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Sheng Y, Liu JM, Wu M. Two-Dimensional Ultrahigh Unconventional Piezoelectricity Driven by Charge Screening. J Phys Chem Lett 2023; 14:3430-3435. [PMID: 37010346 DOI: 10.1021/acs.jpclett.3c00397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
In the past decade, piezoelectricity has been explored in a series of two-dimensional (2D) materials for nanoelectromechanical applications, while their piezoelectric coefficients are mostly much lower than those of prevalent piezoceramics. In this paper, we propose an unconventional approach of inducing 2D ultrahigh piezoelectricity dominated by charge screening instead of lattice distortion and show the first-principles evidence of such piezoelectricity in a series of 2D van der Waals bilayers, where the bandgap can be remarkably tuned via applying a moderate vertical pressure. Their polarizations can switch between the screened and unscreened state by a pressure-driven metal-insulator transition, which can be realized via tuning interlayer hybridization or inhomogeneous electrostatic potential by substrate layer to change the band splitting or tuning the relative energy shift between bands utilizing the vertical polarization of the substrate layer. Such 2D piezoelectric coefficients can be unprecedented and orders of magnitude higher than those of previously studied monolayer piezoelectrics, and their high efficiency of energy harvesting in nanogenerators can be expected.
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Affiliation(s)
- Yuxuan Sheng
- School of Physics and School of Chemistry, Institute of Theoretical Chemistry, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jun-Ming Liu
- Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
| | - Menghao Wu
- School of Physics and School of Chemistry, Institute of Theoretical Chemistry, Huazhong University of Science and Technology, Wuhan 430074, China
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2
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Zhao W, Xu WW, Jiang J, Zhao X, Duan X, Sun Y, Francisco JS, Zeng XC. Evidence of Formation of Monolayer Hydrated Salts in Nanopores. J Am Chem Soc 2022; 144:18976-18985. [PMID: 36197785 DOI: 10.1021/jacs.2c07372] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Despite much effort being devoted to the study of ionic aqueous solutions at the nanoscale, our fundamental understanding of the microscopic kinetic and thermodynamic behaviors in these systems remains largely incomplete. Herein, we reported the first 10 μs molecular dynamics simulation, providing evidence of the spontaneous formation of monolayer hexagonal honeycomb hydrated salts of XCl2·6H2O (X = Ba, Sr, Ca, and Mg) from electrolyte aqueous solutions confined in an angstrom-scale slit under ambient conditions. By using both the classical molecular dynamics simulations and the first-principles Born-Oppenheimer molecular dynamics simulations, we further demonstrated that the hydrated salts were stable not only at ambient temperature but also at elevated temperatures. This phenomenon of formation of hydrated salt in water is contrary to the conventional view. The free energy calculations and dehydration analyses indicated that the spontaneous formation of hydrated salts can be attributed to the interplay between ion hydration and Coulombic attractions in the highly confined water. In addition to providing molecular-level insights into the novel behavior of ionic aqueous solutions at the nanoscale, our findings may have implications for the future exploration of potential existence of water molecules in the saline deposits on hot planets.
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Affiliation(s)
- Wenhui Zhao
- Department of Physics, Ningbo University, Ningbo 315211, China
| | - Wen Wu Xu
- Department of Physics, Ningbo University, Ningbo 315211, China
| | - Jian Jiang
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States.,Department of Materials Science & Engineering, City University of Hong Kong, Kowloon 999077, Hong Kong, China
| | - Xiaorong Zhao
- Department of Physics, Ningbo University, Ningbo 315211, China
| | - Xiangmei Duan
- Department of Physics, Ningbo University, Ningbo 315211, China
| | - Yunxiang Sun
- Department of Physics, Ningbo University, Ningbo 315211, China
| | - Joseph S Francisco
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Xiao Cheng Zeng
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States.,Department of Materials Science & Engineering, City University of Hong Kong, Kowloon 999077, Hong Kong, China
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Zhao X, Liu Y, Lin D, Zhu W, Ma N, Xu WW, Zhao W, Sun Y, Zeng XC. Anomalous Phase Behaviors of Monolayer NaCl Aqueous Solutions Induced by Effective Coulombic Interactions within Angstrom-Scale Slits. J Phys Chem Lett 2022; 13:2704-2710. [PMID: 35302778 DOI: 10.1021/acs.jpclett.2c00501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Interests in subnanofluidic devices have called for molecular dynamics (MD) simulation studies of the thermodynamic behavior of monolayer salt solution within angstrom-scale slits. However, it still remains a grand challenge to accurately describe the Coulombic interactions by incorporating the effects of charge transfer and electronic dielectric screening. Herein, by using the electronic continuum model, where the effective ion charges are fine-tuned with a scaling factor of λ, we present simulation evidence that the effective Coulombic interactions among Na+/Cl- ions can strongly affect the behavior of monolayer ionic aqueous solution. Our microsecond-scale MD simulations show that only the counterions with moderate effective charges (0.3 ≤ λ ≤ 0.8) can dissolve in monolayer water, whereas the high effective charges (λ ≥ 0.85) induce ions to assemble into monolayer nanocrystals, and ions with the low effective charges (λ ≤ 0.2) exhibit gas-like nanobubble. These findings could provide deeper insights into the physical chemistry behind subnanofluidic iontronic devices.
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Affiliation(s)
- Xiaorong Zhao
- Department of Physics, Ningbo University, Ningbo, Zhejiang 315211, China
| | - Yuying Liu
- Department of Physics, Ningbo University, Ningbo, Zhejiang 315211, China
| | - Dongdong Lin
- Department of Physics, Ningbo University, Ningbo, Zhejiang 315211, China
| | - Weiduo Zhu
- Department of Physics, Hefei University of Technology, Hefei, Anhui 230009, China
| | - Nan Ma
- Department of Physics, Ningbo University, Ningbo, Zhejiang 315211, China
| | - Wen Wu Xu
- Department of Physics, Ningbo University, Ningbo, Zhejiang 315211, China
| | - Wenhui Zhao
- Department of Physics, Ningbo University, Ningbo, Zhejiang 315211, China
| | - Yunxiang Sun
- Department of Physics, Ningbo University, Ningbo, Zhejiang 315211, China
| | - Xiao Cheng Zeng
- Department of Chemistry, University of Nebraska─Lincoln, Lincoln, Nebraska 68588, United States
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4
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Yang Y, Liang S, Wu H, Shi G, Fang H. Revisit the Hydrated Cation-π Interaction at the Interface: A New View of Dynamics and Statistics. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:2401-2408. [PMID: 35171618 DOI: 10.1021/acs.langmuir.1c03106] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Carbon-based matter, such as biomolecules and graphitic structures, often form a liquid-solid/soft matter interface in salt solution and continuously affect the surrounding cations through hydrated cation-π interactions. In this Perspective, we revisit the effect of the hydrated cation-π interactions at the interface using statistical physics, which reveals how hydrated cation-π interactions affect every component dynamically and cause a time-dependent statistical effect at the liquid-solid/soft interface. We also highlight several pieces of experimental evidence from a statistical perspective and discuss the remarkable applications related to environmental protection, industrial manufacturing, and biological sciences.
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Affiliation(s)
- Yizhou Yang
- School of Physics, East China University of Science and Technology, Shanghai, 200237, China
| | - Shanshan Liang
- School of Physics, East China University of Science and Technology, Shanghai, 200237, China
| | - Hao Wu
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, Zhejiang 325001, China
- Oujiang Laboratory (Zhejiang Lab for Regenerative Medicine, Vision and Brain Health), Wenzhou, Zhejiang 325001, China
| | - Guosheng Shi
- State Key Laboratory Advanced Special Steel, Shanghai Applied Radiation Institute, Shanghai University, Shanghai 200444, China
| | - Haiping Fang
- School of Physics, East China University of Science and Technology, Shanghai, 200237, China
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, Zhejiang 325001, China
- Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201204, China
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5
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Zhao Y, Zhang Q, Li Y, Chen L, Yi R, Peng B, Nie D, Zhang L, Shi G, Zhang S, Zhang L. Graphitic-like Hexagonal Phase of Alkali Halides in Quasi-Two-Dimensional Confined Space under Ambient Conditions. ACS NANO 2022; 16:2046-2053. [PMID: 35137582 DOI: 10.1021/acsnano.1c07424] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The discovery of specific matter phases with abnormal physical properties in low-dimensional systems and/or on particular substrates, such as the hexagonal phase of ice and two-dimensional (2D) CaCl with an abnormal valence state, continuously reveals more fundamental mechanisms of the nature. Alkali halides, represented by NaCl, are one of the most common compounds and usually thought to be well-understood. In the past decades, many theoretical studies suggested the existence of one particular phase, that is, the graphitic-like hexagonal phase of alkali halides at high pressure or in low-dimension states, with the expectation of improved properties of this matter phase but lacking experimental evidence due to severe technical challenges. Here, by optimized cryo-electron microscopy, we report the direct atomic-resolution observation and in situ characterization of the prevalent and stable graphitic-like alkali halide hexagonal phases, which were spontaneously formed by unsaturated NaCl and LiCl solution, respectively, in the quasi-2D confined space between reduced graphene oxide layers under ambient conditions. Combined with a control experiment, density functional theory calculations, and previous theoretical studies, we believe that a delicate balance among the cation-π interaction of the solute and substrate, electrostatic interactions of anions and cations, solute-solvent interactions, and thermodynamics under confinement synergistically results in the formation of such hexagonal crystalline phases. These findings highlight the effects of the substrate and the confined space on the formation of specific matter phases and provide a universal scheme for the preparation of special graphitic-like hexagonal phases of alkali halides.
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Affiliation(s)
- Yimin Zhao
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Quan Zhang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Yunzhang Li
- Shanghai Applied Radiation Institute, Shanghai University, Shanghai 200444, China
| | - Liang Chen
- School of Physical Science and Technology, Ningbo University, Ningbo 315211, China
- Department of Optical Engineering, Zhejiang Prov Key Lab Carbon Cycling Forest Ecosy, Zhejiang Prov Key Lab of Chemical Utilization of Forestry Biomass, Zhejiang A&F University, Lin'an 311300, China
| | - Ruobing Yi
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, Xi'an 710049, China
- Department of Optical Engineering, Zhejiang Prov Key Lab Carbon Cycling Forest Ecosy, Zhejiang Prov Key Lab of Chemical Utilization of Forestry Biomass, Zhejiang A&F University, Lin'an 311300, China
| | - Bingquan Peng
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Dexi Nie
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Lihao Zhang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Guosheng Shi
- Shanghai Applied Radiation Institute, Shanghai University, Shanghai 200444, China
| | - Shengli Zhang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Lei Zhang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, Xi'an 710049, China
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Tan H, Shan G, Pacchioni G. Prediction of 2D ferromagnetism and monovalent europium ions in EuBr/graphene heterojunctions. Phys Chem Chem Phys 2021; 23:25500-25506. [PMID: 34730141 DOI: 10.1039/d1cp02218k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Europium, one of the rare-earth elements, exhibits +2 and +3 valence states and has been widely used for the magnetic modification of materials. Based on density functional theory calculations, we predicted 2D EuBr/graphene heterojunctions to exhibit metallicity, huge intrinsic-ferromagnetism nearly 7.0 μB per Eu and the special monovalent Eu ions. Electron localization function (ELF), difference charge densities and Bader charge analyses demonstrated that there are cation-π interactions between the EuBr films and graphene. Graphene works as a substrate to enable the stability of EuBr monolayer crystals, where EuBr plays an important role to yield ferromagnetism and enhance metallicity in the heterojunctions. Monte Carlo simulations were used to estimate a Curie temperature of about 7 K, which, together with magnetic configurations, can be further modulated by external strains and charge-carrier doping. In general, our theoretical work predicts the properties of novel 2D ferromagnetic EuBr/graphene heterojunctions, suggesting the possibility of combining 2D intrinsic-ferromagnetic metal halide crystals and graphene, and opening up a new perspective in next-generation electronic, spintronic devices and high-performance sensors.
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Affiliation(s)
- Haoyi Tan
- School of Instrumentation Science and Opto-electronics Engineering & Institute of Precision Instrument and Quantum Sensing, Beihang University, Beijing 100191, China.
| | - Guangcun Shan
- School of Instrumentation Science and Opto-electronics Engineering & Institute of Precision Instrument and Quantum Sensing, Beihang University, Beijing 100191, China. .,Department of Materials Science and Engineering, City University of Hong Kong, Kowloon Tong, Hong Kong SAR
| | - Gianfranco Pacchioni
- Dipartimento di Scienza dei Materiali, Università degli Studi Milano-Bicocca, 20125 Milano, Italy
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Pure Graphene Oxide Vertical p-n Junction with Remarkable Rectification Effect. Molecules 2021; 26:molecules26226849. [PMID: 34833941 PMCID: PMC8618643 DOI: 10.3390/molecules26226849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Revised: 11/08/2021] [Accepted: 11/10/2021] [Indexed: 11/17/2022] Open
Abstract
Graphene p-n junctions have important applications in the fields of optical interconnection and low-power integrated circuits. Most current research is based on the lateral p-n junction prepared by chemical doping and other methods. Here, we report a new type of pure graphene oxide (pGO) vertical p-n junctions which do not dope any other elements but only controls the oxygen content of GO. The I-V curve of the pGO vertical p-n junction demonstrates a remarkable rectification effect. In addition, the pGO vertical p-n junction shows stability of its rectification characteristic over long-term storage for six months when sealed and stored in a PE bag. Moreover, the pGO vertical p-n junctions have obvious photoelectric response and various rectification effects with different thicknesses and an oxygen content of GO, humidity, and temperature. Hall effect test results show that rGO is an n-type semiconductor; theoretical calculations and research show that GO is generally a p-type semiconductor with a bandgap, thereby forming a p-n junction. Our work provides a method for preparing undoped GO vertical p-n junctions with advantages such as simplicity, convenience, and large-scale industrial preparation. Our work demonstrates great potential for application in electronics and highly sensitive sensors.
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