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Yuan J, Gao M, Liu Z, Tang X, Tian Y, Ma G, Ye M, Zheng A. Hyperloop-like diffusion of long-chain molecules under confinement. Nat Commun 2023; 14:1735. [PMID: 36977714 PMCID: PMC10050162 DOI: 10.1038/s41467-023-37455-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 03/14/2023] [Indexed: 03/30/2023] Open
Abstract
The ultrafast transport of adsorbates in confined spaces is a goal pursued by scientists. However, diffusion will be generally slower in nano-channels, as confined spaces inhibit motion. Here we show that the movement of long-chain molecules increase with a decrease in pore size, indicating that confined spaces promote transport. Inspired by a hyperloop running on a railway, we established a superfast pathway for molecules in zeolites with nano-channels. Rapid diffusion is achieved when the long-chain molecules keep moving linearly, as well as when they run along the center of the channel, while this phenomenon do not exist for short-chain molecules. This hyperloop-like diffusion is unique for long-chain molecules in a confined space and is further verified by diffusion experiments. These results offer special insights into molecule diffusion under confinement, providing a reference for the selection of efficient catalysts with rapid transport in the industrial field.
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Affiliation(s)
- Jiamin Yuan
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, People's Republic of China
- University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Mingbin Gao
- National Engineering Laboratory for Methanol to Olefins, Dalian National Laboratory for Clean Energy, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, People's Republic of China
| | - Zhiqiang Liu
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, People's Republic of China.
| | - Xiaomin Tang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, People's Republic of China
| | - Yu Tian
- University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
- National Engineering Laboratory for Methanol to Olefins, Dalian National Laboratory for Clean Energy, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, People's Republic of China
| | - Gang Ma
- College of Chemistry and Materials Science, Hebei University, Baoding, 071002, People's Republic of China
| | - Mao Ye
- National Engineering Laboratory for Methanol to Olefins, Dalian National Laboratory for Clean Energy, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, People's Republic of China.
| | - Anmin Zheng
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, People's Republic of China.
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2
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Nag S, Maiti PK, Yashonath S. Separating a linear C 5 hydrocarbon from a branched C 6 hydrocarbon: n-pentane from 2,2-dimethyl butane using levitation and blow torch effects. Phys Chem Chem Phys 2021; 23:18102-18111. [PMID: 34397066 DOI: 10.1039/d1cp01615f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The separation of linear from branched hydrocarbons is often required in many situations. There are several methods through which they can be separated but none provides a very high degree of purity or works without considerable expenditure of energy. Recently, a novel method was proposed to separate a mixture of neopentane and n-pentane. The present work demonstrates that the method can be used for separating other mixtures of hydrocarbons as well, by attempting the separation of a mixture of 2,2-dimethyl butane and n-pentane. Intermolecular interaction potentials have been modified to reproduce the experimental heat of adsorption and diffusivity of 2,2-dimethyl butane and n-pentane in zeolite NaY. The method involves choosing the correct host zeolite or other porous solids and introducing hot zones at appropriate positions. This result drives both the components to the opposite ends of the zeolite column, thus leading to separation. The achieved separation factors are much higher than what can be obtained with the help of existing methods. Different properties have been computed to understand the process involved in the separation of the mixture. The approach employed here uses very little energy for separation, making it suitable for green chemistry.
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Affiliation(s)
- Shubhadeep Nag
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India.
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3
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Liu Z, Yuan J, van Baten JM, Zhou J, Tang X, Zhao C, Chen W, Yi X, Krishna R, Sastre G, Zheng A. Synergistically enhance confined diffusion by continuum intersecting channels in zeolites. SCIENCE ADVANCES 2021; 7:7/11/eabf0775. [PMID: 33712464 PMCID: PMC7954456 DOI: 10.1126/sciadv.abf0775] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 01/28/2021] [Indexed: 06/12/2023]
Abstract
In separation and catalysis applications, adsorption and diffusion are normally considered mutually exclusive. That is, rapid diffusion is generally accompanied by weak adsorption and vice versa. In this work, we analyze the anomalous loading-dependent mechanism of p-xylene diffusion in a newly developed zeolite called SCM-15. The obtained results demonstrate that the unique system of "continuum intersecting channels" (i.e., channels made of fused cavities) plays a key role in the diffusion process for the molecule-selective pathways. At low pressure, the presence of strong adsorption sites and intersections that provide space for molecule rotation facilitates the diffusion of p-xylene along the Z direction. Upon increasing the molecular uptake, the adsorbates move faster along the X direction because of the effect of continuum intersections in reducing the diffusion barriers and thus maintaining the large diffusion coefficient of the diffusing compound. This mechanism synergistically improves the diffusion in zeolites with continuum intersecting channels.
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Affiliation(s)
- Zhiqiang Liu
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, and Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Jiamin Yuan
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, and Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Jasper M van Baten
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands
| | - Jian Zhou
- Shanghai Research Institute of Petrochemical Technology, SINOPEC, Shanghai 201208, P. R. China
| | - Xiaomin Tang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, and Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Chao Zhao
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou, Henan 450001, P. R. China
| | - Wei Chen
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, and Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Xianfeng Yi
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, and Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Rajamani Krishna
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands
| | - German Sastre
- Instituto de Tecnologia Quimica UPV-CSIC, Universitat Politecnica de Valencia, Av. Los Naranjos s/n, 46022 Valencia, Spain
| | - Anmin Zheng
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, and Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China.
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4
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Khatri N, Burada PS. Diffusion of interacting particles in a channel with reflection boundary conditions. J Chem Phys 2019; 151:094103. [DOI: 10.1063/1.5116330] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Affiliation(s)
- Narender Khatri
- Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur - 721302, India
| | - P. S. Burada
- Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur - 721302, India
- Center for Theoretical Studies, Indian Institute of Technology Kharagpur, Kharagpur - 721302, India
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5
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Liu Y, Zhang B, Liu D, Sheng P, Lai Z. Fabrication and molecular transport studies of highly c-Oriented AFI membranes. J Memb Sci 2017. [DOI: 10.1016/j.memsci.2017.01.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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6
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Bhatia SK, Bonilla MR, Nicholson D. Molecular transport in nanopores: a theoretical perspective. Phys Chem Chem Phys 2011; 13:15350-83. [DOI: 10.1039/c1cp21166h] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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7
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Burada PS, Schmid G. Steering the potential barriers: entropic to energetic. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:051128. [PMID: 21230458 DOI: 10.1103/physreve.82.051128] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Indexed: 05/30/2023]
Abstract
We propose a mechanism to alter the nature of the potential barriers when a biased brownian particle undergoes a constrained motion in narrow periodic channel. By changing the angle of the external bias, the nature of the potential barriers changes from purely entropic to energetic, which in turn affects the diffusion process in the system. At an optimum angle of the bias, the nonlinear mobility exhibits a striking bell-shaped behavior. Moreover, the enhancement of the scaled effective diffusion coefficient can be efficiently controlled by the angle of the bias. This mechanism enables the proper design of channel structures for transport of molecules and small particles. The approximate analytical predictions have been verified by precise brownian dynamics simulations.
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Affiliation(s)
- P S Burada
- Max-Planck Institut für Physik Komplexer Systeme, Nöthnitzer Str. 38, D-01187 Dresden, Germany.
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8
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Giussani L, Fois E, Gianotti E, Tabacchi G, Gamba A, Coluccia S. On the Compatibility Criteria for Protein Encapsulation inside Mesoporous Materials. Chemphyschem 2010; 11:1757-62. [DOI: 10.1002/cphc.200901038] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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9
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Liu Y, Ai BQ. Diffusion in a tilted periodic potential with entropic barriers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:465102. [PMID: 21715900 DOI: 10.1088/0953-8984/21/46/465102] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Diffusion of Brownian particles in a periodic channel is investigated in the presence of a tilted spatially periodic potential. Reduction of spatial dimensionality from two or three dimensions to an effective one-dimensional system entails the appearance of not only an entropic barrier but also an effective diffusion coefficient. It is found that diffusion exhibits striking features which are different from those observed in the previous cases. The interplay between the potential barriers and entropic barriers makes the phenomena richer. Remarkably, two temperature values exist at which the Peclet number takes its maximum.
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Affiliation(s)
- Yang Liu
- Laboratory of Quantum Information Technology, ICMP and SPTE, South China Normal University, Guangzhou, People's Republic of China
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10
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Lucena SM, Cavalcante CL. Adsorption equilibrium in one-dimensional molecular sieve: a study of force fields effect on linear alkanes molecules. MOLECULAR SIMULATION 2008. [DOI: 10.1080/08927020802301896] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Sebastiao M.P. Lucena
- a Grupo de Pesquisa em Separação por Adsorção (GPSA), Departamento de Engenharia Química , Universidade Federal do Ceará , Fortaleza, Ceará, Brazil
| | - Célio L. Cavalcante
- a Grupo de Pesquisa em Separação por Adsorção (GPSA), Departamento de Engenharia Química , Universidade Federal do Ceará , Fortaleza, Ceará, Brazil
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11
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Smit B, Maesen TLM. Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity. Chem Rev 2008; 108:4125-84. [DOI: 10.1021/cr8002642] [Citation(s) in RCA: 586] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Berend Smit
- Department of Chemical Engineering, University of California, Berkeley, California 94720-1462, Van’t Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, and Centre Européen de Calcul Atomique et Moléculaire (CECAM), Ecole Normale Supérieure, 46 Allée d’Italie, 69007 Lyon France
| | - Theo L. M. Maesen
- Chevron, Energy Technology Company, 100 Chevron Way, Richmond, California 94802-0627
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12
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Jakobtorweihen S, Lowe CP, Keil FJ, Smit B. Diffusion of chain molecules and mixtures in carbon nanotubes: The effect of host lattice flexibility and theory of diffusion in the Knudsen regime. J Chem Phys 2007; 127:024904. [PMID: 17640148 DOI: 10.1063/1.2753477] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
A novel algorithm for modeling the influence of the host lattice flexibility in molecular dynamics simulations is extended to chain-like molecules and mixtures. This technique, based on a Lowe-Andersen thermostat, maintains the advantages of both simplicity and efficiency. The same diffusivities and other properties of the flexible framework system are reproduced. Advantageously, the computationally demanding flexible host lattice simulations can be avoided. Using this methodology we study the influence of flexibility on diffusion of n-alkanes inside single-walled carbon nanotubes. Furthermore, results are shown for diffusion of two mixtures (methane-helium and ethane-butane). Using these results we investigate the accuracy of theories describing diffusion in the Knudsen regime. For the dynamics in carbon nanotubes the Knudsen diffusivities are much too low. The Smoluchowski model gives better results. Interestingly, the extended Smoluchowski model can reproduce our simulation results obtained with a rigid host lattice. We modify this model to also treat collisions with a flexible interface correctly. As the tangential momentum accommodation coefficient is needed for the theoretical models, we introduce a simple concept to calculate it.
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Affiliation(s)
- S Jakobtorweihen
- Department of Chemical Reaction Engineering, Hamburg University of Technology, Eissendorfer Strasse 38, D-21073 Hamburg, Germany.
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13
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Mukherjee B, Maiti PK, Dasgupta C, Sood AK. Strong correlations and Fickian water diffusion in narrow carbon nanotubes. J Chem Phys 2007; 126:124704. [PMID: 17411149 DOI: 10.1063/1.2565806] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The authors have used atomistic molecular dynamics (MD) simulations to study the structure and dynamics of water molecules inside an open ended carbon nanotube placed in a bath of water molecules. The size of the nanotube allows only a single file of water molecules inside the nanotube. The water molecules inside the nanotube show solidlike ordering at room temperature, which they quantify by calculating the pair correlation function. It is shown that even for the longest observation times, the mode of diffusion of the water molecules inside the nanotube is Fickian and not subdiffusive. They also propose a one-dimensional random walk model for the diffusion of the water molecules inside the nanotube. They find good agreement between the mean-square displacements calculated from the random walk model and from MD simulations, thereby confirming that the water molecules undergo normal mode diffusion inside the nanotube. They attribute this behavior to strong positional correlations that cause all the water molecules inside the nanotube to move collectively as a single object. The average residence time of the water molecules inside the nanotube is shown to scale quadratically with the nanotube length.
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Affiliation(s)
- Biswaroop Mukherjee
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore, India.
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14
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Jakobtorweihen S, Lowe CP, Keil FJ, Smit B. A novel algorithm to model the influence of host lattice flexibility in molecular dynamics simulations: Loading dependence of self-diffusion in carbon nanotubes. J Chem Phys 2006; 124:154706. [PMID: 16674250 DOI: 10.1063/1.2185619] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
We describe a novel algorithm that includes the effect of host lattice flexibility into molecular dynamics simulations that use rigid lattices. It uses a Lowe-Andersen thermostat for interface-fluid collisions to take the most important aspects of flexibility into account. The same diffusivities and other properties of the flexible framework system are reproduced at a small fraction of the computational cost of an explicit simulation. We study the influence of flexibility on the self-diffusion of simple gases inside single walled carbon nanotubes. Results are shown for different guest molecules (methane, helium, and sulfur hexafluoride), temperatures, and types of carbon nanotubes. We show, surprisingly, that at low loadings flexibility is always relevant. Notably, it has a crucial influence on the diffusive dynamics of the guest molecules.
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Affiliation(s)
- S Jakobtorweihen
- Chemical Reaction Engineering, Hamburg University of Technology, Eissendorfer Strasse 38, D-21073 Hamburg, Germany.
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15
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Reguera D, Schmid G, Burada PS, Rubí JM, Reimann P, Hänggi P. Entropic transport: kinetics, scaling, and control mechanisms. PHYSICAL REVIEW LETTERS 2006; 96:130603. [PMID: 16711977 DOI: 10.1103/physrevlett.96.130603] [Citation(s) in RCA: 183] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Indexed: 05/09/2023]
Abstract
We show that transport in the presence of entropic barriers exhibits peculiar characteristics which makes it distinctly different from that occurring through energy barriers. The constrained dynamics yields a scaling regime for the particle current and the diffusion coefficient in terms of the ratio between the work done to the particles and available thermal energy. This interesting property, genuine to the entropic nature of the barriers, can be utilized to effectively control transport through quasi-one-dimensional structures in which irregularities or tortuosity of the boundaries cause entropic effects. The accuracy of the kinetic description has been corroborated by simulations. Applications to different dynamic situations involving entropic barriers are outlined.
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Affiliation(s)
- D Reguera
- Department de Física Fonamental, Facultat de Física, Universidad de Barcelona, Diagonal 647, E-08028 Barcelona, Spain
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16
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Liu Y, Wang Q, Wu T, Zhang L. Fluid structure and transport properties of water inside carbon nanotubes. J Chem Phys 2005; 123:234701. [PMID: 16392938 DOI: 10.1063/1.2131070] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The fluid structure and transport properties of water confined in single-walled carbon nanotubes (CNTs) with different diameters have been investigated by molecular-dynamics simulation. The effects of CNT diameter, density of water, and temperature on the molecular distributions and transport behaviors of water were analyzed. It is interesting that the water molecules ordered in helix inside the (10, 10) CNT, and the layered distribution was clearly observed. It was found that the axial and radial diffusivities in CNTs were much lower than that of the bulk, and it ever decreased as the diameter of CNT decreases. The axial thermal conductivity and shear viscosity in CNTs are obviously larger than that of the bulk and those in the radial direction, they increase sharply as the diameter of CNT decreases, which is clearly in contrast to the diffusivity. The inner space of CNT and the interactions between water molecules and the confining walls play a key role in the structure and transport properties of water confined in the CNTs.
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Affiliation(s)
- Yingchun Liu
- Department of Chemistry, Zhejiang University, Hangzhou 310027, People's Republic of China
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17
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Lee KH, Sinnott SB. Equilibrium and nonequilibrium transport of oxygen in carbon nanotubes. NANO LETTERS 2005; 5:793-798. [PMID: 15826130 DOI: 10.1021/nl0502219] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The equilibrium and nonequilibrium transport of O(2) through open-ended, hydrogen-terminated, single-walled carbon nanotubes is examined using classical molecular dynamics simulations. It is found in both cases that the O(2) forms well-defined layers around the nanotube interior and/or exterior, and that molecular transport approaches normal mode-diffusion as the nanotube diameter increases. The interactions between the O(2) and the nantubes are stronger than that among the O(2), and this difference increases as the nanotube diameter decreases.
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Affiliation(s)
- Ki-Ho Lee
- Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611-6400, USA
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18
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Supple S, Quirke N. Molecular dynamics of transient oil flows in nanopores. II. Density profiles and molecular structure for decane in carbon nanotubes. J Chem Phys 2005; 122:104706. [PMID: 15836344 DOI: 10.1063/1.1856927] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
We report molecular dynamics simulations of nanotubes imbibing decane at an oil/vapor interface at 300 K. We find that the smallest (7,7) nanotubes imbibe extremely rapidly (< or =800 ms), with the imbibition speed slowing as the tube's radius increases. The density profiles of the imbibing fluid in the pores are analyzed as a function of time. We find that the imbibing liquid is well described by the advection-diffusion equation and present expressions for the density profiles (in x and t) of the imbibing fluid as a function of the adsorption energy and surface friction of the pore. In addition we have analyzed the molecular structure of the imbibed fluid in nanotubes and describe how molecular conformations change with nanotube radius and position in the pore. We are therefore able to provide a complete description of the imbibition of a wetting fluid, decane, for a wide range of nanopores.
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Affiliation(s)
- S Supple
- Department of Chemistry, Imperial College London, London SW7 2AY, United Kingdom
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19
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Ghorai PK, Yashonath S. The Stokes−Einstein Relationship and the Levitation Effect: Size-Dependent Diffusion Maximum in Dense Fluids and Close-Packed Disordered Solids. J Phys Chem B 2005; 109:5824-35. [PMID: 16851635 DOI: 10.1021/jp046312w] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We report a molecular dynamics study of a binary mixture consisting of a large (host) particle and a smaller (guest) particle whose radius is varied over a range. These simulations investigate the possible existence of a diffusion anomaly or levitation effect in dense fluids, previously seen for guest molecules diffusing within porous solids. The voids in the larger component have been characterized in terms of void and neck distributions by means of Voronoi polyhedral analysis. Four different mixtures with differing ratios of guest to host diffusivities (D) have been studied. The results suggest that the diffusion anomaly is seen in both close-packed solids with disorder and dense fluids. In the latter, the void network is constantly and dynamically changing and possesses a considerable degree of disorder. The two regimes, viz., the linear regime (LR) and the anomalous regime (AR), found for porous solids are shown to exist for a dense medium as well. The linear regime is characterized by D(g) proportional to 1/sigma(gg)(2), where sigma(gg) is the diameter of the guest. The anomalous regime exhibits a maximum in D up to rather high temperatures (T = 1.663), even though in porous solids the maximum disappears at higher temperatures. In agreement with previous studies on porous solids, a particle in the AR is associated with lower activation energy, lower friction, and less backscattering in the velocity autocorrelation function when compared to a particle in the LR. Wavevector dependent self-diffusivity, Delta, and decay of the intermediate scattering function, F(s)(k, t), exhibit contrasting behaviors for the LR and AR. For LR, Delta exhibits a minimum at values of k at which there are spatial correlations in S(k) while a smooth decrease with k is seen for AR. For LR, F(s)(k, t) shows a biexponential decay corresponding to two different time scales of motion. Probably, the fast decay is associated with motion within the first shell of solvent neighbors and the slow decay with motion past these shells. For AR, a single-exponential decay is seen. The results indicate a breakdown of the Stokes-Einstein (SE) relationship. The relevant quantity that determines the validity of the SE relationship is the levitation parameter which is indirectly related to the solute/solvent radius ratio and not either the size of the solute or the solvent alone.
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Affiliation(s)
- Pradip Kr Ghorai
- Solid State and Structural Chemistry Unit and Center for Condensed Matter Theory, Indian Institute of Science, Bangalore 560012, India
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Ghorai PK, Yashonath S. Levitation Effect: Distinguishing Anomalous from Linear Regime of Guests Sorbed in Zeolites through the Decay of Intermediate Scattering Function and Wavevector Dependence of Self-Diffusivity. J Phys Chem B 2005; 109:3979-83. [PMID: 16851453 DOI: 10.1021/jp046121t] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Previous work investigating the dependence of self-diffusivity, D, on the size of the guest diffusing within the porous solid such as zeolite has reported the existence of an anomalous maximum in the diffusion coefficient (J. Phys. Chem. 1994, 98, 6368). Two distinct regimes of dependence of D on sigma(gg), diameter of the guest were reported. D proportional to 1/sigma(gg)2, often referred to as linear regime (LR), is found when sigma(gg) is smaller than sigma(v), the diameter of the void. A maximum in D has been observed when sigma(gg) is comparable to sigma(v) and this regime is referred to as anomalous regime (AR). Here we report the intermediate scattering function for a particle from LR and AR in zeolite faujasite. A particle from LR exhibits a biexponential decay while a particle from AR exhibits a single-exponential decay at small k. Variation with k of the full width at half-maximum of the self-part of the dynamic structure factor is nonmonotonic for a particle in the linear regime. In contrast, this variation is monotonic for a particle in the anomalous regime. These results can be understood in terms of the existence of energetic barrier at the bottleneck, the 12-ring window, in the path of diffusion. They provide additional signatures for the linear regime and anomalous regimes and therefore for levitation effect (LE).
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Affiliation(s)
- Pradip Kr Ghorai
- Solid State and Structural Chemistry Unit and Center for Condensed Matter Theory, Indian Institute of Science, Bangalore-560012, India
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Lee KH, Sinnott SB. Computational Studies of Non-Equilibrium Molecular Transport through Carbon Nanotubes. J Phys Chem B 2004. [DOI: 10.1021/jp036791j] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Ki-Ho Lee
- Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611-6400
| | - Susan B. Sinnott
- Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611-6400
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Zeng QH, Yu AB, Lu GQ, Standish RK. Molecular Dynamics Simulation of the Structural and Dynamic Properties of Dioctadecyldimethyl Ammoniums in Organoclays. J Phys Chem B 2004. [DOI: 10.1021/jp037245t] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Q. H. Zeng
- Centre for Simulation and Modeling of Particulate Systems, School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia, ARC Centre for Functional Nanomaterials, School of Engineering, The University of Queensland, Brisbane, QLD 4072, Australia, and School of Mathematics, The University of New South Wales, Sydney, NSW 2052, Australia
| | - A. B. Yu
- Centre for Simulation and Modeling of Particulate Systems, School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia, ARC Centre for Functional Nanomaterials, School of Engineering, The University of Queensland, Brisbane, QLD 4072, Australia, and School of Mathematics, The University of New South Wales, Sydney, NSW 2052, Australia
| | - G. Q. Lu
- Centre for Simulation and Modeling of Particulate Systems, School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia, ARC Centre for Functional Nanomaterials, School of Engineering, The University of Queensland, Brisbane, QLD 4072, Australia, and School of Mathematics, The University of New South Wales, Sydney, NSW 2052, Australia
| | - R. K. Standish
- Centre for Simulation and Modeling of Particulate Systems, School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia, ARC Centre for Functional Nanomaterials, School of Engineering, The University of Queensland, Brisbane, QLD 4072, Australia, and School of Mathematics, The University of New South Wales, Sydney, NSW 2052, Australia
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Ghorai PK, Yashonath S. Diffusion Anomaly at Low Temperatures in Confined Systems from the Rare Events Method. J Phys Chem B 2004. [DOI: 10.1021/jp037777+] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Y. Bhide † S, Yashonath ‡ * S. Anomalous diffusion of linear and branched pentanes within zeolite NaY. Mol Phys 2004. [DOI: 10.1080/00268970410001734305] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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