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255 results on '"Liu, Pingwei"'

1. Ferroelectricity in oxygen-terminated 2D carbides of lanthanide elements

Author

Han, Lin, Sun, Wencong, Liu, Pingwei, Lin, Xianqing, Liu, Dan, and Tomanek, David

Subjects
Condensed Matter - Materials Science
Abstract

We investigate the properties of oxygen-functionalized carbides of lanthanide elements with the composition M2CO2 (M=Gd, Tb,Dy) that form two-dimensional (2D) structures. Our ab initio calculations reveal that oxygen termination turns M2C monolayers into semiconductors with two dynamically stable phases. Of these, the energetically favored alpha-phase becomes ferroelectric, whereas the beta-phase turns anti-ferroelectric. Applying in-plane biaxial strain may transform one phase into the other, changes the ferroelectric polarization of the alpha-phase in a linear fashion, and modifies the size and nature of the fundamental band gap from direct to indirect. The structure with a direct band gap exhibits in-plane isotropic electronic and optical properties. This previously unexplored class of systems also exhibits excellent photon absorption in the ultraviolet range.

Published
2024
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4. An Irreversible Synthetic Route to an Ultra-Strong Two-Dimensional Polymer

Author

Zeng, Yuwen, Gordiichuk, Pavlo, Ichihara, Takeo, Zhang, Ge, Gong, Xun, Emil, Sandoz-Rosado, Wetzel, Eric D., Tresback, Jason, Yang, Jing, Yang, Zhongyue, Kozawa, Daichi, Kuehne, Matthias, Liu, Pingwei, Liu, Albert Tianxiang, Yang, Jingfan, Kulik, Heather J., and Strano, Michael S.

Subjects
Condensed Matter - Soft Condensed Matter, Condensed Matter - Materials Science
Abstract

Polymers that extend covalently in two dimensions have attracted recent attention as a means of combining the mechanical strength and in-plane energy conduction of conventional two-dimensional (2D) materials with the low densities, synthetic processability, and organic composition of their one-dimensional counterparts. Efforts to date have proven successful in forms that do not allow full realization of these properties, such as polymerization at flat interfaces or fixation of monomers in immobilized lattices. A frequently employed synthetic approach is to introduce microscopic reversibility, at the cost of bond stability, to achieve 2D crystals after extensive error correction. Herein we demonstrate a synthetic route to 2D irreversible polycondensation directly in the solution phase, resulting in covalently bonded 2D polymer platelets that are chemically stable and highly processable. Further fabrication offers highly oriented, free-standing films which exhibit exceptional 2D elastic modulus and yield strength at 50.9 +- 15.0 GPa and 0.976 +- 0.113 GPa, respectively. Platelet alignment is evidenced by polarized photoluminescence centered at 580 and 680 nm from different dipole transitions. This new synthetic route provides opportunities for 2D polymers in applications ranging from composite structures to molecular sieving membranes., Comment: 13 pages, 4 figures

Published
2021

5. Observation and Spectral Assignment of a Family of Hexagonal Boron Nitride Lattice Defects

Author

Kozawa, Daichi, Rajan, Ananth Govind, Li, Sylvia Xin, Ichihara, Takeo, Koman, Volodymyr B., Zeng, Yuwen, Kuehne, Matthias, Iyemperumal, Satish Kumar, Silmore, Kevin S., Parviz, Dorsa, Liu, Pingwei, Liu, Albert Tianxiang, Faucher, Samuel, Yuan, Zhe, Xu, Wenshuo, Warner, Jamie H., Blankschtein, Daniel, and Strano, Michael S.

Subjects
Condensed Matter - Materials Science, Quantum Physics
Abstract

Atomic vacancy defects in single unit cell thick hexagonal boron nitride are of significant interest because of their photophysical properties, including single-photon emission, and promising applications in quantum communication and computation. The spectroscopic assignment of emission energies to specific atomic vacancies within the triangular lattice is confounded by the exponential scaling of defect candidates with the number of removed atoms. Herein, we collect more than 1000 spectra consisting of single, isolated zero-phonon lines between 1.69 and 2.25 eV, observing 6 quantized zero-phonon lines arising from hexagonal boron nitride vacancies. A newly developed computational framework for isomer cataloguing significantly narrows the number of candidate vacancies. Direct lattice imaging of hexagonal boron nitride, electronic structure calculations, and subsequent boric acid etching are used to definitively assign the 6 features. Systematic chemical etching supports the assignment by demonstrating the sequence of growth of successively larger vacancy centres from smaller ones, with the defects including a single B vacancy and a 16-atom triangular defect. These features exhibit a range of emission lifetimes from 1 to 6 ns, and phonon sidebands offset by the dominant lattice phonon in hexagonal boron nitride near 1370 cm-1. This assignment should significantly advance the solid-state chemistry and photophysics of such vacancy emitters., Comment: 28 pages, 5 figures, and 40 pages of supplementary information

Published
2019

9. Validated enhancement and temperature modulated absorbance of WS2 monolayer based on planar structure

Author

Yuan, Xueyong, primary, jiang, Guangsheng, additional, Liu, Pingwei, additional, Fu, Qiang, additional, Zhang, Zhi, additional, Liu, Tianqi, additional, Jiang, Yuru, additional, zhao, weiwei, additional, wang, wenhui, additional, Zhao, Bei, additional, Li, Zejun, additional, Liu, Dan, additional, Ni, Zhenhua, additional, and Lu, Junpeng, additional

Published
2024
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12. Irreversible synthesis of an ultrastrong two-dimensional polymeric material

Author

Zeng, Yuwen, Gordiichuk, Pavlo, Ichihara, Takeo, Zhang, Ge, Sandoz-Rosado, Emil, Wetzel, Eric D., Tresback, Jason, Yang, Jing, Kozawa, Daichi, Yang, Zhongyue, Kuehne, Matthias, Quien, Michelle, Yuan, Zhe, Gong, Xun, He, Guangwei, Lundberg, Daniel James, Liu, Pingwei, Liu, Albert Tianxiang, Yang, Jing Fan, Kulik, Heather J., and Strano, Michael S.

Published
2022
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15. Self‐repairable, high‐uniform conductive‐bridge random access memory based on amorphous NbSe2.

Author

Lu, Bojing, Hu, Dunan, Yang, Ruqi, Du, Jigang, Hu, Lingxiang, Li, Siqin, Wang, Fengzhi, Huang, Jingyun, Liu, Pingwei, Zhuge, Fei, Zeng, Yu‐Jia, Ye, Zhizhen, and Lu, Jianguo

Subjects
RANDOM access memory, COPPER
Abstract

Conductive‐bridge random access memory (CBRAM) emerges as a promising candidate for next‐generation memory and storage device. However, CBRAMs are prone to degenerate and fail during electrochemical metallization processes. To address this issue, herein we propose a self‐repairability strategy for CBRAMs. Amorphous NbSe2 was designed as the resistive switching layer, with Cu and Au as the top and bottom electrodes, respectively. The NbSe2 CBRAMs demonstrate exceptional cycle‐to‐cycle and device‐to‐device uniformity, with forming‐free and compliance current‐free resistive switching characteristics, low‐operation voltage, and competitive endurance and retention performance. Most importantly, the self‐repairable behavior is discovered for the first time in CBRAM. The device after failure can recover its performance to the initially normal state by operating with a slightly large reset voltage. The existence of Cu conductive filament and excellent controllability of Cu migration in the NbSe2 switching layer has been revealed by a designed broken‐down point approach, which is responsible for the self‐repairable behavior of NbSe2 CBRAMs. Our self‐repairable and high‐uniform amorphous NbSe2 CBRAM may open the door to the development of memory and storage devices in the future. [ABSTRACT FROM AUTHOR]

Published
2024
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20. Engineering hollow covalent organic framework particle through self‐templated crystallization.

Author

Zheng, Zhenqian, Yang, Yuhao, Chen, Di, Wang, Song, Li, Qiulin, Zhang, Ziyang, Li, Wei, Chen, Bajin, Wang, Wen‐Jun, and Liu, Pingwei

Subjects
CRYSTALLIZATION, CHEMICAL reactions, SCHIFF bases, MICROPORES, OLIGOMERIZATION
Abstract

Nano/microparticles with hollow structures have many applications in various fields. However, engineering hollow covalent organic framework (COF) particles in a simple and efficient manner remains a significant challenge. In this study, we propose a self‐template crystallization method to prepare imine‐based COF microparticles with tailored shell thickness and high crystallinity. This method involves the post‐transformation of amorphous microparticles in a highly reversible reaction system containing monofunctional competitors. The amorphous precursors with high‐Gibbs free energy decompose and reconstruct to form highly crystalline COFs in situ on the particle surface. This process allows for the preparation of various Schiff‐base COF particles with good crystallinity and tailored hollow structures, with diameters ranging from 120 to 680 nm and shell thicknesses of 27–96 nm. These COF particles have well‐defined micropore sizes centered between 1.0 and 4.0 nm and a high‐specific surface area of up to 543 m2 g−1. The resulted COF particles could be used to support ethylene oligomerization catalysts for improving their activity and selectivity, that is, the mass fraction of α‐olefins above C10 increased from almost zero to 52.7% after COF supporting. Our method thus provides an efficient way to precisely tailor the microstructure and morphology of COF materials for advanced applications. [ABSTRACT FROM AUTHOR]

Published
2024
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25. Combinatorial Synthesis of Covalent Organic Framework Particles with Hierarchical Pores and Their Catalytic Application

Author

Li, Wei, primary, Bie, Zhengwei, additional, Zhang, Chi, additional, Xu, Xintong, additional, Wang, Song, additional, Yang, Yuhao, additional, Zhang, Ziyang, additional, Yang, Xuan, additional, Lim, Khak Ho, additional, Wang, Qingyue, additional, Wang, Wen-Jun, additional, Li, Bo-Geng, additional, and Liu, Pingwei, additional

Published
2023
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36. Synthesis and characterization of polyolefin thermoplastic elastomers: A review.

Author

Sun, Minghao, Xiao, Yangke, Liu, Kan, Yang, Xuan, Liu, Pingwei, Jie, Suyun, Hu, Jijiang, Shi, Shengbin, Wang, Qingyue, Lim, Khak Ho, Liu, Zhenxue, Li, Bo‐Geng, and Wang, Wen‐Jun

Subjects
POLYOLEFINS, RANDOM copolymers, BLOCK copolymers, CHEMICAL stability, THERMOPLASTIC elastomers, ELASTOMERS, ELECTRIC insulators & insulation, POLYURETHANE elastomers
Abstract

Polyolefin thermoplastic elastomers (TPE‐Os) are high‐performance polyolefins consisting of both plastic and rubber phases. Compared with other thermoplastic elastomers, the TPE‐Os possess better chemical stability, transparency, re‐processability, and electrical insulation, which renders their broad applications possible. By manipulating chain structures and topologies of the TPE‐Os, differently structured polyolefins with improved thermal and mechanical properties have been developed, including ethylene and α‐olefin random copolymers (POEs), olefin block copolymers (OBCs), comb‐shaped polyolefin elastomers (CPOEs), and dynamically cross‐linked polyolefin elastomers. Herein, we review the synthesis of the POE, OBC, CPOE, and dynamical cross‐linked polyolefin elastomer, including the catalyst systems, polymerization techniques, processes, and kinetic modelling. The characterization of the TPE‐Os and the relationships between the TPE‐O chain structure, aggregated state, and product performance are discussed. The future development of higher‐performance TPE‐Os is envisaged. [ABSTRACT FROM AUTHOR]

Published
2023
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38. List of contributors

Author

Akashi, Nozomi, primary, Anderson, Iain A., additional, Aydin, Yasemin Ozkan, additional, Baechle, Daniel M., additional, Baker, Remmi, additional, Balazs, Anna C., additional, Brooks, Allan M., additional, Correll, Nikolaus, additional, Daalkhaijav, U., additional, Darling, Kristopher A., additional, Fan, Donglei, additional, Gaynor, Andrew, additional, Giri, Anit K., additional, Goldman, Daniel I., additional, Guo, Jianhe, additional, Hubicki, Christian M., additional, Ishii, Hiroshi, additional, Koman, Volodymyr B., additional, Kozawa, Daichi, additional, Li, Tao, additional, Li, Zhaohan, additional, Liang, Zexi, additional, Liu, Pingwei, additional, Liu, Albert Tianxiang, additional, Majidi, Carmel, additional, Henke, E.-F. Markus, additional, McAlpine, Michael C., additional, Mengüç, Y., additional, Moran, Jeffrey L., additional, Mrozek, Randy A., additional, Murphey, Todd, additional, Nakajima, Kohei, additional, Park, Sung Hyun, additional, Pelrine, Ron, additional, Pervan, Ana, additional, Petersen, Kirstin H., additional, Rieser, Jennifer M., additional, Savoie, William, additional, Sen, Ayusman, additional, Shepherd, Robert F., additional, Shklyaev, Oleg E., additional, Shum, Henry, additional, Slipher, Geoffrey A., additional, Strano, Michael S., additional, Su, Ruitao, additional, Walker, S., additional, Walsh, Shawn M., additional, Wildman, Raymond, additional, Wilson, Katherine E., additional, Yang, Jing Fan, additional, Yao, Lining, additional, Yirmibeşoğlu, O.D., additional, and Zhang, Ge, additional

Published
2019
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40. Discretized hexagonal boron nitride quantum emitters and their chemical interconversion

Author

Kozawa, Daichi, primary, Li, Sylvia Xin, additional, Ichihara, Takeo, additional, Rajan, Ananth Govind, additional, Gong, Xun, additional, He, Guangwei, additional, Koman, Volodymyr B, additional, Zeng, Yuwen, additional, Kuehne, Matthias, additional, Silmore, Kevin S, additional, Parviz, Dorsa, additional, Liu, Pingwei, additional, Liu, Albert Tianxiang, additional, Faucher, Samuel, additional, Yuan, Zhe, additional, Warner, Jamie, additional, Blankschtein, Daniel, additional, and Strano, Michael S, additional

Published
2023
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