46 results on '"Lei Wang"'
Search Results
2. Red-Emitting SrGa2O4:Cu2+ Phosphor with Super-Long Persistent Luminescence
- Author
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Lei Wang, Cailu Wang, Yang Chen, Yang Jiang, Lei Chen, Jinzhang Xu, Bingyan Qu, and Hubertus T. Hintzen
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General Chemical Engineering ,Materials Chemistry ,General Chemistry - Published
- 2022
3. Phototunable, Reconfigurable, and Complex Shape Transformation of Fe3+-Containing Bilayer Polymer Materials
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Lei Wang, Jingtao Jiang, Chenghao Dai, Huilan Zeng, Yifan Shang, Yongqi Liu, Qiyan Yin, and Gengsheng Weng
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General Chemical Engineering ,Materials Chemistry ,General Chemistry - Published
- 2022
4. Reaction Pathways toward Sustainable Photosynthesis of Hydrogen Peroxide by Polymer Photocatalysts
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Hao Cheng, Jun Cheng, Lei Wang, and Hangxun Xu
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General Chemical Engineering ,Materials Chemistry ,General Chemistry - Published
- 2022
5. Three-Dimensional Shape Transformation of Eu3+-Containing Polymer Films through Modulating Dynamic Eu3+-Iminodiacetate Coordination
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Qiyan Yin, Lei Wang, Jingtao Jiang, Chenghao Dai, Gengsheng Weng, and Jie He
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General Chemical Engineering ,Materials Chemistry ,General Chemistry - Published
- 2022
6. Regulating the Alloying Degree and Electronic Structure of Pt–Au Nanoparticles for High-Efficiency Direct C2+ Alcohol Fuel Cells
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Xiaoli Zhang, Zewen Zhang, Minghang Jiang, Wenjun Zhang, Zhong Jin, Yi Hu, Songyuan Yang, Junchuan Liang, and Lei Wang
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Alcohol fuel ,Materials science ,General Chemical Engineering ,Electric potential energy ,Nanoparticle ,02 engineering and technology ,General Chemistry ,Electronic structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Degree (temperature) ,Chemical engineering ,Materials Chemistry ,0210 nano-technology - Abstract
Direct alcohol fuel cells represent a promising green and sustainable route for chemical to electrical energy conversion; however, designing highly efficient electrocatalysts for the electro-oxidat...
- Published
- 2021
7. Kinetics Features Conducive to Cache-Type Nonvolatile Phase-Change Memory
- Author
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Evan Ma, Yimin Chen, Jun-Qiang Wang, Wei Zhang, Keyuan Ding, Xiang Shen, Lei Wang, Xierong Zeng, Bin Chen, Feng Rao, Kunlong Li, and Fangying Jiao
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Hardware_MEMORYSTRUCTURES ,Computer science ,General Chemical Engineering ,Kinetics ,02 engineering and technology ,General Chemistry ,Parallel computing ,Type (model theory) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Phase-change memory ,Universal memory ,Path (graph theory) ,Materials Chemistry ,Cache ,0210 nano-technology - Abstract
Cache-type phase-change random-access memory is a remaining challenge on the path to universal memory. The recently designed Sc0.2Sb2Te3 (SST) alloy is one of the most promising phase-change materi...
- Published
- 2019
8. Achieving Balanced Charge Transport and Favorable Blend Morphology in Non-Fullerene Solar Cells via Acceptor End Group Modification
- Author
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Zhenghui Luo, He Yan, Guangye Zhang, Yiqun Xiao, Zhanxiang Chen, Minghui Hao, Chuluo Yang, Cheng Zhong, Lei Wang, Xinhui Lu, Lik Kuen Ma, and Tao Liu
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Materials science ,Fullerene ,Organic solar cell ,Band gap ,Open-circuit voltage ,General Chemical Engineering ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,SMA ,01 natural sciences ,Acceptor ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Materials Chemistry ,0210 nano-technology ,HOMO/LUMO ,Methyl group - Abstract
Generally, the electron-withdrawing substitution on the end-capping group of the acceptor–donor–acceptor type small-molecule acceptor (SMA) narrows the optical bandgap, and the electron-donating group lifts the lowest unoccupied molecular orbital (LUMO) energy level of nonfullerene SMA, which increase the short-circuit current density (JSC) and open circuit voltage (VOC) of the organic solar cells (OSCs), respectively; however, their synergistic effect on the properties of SMA has remained elusive. Here, we first report a new end-capping group (EG), namely, 5-fluoro-6-methyl-3-dicycanovinylindan-1-one (CFDCI), that concurrently possesses an electron-withdrawing fluorine substitute and an electron-donating methyl group. A prototype SMA (namely, ITCF) based on CFDCI and its two control counterparts were prepared to fully understand the structure–property relationship that the new EG exerts on the resultant SMA. The ITCF demonstrated a moderately crystalline morphology in pristine film and more balanced char...
- Published
- 2019
9. Effects of ortho-Linkages on the Molecular Stability of Organic Light-Emitting Diode Materials
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Lian Duan, Yi-Lei Wang, Ruoyun Zhang, Na Lin, Juan Qiao, and Rui Wang
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Steric effects ,Materials science ,Carbazole ,General Chemical Engineering ,Substituent ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Bond-dissociation energy ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chemical bond ,Materials Chemistry ,Molecule ,0210 nano-technology ,Bond cleavage ,Chemical decomposition - Abstract
ortho-Linkages are effective in improving the performance of organic light-emitting diode (OLED) materials but may weaken the local chemical bonds and even incur chemical degradation due to bond cleavage reactions in operating OLEDs, especially for blue-emitting materials. Here, we conducted a systematic theoretical study on a series of carbazole (Cz)-based molecules with typical donor (D)−π−acceptor (A) structures to investigate the influence of ortho-substituents on the bond dissociation energies (BDEf) of their fragile D−π bonds (i.e., C–N bonds), where “fragile” means that the bonds have the minimum or a comparable-to-the-minimum BDE in the molecule. Through calculations, it was found that different substituents or even the same substituent on different sites of the molecule could bring variable effects on the polar D−π bond. Specifically, in the π-group, the effects of a substituent on BDEf mainly depend on the steric hindrance that it brings to the D−π bond. Thus, ortho-CH3 groups hardly affect BDEf...
- Published
- 2018
10. Nanoscale Mixed-Component Metal–Organic Frameworks with Photosensitizer Spatial-Arrangement-Dependent Photochemistry for Multimodal-Imaging-Guided Photothermal Therapy
- Author
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Pengpeng Lei, Lei Wang, Xiaohua Zheng, Ming Liu, Feng Liu, and Zhigang Xie
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Materials science ,Biocompatibility ,General Chemical Engineering ,medicine.medical_treatment ,Nanotechnology ,Photodynamic therapy ,02 engineering and technology ,General Chemistry ,Photothermal therapy ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Porphyrin ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chlorin ,Materials Chemistry ,medicine ,Metal-organic framework ,Photosensitizer ,0210 nano-technology ,Topology (chemistry) - Abstract
The introduction of multiple components into one crystalline metal–organic framework (MOF) provides a feasible approach to fully understand the correlation of component heterogeneity and the whole performance. Herein, photoactive tetratopic chlorin (TCPC) ligands with different geometry and connectivity have been successfully incorporated into the Hf-UiO-66 archetype structure without altering the underlying topology by a facile strategy. Unlike previous porphyrin-nanoscale-MOFs (porphyrin-NMOFs) with homogeneous periodical porphyrin arrangements typically for photodynamic therapy (PDT) usage, we demonstrate that TCPC component heterogeneity within as-synthesized TCPC-UiO possesses both PDT and photothermal therapy (PTT) simultaneously, but PTT takes a more potent antitumor efficacy as proven in several photophysical characterizations and biological experiments in vitro. The high photothermal conversion efficiency, favorable photostability and biocompatibility, and strong X-ray attenuating ability of the ...
- Published
- 2018
11. Surface and Near-Surface Engineering of PtCo Nanowires at Atomic Scale for Enhanced Electrochemical Sensing and Catalysis
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Mingchuan Luo, Yang Yang, Yingjun Sun, Lei Wang, Yingnan Qin, Nuoyan Xu, Yingjie Li, Yi Xing, Dong Wu, Peng Gao, Chunji Li, Shaojun Guo, and Shulin Chen
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Nanostructure ,Materials science ,General Chemical Engineering ,Nanowire ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Surface engineering ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Atomic units ,0104 chemical sciences ,Nanomaterials ,Catalysis ,Adsorption ,Materials Chemistry ,0210 nano-technology - Abstract
Among the most efficient strategies to boost the electrochemical sensing and catalysis of Pt-based multimetallic nanomaterials is atomically manipulating the surface and near-surface nanostructures, which directly govern the adsorption behavior. Using one-dimensional PtCo urchin-like nanowires as the platform, we herein achieve the construction of high-index faceted Pt-skin configuration. Such unique structure shows excellent electrocatalytic performance toward the electrochemical detection of various molecules (H2O2, NH2NH2, dopamine, and acetaminophen), with the capability of real-time monitoring of H2O2 released from living cells and an impressive detection limit of 0.4 nM. Meanwhile, the combination of high-index facet and Pt-skin architecture also enables enhanced catalytic activity for the electro-reduction of oxygen in acid, realizing a very high mass activity of 2.2 A/mgPt. Our study demonstrates the great potential of surface and near-surface engineering at the atomic level in promoting the elect...
- Published
- 2018
12. Atomic Scale Account of the Surface Effect on Ionic Transport in Silver Hollandite
- Author
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Yimei Zhu, Kenneth J. Takeuchi, Xiaobing Hu, Amy C. Marschilok, Lijun Wu, Qingping Meng, Esther S. Takeuchi, M. V. Fernandez-Serra, Jianping Huang, Merzuk Kaltak, Lei Wang, and Mark S. Hybertsen
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Materials science ,Valence (chemistry) ,General Chemical Engineering ,Ionic bonding ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Atomic units ,Oxygen ,0104 chemical sciences ,chemistry ,Chemical physics ,Hollandite ,Materials Chemistry ,Nanorod ,Density functional theory ,0210 nano-technology - Abstract
Nanosized electrodes for Li-ion batteries typically display improved electrochemical properties, which are generally attributed to the reduced dimensionality for lithiation. However, the intriguing roles of surface defects and disorder associated with the nanosized materials are often overlooked. Here, combining atomically resolved structural analysis with density functional theory calculations, we reveal that the formation of intrinsic oxygen vacancies near surface in silver hollandite nanorods modifies the local atomic structure and valence state. These surface reconstructions resulted from oxygen vacancies can significantly affect the diffusion pathways in what are otherwise one-dimensional (1D) tunneled structures. On the basis of energy barrier calculations, we demonstrate that the oxygen vacancies boost ionic transport through the edge sharing MnO6 polyhedra in the a–b plane. Thus, within a single rod different from the inherent 1D tunnel diffusion in the interior, the ionic transport at oxygen vaca...
- Published
- 2018
13. Synthesis and Evaluation of Ideal Core/Shell Quantum Dots with Precisely Controlled Shell Growth: Nonblinking, Single Photoluminescence Decay Channel, and Suppressed FRET
- Author
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Huaibin Shen, Lei Wang, Zhaohan Li, Yanmin Kuang, Hongzhe Wang, Lin Song Li, Ning Li, Lijun Guo, and Fei Chen
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Materials science ,Photoluminescence ,business.industry ,General Chemical Engineering ,Dispersity ,Shell (structure) ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Core shell ,Core (optical fiber) ,Förster resonance energy transfer ,Quantum dot ,Monolayer ,Materials Chemistry ,Optoelectronics ,0210 nano-technology ,business - Abstract
Due to the unique optical properties, colloidal quantum dots (QDs) are excellent candidates for developing next-generation display and solid-state lighting technologies. However, some factors including photoluminescence blinking and Forster resonance energy transfer (FRET) still affect their practical applications. Herein, a series of ZnCdSe-based core/shell QDs with low optical polydispersity have been successfully synthesized by a “low-temperature injection and high-temperature growth” precisely controlled method. The alloyed ZnCdSe core with a certain ratio of Cd and Zn was presynthesized first. Followed by accurate ZnS shell growth, the as-synthesized core/shell QDs are nonblinking with the nonblinking threshold volume of ∼137 nm3. The PL decay dynamics are all single-exponential for both QDs in solutions and close-packed solid films when ZnS shell thickness varying from 2 to 20 monolayers. FRET can be effectively suppressed after growing 10 monolayers of ZnS shell. All of these superb characteristics...
- Published
- 2018
14. Tunable Band Gap and Long Carrier Recombination Lifetime of Stable Mixed CH3NH3PbxSn1–xBr3 Single Crystals
- Author
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Dianxing Ju, Xiaobo Hu, Alex K.-Y. Jen, Lei Wang, Zonglong Zhu, Yangyang Dang, Chu-Chen Chueh, Xutang Tao, Hongbin Liu, and Xiaosong Li
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Electron mobility ,Materials science ,Absorption spectroscopy ,business.industry ,Band gap ,General Chemical Engineering ,Halide ,02 engineering and technology ,General Chemistry ,Carrier lifetime ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Hall effect ,Photovoltaics ,Materials Chemistry ,Optoelectronics ,0210 nano-technology ,business ,Perovskite (structure) - Abstract
The mixed metal Pb/Sn halide perovskites have drawn significant attentions in perovskite photovoltaics due to their broad absorption spectra and tunable band gaps. To obtain a deeper understanding of these materials properties, single crystals are regarded as the best platform among various building blocks for fundamental study. Here, we report the mixed-metal MAPbxSn1–xBr3 (MA = CH3NH3) perovskite single crystals grown by top seeded solution growth (TSSG) method. Systematical characterizations were applied to investigating their structures and optoelectronic properties. These single crystals kept higher stability even exposed to air over one month than that of MASnBr3. The outstanding electrical properties, such as lower trap-state density and higher carrier mobility, were investigated by space charge-limited current (SCLC) and the Hall Effect measurements. More importantly, these perovskite single crystals exhibited much narrower optical band gap (1.77 eV) and longer carrier lifetime (∼2 μs) than those ...
- Published
- 2018
15. Structural and Electrochemical Characteristics of Ca-Doped 'Flower-like' Li4Ti5O12 Motifs as High-Rate Anode Materials for Lithium-Ion Batteries
- Author
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Esther S. Takeuchi, Stanislaus S. Wong, Haoyue Guo, Xiao Tong, Kenneth J. Takeuchi, Ping Liu, Jing Li, Eric A. Stach, Amy C. Marschilok, Yiman Zhang, and Lei Wang
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Materials science ,Dopant ,Scanning electron microscope ,General Chemical Engineering ,Energy-dispersive X-ray spectroscopy ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Dielectric spectroscopy ,Chemical engineering ,X-ray photoelectron spectroscopy ,Transmission electron microscopy ,Materials Chemistry ,Inductively coupled plasma ,Cyclic voltammetry ,0210 nano-technology - Abstract
Doped motifs offer an intriguing structural pathway toward improving conductivity for battery applications. Specifically, Ca-doped, three-dimensional “flower-like” Li4–xCaxTi5O12 (“x” = 0, 0.1, 0.15, and 0.2) micrometer-scale spheres have been successfully prepared for the first time using a simple and reproducible hydrothermal reaction followed by a short calcination process. The products were experimentally characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) mapping, inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge testing. Calcium dopant ions were shown to be uniformly distributed within the LTO structure without altering the underlying “flower-like” morphology. The largest lattice expansion and the highest Ti3+ ratios were noted ...
- Published
- 2018
16. Improved Stability and Performance of Visible Photoelectrochemical Water Splitting on Solution-Processed Organic Semiconductor Thin Films by Ultrathin Metal Oxide Passivation
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Danhua Yan, Javier J. Concepcion, Bobby Layne, Xinyi Ye, Lei Wang, Chang-Yong Nam, David W. Shaffer, and Mingzhao Liu
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Materials science ,Passivation ,business.industry ,Band gap ,General Chemical Engineering ,02 engineering and technology ,General Chemistry ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Organic semiconductor ,Atomic layer deposition ,Materials Chemistry ,Photocatalysis ,Optoelectronics ,Water splitting ,Thin film ,0210 nano-technology ,business - Abstract
Solution-processable organic semiconductors have potentials as visible photoelectrochemical (PEC) water splitting photoelectrodes due to their tunable small band gap and electronic energy levels, but they are typically limited by poor stability and photocatalytic activity. Here, we demonstrate the direct visible PEC water oxidation on solution-processed organic semiconductor thin films with improved stability and performance by ultrathin metal oxide passivation layers. N-type fullerene-derivative thin films passivated by sub-2 nm ZnO via atomic layer deposition enabled the visible PEC water oxidation at wavelengths longer than 600 nm in harsh alkaline electrolyte environments with up to 30 μA/cm2 photocurrents at the thermodynamic water-oxidation equilibrium potential and the photoanode half-lifetime extended to ∼1000 s. The systematic investigation reveals the enhanced water oxidation catalytic activity afforded by ZnO passivation and the charge tunneling governing the hole transfer through passivation l...
- Published
- 2018
17. A Strategy of Antifogging: Air-Trapped Hollow Microsphere Nanocomposites
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Mingqian Zhang, Yongmei Zheng, Lei Wang, and Shile Feng
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Nanostructure ,Materials science ,Nanocomposite ,business.industry ,General Chemical Engineering ,Composite film ,Nanotechnology ,Crystal growth ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Microsphere ,Thermal insulation ,Materials Chemistry ,Nanorod ,Composite material ,0210 nano-technology ,Supercooling ,business - Abstract
Excellent durable antifogging film, which is composed of hollow microspheres and ZnO nanorods, is fabricated via combining airless spray and crystal growth methods. Because the thermal insulation effect of hollow microspheres strengthens the superhydrophobicity of the micro- and nanostructure composite film at lower temperatures, durable antifogging is realized successfully. When the film is placed in a low-temperature, high-humidity environment, supercooled tiny water droplets cannot spread on it and can easily coalesce and jump off from the surface, exhibiting the robust superhydrophobic and antifogging performance for a significantly long time. This investigation provides insight into designing structured thermal insulation surface materials to realize antifogging that can be applied into microdevices used in cold, high-humidity environments.
- Published
- 2017
18. Metal–Organic Framework@Porous Organic Polymer Nanocomposite for Photodynamic Therapy
- Author
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Shi Liu, Qing Pei, Lei Wang, Xiaohua Zheng, Zhigang Xie, and Shasha He
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chemistry.chemical_classification ,Nanocomposite ,Materials science ,General Chemical Engineering ,Composite number ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,chemistry ,law ,Materials Chemistry ,Metal-organic framework ,Amine gas treating ,Crystallization ,0210 nano-technology ,Porosity ,Nanoscopic scale - Abstract
The limitation for the biomedical application of porous organic polymers (POPs) is the big size and poor dispersibility in aqueous media. Herein, a nanoscale metal–organic framework (MOF)@POP composite, named UNM, has been synthesized by epitaxial growth of the photoactive porphyrin-POPs (H2P-POP) on the outer surface of amine containing UiO-66 (UiO-AM). After the growth of POPs, the crystallization, pore structure, and size distribution of UNM are retained well. The formed UNM possesses a small size of less than 200 nm and could be internalized by cancer cells. Such light-activated UNM exhibits efficient ability to generate 1O2 under various experimental conditions, which can be further applied for PDT efficacy. The present work demonstrates the great potential of nanoscale porous polymers in biomedical fields and cancer treatment.
- Published
- 2017
19. Crystallographic Investigations into Properties of Acentric Hybrid Perovskite Single Crystals NH(CH3)3SnX3 (X = Cl, Br)
- Author
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Haibing Xia, Guodong Zhang, Lei Wang, Sheng-Qing Xia, Yangyang Dang, Cheng Zhong, Dianxing Ju, and Xutang Tao
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Chemistry ,Band gap ,General Chemical Engineering ,02 engineering and technology ,General Chemistry ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Crystal ,Crystallography ,Materials Chemistry ,Orthorhombic crystal system ,0210 nano-technology ,Electronic band structure ,Single crystal ,Monoclinic crystal system ,Perovskite (structure) - Abstract
The hybrid perovskites with special optoelectronic properties have attracted more attention to the scientific and industrial applications. However, because of the toxicity and instability of lead complexes, there is interest in finding a nontoxic substitute for the lead in the halides perovskites and solving the ambiguous crystal structures and phase transition of NH(CH3)3SnX3 (X = Cl, Br). Here, we report the bulk crystal growths and different crystal morphologies of orthorhombic hybrid perovskites NH(CH3)3SnX3 (X = Cl, Br) in an ambient atmosphere by bottom-seeded solution growth (BSSG) method. More importantly, detailed structural determination and refinements, phase transition, band gap, band structure calculations, nonlinear optical (NLO) properties, XPS, thermal properties, and stability of NH(CH3)3SnX3 (X = Cl, Br) single crystals are demonstrated. NH(CH3)3SnCl3 single crystal undergoes reversible structural transformation from orthorhombic space group Cmc21 (no. 36) to monoclinic space group Cc (n...
- Published
- 2016
20. Invar-like Behavior of Antiperovskite Mn3+xNi1–xN Compounds
- Author
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Hui Wu, Laifeng Li, Kewen Shi, Lei Wang, Sihao Deng, Rongjin Huang, Cong Wang, Huiqing Lu, Ying Sun, Muhammad Imran Malik, Qingzhen Huang, and Jun Yan
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Materials science ,Magnetic structure ,Condensed matter physics ,General Chemical Engineering ,Doping ,Neutron diffraction ,General Chemistry ,engineering.material ,Thermal expansion ,Antiperovskite ,Ferromagnetism ,Materials Chemistry ,engineering ,Antiferromagnetism ,Condensed Matter::Strongly Correlated Electrons ,Invar - Abstract
The antiperovskite Mn3+xNi1–xN compounds have been synthesized and characterized by a variety of experimental techniques. After Mn doping at the Ni site, both ferromagnetic characteristics and an Invar-like effect were observed in the antiferromagnetic host material. The observed Invar-like behavior was assumed to be related to the characteristic magnetic structure induced by the doping. Neutron diffraction results prove that the Mn doping stabilizes the special Γ5g antiferromagnetic phase with strong spin–lattice coupling that can be tuned to achieve Invar-like behavior. The magnetovolume effect (MVE) and significant correlation between spin and lattice were confirmed for the Γ5g magnetic phase by the first-principles calculations. Moreover, Mn 3d electrons were revealed to be the key factor for the MVE from the calculations. Our study presents a new mechanism for precisely controlling the zero thermal expansion of a single compound by achieving the special Γ5g magnetic phase of Mn atoms.
- Published
- 2015
21. Mechanistic Study of the Persistent Luminescence of CaAl2O4:Eu,Nd
- Author
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Bo Zhang, Rulong Zhou, Lei Wang, Bingyan Qu, and Xiao Cheng Zeng
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Free electron model ,Materials science ,Dopant ,Band gap ,business.industry ,General Chemical Engineering ,Doping ,General Chemistry ,Electron ,Molecular physics ,Persistent luminescence ,Excited state ,Materials Chemistry ,Optoelectronics ,business ,Luminescence - Abstract
CaAl2O4:Eu is a persistent luminescence (PL) material in the blue light region with potentially wide commercial applications. With the doping of Nd, the decay time can be elongated to more than 19 h. These excellent properties are believed to be in close relation with the electronic structures of the dopants, the defects, and the host material. In this work, we attempt to achieve a better understanding of the PL mechanism of CaAl2O4:Eu based on first-principles calculations. The electronic structures of the host CaAl2O4, the luminescent center Eu, the O and Ca vacancies, and the dopant Nd are systematically studied. According to the calculations, the 4f and 5d levels of Eu are located within the band gap and slightly above the conduction band minimum (CBM), respectively. The electrons on the 4f levels can be excited into the 5d levels via ultraviolet radiation. The excited electrons on the 5d levels can move to the conduction bands and become free electron carriers. The electron carriers can be trapped fo...
- Published
- 2015
22. Probing Structure-Induced Optical Behavior in a New Class of Self-Activated Luminescent 0D/1D CaWO4 Metal Oxide–CdSe Nanocrystal Composite Heterostructures
- Author
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Jessica Hoy, Matthew Y. Sfeir, Lei Wang, Zhuo-Qun Li, Daniel A. Fischer, Jinkyu Han, Stanislaus S. Wong, Gordon T. Taylor, Haiqing Liu, Cherno Jaye, Coray McBean, and James A. Misewich
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Photoluminescence ,Materials science ,General Chemical Engineering ,Nanowire ,Heterojunction ,Nanotechnology ,General Chemistry ,Photochemistry ,Photoinduced electron transfer ,Nanocrystalline material ,symbols.namesake ,Nanocrystal ,Quantum dot ,Materials Chemistry ,symbols ,Raman spectroscopy - Abstract
In this report, we synthesize and characterize the structural and optical properties of novel heterostructures composed of (i) semiconducting nanocrystalline CdSe quantum dots (QDs) coupled with (ii) both one- and zero-dimensional (1D and 0D) motifs of self-activated luminescent CaWO4 metal oxides. Specifically, ∼4 nm CdSe QDs have been anchored onto (i) high-aspect ratio 1D nanowires, measuring ∼230 nm in diameter and ∼3 μm in length, as well as onto (ii) crystalline 0D nanoparticles (possessing an average diameter of ∼80 nm) of CaWO4 through the mediation of 3-mercaptopropionic acid (MPA) as a connecting linker. Composite formation was confirmed by complementary electron microscopy and spectroscopy (i.e., IR and Raman) data. In terms of luminescent properties, our results show that our 1D and 0D heterostructures evince photoluminescence (PL) quenching and shortened PL lifetimes of CaWO4 as compared with unbound CaWO4. We propose that a photoinduced electron transfer process occurs from CaWO4 to CdSe QDs...
- Published
- 2015
23. Thiophene Polymer-Grafted Barium Titanate Nanoparticles toward Nanodielectric Composites
- Author
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Brian C. Benicewicz, Chuanbing Tang, Jiuyang Zhang, Yi Yan, Harry J. Ploehn, Lei Wang, Md. Sayful Islam, and Yali Qiao
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chemistry.chemical_classification ,Nanocomposite ,Materials science ,General Chemical Engineering ,Nanoparticle ,Chain transfer ,General Chemistry ,Polymer ,Dielectric ,chemistry.chemical_compound ,chemistry ,Polymerization ,Barium titanate ,Materials Chemistry ,Dielectric loss ,Composite material - Abstract
This paper reports a strategy for controlling surface chemistry of barium titanate (BaTiO3) using surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization of an oligothiophene monomer. The modular chemistry on the engineering of nanoparticles provides a facile pathway to compatibilizing dielectric nanofillers in a matrix of oligothiophene polymers, leading to the formation of nanodielectric composites with permittivity at ∼20 and dielectric loss
- Published
- 2014
24. Construction of High Tg Bipolar Host Materials with Balanced Electron–Hole Mobility Based on 1,2,4-Thiadiazole for Phosphorescent Organic Light-Emitting Diodes
- Author
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Guanyuan Mu, Dongge Ma, Hong Huang, Peng Xu, Jiangjiang Jin, Lei Wang, Bo Wang, Wenzhi Zhang, and Jiangshan Chen
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Materials science ,business.industry ,Carbazole ,General Chemical Engineering ,General Chemistry ,Electron hole ,Photochemistry ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,OLED ,Optoelectronics ,Molecule ,Moiety ,Phosphorescence ,business ,Glass transition ,Diode - Abstract
A novel electron-transporting moiety, 1,2,4-thiadiazole, was first introduced to construct bipolar host molecules for phosphorescent organic light-emitting diodes (PhOLEDs). By incorporating 1,2,4-thiadiazole with typical hole-transporting carbazole moieties, a series of thiadiazole/carbazole hybrids, o-CzTHZ, m-CzTHZ, and p-CzTHZ, were synthesized. All the hybrids exhibit very high glass transition temperatures (Tg ≥ 167 °C) and show good thermal and morphological stability in films. Moreover, these host materials possess good bipolar charge transporting properties; electron and hole mobilities of these bipolar thiadiazole/carbazole hybrids can be tuned by simply adjusting the linkage modes between thiadiazole and carbazole moieties. The maximum external quantum efficiencies (ηEQE, max) in the green PhOLEDs with o-CzTHZ, m-CzTHZ, and p-CzTHZ as the hosts reached 26.1%, 24.0%, and 22.9%, respectively, and their EQE were still over 20% even at the high luminance of 10,000 cd/m2. This study demonstrates tha...
- Published
- 2014
25. Self-Assembled Columnar Structures of Swallow-Shaped Tetrathiafulvalene-Based Molecules
- Author
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Myong-Hoon Lee, Shiao-Wei Kuo, Soo-Jin Park, Lei Wang, Stephen Z. D. Cheng, Ryan M. Van Horn, Se-Hyun Lee, Yun-Bae Kook, Kwang-Un Jeong, and Young-Jin Kim
- Subjects
chemistry.chemical_classification ,Phase transition ,Chemistry ,Stereochemistry ,General Chemical Engineering ,Mesogen ,General Chemistry ,chemistry.chemical_compound ,Crystallography ,Differential scanning calorimetry ,Liquid crystal ,Phase (matter) ,Materials Chemistry ,Molecule ,Alkyl ,Tetrathiafulvalene - Abstract
A series of swallow-shaped tetrathiafulvalene (TTF)-based liquid crystal (LC) molecules (a-6TTFn, where 6 represents the number of carbon atoms in the two tails of a-6TTFn and n is the even number of carbon atoms in the alkyl chains attached to the side of the asymmetric TTF mesogen, n = 6−12) was designed and synthesized. One of this series of swallow-shaped asymmetric TTF molecules (abbreviated as a-6TTF12) having 12 carbon atoms in the alkyl chains attached to the side of the asymmetric TTF mesogen served as an example in this study. Major phase transitions and their origins in a-6TTF12 were studied with combined techniques of differential scanning calorimetry (DSC), one-dimensional (1D) wide-angle X-ray diffraction (WAXD) and solid-state carbon-13 (13C) nuclear magnetic resonance (NMR) experiments. a-6TTF12 formed a highly ordered liquid crystalline (ΦLC) phase at higher temperatures and a crystalline (ΦCr) phase at lower temperatures. On the basis of the experimental results, it was found that the hi...
- Published
- 2009
26. Li−Fe−P−O2 Phase Diagram from First Principles Calculations
- Author
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Shyue Ping Ong, Byoungwoo Kang, Gerbrand Ceder, and Lei Wang
- Subjects
General Chemical Engineering ,Ab initio ,Ellingham diagram ,chemistry.chemical_element ,Thermodynamics ,General Chemistry ,Partial pressure ,Oxygen ,Entropy (classical thermodynamics) ,chemistry ,Materials Chemistry ,Density functional theory ,Physics::Chemical Physics ,CALPHAD ,Phase diagram - Abstract
We present an efficient way to calculate the phase diagram of the quaternary Li−Fe−P−O2 system using ab initio methods. The ground-state energies of all known compounds in the Li−Fe−P−O2 system were calculated using the generalized gradient approximation (GGA) approximation to density functional theory (DFT) and the DFT+U extension to it. Considering only the entropy of gaseous phases, the phase diagram was constructed as a function of oxidation conditions, with the oxygen chemical potential, μO2, capturing both temperature and oxygen partial pressure dependence. A modified Ellingham diagram was also developed by incorporating the experimental entropy data of gaseous phases. The phase diagram shows LiFePO4 to be stable over a wide range of oxidation environments, being the first Fe2+-containing phase to appear upon reduction at μO2 = −11.52 eV and the last of the Fe-containing phosphates to be reduced at μO2 = −16.74 eV. Lower μO2 represents more reducing conditions, which generally correspond to higher t...
- Published
- 2008
27. A New Series of Chalcohalide Semiconductors with Composite CdBr2/Sb2Se3 Lattices: Synthesis and Characterization of CdSb2Se3Br2 and Indium Derivatives InSb2S4X (X = Cl and Br) and InM2Se4Br (M = Sb and Bi)
- Author
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Lei Wang and Shiou-Jyh Hwu
- Subjects
Diffraction ,Materials science ,business.industry ,General Chemical Engineering ,Composite number ,chemistry.chemical_element ,General Chemistry ,Crystallography ,Semiconductor ,Octahedron ,chemistry ,Antimony ,Materials Chemistry ,business ,Stoichiometry ,Indium ,Monoclinic crystal system - Abstract
A new series of mixed-framework compounds in the chalcohalide family has been synthesized using the conventional solid-state reactions. These include CdSb2Se3Br2 1 and its isoelectronic indium derivatives InSb2S4X (X = Cl 2 and Br 3) and InM2Se4Br (M = Sb 4 and Bi 5). Single crystals were grown from direct interaction of stoichiometric mixtures of respective elemental and binary compounds. The parent compound cadmium antimony selenobromide, CdSb2Se3Br2, was synthesized by heating the stoichiometric mixture of CdBr2 and Sb and Se at 450 °C followed by slow cooling. Single-crystal structure analysis was carried out by employing X-ray diffraction methods, showing that this compound crystallizes in the monoclinic crystal system (C2/m, No. 12) with a = 20.998(4) A, b = 4.0260(8) A, c = 12.149(2) A, β = 119.00(3)°, and V = 898.3(3) A3. The framework exhibits mixed CdBr2 and Sb2Se3 sublattices, respectively, adopting the (110) and (100) NaCl-type structures. The former consists of dual octahedral chains of Cd-ce...
- Published
- 2007
28. Facile Synthesis of Co−Pt Hollow Sphere Electrocatalyst
- Author
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and Lei Zhang, Zhenyao Wang, Ge Chen, Jiujun Zhang, Dingguo Xia, Lei Wang, and Zuoren Nie
- Subjects
General Chemical Engineering ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,Electrocatalyst ,Chemical synthesis ,Anode ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Pulmonary surfactant ,Materials Chemistry ,Methanol ,Sodium dodecyl sulfate ,Platinum ,Cobalt - Abstract
In this paper, successful one-step chemical synthesis of Co−Pt hollow spheres with adjustable composition was developed in an effort to explore new synthesis methods, simplify the synthesis procedure, and improve the synthetic efficiency. In this synthesis, a direct thermolytic reduction of platinum acetylacetonate [Pt(CH3COHCOCH3)2] and cobalt(II) acetate [Co(CH3COO)2] in refluxing ethyl glycol was explored. In the reacting mixture, an anionic surfactant sodium dodecyl sulfate (SDS) was used as the capping and structure-directing agent. These Co−Pt hollow spheres demonstrated enhanced electrocatalytic activity toward methanol oxidation in comparison with Pt nanoparticles, which is crucial for anode electrocatalysis in DMFCs.
- Published
- 2007
29. A First-Principles Approach to Studying the Thermal Stability of Oxide Cathode Materials
- Author
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Thomas Maxisch, Lei Wang, and Gerbrand Ceder
- Subjects
Exothermic reaction ,Chemistry ,General Chemical Engineering ,Spinel ,Thermal decomposition ,Thermodynamics ,General Chemistry ,engineering.material ,Endothermic process ,Cathode ,law.invention ,law ,Heat generation ,Phase (matter) ,Materials Chemistry ,engineering ,Phase diagram - Abstract
We present a new method for predicting the thermodynamics of thermal degradation of charged cathode materials for rechargeable Li batteries and demonstrate it on three cathode materials, LixNiO2, LixCoO2, and LixMn2O4. The decomposition of LixNiO2 is a two-step process: the first step is a kinetically controlled exothermic conversion in which the layered structure transforms to the stable spinel structure. The second step is an endothermic decomposition of the spinel into a rocksalt phase, accompanied by the loss of oxygen. The heat generation for the overall reaction from the layered to the rocksalt structure is exothermic when x 0.5. From the calculated phase diagram, a similar mechanism is expected for LixCoO2, but the high migration barrier for Co may inhibit the layered-to-spinel transformation and lead to decomposition into LiCoO2 and Co3O4. For the stable spinel LiMn2O4, high temperature is needed to provide enough thermodynamic driving force for its endothermic deco...
- Published
- 2006
30. Synthesis, Structure, and Properties of a New Family of Mixed-Framework Chalcohalide Semiconductors: CdSbS2X (X = Cl, Br), CdBiS2X (X = Cl, Br), and CdBiSe2X (X = Br, I)
- Author
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Yi-Chung Hung, Hyun-Joo Koo, Shiou-Jyh Hwu, Myung-Hwan Whangbo, and Lei Wang
- Subjects
Materials science ,business.industry ,General Chemical Engineering ,Structure (category theory) ,General Chemistry ,Crystal structure ,Type (model theory) ,Crystallography ,Semiconductor ,Octahedron ,Group (periodic table) ,Materials Chemistry ,Orthorhombic crystal system ,business ,Monoclinic crystal system - Abstract
A new family of quaternary mixed-framework chalcohalide semiconductors has been synthesized by conventional solid-state reactions in an intermediate temperature region of 400−430 °C. These include CdSbS2Cl (1), CdSbS2Br (2), CdBiS2Cl (3), CdBiS2Br (4), CdBiSe2Br (5), and CdBiSe2I (6). Single-crystal structure analyses of this compound series reveal two types of crystal structures depending upon the combination of chalcohalide anions, and they crystallize in an orthorhombic Pnma (type I) and monoclinic C2/m (type II) space group. Type I is adopted by two sulfochlorides, 1 and 3, and one selenobromide, 5. Type II is adopted by two sulfobromides, 2 and 4, and one selenoiodide, 6. Both structure types have slabs built of corner and edge shared Cd-centered CdQ6-xXx (Q = S, Se; X = Cl, Br, I; x = 0, 2, 4) octahedra that resemble the (110) plane of a distorted NaCl-type structure. In the type I structure, this slab contains only CdQ4X2 octahedra, while type II shows alternating CdQ6 and CdQ2X4 octahedra. In both...
- Published
- 2006
31. Laminated TaS2/Polymer Nanocomposites through Encapsulative Precipitation of Exfoliated Layers
- Author
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Mercouri G. Kanatzidis and Lei Wang
- Subjects
chemistry.chemical_classification ,Materials science ,Nanocomposite ,Polymer nanocomposite ,Ethylene oxide ,Precipitation (chemistry) ,General Chemical Engineering ,Imine ,General Chemistry ,Polymer ,Polyethylene ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Polymer chemistry ,Materials Chemistry ,Molecule - Abstract
Several TaS2/polymer nanocomposites prepared through the encapsulative precipitation method are described. Namely, the encapsulation of poly(ethylene oxide) (PEO), polyethylene imine (PEI), and poly(vinylpyrrolidinone) (PVP) into TaS2 was examined in detail, and the nanocomposites were characterized by a wide variety of techniques. The nanocomposites disperse in water and are easily cast into free-standing films. The flexible metallic TaS2/polymer nanocomposite films display bulk superconductivity. In addition, in this work the exfoliation properties of LixTaS2 were systematically explored, and it was found that material prepared from controlled lithiation with 0.2 equiv of LiBH4 exfoliates well in water and has high affinity for various polymers. The likely conformation of PEO molecules sandwiched between the TaS2 slabs was explored with analysis of the X-ray diffraction patterns of a highly oriented Lix(PEO)yTaS2 nanocomposite films. The one-dimensional electron density maps, obtained for Lix(PEO)yTaS2,...
- Published
- 2001
32. Synthesis and Evaluation of Ideal Core/Shell Quantum Dots with Precisely Controlled Shell Growth: Nonblinking, Single Photoluminescence Decay Channel, and Suppressed FRET.
- Author
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Zhaohan Li, Fei Chen, Lei Wang, Huaibin Shen, Lijun Guo, Yanmin Kuang, Hongzhe Wang, Ning Li, and Lin Song Li
- Published
- 2018
- Full Text
- View/download PDF
33. Tunable Band Gap and Long Carrier Recombination Lifetime of Stable Mixed CH3NH3PbxSn1-xBr3 Single Crystals.
- Author
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Dianxing Ju, Yangyang Dang, Zonglong Zhu, Hongbin Liu, Chu-Chen Chueh, Xiaosong Li, Lei Wang, Xiaobo Hu, Jen, Alex K.-Y., and Xutang Tao
- Published
- 2018
- Full Text
- View/download PDF
34. Structural and Electrochemical Characteristics of Ca-Doped "Flower-like" Li4Ti5O12 Motifs as High-Rate Anode Materials for Lithium-Ion Batteries.
- Author
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Lei Wang, Yiman Zhang, Haoyue Guo, Jing Li, Stach, Eric A., Xiao Tong, Takeuchi, Esther S., Takeuchi, Kenneth J., Ping Liu, Marschilok, Amy C., and Wong, Stanislaus S.
- Subjects
- *
LITHIUM-ion batteries , *CRYSTAL structure , *ELECTROCHEMICAL analysis , *CALCIUM , *DOPED semiconductors , *LITHIUM compounds , *ANODES - Abstract
Doped motifs offer an intriguing structural pathway toward improving conductivity for battery applications. Specifically, Ca-doped, three-dimensional "flower-like" Li4-xCaxTi5O12 ("x" = 0, 0.1, 0.15, and 0.2) micrometer-scale spheres have been successfully prepared for the first time using a simple and reproducible hydrothermal reaction followed by a short calcination process. The products were experimentally characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) mapping, inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge testing. Calcium dopant ions were shown to be uniformly distributed within the LTO structure without altering the underlying "flower-like" morphology. The largest lattice expansion and the highest Ti3+ ratios were noted with XRD and XPS, respectively, whereas increased charge transfer conductivity and decreased Li+-ion diffusion coefficients were displayed in EIS for the Li4-xCaxTi5O12 ("x" = 0.2) sample. The "x" = 0.2 sample yielded a higher rate capability, an excellent reversibility, and a superior cycling stability, delivering 151 and 143 mAh/g under discharge rates of 20C and 40C at cycles 60 and 70, respectively. In addition, a high cycling stability was demonstrated with a capacity retention of 92% after 300 cycles at a very high discharge rate of 20C. In addition, first-principles calculations based on density functional theory (DFT) were conducted with the goal of further elucidating and understanding the nature of the doping mechanism in this study. The DFT calculations not only determined the structure of the Ca-doped Li4Ti5O12, which was found to be in accordance with the experimentally measured XPD pattern, but also yielded valuable insights into the doping-induced effect on both the atomic and electronic structures of Li4Ti5O12. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
35. Improved Stability and Performance of Visible Photoelectrochemical Water Splitting on Solution-Processed Organic Semiconductor Thin Films by Ultrathin Metal Oxide Passivation.
- Author
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Lei Wang, Danhua Yan, Shaffer, David W., Xinyi Ye, Layne, Bobby H., Concepcion, Javier J., Mingzhao Liu, and Chang-Yong Nam
- Subjects
- *
WATER electrolysis , *ORGANIC semiconductor thin films , *PHOTOELECTROCHEMICAL cells , *CHEMICAL stability , *METALLIC oxides , *PASSIVATION , *THIN films testing - Abstract
Solution-processable organic semiconductors have potentials as visible photoelectrochemical (PEC) water splitting photoelectrodes due to their tunable small band gap and electronic energy levels, but they are typically limited by poor stability and photocatalytic activity. Here, we demonstrate the direct visible PEC water oxidation on solution-processed organic semiconductor thin films with improved stability and performance by ultrathin metal oxide passivation layers. N-type fullerene-derivative thin films passivated by sub-2 nm ZnO via atomic layer deposition enabled the visible PEC water oxidation at wavelengths longer than 600 nm in harsh alkaline electrolyte environments with up to 30 μA/cm2 photocurrents at the thermodynamic water-oxidation equilibrium potential and the photoanode half-lifetime extended to ~1000 s. The systematic investigation reveals the enhanced water oxidation catalytic activity afforded by ZnO passivation and the charge tunneling governing the hole transfer through passivation layers. Further enhanced PEC performances were realized by improving the bottom ohmic contact to the organic semiconductor, achieving ~60 μA/cm2 water oxidation photocurrent at the equilibrium potential, the highest values reported for organic semiconductor thin films to our knowledge. The improved stability and performance of passivated organic photoelectrodes and discovered design rationales provide useful guidelines for realizing the stable visible solar PEC water splitting based on organic semiconductor thin films. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
36. A New Redox Host for Intercalative Polymerization: Insertion of Polyaniline into α-RuCl3
- Author
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Mercouri G. Kanatzidis, Paul Brazis, Lei Wang, Carl R. Kannewurf, and Melissa Rocci
- Subjects
Conductive polymer ,chemistry.chemical_classification ,General Chemical Engineering ,Intercalation (chemistry) ,technology, industry, and agriculture ,macromolecular substances ,General Chemistry ,Polymer ,Redox ,chemistry.chemical_compound ,Aniline ,chemistry ,Polymerization ,Polymer chemistry ,Polyaniline ,Materials Chemistry ,Molecule - Abstract
α-RuCl3 is a new host for polymer intercalation using an in situ redox intercalative polymerization recaction. With the aid of ambient oxygen, aniline molecules get oxidatively polymerized by the R...
- Published
- 1998
37. Metal-Organic Framework@Porous Organic Polymer Nanocomposite for Photodynamic Therapy.
- Author
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Xiaohua Zheng, Lei Wang, Qing Pei, Shasha He, Shi Liu, and Zhigang Xie
- Subjects
- *
METAL-organic frameworks , *POLYMERIC nanocomposites , *PHOTODYNAMIC therapy , *PORPHYRINS , *CRYSTALLIZATION - Abstract
The limitation for the biomedical application of porous organic polymers (POPs) is the big size and poor dispersibility in aqueous media. Herein, a nanoscale metal-organic framework (MOF)@POP composite, named UNM, has been synthesized by epitaxial growth of the photoactive porphyrin-POPs (H2P-POP) on the outer surface of amine containing UiO-66 (UiO-AM). After the growth of POPs, the crystallization, pore structure, and size distribution of UNM are retained well. The formed UNM possesses a small size of less than 200 nm and could be internalized by cancer cells. Such light-activated UNM exhibits efficient ability to generate ¹O2 under various experimental conditions, which can be further applied for PDT efficacy. The present work demonstrates the great potential of nanoscale porous polymers in biomedical fields and cancer treatment. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
38. Crystallographic Investigations into Properties of Acentric Hybrid Perovskite Single Crystals NH(CH3)3SnX3 (X = Cl, Br).
- Author
-
Yangyang Dang, Cheng Zhong, Guodong Zhang, Dianxing Ju, Lei Wang, Shengqing Xia, Haibing Xia, and Xutang Tao
- Published
- 2016
- Full Text
- View/download PDF
39. Multicolor Emissions by the Synergism of Intra/Intermolecular Slippedπ–π Stackings of Tetraphenylethylene-DiBODIPY Conjugate.
- Author
-
Hai-Tao Feng, Jia-Bin Xiong, Yan-Song Zheng, Biao Pan, Chun Zhang, Lei Wang, and Yongshu Xie
- Published
- 2015
- Full Text
- View/download PDF
40. Tantalum Nitride Nanorod Arrays: Introducing Ni–FeLayered Double Hydroxides as a Cocatalyst Strongly Stabilizing Photoanodesin Water Splitting.
- Author
-
Lei Wang, Fabio Dionigi, Nhat Truong Nguyen, Robin Kirchgeorg, Manuel Gliech, Sabina Grigorescu, Peter Strasser, and Patrik Schmuki
- Subjects
- *
TANTALUM compounds , *HYDROXIDES , *CATALYSIS , *ELECTRODES , *IRRADIATION - Abstract
Ta3N5nanostructuresare widely explored as anodesfor photoelectrochemical (PEC) water splitting. Although the materialshows excellent semiconductive properties for this purpose, the keychallenge is its severe photocorrosion when used in typical aqueousenvironments. In the present work we introduce a NiFe layered doublehydroxide (LDH) cocatalyst that dramatically reduces photocorrosioneffects. To fabricate the Ta3N5electrode, weuse through-template anodization of Ta and obtain oxide nanorod arraysthat then are converted to Ta3N5by high temperaturenitridation. After modification with our cocatalyst system, we obtainedsolar photocurrents of 6.3 mA cm–2at 1.23 VRHEin 1 M KOH, and an electrode maintains about 80% of theinitial activity for extended irradiation times. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
41. Invar-like Behavior of Antiperovskite Mn3+xNi1–xN Compounds.
- Author
-
Sihao Deng, Ying Sun, Hui Wu, Qingzhen Huang, Jun Yan, Kewen Shi, Muhammad Imran Malik, Huiqing Lu, Lei Wang, Rongjin Huang, Laifeng Li, and Cong Wang
- Published
- 2015
- Full Text
- View/download PDF
42. Mechanistic Study of the Persistent Luminescence of CaAl2O4:Eu,Nd.
- Author
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Bingyan Qu, Bo Zhang, Lei Wang, Rulong Zhou, and Xiao Cheng Zeng
- Published
- 2015
- Full Text
- View/download PDF
43. Self-Assembled Columnar Structures of Swallow-Shaped Tetrathiafulvalene-Based Molecules.
- Author
-
Lei Wang, Soo-Jin Park, Se-Hyun Lee, Young-Jin Kim, Yun-Bae Kook, Shiao-Wei Kuo, Ryan M. Van Horn, Stephen Z. D. Cheng, Myong-Hoon Lee, and Kwang-Un Jeong
- Subjects
- *
MOLECULAR self-assembly , *TETRATHIAFULVALENE , *LIQUID crystals , *PHASE transitions , *CHEMICAL structure , *ASYMMETRY (Chemistry) , *CALORIMETRY , *TEMPERATURE effect - Abstract
A series of swallow-shaped tetrathiafulvalene (TTF)-based liquid crystal (LC) molecules (a-6TTFn, where 6 represents the number of carbon atoms in the two tails of a-6TTFnand nis the even number of carbon atoms in the alkyl chains attached to the side of the asymmetric TTF mesogen, n= 6−12) was designed and synthesized. One of this series of swallow-shaped asymmetric TTF molecules (abbreviated as a-6TTF12) having 12 carbon atoms in the alkyl chains attached to the side of the asymmetric TTF mesogen served as an example in this study. Major phase transitions and their origins in a-6TTF12 were studied with combined techniques of differential scanning calorimetry (DSC), one-dimensional (1D) wide-angle X-ray diffraction (WAXD) and solid-state carbon-13 (13C) nuclear magnetic resonance (NMR) experiments. a-6TTF12 formed a highly ordered liquid crystalline (ΦLC) phase at higher temperatures and a crystalline (ΦCr) phase at lower temperatures. On the basis of the experimental results, it was found that the highly organized columns in the ΦLCphase partially lost their long-range positional order compared with the ΦCrphase at lower temperatures due to the distinct molecular packing of alkyl chains during the transition from ΦLC↔ ΦCr. Furthermore, it was realized that there are two main driving forces in the formation of the ordered columnar phases. One was the π−π interaction among the TTF-based mesogens, and the other was the nanophase separation between the rigid TTF-based mesogens and the flexible alkyl chains. The structure, molecular packing symmetry, and morphology of a-6TTF12 in different phases were identified using 2D WAXD together with selected area electron diffraction (SAED) from transmission electron microscopy (TEM). Bright-field TEM images of polyethylene-decorated films of a-6TTF12 allow us to confirm its molecular self-organization which was first identified by SAED as well as by 2D WAXD from oriented films. Morphological observations utilizing cross-polarized optical microscopy (POM) on the micrometer length scale validated the phase transitions and molecular orientation in the macroscopically oriented film. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
44. Li−Fe−P−O2Phase Diagram from First Principles Calculations.
- Author
-
Shyue Ping Ong, Lei Wang, Byoungwoo Kang, and Gerbrand Ceder
- Subjects
- *
CHINESE ethics , *CONFUCIAN ethics , *CONFUCIANISM , *RELIGION & ethics - Abstract
We present an efficient way to calculate the phase diagram of the quaternary Li−Fe−P−O 2system using ab initio methods. The ground-state energies of all known compounds in the Li−Fe−P−O 2system were calculated using the generalized gradient approximation (GGA) approximation to density functional theory (DFT) and the DFT+U extension to it. Considering only the entropy of gaseous phases, the phase diagram was constructed as a function of oxidation conditions, with the oxygen chemical potential, μ O 2, capturing both temperature and oxygen partial pressure dependence. A modified Ellingham diagram was also developed by incorporating the experimental entropy data of gaseous phases. The phase diagram shows LiFePO 4to be stable over a wide range of oxidation environments, being the first Fe 2+-containing phase to appear upon reduction at μ O 2= −11.52 eV and the last of the Fe-containing phosphates to be reduced at μ O 2= −16.74 eV. Lower μ O 2represents more reducing conditions, which generally correspond to higher temperatures and/or lower oxygen partial pressures and/or the presence of reducing agents. The predicted phase relations and reduction conditions compare well to experimental findings on stoichiometric and Li-off-stoichiometric LiFePO 4. For Li-deficient stoichiometries, the formation of iron phosphate phases (Fe 7(PO 4) 6and Fe 2P 2O 7) commonly observed under moderately reducing conditions during LiFePO 4synthesis and the formation of iron phosphides (Fe 2P) under highly reducing conditions are consistent with the predictions from our phase diagram. Our diagrams also predict the formation of Li 3PO 4and iron oxides for Li-excess stoichiometries under all but the most reducing conditions, again in agreement with experimental observations. For stoichiometric LiFePO 4, the phase diagram gives the correct oxidation products of Li 3Fe 2(PO 4) 3and Fe 2O 3. The predicted carbothermal reduction temperatures for LiFePO 4from the Ellingham diagram are also within the range observed in experiments (800–900 °C). The diagrams developed provide a better understanding of phase relations within the Li−Fe−P−O 2system and serve as a guide for future experimental efforts in materials processing, in particular, for the optimization of synthesis routes for LiFePO 4. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
45. A New Series of Chalcohalide Semiconductors with Composite CdBr2/Sb2Se3Lattices: Synthesis and Characterization of CdSb2Se3Br2and Indium Derivatives InSb2S4X (X = Cl and Br) and InM2Se4Br (M = Sb and Bi).
- Author
-
Lei Wang and Shiou-Jyh Hwu
- Subjects
- *
IONS , *INTERMEDIATES (Chemistry) , *PROPERTIES of matter , *PHYSICS , *SOLUTION (Chemistry) - Abstract
A new series of mixed-framework compounds in the chalcohalide family has been synthesized using the conventional solid-state reactions. These include CdSb 2Se 3Br 21and its isoelectronic indium derivatives InSb 2S 4X (X = Cl 2and Br 3) and InM 2Se 4Br (M = Sb 4and Bi 5). Single crystals were grown from direct interaction of stoichiometric mixtures of respective elemental and binary compounds. The parent compound cadmium antimony selenobromide, CdSb 2Se 3Br 2, was synthesized by heating the stoichiometric mixture of CdBr 2and Sb and Se at 450 °C followed by slow cooling. Single-crystal structure analysis was carried out by employing X-ray diffraction methods, showing that this compound crystallizes in the monoclinic crystal system ( C2/ m, No. 12) with a= 20.998(4) Å, b= 4.0260(8) Å, c= 12.149(2) Å, β = 119.00(3)°, and V= 898.3(3) Å 3. The framework exhibits mixed CdBr 2and Sb 2Se 3sublattices, respectively, adopting the (110) and (100) NaCl-type structures. The former consists of dual octahedral chains of Cd-centered [CdBr 5Se] units sharing cisBr edges, and the chains propagate along the baxis via sharing transBr edges of the octahedra. The Sb 2Se 3sublattice is made of three edge-shared [SbSe 5] square-pyramidal units, features commonly seen in antimony and Sb-containing selenides. The apex selenium atoms of the aforementioned [CdBr 5Se] unit are corner-shared with [SbSe 5] sublattices to form a composite slab along the (−101) plane. The lone-pair electrons of Sb 3+cations point into the space between the stacked slabs. The indium derivatives 2– 5were synthesized by substituting the trivalent In 3+for divalent Cd 2+cations, along with a stoichiometric amount of charge-compensating halide anions. These four new In derivatives are isostructural with 1and can be formulated as (InSX)(Sb 2S 3) (X = Cl and Br), and (InSeBr)(M 2Se 3) (M = Sb and Bi) with respect to the composite lattices of CdBr 2and Sb 2Se 3. The UV–vis reflectance spectroscopy and band structure calculations confirm that these compounds are semiconductors with steep band gap absorption edges around 1.1–1.8 eV. In light of the observed blue shift in the absorption edge with respect to the dimensionally reduced post-transition-metal chalcogenide M 2Q 3sublattices, we claim quantum confinement effect of the optical band gap, which is the first example among inorganic mixed-anion compounds reported thus far. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
46. Facile Synthesis of Co−Pt Hollow Sphere Electrocatalyst.
- Author
-
Ge Chen, Dingguo Xia, Zuoren Nie, Zhenyao Wang, Lei Wang, Lei Zhang, and Jiujun Zhang
- Published
- 2007
- Full Text
- View/download PDF
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