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Salzmann H, Rasmussen AP, Eaves JD, Weber JM. Competition between Water-Water Hydrogen Bonds and Water-π Bonds in Pyrene-Water Cluster Anions. J Phys Chem A 2024; 128:2772-2781. [PMID: 38564313 DOI: 10.1021/acs.jpca.4c00997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
We present infrared spectra and density functional theory calculations of hydrated pyrene anion clusters with up to four water molecules. The experimental spectra were acquired by using infrared Ar messenger photodissociation spectroscopy. Water molecules form clusters on the surface of the pyrene, forming hydrogen bonds with the π-system. The structures of the water clusters and their interaction with the π-system are encoded in OH stretching vibrational modes. We find that the interactions between water molecules are stronger than the interactions between water molecules and the π-system. While all clusters show multiple conformers, three- and four-membered rings are the lowest energy structures in the larger hydrates.
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Affiliation(s)
- Heinrich Salzmann
- JILA, University of Colorado, Boulder, Colorado 80309-0440, United States
- Department of Chemistry, University of Colorado, Boulder, Colorado 80309-0215, United States
| | - Anne P Rasmussen
- JILA, University of Colorado, Boulder, Colorado 80309-0440, United States
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus, Denmark
| | - Joel D Eaves
- Department of Chemistry, University of Colorado, Boulder, Colorado 80309-0215, United States
| | - J Mathias Weber
- JILA, University of Colorado, Boulder, Colorado 80309-0440, United States
- Department of Chemistry, University of Colorado, Boulder, Colorado 80309-0215, United States
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2
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Papaderakis AA, Roh JS, Polus K, Yang J, Bissett MA, Walton A, Juel A, Dryfe RAW. Dielectric-free electrowetting on graphene. Faraday Discuss 2023; 246:307-321. [PMID: 37409473 DOI: 10.1039/d3fd00037k] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
Electrowetting is a simple way to induce the spreading and retraction of electrolyte droplets. This method is widely used in "device" applications, where a dielectric layer is applied between the electrolyte and the conducting substrate. Recent work, including contributions from our own laboratory, have shown that reversible electrowetting can be achieved directly on conductors. We have shown that graphite surfaces, in particular when combined with highly concentrated electrolyte solutions, show a strong wetting effect. The process is driven by the interactions between the electrolyte ions and the surface, hence models of double-layer capacitance are able to explain changes in the equilibrium contact angles. Herein, we extend the approach to the investigation of electrowetting on graphene samples of varying thickness, prepared by chemical vapor deposition. We show that the use of highly concentrated aqueous electrolytes induces a clear yet subtle electrowetting response due to the adsorption of ions and the suppression of the negative effect introduced by the surface impurities accumulating during the transfer process. The latter have been previously reported to fully hinder electrowetting at lower electrolyte concentrations. An amplified wetting response is recorded in the presence of strongly adsorbed/intercalated anions in both aqueous and non-aqueous electrolytes. The phenomenon is interpreted based on the anion-graphene interactions and their influence on the energetics of the interface. By monitoring the dynamics of wetting, an irreversible behaviour is identified in all cases as a consequence of the irreversibility of anion adsorption and/or intercalation. Finally, the effect of the underlying reactions on the timescales of wetting is also examined.
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Affiliation(s)
- Athanasios A Papaderakis
- Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
- Henry Royce Institute, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Ji Soo Roh
- National Graphene Institute, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
- Department of Materials, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Kacper Polus
- Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
- Photon Science Institute, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Jing Yang
- Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
- Henry Royce Institute, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Mark A Bissett
- National Graphene Institute, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
- Department of Materials, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Alex Walton
- Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
- Photon Science Institute, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Anne Juel
- Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Robert A W Dryfe
- Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
- Henry Royce Institute, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
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3
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Cline C, Wang H, Kong J, Li T, Liu J, Wegst UGK. Heterogeneous Ice Nucleation Studied with Single-Layer Graphene. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:15121-15131. [PMID: 36448835 DOI: 10.1021/acs.langmuir.2c02144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Control of heterogeneous ice nucleation (HIN) is critical for applications that range from iceophobic surfaces to ice-templated materials. HIN on 2D materials is a particular interesting topic that still lacks extensive experimental investigations. Here, we focus on the HIN on single-layer graphene (SLG) transferred onto different substrates, including silicon, silica, and thermal oxide on silicon. Complemented by other samples without SLG, we obtain a large range of wetting contact angles (WCAs) from 2° to 95°. All pristine SLG samples exhibit a large contact angle of ∼95°, which is close to the theoretical value of 96° for free-standing SLG, irrespective of the substrate and even in the presence of nanoscale wrinkles on SLG, which are due to the transfer process, indicating that the topographical features have little impact on the wetting behavior. Interestingly, SLG displays changes in hydrophobicity upon repeated water droplet freezing-melting-drying cycles due to a shift in Fermi level and/or enhanced water-substrate polar molecular interactions, likely induced by residual adsorption of H2O molecules. We found that a 0.04 eV decrease in SLG Fermi level reduces the SLG/water interface energy by ∼6 mJ/m2, thereby making SLG less hydrophobic. Counterintuitively, the reduction in SLG/water interface energy and the enhanced hydrophilicity after repeated freezing-melting-evaporation cycles actually decreases the freezing temperature by ∼3-4 °C, thereby slightly retarding rather than enhancing HIN. We also found that the water droplet freezing temperature differed by only ∼1 °C on different substrates with WCAs from 2° to 95°, an intriguing and yet reasonable result that confirms that wettability alone is not a good indicator of HIN capability. The HIN rate is rather determined by the difference between substrate/water and substrate/ice interface energies, which was found to stay almost constant for substrates weakly interacting with water/ice via van der Waals or hydrogen bonds, irrespective of hydrophilicity.
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Affiliation(s)
- Cory Cline
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Haozhe Wang
- Department of Materials Science and Engineering, Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Boston, Massachusetts 02139, United States
| | - Jing Kong
- Department of Materials Science and Engineering, Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Boston, Massachusetts 02139, United States
| | - Tianshu Li
- Department of Civil and Environmental Engineering, George Washington University, Washington, D.C. 20052, United States
| | - Jifeng Liu
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Ulrike G K Wegst
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, United States
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, United States
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4
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Pan X, Cao Q, Liu D, Wu Z. Effects of Contact Behavior and Electric Field on Electrohydrodynamics of Nanodroplets. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2022. [DOI: 10.1134/s0036024422130222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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5
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Lee G, Oh Y, Nam JT, Ji S, Jang AR, Jeong DW, Kang M, Lee SS, Chae S, Cho D, Hwang JY, Lee K, Lee JO. Multifunctional-high resolution imaging plate based on hydrophilic graphene for digital pathology. NANOTECHNOLOGY 2022; 33:505101. [PMID: 36095982 DOI: 10.1088/1361-6528/ac9143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 09/12/2022] [Indexed: 06/15/2023]
Abstract
In the present study, we showed that hydrophilic graphene can serve as an ideal imaging plate for biological specimens. Graphene being a single-atom-thick semi-metal with low secondary electron emission, array tomography analysis of serial sections of biological specimens on a graphene substrate showed excellent image quality with improvedz-axis resolution, without including any conductive surface coatings. However, the hydrophobic nature of graphene makes the placement of biological specimens difficult; graphene functionalized with polydimethylsiloxane oligomer was fabricated using a simple soft lithography technique and then processed with oxygen plasma to provide hydrophilic graphene with minimal damage to graphene. High-quality scanning electron microscopy images of biological specimens free from charging effects or distortion were obtained, and the optical transparency of graphene enabled fluorescence imaging of the specimen; high-resolution correlated electron and light microscopy analysis of the specimen became possible with the hydrophilic graphene plate.
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Affiliation(s)
- Geonhee Lee
- Advanced Materials Division, Korea Research Institute of Chemical Technology, Gajeongro 141, Daejeon, Republic of Korea
| | - Yuna Oh
- Korea Institute of Science and Technology, 5. Hwarang-ro 14-gil, Seongbuk-gu, Seoul, Republic of Korea
| | - Jung Tae Nam
- Institute of Advanced Composite Materials, Korea Institute of Science and Technology, Jeonbuk, 55324, Republic of Korea
| | - Seulgi Ji
- Advanced Materials Division, Korea Research Institute of Chemical Technology, Gajeongro 141, Daejeon, Republic of Korea
| | - A-Rang Jang
- Division of Electrical, Electronic and Control Engineering, Kongju National University, Cheonan 31080, Republic of Korea
| | - Du Won Jeong
- Advanced Materials Division, Korea Research Institute of Chemical Technology, Gajeongro 141, Daejeon, Republic of Korea
| | - MinSoung Kang
- Advanced Materials Division, Korea Research Institute of Chemical Technology, Gajeongro 141, Daejeon, Republic of Korea
| | - Sun Sook Lee
- Advanced Materials Division, Korea Research Institute of Chemical Technology, Gajeongro 141, Daejeon, Republic of Korea
| | - Soosang Chae
- Department of Nanostructured Materials, Leibniz Institute of Polymer Research Dresden, D-01069, Dresden, Germany
| | - Donghwi Cho
- Advanced Materials Division, Korea Research Institute of Chemical Technology, Gajeongro 141, Daejeon, Republic of Korea
| | - Jun Yeon Hwang
- Institute of Advanced Composite Materials, Korea Institute of Science and Technology, Jeonbuk, 55324, Republic of Korea
| | - Kyungeun Lee
- Korea Institute of Science and Technology, 5. Hwarang-ro 14-gil, Seongbuk-gu, Seoul, Republic of Korea
| | - Jeong-O Lee
- Advanced Materials Division, Korea Research Institute of Chemical Technology, Gajeongro 141, Daejeon, Republic of Korea
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6
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Montenegro A, Dutta C, Mammetkuliev M, Shi H, Hou B, Bhattacharyya D, Zhao B, Cronin SB, Benderskii AV. Asymmetric response of interfacial water to applied electric fields. Nature 2021; 594:62-65. [PMID: 34079138 DOI: 10.1038/s41586-021-03504-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Accepted: 03/29/2021] [Indexed: 11/09/2022]
Abstract
Our understanding of the dielectric response of interfacial water, which underlies the solvation properties and reaction rates at aqueous interfaces, relies on the linear response approximation: an external electric field induces a linearly proportional polarization. This implies antisymmetry with respect to the sign of the field. Atomistic simulations have suggested, however, that the polarization of interfacial water may deviate considerably from the linear response. Here we present an experimental study addressing this issue. We measured vibrational sum-frequency generation spectra of heavy water (D2O) near a monolayer graphene electrode, to study its response to an external electric field under controlled electrochemical conditions. The spectra of the OD stretch show a pronounced asymmetry for positive versus negative electrode charge. At negative charge below 5 × 1012 electrons per square centimetre, a peak of the non-hydrogen-bonded OD groups pointing towards the graphene surface is observed at a frequency of 2,700 per centimetre. At neutral or positive electrode potentials, this 'free-OD' peak disappears abruptly, and the spectra display broad peaks of hydrogen-bonded OD species (at 2,300-2,650 per centimetre). Miller's rule1 connects the vibrational sum-frequency generation response to the dielectric constant. The observed deviation from the linear response for electric fields of about ±3 × 108 volts per metre calls into question the validity of treating interfacial water as a simple dielectric medium.
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Affiliation(s)
- Angelo Montenegro
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Chayan Dutta
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | | | - Haotian Shi
- Department of Electrical Engineering, University of Southern California, Los Angeles, CA, USA
| | - Bingya Hou
- Department of Electrical Engineering, University of Southern California, Los Angeles, CA, USA
| | | | - Bofan Zhao
- Department of Electrical Engineering, University of Southern California, Los Angeles, CA, USA
| | - Stephen B Cronin
- Department of Electrical Engineering, University of Southern California, Los Angeles, CA, USA
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7
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Shellard PM, Srisubin T, Hartmann M, Butcher J, Fei F, Cox H, McNamara TP, McArdle T, Shepherd AM, Jacobs RMJ, Waigh TA, Flitsch SL, Blanford CF. A versatile route to edge-specific modifications to pristine graphene by electrophilic aromatic substitution. JOURNAL OF MATERIALS SCIENCE 2020; 55:10284-10302. [PMID: 32536720 PMCID: PMC7266800 DOI: 10.1007/s10853-020-04662-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 04/07/2020] [Indexed: 06/11/2023]
Abstract
Electrophilic aromatic substitution produces edge-specific modifications to CVD graphene and graphene nanoplatelets that are suitable for specific attachment of biomolecules.
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Affiliation(s)
- Philippa M. Shellard
- Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL UK
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN UK
| | - Thunyaporn Srisubin
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN UK
- Department of Materials, University of Manchester, Oxford Road, Manchester, M13 9PL UK
| | - Mirja Hartmann
- Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL UK
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN UK
| | - Joseph Butcher
- Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL UK
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN UK
| | - Fan Fei
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN UK
- Department of Materials, University of Manchester, Oxford Road, Manchester, M13 9PL UK
| | - Henry Cox
- Biological Physics, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL UK
- Photon Science Institute, University of Manchester, Alan Turing Building, Oxford Road, Manchester, M13 9PL UK
| | - Thomas P. McNamara
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN UK
- Department of Materials, University of Manchester, Oxford Road, Manchester, M13 9PL UK
| | - Trevor McArdle
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN UK
- Department of Materials, University of Manchester, Oxford Road, Manchester, M13 9PL UK
| | - Ashley M. Shepherd
- Chemical Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA UK
| | - Robert M. J. Jacobs
- Chemical Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA UK
| | - Thomas A. Waigh
- Biological Physics, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL UK
- Photon Science Institute, University of Manchester, Alan Turing Building, Oxford Road, Manchester, M13 9PL UK
| | - Sabine L. Flitsch
- Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL UK
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN UK
| | - Christopher F. Blanford
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN UK
- Department of Materials, University of Manchester, Oxford Road, Manchester, M13 9PL UK
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8
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Feng J, Guo Z. Wettability of graphene: from influencing factors and reversible conversions to potential applications. NANOSCALE HORIZONS 2019; 4:339-364. [PMID: 32254088 DOI: 10.1039/c8nh00348c] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
As a member of the carbon material family, graphene has long been the focus of research on account of its abundant excellent properties. Nevertheless, many previous research works have attached much importance to its mechanical capacity and electrical properties, and not to its surface wetting properties with respect to water. In this review, a series of methods are put forward for characterization of the water contact angle of graphene, such as experimental measurements, classic molecular dynamics simulations, and formula calculations. A series of factors that affect the wettability of graphene, including defects, controllable atmosphere, doping, and electric field, are also discussed in detail, and have rarely have been covered in other review articles before. Finally, with the developments of smart surfaces, a reversible wettability variation of graphene from hydrophobic to hydrophilic is important in the presence of external stimulation and is discussed in detail herein. It is anticipated that graphene could serve as a tunable wettability coating for further developments in electronic devices and brings a new perspective to the construction of smart material surfaces.
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Affiliation(s)
- Jing Feng
- Hubei Collaborative Innovation Centre for Advanced Organic Chemical Materials and Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan 430062, People's Republic of China
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9
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Liu J, Pantelides ST. Electrowetting on 2D dielectrics: a quantum molecular dynamics investigation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:375001. [PMID: 30079895 DOI: 10.1088/1361-648x/aad838] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Electrowetting on dielectrics (EWOD) is widely used to manipulate the spreading of a conductive liquid on a dielectric surface by applying an electric field. 2D hydrophobic dielectrics are promising candidates for EWOD applications. In this study, extensive quantum molecular dynamics (MD) simulations are performed to investigate the electrowetting behavior of salty water on hexagonal boron nitride (h-BN) monolayer. The proximal adsorption of salt ions and the associated realignment of the dipole moments of interfacial water with the applied electric field are found to be the physical origin of the electrowetting behavior. At low salt concentration and low electric fields, the proximal adsorption and the realignment follow the applied electric field, and the cosine of the water contact angle (WCA) follows a quadratic dependence on the applied electric field. At high salt concentration and high electric fields, the proximal adsorption saturates, which restricts further realignment and causes a saturation of the WCA. This case study provides physical insights into the much debated mechanism that underlies the contact angle saturation (CAS) found in macroscopic electrowetting phenomena and also provides an avenue for further studies of electrowetting at the atomic scale.
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Affiliation(s)
- Jian Liu
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, United States of America
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10
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Zeng J, Zhang S, Tang K, Chen G, Yuan W, Tang Y. 3-D manipulation of a single nano-droplet on graphene with an electrowetting driving scheme: critical condition and tunability. NANOSCALE 2018; 10:16079-16086. [PMID: 30109343 DOI: 10.1039/c8nr03330g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The next generation of micro/nano-fluidic systems, featuring manipulation of a single nanoliter volume of a chemical reactant or bio-substance, is greatly dependent on the accurate manipulation of a single nano-droplet. In this paper, to resolve the lack of efficient methods for 3-D actuation of nano-droplets with high tunability, we proposed an electro-wetting-on-dielectric (EWOD) driving scheme on a graphene surface. The droplet could be actuated when the EWOD-saturated contact angle was reached, which determined the critical magnitude of the E-field. The droplet velocity agreed well with the vcom ∼ E1/2C-O law due to the film-detachment mechanism, which indicated the low viscous dissipation and good tunability of the proposed technique. The droplet velocity could also be tuned by changing the initial wettability of the graphene surface. Detailed examination of the liquid-solid interface revealed significant penetration of water molecules into the inner Helmholtz plane (IHP) before the induction of droplet detachment when the electric energy was converted into surface energy. For all the studied cases, the saturated contact angle served as a sufficient condition for the actuation of droplets.
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Affiliation(s)
- Jian Zeng
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA 92093, USA
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11
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Song F, Ma L, Fan J, Chen Q, Zhang L, Li BQ. Wetting Behaviors of a Nano-Droplet on a Rough Solid Substrate under Perpendicular Electric Field. NANOMATERIALS (BASEL, SWITZERLAND) 2018; 8:E340. [PMID: 29772828 PMCID: PMC5977354 DOI: 10.3390/nano8050340] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 05/14/2018] [Accepted: 05/15/2018] [Indexed: 12/27/2022]
Abstract
Molecular dynamic simulations were adopted to study the wetting properties of nanoscale droplets on rough silicon solid substrate subject to perpendicular electric fields. The effect of roughness factor and electric field strength on the static and dynamic wetting behaviors of a nano-droplet on a solid surface was investigated at the molecular level. Results show that the static contact angle tends to decrease slightly and show small difference with the increase of roughness factor, while it shows an obvious increase for the ramp-shaped surface because the appearing bottom space reduces the wettability of solid surface. Additionally, under the electric field, a nano-droplet was elongated in the field direction and the equilibrium contact angle increases with the increase of electric field strength. The nano-droplet was completely stretched to be column-shaped at a threshold value of the field. Besides, accompanied by the shape variation of water droplets, the molecular dipole orientations of water molecules experience a remarkable change from a random disordered distribution to an ordered profile because of the realignment of water molecules induced by electric fields.
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Affiliation(s)
- Fenhong Song
- School of Energy and Power Engineering, Northeast Electric Power University, Jilin 132012, China.
| | - Long Ma
- School of Energy and Power Engineering, Northeast Electric Power University, Jilin 132012, China.
| | - Jing Fan
- School of Energy and Power Engineering, Northeast Electric Power University, Jilin 132012, China.
| | - Qicheng Chen
- School of Energy and Power Engineering, Northeast Electric Power University, Jilin 132012, China.
| | - Lihui Zhang
- Key Laboratory of Special Purpose Equipment and Advanced Processing Technology, Ministry of Education, Zhejiang University of Technology, Hangzhou 310014, China.
| | - Ben Q Li
- Department of Mechanical Engineering, University of Michigan, Dearborn, MI 48128, USA.
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12
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Song F, Ma L, Fan J, Chen Q, Lei G, Li BQ. Electro-wetting of a nanoscale water droplet on a polar solid surface in electric fields. Phys Chem Chem Phys 2018; 20:11987-11993. [DOI: 10.1039/c8cp00956b] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Water molecules interact with a polar surface in an electric field to realign their point dipoles, which determine the spreading behaviors of the droplets.
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Affiliation(s)
- Fenhong Song
- School of Energy and Power Engineering
- Northeast Electric Power University
- Jilin 132012
- China
| | - Long Ma
- School of Energy and Power Engineering
- Northeast Electric Power University
- Jilin 132012
- China
| | - Jing Fan
- School of Energy and Power Engineering
- Northeast Electric Power University
- Jilin 132012
- China
| | - Qicheng Chen
- School of Energy and Power Engineering
- Northeast Electric Power University
- Jilin 132012
- China
| | - Guangping Lei
- School of Energy and Power Engineering
- North University of China
- Taiyuan 030051
- China
| | - Ben Q. Li
- Department of Mechanical Engineering
- University of Michigan
- Dearborn
- USA
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13
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Tian T, Lin S, Li S, Zhao L, Santos EJG, Shih CJ. Doping-Driven Wettability of Two-Dimensional Materials: A Multiscale Theory. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:12827-12837. [PMID: 29058907 DOI: 10.1021/acs.langmuir.7b03165] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Engineering molecular interactions at two-dimensional (2D) materials interfaces enables new technological opportunities in functional surfaces and molecular epitaxy. Understanding the wettability of 2D materials represents the crucial first step toward quantifying the interplay between the interfacial forces and electric potential of 2D materials interfaces. Here we develop the first theoretical framework to model the wettability of the doped 2D materials by properly bridging the multiscale physical phenomena at the 2D interfaces, including (i) the change of 2D materials surface energy (atomistic scale, several angstroms), (ii) the molecular reorientation of liquid molecules adjacent to the interface (molecular scale, 100-101 nm), and (iii) the electrical double layer (EDL) formed in the liquid phase (mesoscopic scales, 100-104 nm). The latter two effects are found to be the major mechanisms responsible for the contact angle change upon doping, while the surface energy change of a pure 2D material has no net effect on the wetting property. When the doping level is electrostatically tuned, we demonstrate that 2D materials with high quantum capacitances (e.g., transition metal dichalcogenides, TMDCs) possess a wider range of tunability in the interfacial tension, under the same applied gate voltage. Furthermore, practical considerations such as defects and airborne contamination are also quantitatively discussed. Our analysis implies that the doping level can be another variable to modulate the wettability at 2D materials interfaces, as well as the molecular packing behavior on a 2D material-coated surface, essentially facilitating the interfacial engineering of 2D materials.
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Affiliation(s)
- Tian Tian
- Institute for Chemical and Bioengineering, ETH Zürich , Vladimir Prelog Weg 1, CH-8093 Zürich, Switzerland
| | - Shangchao Lin
- Department of Mechanical Engineering, Materials Science and Engineering Program, FAMU-FSU College of Engineering, Florida State University , Tallahassee, Florida 32310, United States
| | - Siyu Li
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University , Nanjing, Jiangsu 210096, China
| | - Lingling Zhao
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University , Nanjing, Jiangsu 210096, China
| | - Elton J G Santos
- School of Mathematics and Physics, Queen's University Belfast , Belfast BT7 1NN, United Kingdom
| | - Chih-Jen Shih
- Institute for Chemical and Bioengineering, ETH Zürich , Vladimir Prelog Weg 1, CH-8093 Zürich, Switzerland
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Dollekamp E, Bampoulis P, Faasen DP, Zandvliet HJW, Kooij ES. Charge Induced Dynamics of Water in a Graphene-Mica Slit Pore. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:11977-11985. [PMID: 28985466 PMCID: PMC5677248 DOI: 10.1021/acs.langmuir.7b02759] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 10/05/2017] [Indexed: 05/22/2023]
Abstract
We use atomic force microscopy to in situ investigate the dynamic behavior of confined water at the interface between graphene and mica. The graphene is either uncharged, negatively charged, or positively charged. At high humidity, a third water layer will intercalate between graphene and mica. When graphene is negatively charged, the interface fills faster with a complete three layer water film, compared to uncharged graphene. As charged positively, the third water layer dewets the interface, either by evaporation into the ambient or by the formation of three-dimensional droplets under the graphene, on top of the bilayer. Our experimental findings reveal novel phenomena of water at the nanoscale, which are interesting from a fundamental point of view and demonstrate the direct control over the wetting properties of the graphene/water interface.
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Affiliation(s)
- Edwin Dollekamp
- Physics of Interfaces and Nanomaterials and Physics of Fluids,
J.M. Burgers
Centre for Fluid Mechanics and Max Planck Center for Complex Fluid
Dynamics, MESA+ Institute for Nanotechnology,
University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
- E-mail:
| | - Pantelis Bampoulis
- Physics of Interfaces and Nanomaterials and Physics of Fluids,
J.M. Burgers
Centre for Fluid Mechanics and Max Planck Center for Complex Fluid
Dynamics, MESA+ Institute for Nanotechnology,
University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Daniël P. Faasen
- Physics of Interfaces and Nanomaterials and Physics of Fluids,
J.M. Burgers
Centre for Fluid Mechanics and Max Planck Center for Complex Fluid
Dynamics, MESA+ Institute for Nanotechnology,
University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Harold J. W. Zandvliet
- Physics of Interfaces and Nanomaterials and Physics of Fluids,
J.M. Burgers
Centre for Fluid Mechanics and Max Planck Center for Complex Fluid
Dynamics, MESA+ Institute for Nanotechnology,
University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - E. Stefan Kooij
- Physics of Interfaces and Nanomaterials and Physics of Fluids,
J.M. Burgers
Centre for Fluid Mechanics and Max Planck Center for Complex Fluid
Dynamics, MESA+ Institute for Nanotechnology,
University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
- E-mail:
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15
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Tian T, Shih CJ. Molecular Epitaxy on Two-Dimensional Materials: The Interplay between Interactions. Ind Eng Chem Res 2017. [DOI: 10.1021/acs.iecr.7b02669] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Tian Tian
- Institute for Chemical and
Bioengineering, ETH Zürich, Vladimir Prelog Weg 1, CH-8093 Zürich, Switzerland
| | - Chih-Jen Shih
- Institute for Chemical and
Bioengineering, ETH Zürich, Vladimir Prelog Weg 1, CH-8093 Zürich, Switzerland
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16
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Strong SE, Eaves JD. Linear Response Theory for Water Transport Through Dry Nanopores. J Phys Chem A 2017; 121:5377-5382. [PMID: 28598162 DOI: 10.1021/acs.jpca.7b03192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Porous two-dimensional crystals like graphene have the potential to revolutionize reverse-osmosis membrane technology. The permeability is a common figure of merit that describes the ease with which water flows through a membrane. For two-dimensional crystals, the permeability can be orders of magnitude higher than it is in conventional reverse-osmosis membranes. We apply our Gaussian Dynamics nonequilibrium molecular dynamics simulation method to very hydrophobic two-dimensional membranes and find that the current-pressure drop relationship becomes nonlinear. In this regime, the conventional permeability is an inadequate descriptor of the passage process, and the transport mechanism becomes a two-step one. The backing pressure first causes the pore to wet, and after it reaches a threshold pressure, water transport takes place from the wet state. We recover a simple description of the transport process by applying linear response theory with respect to the wet reference state rather than the dry one. A macroscopic thermodynamic argument supports our mechanistic description and predicts the wetting threshold pressure as a function of the contact angle.
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Affiliation(s)
- Steven E Strong
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
| | - Joel D Eaves
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
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17
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Sun J, Finklea HO, Liu Y. Characterization and electrolytic cleaning of poly(methyl methacrylate) residues on transferred chemical vapor deposited graphene. NANOTECHNOLOGY 2017; 28:125703. [PMID: 28163262 DOI: 10.1088/1361-6528/aa5e55] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Poly(methyl methacrylate) (PMMA) residue has long been a critical challenge for practical applications of the transferred chemical vapor deposited (CVD) graphene. Thermal annealing is empirically used for the removal of the PMMA residue; however experiments imply that there are still small amounts of residues left after thermal annealing which are hard to remove with conventional methods. In this paper, the thermal degradation of the PMMA residue upon annealing was studied by Raman spectroscopy. The study reveals that post-annealing residues are generated by the elimination of methoxycarbonyl side chains in PMMA and are believed to be absorbed on graphene via the π-π interaction between the conjugated unsaturated carbon segments and graphene. The post-annealing residues are difficult to remove by further annealing in a non-oxidative atmosphere due to their thermal and chemical stability. An electrolytic cleaning method was shown to be effective in removing these post-annealing residues while preserving the underlying graphene lattice based on Raman spectroscopy and atomic force microscopy studies. Additionally, a solution-gated field effect transistor was used to study the transport properties of the transferred CVD graphene before thermal annealing, after thermal annealing, and after electrolytic cleaning, respectively. The results show that the carrier mobility was significantly improved, and that the p-doping was reduced by removing PMMA residues and post-annealing residues. These studies provide a more in-depth understanding on the thermal annealing process for the removal of the PMMA residues from transferred CVD graphene and a new approach to remove the post-annealing residues, resulting in a residue-free graphene.
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Affiliation(s)
- Jianbo Sun
- Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV 26506, United States of America
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18
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Watanabe M, Thomas ML, Zhang S, Ueno K, Yasuda T, Dokko K. Application of Ionic Liquids to Energy Storage and Conversion Materials and Devices. Chem Rev 2017; 117:7190-7239. [PMID: 28084733 DOI: 10.1021/acs.chemrev.6b00504] [Citation(s) in RCA: 696] [Impact Index Per Article: 99.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ionic liquids (ILs) are liquids consisting entirely of ions and can be further defined as molten salts having melting points lower than 100 °C. One of the most important research areas for IL utilization is undoubtedly their energy application, especially for energy storage and conversion materials and devices, because there is a continuously increasing demand for clean and sustainable energy. In this article, various application of ILs are reviewed by focusing on their use as electrolyte materials for Li/Na ion batteries, Li-sulfur batteries, Li-oxygen batteries, and nonhumidified fuel cells and as carbon precursors for electrode catalysts of fuel cells and electrode materials for batteries and supercapacitors. Due to their characteristic properties such as nonvolatility, high thermal stability, and high ionic conductivity, ILs appear to meet the rigorous demands/criteria of these various applications. However, for further development, specific applications for which these characteristic properties become unique (i.e., not easily achieved by other materials) must be explored. Thus, through strong demands for research and consideration of ILs unique properties, we will be able to identify indispensable applications for ILs.
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Affiliation(s)
- Masayoshi Watanabe
- Department of Chemistry and Biotechnology, Yokohama National University , 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
| | - Morgan L Thomas
- Department of Chemistry and Biotechnology, Yokohama National University , 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
| | - Shiguo Zhang
- Department of Chemistry and Biotechnology, Yokohama National University , 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
| | - Kazuhide Ueno
- Department of Applied Chemistry, Graduate School of Sciences and Technology for Innovation, Yamaguchi University , 2-16-1 Tokiwadai, Ube 755-8611, Japan
| | - Tomohiro Yasuda
- Institute of Catalysis, Hokkaido University , Kita 21. Nishi 10, Kita-ku, Sapporo 001-0021, Japan
| | - Kaoru Dokko
- Department of Chemistry and Biotechnology, Yokohama National University , 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.,Unit of Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University , Kyoto 615-8510, Japan
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19
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Cao Q, Li L, Huang F, Zuo C. Ion-Specific Effects on the Elongation Dynamics of a Nanosized Water Droplet in Applied Electric Fields. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:428-437. [PMID: 27996273 DOI: 10.1021/acs.langmuir.6b04101] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report an all-atom molecular dynamics study of the structures and dynamics of salty water droplets on a silicon surface under the influence of applied electric field. Our simulation results support ion-specific effects on the elongation dynamics of salty nanodroplets, induced by the field. This feature has not been explored up to now in monovalent salts. Nevertheless, the importance of ion-specific effects is widely confirmed in biological and colloidal systems. In particular, the increase of salt concentration enhances the effect of the nature of ions on the wetting properties of droplets. In the presence of electric field (0.05 V Å-1), a complete spreading is implemented in a short time for different droplets at a concentration of 1 M, and the droplet morphology is stable, observed at long time scales. However, a higher salt concentration of 4 M considerably suppresses the spreading process owing to the increase of surface tension. It was found that the NaCl droplet shows deformation oscillations along the external field, but cannot fully wet the substrate surface. By contrast, the CsCl droplet reaches complete elongation rapidly and adopts a steady strip shape. The KCl droplet undergoes frequent transitions between breakup and connection. Additionally, the droplets can be elongated only when the electric field strength exceeds a threshold value. The dipole orientation of interfacial water and the ionic diffusion exhibit ion-specific dependences, but the hydrogen bond network is scarcely disturbed, excluding a concentration-dependent effect.
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Affiliation(s)
- Qianqian Cao
- College of Mechanical and Electrical Engineering, Jiaxing University , Jiaxing 314001, P.R. China
| | - Lujuan Li
- College of Mechanical and Electrical Engineering, Jiaxing University , Jiaxing 314001, P.R. China
| | - Fengli Huang
- College of Mechanical and Electrical Engineering, Jiaxing University , Jiaxing 314001, P.R. China
| | - Chuncheng Zuo
- College of Mechanical and Electrical Engineering, Jiaxing University , Jiaxing 314001, P.R. China
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20
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Abstract
Porous two-dimensional crystals offer many promises for water desalination applications. For computer simulation to play a predictive role in this area, however, one needs to have reliable methods for simulating an atomistic system with hydrodynamic currents and interpretative tools to relate microscopic interactions to emergent macroscopic dynamical quantities, such as friction, slip length, and permeability. In this article, we use Gaussian dynamics, a nonequilibrium molecular dynamics method that provides microscopic insights into the interactions that control the flows of both simple liquids and liquid water through atomically small channels. In simulations of aqueous transport, we mimic the effect of changing the membrane chemical composition by adjusting the attractive strength of the van der Waals interactions between the membrane atoms and water. We find that the wetting contact angle, a common measure of a membrane's hydrophobicity, does not predict the permeability of a membrane. Instead, the hydrophobic effect is subtle, with both static and dynamic effects that can both help and hinder water transport through these materials. The competition between the static and dynamical hydrophobicity balances an atomic membrane's tendency to wet against hydrodynamic friction, and determines an optimal contact angle for water passage through nonpolar membranes. To a reasonable approximation, the optimal contact angle depends only on the aspect ratio of the pore. We also find that water molecules pass through the most hydrophobic membranes in a punctuated series of bursts that are separated by long pauses. A continuous-time Markov model of these data provides evidence of a molecular analogue to the clogging transition, a phenomenon observed in driven granular flows.
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Affiliation(s)
- Steven E Strong
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
| | - Joel D Eaves
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
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21
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Ashraf A, Wu Y, Wang MC, Yong K, Sun T, Jing Y, Haasch RT, Aluru NR, Nam S. Doping-Induced Tunable Wettability and Adhesion of Graphene. NANO LETTERS 2016; 16:4708-4712. [PMID: 27351580 DOI: 10.1021/acs.nanolett.6b02228] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report that substrate doping-induced charge carrier density modulation leads to the tunable wettability and adhesion of graphene. Graphene's water contact angle changes by as much as 13° as a result of a 300 meV change in doping level. Upon either n- or p-type doping with subsurface polyelectrolytes, graphene exhibits increased hydrophilicity. Adhesion force measurements using a hydrophobic self-assembled monolayer-coated atomic force microscopy probe reveal enhanced attraction toward undoped graphene, consistent with wettability modulation. This doping-induced wettability modulation is also achieved via a lateral metal-graphene heterojunction or subsurface metal doping. Combined first-principles and atomistic calculations show that doping modulates the binding energy between water and graphene and thus increases its hydrophilicity. Our study suggests that the doping-induced modulation of the charge carrier density in graphene influences its wettability and adhesion [corrected]. This opens up unique and new opportunities for the tunable wettability and adhesion of graphene for advanced coating materials and transducers.
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Affiliation(s)
- Ali Ashraf
- Department of Mechanical Science and Engineering and ‡Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Yanbin Wu
- Department of Mechanical Science and Engineering and ‡Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Michael Cai Wang
- Department of Mechanical Science and Engineering and ‡Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Keong Yong
- Department of Mechanical Science and Engineering and ‡Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Tao Sun
- Department of Mechanical Science and Engineering and ‡Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Yuhang Jing
- Department of Mechanical Science and Engineering and ‡Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Richard T Haasch
- Department of Mechanical Science and Engineering and ‡Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Narayana R Aluru
- Department of Mechanical Science and Engineering and ‡Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - SungWoo Nam
- Department of Mechanical Science and Engineering and ‡Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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22
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Strong SE, Eaves JD. Atomistic Hydrodynamics and the Dynamical Hydrophobic Effect in Porous Graphene. J Phys Chem Lett 2016; 7:1907-1912. [PMID: 27139634 DOI: 10.1021/acs.jpclett.6b00748] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Mirroring their role in electrical and optical physics, two-dimensional crystals are emerging as novel platforms for fluid separations and water desalination, which are hydrodynamic processes that occur in nanoscale environments. For numerical simulation to play a predictive and descriptive role, one must have theoretically sound methods that span orders of magnitude in physical scales, from the atomistic motions of particles inside the channels to the large-scale hydrodynamic gradients that drive transport. Here, we use constraint dynamics to derive a nonequilibrium molecular dynamics method for simulating steady-state mass flow of a fluid moving through the nanoscopic spaces of a porous solid. After validating our method on a model system, we use it to study the hydrophobic effect of water moving through pores of electrically doped single-layer graphene. The trend in permeability that we calculate does not follow the hydrophobicity of the membrane but is instead governed by a crossover between two competing molecular transport mechanisms.
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Affiliation(s)
- Steven E Strong
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
| | - Joel D Eaves
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
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23
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Taherian F, Leroy F, Heim LO, Bonaccurso E, van der Vegt NFA. Mechanism for Asymmetric Nanoscale Electrowetting of an Ionic Liquid on Graphene. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:140-150. [PMID: 26652691 DOI: 10.1021/acs.langmuir.5b04161] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The electrowetting behavior of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) confined between two oppositely charged graphene layers is investigated using molecular dynamics simulations. By introducing charges on the surface, counterions are attracted to the surface and co-ions are repelled from it, leading to the reduction of the solid-liquid interfacial free energy and consequently the contact angle. Recently, we have shown that changes in the contact angle upon charging the surface are asymmetric with respect to surface polarity and opposite to the changes in the solid-liquid interfacial free energy. In this work, the asymmetry of the solid-liquid interfacial free energy is shown to originate from differences in structural organization of the ions at the interface, with positively polarized surfaces inducing a more favorable electrostatic arrangement of the ions. Analysis of the liquid structure in the vicinity of the three phase contact line, however, shows that the ion size asymmetry, together with differences in orientational ordering of the cations on oppositely polarized surfaces, instead leads to enhanced spreading on the negatively polarized surfaces, resulting in a corresponding contact angle asymmetry.
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Affiliation(s)
- Fereshte Taherian
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt , Alarich-Weiss-Straße 10, D-64287 Darmstadt, Germany
| | - Frédéric Leroy
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt , Alarich-Weiss-Straße 10, D-64287 Darmstadt, Germany
| | - Lars-Oliver Heim
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt , Alarich-Weiss-Straße 10, D-64287 Darmstadt, Germany
| | - Elmar Bonaccurso
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt , Alarich-Weiss-Straße 10, D-64287 Darmstadt, Germany
| | - Nico F A van der Vegt
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt , Alarich-Weiss-Straße 10, D-64287 Darmstadt, Germany
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24
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Sanders S, Cabrero-Vilatela A, Kidambi PR, Alexander-Webber JA, Weijtens C, Braeuninger-Weimer P, Aria AI, Qasim MM, Wilkinson TD, Robertson J, Hofmann S, Meyer J. Engineering high charge transfer n-doping of graphene electrodes and its application to organic electronics. NANOSCALE 2015; 7:13135-13142. [PMID: 26176814 DOI: 10.1039/c5nr03246f] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Using thermally evaporated cesium carbonate (Cs2CO3) in an organic matrix, we present a novel strategy for efficient n-doping of monolayer graphene and a ∼90% reduction in its sheet resistance to ∼250 Ohm sq(-1). Photoemission spectroscopy confirms the presence of a large interface dipole of ∼0.9 eV between graphene and the Cs2CO3/organic matrix. This leads to a strong charge transfer based doping of graphene with a Fermi level shift of ∼1.0 eV. Using this approach we demonstrate efficient, standard industrial manufacturing process compatible graphene-based inverted organic light emitting diodes on glass and flexible substrates with efficiencies comparable to those of state-of-the-art ITO based devices.
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Affiliation(s)
- Simon Sanders
- Philips Research, Philipsstrasse 8, 52068 Aachen, Germany.
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25
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Taherian F, Leroy F, van der Vegt NFA. Interfacial tension does not drive asymmetric nanoscale electrowetting on graphene. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:4686-4695. [PMID: 25860129 DOI: 10.1021/acs.langmuir.5b00625] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report molecular dynamics simulations of the electrowetting behavior of liquids in confinement between two oppositely charged graphene sheets. We observe that changes in the static contact angles of water, salty (4 M NaCl) water, and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) (a room temperature ionic liquid) exhibit an asymmetric dependence on electric field polarity. The solid-liquid interfacial tension, which is expected to drive these changes, has been calculated independently by integrating the reversible work performed upon introducing positive and negative surface charges. This quantity shows either no dependence on the polarity of the electric field (water) or a dependence exactly opposite to the one obtained by applying the Young-Lippmann equation to the observed contact angles ([bmim][BF4]). Our analysis indicates that the observed contact angle asymmetry finds its origin in the liquid structure in the vicinity of the three-phase contact line. In particular, it is suggested that the molecular orientation properties are crucial to determine the asymmetric wetting behavior of pure water; in addition, the contrast in the strength of the ion hydration shells has a decisive influence on the NaCl solution behavior.
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Affiliation(s)
- Fereshte Taherian
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, D-64287 Darmstadt, Germany
| | - Frédéric Leroy
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, D-64287 Darmstadt, Germany
| | - Nico F A van der Vegt
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, D-64287 Darmstadt, Germany
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26
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Zhai P, Lee CC, Chang YH, Liu C, Wei TC, Feng SP. A significant improvement in the electrocatalytic stability of N-doped graphene nanosheets used as a counter electrode for [Co(bpy)3](3+/2+) based porphyrin-sensitized solar cells. ACS APPLIED MATERIALS & INTERFACES 2015; 7:2116-2123. [PMID: 25556598 DOI: 10.1021/am5083705] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A significant improvement in efficiency is achieved for porphyrin (YD2-o-C8) based dye-sensitized solar cells, coupled with [Co(bpy)3](3+/2+) mediator electrolyte. However, the poison of the counter electrode (CE) by the [Co(bpy)3](3+/2+) mediator remains a significant barrier to producing a reliable high-performance device. In this paper, nitrogen-doped graphene nanosheets (NG) are produced using a low-cost solution-based process and are used as the CE for [Co(bpy)3](3+/2+) based porphyrin-sensitized solar cells. These produce significantly better electrocatalytic activity than the commonly used Pt CE. The superior performance is a result of the increased number of catalytic sites and the wettable surface that is caused by the substitution of pyridinic and pyrrolic N into the carbon-conjugated lattice. To the authors' best knowledge, the significantly improved cycling stability (>1000 times) of NG CE for [Co(bpy)3](3+/2+) redox complexes is demonstrated for the first time.
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Affiliation(s)
- Peng Zhai
- Department of Mechanical Engineering, The University of Hong Kong , Pokfulam 852, Hong Kong
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27
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Sui ZY, Meng YN, Xiao PW, Zhao ZQ, Wei ZX, Han BH. Nitrogen-doped graphene aerogels as efficient supercapacitor electrodes and gas adsorbents. ACS APPLIED MATERIALS & INTERFACES 2015; 7:1431-1438. [PMID: 25545306 DOI: 10.1021/am5042065] [Citation(s) in RCA: 159] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Nitrogen-doped graphene has been demonstrated to be an excellent multifunctional material due to its intriguing features such as outstanding electrocatalytic activity, high electrical conductivity, and good chemical stability as well as wettability. However, synthesizing the nitrogen-doped graphene with a high nitrogen content and large specific surface area is still a challenge. In this study, we prepared a nitrogen-doped graphene aerogel (NGA) with high porosity by means of a simple hydrothermal reaction, in which graphene oxide and ammonia are adopted as carbon and nitrogen source, respectively. The microstructure, morphology, porous properties, and chemical composition of NGA were well-disclosed by a variety of characterization methods, such as scanning electron microscopy, nitrogen adsorption-desorption measurements, X-ray photoelectron spectroscopy, and Raman spectroscopy. The as-made NGA displays a large Brunauer-Emmett-Teller specific surface area (830 m(2) g(-1)), high nitrogen content (8.4 atom %), and excellent electrical conductivity and wettability. On the basis of these features, the as-made NGA shows superior capacitive behavior (223 F g(-1) at 0.2 A g(-1)) and long-term cycling performance in 1.0 mol L(-1) H2SO4 electrolyte. Furthermore, the NGA also possesses a high carbon dioxide uptake capacity at 1.0 bar and 273 K (11.3 wt %).
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Affiliation(s)
- Zhu-Yin Sui
- National Center for Nanoscience and Technology , Beijing 100190, China
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