1
|
Dahanayaka M, Liu B, Hu Z, Chen Z, Law AWK, Zhou K. Corrugated graphene layers for sea water desalination using capacitive deionization. Phys Chem Chem Phys 2018; 19:8552-8562. [PMID: 28289740 DOI: 10.1039/c7cp00389g] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The effect of the electric field and surface morphology of corrugated graphene (GE) layers on their capacitive deionization process is studied using molecular dynamics simulations. Deionization performances are evaluated in terms of water flow rate and ion adsorption and explained by analysing the water density distribution, radial distribution function and distribution of the ions inside the GE layers. The simulation results reveal that corrugation of GE layers reduces the water flow rate but largely enhances ion adsorption in comparison to the flat GE layers. Such enhancement is mainly due to the adsorption of ions on the GE layers due to the anchoring effect in the regions with wide interlayer distances. Moreover, it reveals that the entrance configuration of the GE layers also has a significant effect on the performance of deionization. Overall, the results from this study will be helpful in designing effective electrode configurations for capacitive deionization.
Collapse
Affiliation(s)
- Madhavi Dahanayaka
- Environmental Process Modeling Center, Nanyang Environment and Water Research Institute, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. and Interdisciplinary Graduate School, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Bo Liu
- Environmental Process Modeling Center, Nanyang Environment and Water Research Institute, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. and School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Zhongqiao Hu
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Zhong Chen
- School of Material Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Adrian Wing-Keung Law
- Environmental Process Modeling Center, Nanyang Environment and Water Research Institute, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. and School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Kun Zhou
- Environmental Process Modeling Center, Nanyang Environment and Water Research Institute, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. and School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| |
Collapse
|
2
|
Three-dimensional surface topography of graphene by divergent beam electron diffraction. Nat Commun 2017; 8:14440. [PMID: 28195123 PMCID: PMC5316882 DOI: 10.1038/ncomms14440] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 12/30/2016] [Indexed: 11/17/2022] Open
Abstract
There are only a handful of scanning techniques that can provide surface topography at nanometre resolution. At the same time, there are no methods that are capable of non-invasive imaging of the three-dimensional surface topography of a thin free-standing crystalline material. Here we propose a new technique—the divergent beam electron diffraction (DBED) and show that it can directly image the inhomogeneity in the atomic positions in a crystal. Such inhomogeneities are directly transformed into the intensity contrast in the first-order diffraction spots of DBED patterns and the intensity contrast linearly depends on the wavelength of the employed probing electrons. Three-dimensional displacement of atoms as small as 1 angstrom can be detected when imaged with low-energy electrons (50–250 eV). The main advantage of DBED is that it allows visualization of the three-dimensional surface topography and strain distribution at the nanometre scale in non-scanning mode, from a single shot diffraction experiment. Graphene, and other 2D materials, do not exist as strictly planar sheets but instead have topographic ripples on the sub-nanometre scale. Here, Latychevskaia et al. present a method to non-invasively image ripples in 2D materials with a single-shot, wide-area, electron diffraction measurement.
Collapse
|
3
|
Abstract
Here, using ultrafast electron crystallography (UEC), we report the observation of rippling dynamics in suspended monolayer graphene, the prototypical and most-studied 2D material. The high scattering cross-section for electron/matter interaction, the atomic-scale spatial resolution, and the ultrafast temporal resolution of UEC represent the key elements that make this technique a unique tool for the dynamic investigation of 2D materials, and nanostructures in general. We find that, at early time after the ultrafast optical excitation, graphene undergoes a lattice expansion on a time scale of 5 ps, which is due to the excitation of short-wavelength in-plane acoustic phonon modes that stretch the graphene plane. On a longer time scale, a slower thermal contraction with a time constant of 50 ps is observed and associated with the excitation of out-of-plane phonon modes, which drive the lattice toward thermal equilibrium with the well-known negative thermal expansion coefficient of graphene. From our results and first-principles lattice dynamics and out-of-equilibrium relaxation calculations, we quantitatively elucidate the deformation dynamics of the graphene unit cell.
Collapse
|
4
|
Tewary V, Quardokus RC, DelRio FW. Green's function modeling of response of two-dimensional materials to point probes for scanning probe microscopy. PHYSICS LETTERS. A 2016; 380:1750-1756. [PMID: 28736478 PMCID: PMC5520644 DOI: 10.1016/j.physleta.2016.03.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A Green's function (GF) method is developed for interpreting scanning probe microscopy (SPM) measurements on new two-dimensional (2D) materials. GFs for the Laplace/Poisson equations are calculated by using a virtual source method for two separate cases of a finite material containing a rectangular defect and a hexagonal defect. The prescribed boundary values are reproduced almost exactly by the calculated GFs. It is suggested that the GF is not just a mathematical artefact but a basic physical characteristic of material systems, which can be measured directly by SPM for 2D solids. This should make SPM an even more powerful technique for characterization of 2D materials.
Collapse
Affiliation(s)
- V.K. Tewary
- Applied Chemicals and Materials Division, NIST, Boulder, CO 80305, USA
| | | | - Frank W. DelRio
- Applied Chemicals and Materials Division, NIST, Boulder, CO 80305, USA
| |
Collapse
|
5
|
Paulechka E, Wassenaar TA, Kroenlein K, Kazakov A, Smolyanitsky A. Nucleobase-functionalized graphene nanoribbons for accurate high-speed DNA sequencing. NANOSCALE 2016; 8:1861-1867. [PMID: 26731166 DOI: 10.1039/c5nr07061a] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We propose a water-immersed nucleobase-functionalized suspended graphene nanoribbon as an intrinsically selective device for nucleotide detection. The proposed sensing method combines Watson-Crick selective base pairing with graphene's capacity for converting anisotropic lattice strain to changes in an electrical current at the nanoscale. Using detailed atomistic molecular dynamics (MD) simulations, we study sensor operation at ambient conditions. We combine simulated data with theoretical arguments to estimate the levels of measurable electrical signal variation in response to strains and determine that the proposed sensing mechanism shows significant promise for realistic DNA sensing devices without the need for advanced data processing, or highly restrictive operational conditions.
Collapse
Affiliation(s)
- Eugene Paulechka
- Applied Chemicals and Materials Division, National Institute of Standards and Technology, Boulder, CO 80301, USA.
| | - Tsjerk A Wassenaar
- Department of Biology, Friedrich-Alexander University of Erlangen-Nürnberg, 91058 Erlangen, Germany and Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Kenneth Kroenlein
- Applied Chemicals and Materials Division, National Institute of Standards and Technology, Boulder, CO 80301, USA.
| | - Andrei Kazakov
- Applied Chemicals and Materials Division, National Institute of Standards and Technology, Boulder, CO 80301, USA.
| | - Alex Smolyanitsky
- Applied Chemicals and Materials Division, National Institute of Standards and Technology, Boulder, CO 80301, USA.
| |
Collapse
|
6
|
Liu X, Wang F, Wu H. Anisotropic growth of buckling-driven wrinkles in graphene monolayer. NANOTECHNOLOGY 2015; 26:065701. [PMID: 25597449 DOI: 10.1088/0957-4484/26/6/065701] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We theoretically and numerically investigate the growth of buckling-driven wrinkles in graphene monolayers. It is found that the growth of buckling-driven wrinkles in a graphene monolayer is remarkably chirality- and size-dependent. In small sizes, the flexural response of a graphene sheet cannot be accurately described by the classical Euler regime, and the non-continuum effect leads to zigzag-along-preferred buckling. With the increase of size, the width/length ratio α of the compressed region plays an important role in the growth of buckling-driven wrinkles. When α < 0.5, the oblique buckling happens in armchair-along compression; when 0.5 < α < 1.0, the effect of edge warp leads to zigzag-along-preferred buckling. When 1.0 < α < 3.0, the potential energy density difference due to chiral bending stiffness leads to armchair-along-preferred buckling. When α > 3.0, the non-continuum effect and chiral bending stiffness can both be neglected, and the buckling in a graphene monolayer is isotropic. The chirality-along-preferred transition of compressed buckling in a graphene monolayer leads to an improved fundamental understanding of the dynamics mechanism of graphene-based nanodevices, especially for the nanodevices with high frequency response.
Collapse
Affiliation(s)
- XiaoYi Liu
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, People's Republic of China
| | | | | |
Collapse
|
7
|
Li Y. Shear displacement controlled periodic wrinkles in hexagonal boron nitride sheet. NANOTECHNOLOGY 2015; 26:015706. [PMID: 25493950 DOI: 10.1088/0957-4484/26/1/015706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The initiation and geometry pattern of wrinkles in a single-layer hexagonal boron nitride sheet induced by in-plane shear displacement are studied. The periodic wrinkles in the central region are parallel to each other with an angle of approximate 50° to the fix edges, and the longitudinal shape of the wrinkle matches the sinusoidal mode shape well. The wrinkle wavelength decreases with an increase in shear loading, while the amplitude is found to initially increase and then become stable. The dependence of the wrinkle geometry on chirality and shear direction is further elucidated. This study theoretically provides a powerful way to produce uniform wrinkles in two-dimensional membranes and to tune their properties in devices.
Collapse
Affiliation(s)
- Yunfang Li
- College of Mechanical Engineering, Linyi University, Linyi, Shandong 276005, People's Republic of China
| |
Collapse
|
8
|
Smolyanitsky A. Effects of thermal rippling on the frictional properties of free-standing graphene. RSC Adv 2015. [DOI: 10.1039/c5ra01581b] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A unique case of dynamically corrugated surfaces is presented for the first time, attributed to the effect of significant thermally excited flexural waves in atomically thin layers on kinetic friction.
Collapse
Affiliation(s)
- A. Smolyanitsky
- Applied Chemicals and Materials Division
- National Institute of Standards and Technology
- Boulder
- USA
| |
Collapse
|
9
|
Smolyanitsky A. Molecular dynamics simulation of thermal ripples in graphene with bond-order-informed harmonic constraints. NANOTECHNOLOGY 2014; 25:485701. [PMID: 25380352 DOI: 10.1088/0957-4484/25/48/485701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We describe the results of atomistic molecular dynamics simulations of thermal rippling in graphene with the use of a generic harmonic constraint model. The distance and angular constraint constants are calculated directly from the second-generation bond-order interatomic potential that describes carbon binding in graphene. We quantify the thermal rippling process in detail by calculating the overall rippling averages, the normal-normal correlation distributions and the height distributions. In addition, we consider the effect of a dihedral angular constraint, as well as the effect of sample size on the simulated rippling averages. The dynamic corrugation morphologies of simulated graphene samples obtained with the harmonic constraint model at various temperatures are, overall, consistent with those obtained with the bond-order potential and are in qualitative accord with previously reported findings. Given the wide availability of the harmonic constraint model in various molecular mechanics implementations, along with its high computational efficiency, our results indicate a possible use for the presented model in multicomponent dynamic simulations, including atomically thin layers.
Collapse
Affiliation(s)
- Alex Smolyanitsky
- Applied Chemicals and Materials Division, National Institute of Standards and Technology, Boulder, CO 80301 USA. Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899 USA
| |
Collapse
|
10
|
Xu P, Neek-Amal M, Barber SD, Schoelz JK, Ackerman ML, Thibado PM, Sadeghi A, Peeters FM. Unusual ultra-low-frequency fluctuations in freestanding graphene. Nat Commun 2014; 5:3720. [DOI: 10.1038/ncomms4720] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 03/26/2014] [Indexed: 11/09/2022] Open
|