculations and experiments to further understand the underlying mechanisms associated within the p -BQ/UV process. Theoretically, the UV photolysis of p -BQ at 253.7 nm in the presence of H 2 O could induce the formation of p -HOC 6 H 4 OH and hydroxy- p -benzoquinone, which was almost independent of the addition of CH 3 OH. While, the first triplet state of hydroxy- p -benzoquinone preferred to react with CH 3 OH (rather than H 2 O) to release the corresponding semiquinone radical and hydroxymethyl radical ( CH 2 OH). These two radicals could induce the reduction of p -BQ to p -benzosemiquinone radical and thus enhanced the formation of p -HOC 6 H 4 OH as the precursor of e aq − . Experimentally, the detection of e aq − generated in the process was accomplished by the degradation of monochloroacetic acid (MCAA) (the probe of e aq − ). With the addition of CH 3 OH, the degradation of MCAA was accelerated in the p -BQ/UV process. A similar acceleration was also observed by the addition of ethanol or 2-propanol with the α-H. However, tert -butanol, which is without the α-H in the structure, didn’t induce the acceleration. Since the quinone-like and alcoholic groups are widely distributed in the environment, these findings may improve the understanding of the photochemistry of quinones in the presence of alcohols with the α-H.
- Published
- 2018
36. Strong electron-polarized atom chain in amorphous phase-change memory Ge Sb Te alloy
- Author
-
Nian-Ke Chen, Xue-Peng Wang, Hong-Bo Sun, Wei Quan Tian, Shengbai Zhang, and Xian-Bin Li
- Subjects
Materials science ,Polymers and Plastics ,Alloy ,Nanotechnology ,02 engineering and technology ,Electron ,GeSbTe ,engineering.material ,01 natural sciences ,chemistry.chemical_compound ,0103 physical sciences ,Atom ,010306 general physics ,Amorphous metal ,business.industry ,Metals and Alloys ,Material Design ,021001 nanoscience & nanotechnology ,Electronic, Optical and Magnetic Materials ,Amorphous solid ,Phase-change memory ,chemistry ,Ceramics and Composites ,engineering ,Optoelectronics ,0210 nano-technology ,business - Abstract
Phase-change memory (PCM) material is the promising material system for nonvolatile-memory technology. Performance optimization of PCM device urgently requires the deeper clarification of its material “Gene”. In this study, through first-principles calculations, p-orbital-aligned atom chains are identified to play important roles in governing optoelectronic reflectivity in amorphous Ge2Sb2Te5. These atom chains make the electronic state of the amorphous Ge2Sb2Te5 hold strong electron-polarized components, thereby governing the optical property. The present study offers a new understanding of “Gene” for PCM materials which benefit the material design and the performance improvement of PCM devices.
- Published
- 2018
37. Metal–Insulator Transition of Ge–Sb–Te Superlattice: An Electron Counting Model Study
- Author
-
Nian-Ke Chen, Sheng-Yi Xie, Xian-Bin Li, Shengbai Zhang, Xue-Peng Wang, Hong-Bo Sun, and Wei Quan Tian
- Subjects
010302 applied physics ,Work (thermodynamics) ,Materials science ,Condensed matter physics ,Band gap ,Superlattice ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Computer Science Applications ,symbols.namesake ,Atomic layer deposition ,0103 physical sciences ,symbols ,Electrical and Electronic Engineering ,Metal–insulator transition ,van der Waals force ,0210 nano-technology ,Electron counting ,Stoichiometry - Abstract
Ge–Sb–Te superlattice (GST-SL) is a newly emerging electronic material for nonvolatile phase-change memory with ultralow energy cost. However, its switching mechanism is still unclear with intensive debates. In this work, by first-principles calculations and an electron counting model study, we study the possible mechanism of phase change and the accompanying property transition of GST-SL. GST-SL are separated into individual layers by van der Waals gaps. We demonstrate that both the global chemical stoichiometry of the material and the local chemical stoichiometry of individual layer block are required to have an insulating band gap according to an electron counting model analysis. The electrical property can be adjusted by changing the local stoichiometry, such as producing defects around van der Waals gaps. Inspired by a previous experiment, we propose that a stacking-fault motion can spontaneously alter the band gap and results in a metal–insulator transition. This transition may provide a significant change of carrier concentration and indicate an ultralow energy-consumption process with a low energy barrier. The present investigations reveal a picture of electrical transition in GST-SL and may guide us to improve its device performances.
- Published
- 2018
38. Double-helix PnLin chains: novel potential nonlinear optical materials
- Author
-
Yangyang Hu, Weiqi Li, Yingjie Jiang, Yunan Feng, Guiling Zhang, Xiudong Sun, Wei Quan Tian, and Xiaodong Xu
- Subjects
Circular dichroism ,Materials science ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Quantum chemistry ,Molecular electronic transition ,Spectral line ,0104 chemical sciences ,Atomic electron transition ,Chemical physics ,Helix ,Physical and Theoretical Chemistry ,0210 nano-technology ,HOMO/LUMO ,Excitation - Abstract
The structures, circular dichroism (CD) spectra and nonlinear optical (NLO) responses of a series of inorganic double-helix chains, PnLin (n = 6–12), have been investigated using the quantum chemistry method. P–P and P–Li interactions play a major role in stabilizing double-helix chains. The distinctive CD spectra of the double-helix frameworks (namely, a sharp negative CD band at short-wavelength region and a positive CD band at long-wavelength region) become obvious with increasing number of PLi units. The NLO response augments with the length of the double-helix chains, and the contribution of the axial component along the chain direction gradually becomes crucial simultaneously. Synergistic effects, a decrease of crucial electronic transition energies and charge transfer excitation give rise to enhanced NLO responses. In particular, the electronic transitions from the highest occupied molecular orbital to the lowest unoccupied molecular orbital make significant contributions not only to the positive CD bands in the long-wavelength region, but also to the NLO responses of the double-helix PnLin (n = 6–12) chains.
- Published
- 2018
39. Ozonization at the vacancy defect site of the single-walled carbon nanotube
- Author
-
Liu, Lei Vincent, Wei Quan Tian, and Wang, Yan Alexander
- Subjects
Ozonization -- Analysis ,Nanotubes -- Structure ,Nanotubes -- Chemical properties ,Molecular dynamics -- Analysis ,Chemicals, plastics and rubber industries - Abstract
The ozonization at the vacancy defect site of the single-walled carbon nanotube (SWCNT) is studied by static quantum mechanics and atom-centered density matrix propagation based ab initio molecular dynamics within a two-layered ONIOM method. The chirality of the SWCNT has an important effect on the reactivity of the vacancy defect than the diameter of the SWCNT, since the chirality of the SWCNT can readily modify the structure of the vacancy defect.
- Published
- 2006
40. Chemical reaction of nitric oxides with the 5-IDB defect of the single-walled carbon nanotube
- Author
-
Lei Vincent Liu, Wei Quan Tian, and Yan Alexander Wang
- Subjects
Nitric oxide -- Electric properties ,Chemical reactions -- Research ,Molecular orbitals -- Research ,Chemicals, plastics and rubber industries - Abstract
The chemical reactivity of the 5-1DB defects are assessed from the analyses of the frontier molecular orbitals (FMOS) and local density of states (LDOS) and the reaction of nitric oxides (NOs) with the 5-1DB defects on the single-walled carbon nanotube (SWCNT) is described. It is indicated that the 5-1DB defects on the SWCNT is chemically reactive and can be used as the active site for the functionalization of SWCNT.
- Published
- 2006
41. Engineering two-dimensional electronics by semiconductor defects
- Author
-
Wei Quan Tian, Dong Han, Dan Wang, Hong-Bo Sun, and Xian-Bin Li
- Subjects
Materials science ,business.industry ,Biomedical Engineering ,Pharmaceutical Science ,Defect engineering ,Bioengineering ,Nanotechnology ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Semiconductor ,Nanoelectronics ,0103 physical sciences ,Theoretical methods ,Electrical performance ,General Materials Science ,Electronics ,010306 general physics ,0210 nano-technology ,business ,Electrical conductor ,Biotechnology ,Electronic properties - Abstract
Two-dimensional (2D) semiconductors have attracted considerable attentions from electronic-engineering community due to their unique electronic properties. Especially, the inherent advantage of scaling semiconductor into atomic thickness has raised the prospect of possible extension of the Moore’s law. To achieve 2D electronics, a full comprehension of semiconductor defect physics and chemistry is indispensable due to its controlling electrical performance of 2D materials and functionalizing their devices. In this review, first we explain why 2D semiconductors is important for nanoelectronics and optoelectronics. Second, we elucidate how native defects or intentional impurities affect and control electrical characteristic in 2D semiconductors, such as carrier concentration and their conductive type. In this section, experimental pictures of defects and several updated theoretical methods to evaluate carrier ionization energies of defects and their conductive type are introduced in detail. Third, typical device experiments are shown to demonstrate a direct role of defects to functionalize 2D electronic device. Furthermore, a database of popular defects and their electrical properties in current popular 2D semiconductors is summarized for references. Last, we discuss the challenges and potential prospects of defect engineering for 2D devices. The present paper offers important viewpoints from semiconductor defects to design the emerging 2D electronics.
- Published
- 2017
42. Bimetallic clusters Pt6Au: Geometric and electronic structures within density functional theory
- Author
-
Wei Quan Tian, Ge, Maofa, Fenglong Gu, and Yuriko Aoki
- Subjects
Platinum -- Structure ,Platinum -- Atomic properties ,Gold compounds -- Structure ,Gold compounds -- Atomic properties ,Density functionals -- Usage ,Chemicals, plastics and rubber industries - Abstract
The geometric and electronic structures of the bimetallic cluster Pt6Au are extensively studied and compared with the pure Pt7 cluster. The relative stabilities of the Pt6Au clusters lie very close to each other, thus causing difficulty in isolating the Pt6Au conformation in experiment.
- Published
- 2005
43. Theoretical studies on the structure and aromaticity of Ti2P6(super +)
- Author
-
Wei-Qi Li, Wei Quan Tian, Ji-Kang Feng, Zi-Zhong Liu, Ai-Min Ren, and Zhang, Gang
- Subjects
Titanium compounds -- Chemical properties ,Titanium compounds -- Structure ,Phosphorus compounds -- Chemical properties ,Phosphorus compounds -- Structure ,Density functionals -- Usage ,Chemicals, plastics and rubber industries - Abstract
Cationic cluster Ti2P6(super +) is studied within density functional theory. The structure of this cluster is predicted to be a slightly distorted tetragonal prism and the dissociation energy of this cationic cluster is higher than that of the known compound, [(P5)2Ti](super 2-), because of the different bonding in these two compounds.
- Published
- 2005
44. Theoretical study on structures and aromaticities of P(sub 5)- anion, [Ti (mu(super 5)-P5)]- and sandwich complex [Ti(mu(super 5)-P5)(sub 2)](super 2-)
- Author
-
Zi-Zhong Liu, Wei-Quan Tian, Ji-Kang Feng, Gang Zhang, and Wei-Qi Li
- Subjects
Titanium compounds -- Chemical properties ,Titanium compounds -- Structure ,Phosphorus compounds -- Chemical properties ,Phosphorus compounds -- Structure ,Aromatic compounds -- Chemical properties ,Chemicals, plastics and rubber industries - Abstract
The equilibrium geometries, energies, harmonic vibrational frequencies, and nucleus independent chemical shifts (NICSs) of the ground state of P(sub 5)- anion, [Ti (mu(super 5)-P5)]- and sandwich complex [Ti(mu(super 5)-P5)(sub 2)](super 2-) are calculated. The results revealed that in each of the three molecules, the P-P and Ti-P bond distances are perfectly equal.
- Published
- 2005
45. Hydrated electron (e aq − ) generation from p -benzoquinone/UV: Combined experimental and theoretical study
- Author
-
Jianqiao Zhang, Wei Quan Tian, Shaofang Sun, Jin Jiang, Ling Yang, Jia Gu, Huizhong Chi, Jun Ma, Jingxin Yang, and Yang Song
- Subjects
Quantum chemical ,Hydroquinone ,Process Chemistry and Technology ,Photodissociation ,Inorganic chemistry ,02 engineering and technology ,010501 environmental sciences ,021001 nanoscience & nanotechnology ,Solvated electron ,01 natural sciences ,Benzoquinone ,Catalysis ,chemistry.chemical_compound ,chemistry ,Molar ratio ,Physical chemistry ,Irradiation ,Triplet state ,0210 nano-technology ,0105 earth and related environmental sciences ,General Environmental Science - Abstract
A p -benzoquinone ( p -BQ)/UV process to induce hydrated electron (e aq − ) generation was predicted by quantum chemical calculations and validated by experiment in this work. Theoretically, the photolysis of p -BQ under UV irradiation at 253.7 nm could induce water to generate e aq − with a molar ratio of 1:2 via the direct triplet mechanism, in which 1,4-addition reaction of the first triplet state of p -BQ with water was the key step. Experimentally, monochloroacetic acid (MCAA) (the probe of e aq − ) was used to detect e aq − generated in the p -BQ/UV process. The generation efficiency showed a positive linear dependence on the p -BQ concentration, which illustrated the crucial role of p -BQ on the generation of e aq − . During the photolysis, p -hydroquinone was the primary intermediate for the generation of e aq − . Kinetically, the energy barriers of the e aq − generation from p -HOC 6 H 4 OH, p -HOC 6 H 4 O − and p - − OC 6 H 4 O − were 100.8 kcal mol −1 , 46.5 kcal mol −1 and 5.6 kcal mol −1 , respectively. Both the experimental and theoretical results show that the generation of e aq − was much more efficient from the anions than that from p -HOC 6 H 4 OH. The findings in the present study may help to understand the mechanism of e aq − generation from natural organic matters (NOM), since quinone-like groups are usually contained in NOM.
- Published
- 2017
46. Spatial manipulating spin-polarization and tunneling patterns in graphene spirals via periphery structural modification
- Author
-
Qiang Wang, Weiqi Li, Xin Zhou, Linhua Liu, Guiling Zhang, Yongyuan Jiang, Xiaodong Xu, Ruihuan Tian, and Wei Quan Tian
- Subjects
Coupling ,Materials science ,Spintronics ,Spin polarization ,Condensed matter physics ,Graphene ,Nanotechnology ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,Position (vector) ,law ,First principle ,General Materials Science ,Spiral (railway) ,0210 nano-technology ,Quantum tunnelling - Abstract
A new carbon-based morphology, graphene spirals (GSs), possesses interesting electronic features with inter-layer interaction and intra-layer interaction, ascribed to its unique intra-system electronic coupling states. The spin-polarization and the tunneling patterns of GSs manipulated by the periphery structural modification were investigated in detail with first principle calculations. The spin-polarized edge-states and transport properties can be enhanced and modulated by the constructed trigonal corners efficiently. Governed by the position and the number of the introduced carbon-hexagons, diverse spin-polarized tunneling states and various edge-state couplings between central spiral structure and electrodes can be achieved. More significantly, the contribution of inter-layer tunneling and intra-layer tunneling can be dominated by the topological signatures of GSs. For all spiral conformations, inter-layer tunneling always contributes to the net spin-dependent current. Remarkably, when carbon-hexagons are introduced at some typical positions, the complete spiral current along spiral construction is induced by intra-layer tunneling. Those features provide a good tunability of spin-polarized couplings and tunneling patterns in GSs for spintronic applications.
- Published
- 2017
47. Hydrated electron (eaq−) generation from phenol/UV: Efficiency, influencing factors, and mechanism
- Author
-
Wei Quan Tian, Jun Ma, Shaofang Sun, Jin Jiang, Huizhong Chi, Ling Yang, Jingxin Yang, Jianqiao Zhang, Yang Song, and Jia Gu
- Subjects
Hydrogen ,Chemistry ,Process Chemistry and Technology ,Inorganic chemistry ,chemistry.chemical_element ,Phenoxyl radical ,010501 environmental sciences ,010402 general chemistry ,Hydrogen atom abstraction ,Solvated electron ,Photochemistry ,01 natural sciences ,Acceptor ,Catalysis ,0104 chemical sciences ,Adduct ,chemistry.chemical_compound ,Phenol ,0105 earth and related environmental sciences ,General Environmental Science ,Hydroxyl ion - Abstract
A phenol/UV (253.7 nm) process to generate hydrated electron (eaq−) was experimentally and theoretically studied in the present work, where monochloroacetic acid (MCAA) was selected as the probe of eaq−. It was demonstrated that the eaq− generation efficiency was dependent on the phenol concentration and pH. To interpret the dependence, a mechanism for the generation of eaq− from phenol was proposed and confirmed by the quantum chemical calculations. Theoretically, phenol could eject eaq− and phenoxyl radical (C6H5O ), followed by the addition of hydroxyl ion (OH−) to C6H5O , and the simultaneous formation of phenol and p-hydroquinone was accomplished by hydrogen abstraction of the adduct with C6H5O as hydrogen acceptor (period I). The generated p-hydroquinone could also release eaq− with p-benzoquinone as the product (period II). Totally, one mole of phenol could generate four moles of eaq− via two periods, and two moles were generated in period I and two moles were in period II. Experimentally, eaq− could be ejected from phenol and phenolate, and the molar ratios of the species were determined by pH. Kinetically, the energy barriers of the electron release from phenol and phenolate were 63.7 kcal mol−1 and 62.3 kcal mol−1, respectively, which confirmed that the generation of eaq− from phenolate was much more efficient than that from phenol. These results may promote the development of novel eaq− reduction processes based on the phenolic compounds, since they are abundant in the environment.
- Published
- 2017
48. Excitation to defect-bound band edge states in two-dimensional semiconductors and its effect on carrier transport
- Author
-
Sheng-Yi Xie, Dong Han, Xian-Bin Li, Dan Wang, Damien West, Shengbai Zhang, Nian-Ke Chen, Wei Quan Tian, and Vincent Meunier
- Subjects
lcsh:Computer software ,Materials science ,Dopant ,business.industry ,Molecular physics ,Computer Science Applications ,Delocalized electron ,lcsh:QA76.75-76.765 ,Semiconductor ,Mechanics of Materials ,Modeling and Simulation ,Excited state ,Ionization ,lcsh:TA401-492 ,Physics::Atomic and Molecular Clusters ,lcsh:Materials of engineering and construction. Mechanics of materials ,General Materials Science ,Charge carrier ,Ionization energy ,business ,Excitation - Abstract
The ionization of dopants is a crucial process for electronics, yet it can be unexpectedly difficult in two-dimensional materials due to reduced screening and dimensionality. Using first-principles calculations, here we propose a dopant ionization process for two-dimensional semiconductors where charge carriers are only excited to a set of defect-bound band edge states, rather than to the true band edge states, as is the case in three-dimensions. These defect-bound states have small enough ionization energies but large enough spatial delocalization. With a modest defect density, carriers can transport through band by such states.
- Published
- 2019
49. Graphene-based monoatomic chain spintronics: contact-derived half-metallicity, sp2 vs sp
- Author
-
Xiaodong Xu, Linhua Liu, Guiling Zhang, Yongyuan Jiang, Yangyang Hu, Weiqi Li, and Wei Quan Tian
- Subjects
Materials science ,Spin states ,02 engineering and technology ,01 natural sciences ,law.invention ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,law ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,010306 general physics ,Spin (physics) ,Quantum tunnelling ,Condensed matter physics ,Spintronics ,Graphene ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Zigzag ,Nanoelectronics ,chemistry ,Boron nitride ,0210 nano-technology - Abstract
Because of the remarkable semi-metallicity and edge states, graphene-based nanoelectronics has become an intense arena in low-dimensional atomic device science and technology. Nowadays, various single atomic chains have been successfully fabricated, which can serve as multi-functional interconnects to bridge atomic devices. Using first principles approach, the spintronic applications of graphene-based carbon atomic chains and boron nitride atomic chains MTJs (magnetic tunnelling junctions) are systematically investigated in this work. The results show that the half-metallicity is only contact-dominated (sp and sp2 contacts), which cannot be switched by gate voltages, strain, the length of atomic chains, or the width of zigzag graphene nanoribbon leads. The intrinsic physics is that the electronic coupling in sp junctions provides partial transmission states for both spin currents, while one spin state is completely blocked by the electronic coupling in sp2 junctions. Therefore, the sp2 junctions present half-metallicity and remarkable tunnelling magneto-resistance (105%–106%), demonstrating the potential applications as spin-valve.
- Published
- 2021
50. Temperature differentiated synthesis of hierarchically structured N,S-Doped carbon nanotubes/graphene hybrids as efficient electrocatalyst for hydrogen evolution reaction
- Author
-
Bingyan Xiong, Meng Nie, Yan Jin, Wenbin Zhao, Jiao Ye, Pengyu Fan, Wei Quan Tian, Liang Fang, Baoshan Hu, and Qian Yang
- Subjects
Materials science ,Graphene ,Mechanical Engineering ,Metals and Alloys ,chemistry.chemical_element ,Carbon nanotube ,Chemical vapor deposition ,Overpotential ,Electrocatalyst ,Electrochemistry ,law.invention ,Catalysis ,chemistry ,Chemical engineering ,Mechanics of Materials ,law ,Materials Chemistry ,Carbon - Abstract
The development of carbon-based catalysts with excellent activity for hydrogen evolution reaction (HER) is highly desirable but still remains a significant challenge. Chemical doping and morphology engineering are paramount to enhance their catalytic performance toward HER. Herein, we present a novel and effective strategy to synthesize heteroatoms-doped three-dimensional (3D) carbon nanotubes/graphene hierarchical architecture (N,S-CNTs/N,S-G) on layered double oxide substrates, in which the N,S-doped CNTs are in-situ grown on both sides of N,S-doped graphene, by two differentiated chemical vapor deposition (CVD) processes. The high concentrations of N and S dopants (up to 6.5 at.%) provide sufficient catalytic active sites for HER, while the CNTs seamlessly grafted on graphene ensure the excellent electric conductivity of N,S-CNTs/N,S-G hybrids. Consequently, the 3D N,S-CNTs/N,S-G composites display superior electrocatalytic activity for HER with an onset potential of 62 mV vs. RHE (achieve current density of 1 mA cm−2) and a small overpotential of 126 mV at 10 mA cm−2, which outperforms most of reported chemical doped carbon-based composites. The synthetic strategy facilitates the fabrication of other heteroatoms-doped 3D electrochemical catalysts.
- Published
- 2020
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