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Cheon S, Cho WJ, Yi GR, Kang B, Oh SS. Ultrafast and Reversible Superwettability Switching of 3D Graphene Foams via Solvent-Exclusive Plasma Treatments. ACS NANO 2024; 18:24012-24023. [PMID: 39033415 DOI: 10.1021/acsnano.4c03102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/23/2024]
Abstract
For highly active electron transfer and ion diffusion, controlling the surface wettability of electrically and thermally conductive 3D graphene foams (3D GFs) is required. Here, we present ultrasimple and rapid superwettability switching of 3D GFs in a reversible and reproducible manner, mediated by solvent-exclusive microwave arcs. As the 3D GFs are prepared with vapors of nonpolar acetone or polar water exclusively, short microwave radiation (≤10 s) leads to plasma hotspot-mediated production of methyl and hydroxyl radicals, respectively. Upon immediate radical chemisorption, the 3D surfaces become either superhydrophobic (water contact angle = ∼170°) or superhydrophilic (∼0°), and interestingly, the wettability transition can be repeated many times due to the facile exchange between previously chemisorbed and newly introduced radicals via the formation of methanol-like intermediates. When 3D GFs of different surficial polarities are incorporated into electric double-layer capacitors with nonpolar ionic liquids or polar aqueous electrolytes, the polarity matching between graphene surfaces and electrolytes results in ≥548.0 times higher capacitance compared to its mismatching at ≥0.5 A g-1, demonstrating the significance of wettability-controlled 3D GFs.
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Affiliation(s)
- Soomin Cheon
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, South Korea
| | - Won-Jang Cho
- Department of Chemical Engineering, POSTECH, Pohang 37673, South Korea
| | - Gi-Ra Yi
- Department of Chemical Engineering, POSTECH, Pohang 37673, South Korea
| | - Byoungwoo Kang
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, South Korea
| | - Seung Soo Oh
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, South Korea
- Department of Chemical Engineering, POSTECH, Pohang 37673, South Korea
- Institute for Convergence Research and Education in Advanced Technology (I-CREATE), Yonsei University, Incheon 21983, South Korea
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2
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Hmam O, Côté-Dubuc F, Badia A. Gold-Supported Lipid Membranes Formed by Redox-Triggered Vesicle Fusion on Binary Self-Assembled Monolayers: Ion-Pairing Association and Surface Hydrophilicity. ACS APPLIED MATERIALS & INTERFACES 2023. [PMID: 37223998 DOI: 10.1021/acsami.3c03526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The assembly of biomimetic, planar supported lipid bilayers (SLBs) by the popular vesicle fusion method, which relies on the spontaneous adsorption and rupture of small unilamellar vesicles from aqueous solution on a solid surface, typically works with a limited range of support materials and lipid systems. We previously reported a conceptual advance in the formation of SLBs from vesicles in the gel or fluid phase using the interfacial ion-pairing association of charged phospholipid headgroups with electrochemically generated cationic ferroceniums bound to a self-assembled monolayer (SAM) chemisorbed to gold. This redox-driven approach lays down a single bilayer membrane on the SAM-modified gold surface at room temperature within minutes and is compatible with both anionic and zwitterionic phospholipids. The present work explores the effects of the surface ferrocene concentration and hydrophobicity/hydrophilicity on the formation of continuous SLBs of dialkyl phosphatidylserine, dialkyl phosphatidylglycerol, and dialkyl phosphatidylcholine using binary SAMs of ferrocenylundecanethiolate (FcC11S) and dodecanethiolate (CH3C11S) or hydroxylundecanethiolate (HOC11S) comprising different surface mole fractions of ferrocene (χFcsurf). An increase in the surface hydrophilicity and surface free energy of the FcC11S/HOC11S SAM mitigates the decrease in the attractive ion-pairing interactions resulting from a reduced χFcsurf. SLBs of ≳80% area coverage form on the FcC11S/HOC11S SAM for all the phospholipid types down to χFcsurf of at least 0.2, composition yielding a water contact angle (θW) of 44 ± 4°. By contrast, a greater number of ion-pairing interactions is required on the hydrophobic FcC11S/CH3C11S surface to drive the vesicle fusion process; bilayers or bilayer patches form at χFcsurf ≳ 0.6 (θW = 97 ± 3°). These findings will aid in tailoring the surface chemistry of redox-active modified surfaces to widen the conditions that yield supported lipid membranes.
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Affiliation(s)
- Ons Hmam
- Département de chimie, Quebec Centre for Advanced Materials and Regroupement québécois sur les matériaux de pointe, Université de Montréal, Complexe des sciences, C.P. 6128, succursale Centre-ville, Montréal, Quebec H3C 3J7, Canada
| | - Félix Côté-Dubuc
- Département de chimie, Quebec Centre for Advanced Materials and Regroupement québécois sur les matériaux de pointe, Université de Montréal, Complexe des sciences, C.P. 6128, succursale Centre-ville, Montréal, Quebec H3C 3J7, Canada
| | - Antonella Badia
- Département de chimie, Quebec Centre for Advanced Materials and Regroupement québécois sur les matériaux de pointe, Université de Montréal, Complexe des sciences, C.P. 6128, succursale Centre-ville, Montréal, Quebec H3C 3J7, Canada
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3
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Learning the relationship between nanoscale chemical patterning and hydrophobicity. Proc Natl Acad Sci U S A 2022; 119:e2200018119. [PMID: 36409904 PMCID: PMC9860318 DOI: 10.1073/pnas.2200018119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The hydrophobicity of proteins and similar surfaces, which display chemical heterogeneity at the nanoscale, drives countless aqueous interactions and assemblies. However, predicting how surface chemical patterning influences hydrophobicity remains a challenge. Here, we address this challenge by using molecular simulations and machine learning to characterize and model the hydrophobicity of a diverse library of patterned surfaces, spanning a wide range of sizes, shapes, and chemical compositions. We find that simple models, based only on polar content, are inaccurate, whereas complex neural network models are accurate but challenging to interpret. However, by systematically incorporating chemical correlations between surface groups into our models, we are able to construct a series of minimal models of hydrophobicity, which are both accurate and interpretable. Our models highlight that the number of proximal polar groups is a key determinant of hydrophobicity and that polar neighbors enhance hydrophobicity. Although our minimal models are trained on particular patch size and shape, their interpretability enables us to generalize them to rectangular patches of all shapes and sizes. We also demonstrate how our models can be used to predict hot-spot locations with the largest marginal contributions to hydrophobicity and to design chemical patterns that have a fixed polar content but vary widely in their hydrophobicity. Our data-driven models and the principles they furnish for modulating hydrophobicity could facilitate the design of novel materials and engineered proteins with stronger interactions or enhanced solubilities.
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4
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Weiand E, Ewen JP, Koenig PH, Roiter Y, Page SH, Angioletti-Uberti S, Dini D. Coarse-grained molecular models of the surface of hair. SOFT MATTER 2022; 18:1779-1792. [PMID: 35112700 DOI: 10.1039/d1sm01720a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
We present a coarse-grained molecular model of the surface of human hair, which consists of a supported lipid monolayer, in the MARTINI framework. Using coarse-grained molecular dynamics (MD) simulations, we identify a lipid grafting distance that yields a monolayer thickness consistent with both atomistic MD simulations and experimental measurements of the hair surface. Coarse-grained models for fully-functionalised, partially damaged, and fully damaged hair surfaces are created by randomly replacing neutral thioesters with anionic sulfonate groups. This mimics the progressive removal of fatty acids from the hair surface by bleaching and leads to chemically heterogeneous surfaces. Using molecular dynamics (MD) simulations, we study the island structures formed by the lipid monolayers at different degrees of damage in vacuum and in the presence of polar (water) and non-polar (n-hexadecane) solvents. We also use MD simulations to compare the wetting behaviour of water and n-hexadecane droplets on the model surfaces through contact angle measurements, which are compared to experiments using virgin and bleached hair. The model surfaces capture the experimentally-observed transition of the hair surface from hydrophobic (and oleophilic) to hydrophilic (and oleophobic) as the level of bleaching damage increases. By selecting surfaces with specific damage ratios, we obtain contact angles from the MD simulations that are in good agreement with experiments for both solvents on virgin and bleached human hairs. To negate the possible effects of microscale curvature and roughness of real hairs on wetting, we also conduct additional experiments using biomimetic surfaces that are co-functionalised with fatty acids and sulfonate groups. In both the MD simulations and experiments, the cosine of the water contact angle increases linearly with the sulfonate group surface coverage with a similar slope. We expect that the proposed systems will be useful for future molecular dynamics simulations of the adsorption and tribological behaviour of hair, as well as other chemically heterogeneous surfaces.
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Affiliation(s)
- Erik Weiand
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK.
- Institute of Molecular Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Thomas Young Centre for the Theory and Simulation of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
| | - James P Ewen
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK.
- Institute of Molecular Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Thomas Young Centre for the Theory and Simulation of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
| | - Peter H Koenig
- Corporate Functions Analytical and Data & Modeling Sciences, Mason Business Center, The Procter and Gamble Company, Cincinnati, 45224 Ohio, USA
| | - Yuri Roiter
- Corporate Functions Analytical and Data & Modeling Sciences, Mason Business Center, The Procter and Gamble Company, Cincinnati, 45224 Ohio, USA
| | - Steven H Page
- Corporate Functions Analytical and Data & Modeling Sciences, Mason Business Center, The Procter and Gamble Company, Cincinnati, 45224 Ohio, USA
| | - Stefano Angioletti-Uberti
- Institute of Molecular Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Thomas Young Centre for the Theory and Simulation of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Department of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
| | - Daniele Dini
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK.
- Institute of Molecular Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Thomas Young Centre for the Theory and Simulation of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
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5
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Kelkar AS, Dallin BC, Van Lehn RC. Identifying nonadditive contributions to the hydrophobicity of chemically heterogeneous surfaces via dual-loop active learning. J Chem Phys 2022; 156:024701. [PMID: 35032988 DOI: 10.1063/5.0072385] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Hydrophobic interactions drive numerous biological and synthetic processes. The materials used in these processes often possess chemically heterogeneous surfaces that are characterized by diverse chemical groups positioned in close proximity at the nanoscale; examples include functionalized nanomaterials and biomolecules, such as proteins and peptides. Nonadditive contributions to the hydrophobicity of such surfaces depend on the chemical identities and spatial patterns of polar and nonpolar groups in ways that remain poorly understood. Here, we develop a dual-loop active learning framework that combines a fast reduced-accuracy method (a convolutional neural network) with a slow higher-accuracy method (molecular dynamics simulations with enhanced sampling) to efficiently predict the hydration free energy, a thermodynamic descriptor of hydrophobicity, for nearly 200 000 chemically heterogeneous self-assembled monolayers (SAMs). Analysis of this dataset reveals that SAMs with distinct polar groups exhibit substantial variations in hydrophobicity as a function of their composition and patterning, but the clustering of nonpolar groups is a common signature of highly hydrophobic patterns. Further molecular dynamics analysis relates such clustering to the perturbation of interfacial water structure. These results provide new insight into the influence of chemical heterogeneity on hydrophobicity via quantitative analysis of a large set of surfaces, enabled by the active learning approach.
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Affiliation(s)
- Atharva S Kelkar
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, USA
| | - Bradley C Dallin
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, USA
| | - Reid C Van Lehn
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, USA
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6
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Sun C, McClure J, Berg S, Mostaghimi P, Armstrong RT. Universal description of wetting on multiscale surfaces using integral geometry. J Colloid Interface Sci 2021; 608:2330-2338. [PMID: 34774316 DOI: 10.1016/j.jcis.2021.10.152] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2021] [Revised: 10/11/2021] [Accepted: 10/25/2021] [Indexed: 10/19/2022]
Abstract
HYPOTHESIS Emerging energy-related technologies deal with multiscale hierarchical structures, intricate surface morphology, non-axisymmetric interfaces, and complex contact lines where wetting is difficult to quantify with classical methods. We hypothesise that a universal description of wetting on multiscale surfaces can be developed by using integral geometry coupled to thermodynamic laws. The proposed approach separates the different hierarchy levels of physical description from the thermodynamic description, allowing for a universal description of wetting on multiscale surfaces. THEORY AND SIMULATIONS The theoretical framework is presented followed by application to limiting cases of wetting on multiscale surfaces. Limiting cases include those considered in the Wenzel, Cassie-Baxter, and wicking state models. Wetting characterisation of multiscale surfaces is explored by conducting simulations of a fluid droplet on a structurally rough surface and a chemically heterogeneous surface. FINDINGS The underlying origin of the classical wetting models is shown to be rooted within the proposed theoretical framework. Integral geometry provides a topological-based wetting metric that is not contingent on any type of wetting state. The wetting metric is demonstrated to account for multiscale features along the common line in a scale consistent way; providing a universal description of wetting for multiscale surfaces.
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Affiliation(s)
- Chenhao Sun
- State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
| | - James McClure
- Advanced Research Computing, Virginia Tech, Wright House, W. Campus Drive, Blacksburg, VA 24061, USA
| | - Steffen Berg
- Shell Global Solutions International B.V., Grasweg 31, 1031 WG Amsterdam, Netherlands; Imperial College London, Department of Earth Science & Engineering and Chemical Engineering, Exhibition Rd, South Kensington, London SW7 2BX, United Kingdom
| | - Peyman Mostaghimi
- School of Minerals & Energy Resources Engineering, University of New South Wales, Kensington, New South Wales 2052, Australia
| | - Ryan T Armstrong
- School of Minerals & Energy Resources Engineering, University of New South Wales, Kensington, New South Wales 2052, Australia.
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7
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Identifying hydrophobic protein patches to inform protein interaction interfaces. Proc Natl Acad Sci U S A 2021; 118:2018234118. [PMID: 33526682 DOI: 10.1073/pnas.2018234118] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Interactions between proteins lie at the heart of numerous biological processes and are essential for the proper functioning of the cell. Although the importance of hydrophobic residues in driving protein interactions is universally accepted, a characterization of protein hydrophobicity, which informs its interactions, has remained elusive. The challenge lies in capturing the collective response of the protein hydration waters to the nanoscale chemical and topographical protein patterns, which determine protein hydrophobicity. To address this challenge, here, we employ specialized molecular simulations wherein water molecules are systematically displaced from the protein hydration shell; by identifying protein regions that relinquish their waters more readily than others, we are then able to uncover the most hydrophobic protein patches. Surprisingly, such patches contain a large fraction of polar/charged atoms and have chemical compositions that are similar to the more hydrophilic protein patches. Importantly, we also find a striking correspondence between the most hydrophobic protein patches and regions that mediate protein interactions. Our work thus establishes a computational framework for characterizing the emergent hydrophobicity of amphiphilic solutes, such as proteins, which display nanoscale heterogeneity, and for uncovering their interaction interfaces.
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8
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Zhang F, Yu L, Zhang W, Liu L, Wang C. A minireview on the perturbation effects of polar groups to direct nanoscale hydrophobic interaction and amphiphilic peptide assembly. RSC Adv 2021; 11:28667-28673. [PMID: 35478591 PMCID: PMC9038178 DOI: 10.1039/d1ra05463e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 08/23/2021] [Indexed: 12/29/2022] Open
Abstract
Hydrophobic interaction provides the essential driving force for creating diverse native and artificial supramolecular architectures. Accumulating evidence leads to a hypothesis that the hydrophobicity of a nonpolar patch of a molecule is non-additive and susceptible to the chemical context of a judicious polar patch. However, the quantification of the hydrophobic interaction at the nanoscale remains a central challenge to validate the hypothesis. In this review, we aim to outline the recent efforts made to determine the hydrophobic interaction at a nanoscopic length scale. The advances achieved in the understanding of proximal polar groups perturbing the magnitude of hydrophobic interaction generated by the nonpolar patch are introduced. We will also discuss the influence of chemical heterogeneity on the modulation of amphiphilic peptide/protein assembly and molecular recognition. Hydrophobic interaction provides the essential driving force for creating diverse native and artificial supramolecular architectures.![]()
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Affiliation(s)
- Feiyi Zhang
- Institute for Advanced Materials, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Lanlan Yu
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine Peking Union Medical College, Beijing 100005, China
| | - Wenbo Zhang
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine Peking Union Medical College, Beijing 100005, China
| | - Lei Liu
- Institute for Advanced Materials, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Chenxuan Wang
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine Peking Union Medical College, Beijing 100005, China
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9
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Kelkar AS, Dallin BC, Van Lehn RC. Predicting Hydrophobicity by Learning Spatiotemporal Features of Interfacial Water Structure: Combining Molecular Dynamics Simulations with Convolutional Neural Networks. J Phys Chem B 2020; 124:9103-9114. [DOI: 10.1021/acs.jpcb.0c05977] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Atharva S. Kelkar
- Department of Chemical and Biological Engineering, University of Wisconsin—Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, United States
| | - Bradley C. Dallin
- Department of Chemical and Biological Engineering, University of Wisconsin—Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, United States
| | - Reid C. Van Lehn
- Department of Chemical and Biological Engineering, University of Wisconsin—Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, United States
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10
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Fischer NG, Moussa DG, Skoe EP, De Jong DA, Aparicio C. Keratinocyte-Specific Peptide-Based Surfaces for Hemidesmosome Upregulation and Prevention of Bacterial Colonization. ACS Biomater Sci Eng 2020; 6:4929-4939. [PMID: 32953986 PMCID: PMC7494210 DOI: 10.1021/acsbiomaterials.0c00845] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Percutaneous devices like orthopedic prosthetic implants for amputees, catheters, and dental implants suffer from high infection rates. A critical aspect mediating peri-implant infection of dental implants is the lack of a structural barrier between the soft tissue and the implant surface which could impede bacteria access and colonization of exposed implant surfaces. Parafunctional soft tissue regeneration around dental implants is marked by a lack of hemidesmosome formation and thereby weakened mechanical attachment. In response to this healthcare burden, a simultaneously hemidesmosome-inducing, antimicrobial, multifunctional implant surface was engineered. A designer antimicrobial peptide, GL13K, and a laminin-derived peptide, LamLG3, were coimmobilized with two different surface fractional areas. The coimmobilized peptide surfaces showed antibiofilm activity against Streptococcus gordonii while enhancing proliferation, hemidesmosome formation, and mechanical attachment of orally derived keratinocytes. Notably, the coatings demonstrated specific activation of keratinocytes: the coatings showed no effects on gingival fibroblasts which are known to impede the quality of soft tissue attachment to dental implants. These coatings demonstrated stability and retained activity against mechanical and thermochemical challenges, suggesting their intraoral durability. Overall, these multifunctional surfaces may be able to reduce peri-implantitis rates and enhance the success rates of all percutaneous devices via strong antimicrobial activity and enhanced soft tissue attachment to implants.
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Affiliation(s)
- Nicholas G Fischer
- MDRCBB-Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Dina G Moussa
- MDRCBB-Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Erik P Skoe
- MDRCBB-Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - David A De Jong
- MDRCBB-Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Conrado Aparicio
- MDRCBB-Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota, Minneapolis, Minnesota 55455, United State
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11
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Yadav HOS, Kuo AT, Urata S, Shinoda W. Effects of Packing Density and Chain Length on the Surface Hydrophobicity of Thin Films Composed of Perfluoroalkyl Acrylate Chains: A Molecular Dynamics Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:14316-14323. [PMID: 31596100 DOI: 10.1021/acs.langmuir.9b02656] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
A good understanding of the surface hydrophobicity of fluorinated materials is useful for their application as coating materials. The present study investigates the surface hydrophobicity of perfluoroalkyl acrylate (PFA) thin films using molecular dynamics simulations. Surface hydrophobicity is characterized by examining the contact angle of a water droplet on PFA surfaces and the cavity formation free energy in the vicinity of the surface. It is found that the calculated microscopic contact angles are in good agreement with the experimental results and partially capture the difference in the hydrophobicity of the surface arising from the variation of packing density and side chain length of PFA. The variations of cavity formation free energy in the vicinity of the surface elucidate that the surface hydrophobicity is mainly governed by the packing density rather than the chain length of PFA. The hydrophobicity generally increases with decreasing the packing density to some extent and then turns to decrease as further reducing the packing density. At higher packing density, the surface hydrophobicity slightly decreases with increasing the chain length, while at the lower packing density, the surface hydrophobicity is increased when chain length of PFA is longer than six carbons. Furthermore, we found that the influence of packing density on the surface hydrophobicity is directly related to the variation of the surface roughness and chain flexibility, that is, the surface hydrophobicity increases with increase in the surface roughness, while the chain flexibility plays a secondary role in the enhancement by affecting the stability of water staying near the interface. The study provides a significant insight into the local hydrophobicity and microscopic structure of the PFA surfaces, which would be useful for the application of surface modification.
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Affiliation(s)
- Hari O S Yadav
- Department of Materials Chemistry , Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8603 , Japan
| | - An-Tsung Kuo
- Innovative Technology Laboratories , AGC Inc. , Yokohama , Kanagawa 230-0045 , Japan
| | - Shingo Urata
- Innovative Technology Laboratories , AGC Inc. , Yokohama , Kanagawa 230-0045 , Japan
| | - Wataru Shinoda
- Department of Materials Chemistry , Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8603 , Japan
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12
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Jiang H, Fialoke S, Vicars Z, Patel AJ. Characterizing surface wetting and interfacial properties using enhanced sampling (SWIPES). SOFT MATTER 2019; 15:860-869. [PMID: 30644500 DOI: 10.1039/c8sm02317d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We introduce an accurate and efficient method for characterizing surface wetting and interfacial properties, such as the contact angle made by a liquid droplet on a solid surface, and the vapor-liquid surface tension of a fluid. The method makes use of molecular simulations in conjunction with the indirect umbrella sampling technique to systematically wet the surface and estimate the corresponding free energy. To illustrate the method, we study the wetting of a family of Lennard-Jones surfaces by water. For surfaces with a wide range of attractions for water, we estimate contact angles using our method, and compare them with contact angles obtained using droplet shapes. Notably, our method is able to capture the transition from partial to complete wetting as surface-water attractions are increased. Moreover, the method is straightforward to implement and is computationally efficient, providing accurate contact angle estimates in roughly 5 nanoseconds of simulation time.
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Affiliation(s)
- Hao Jiang
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
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13
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Rego NB, Xi E, Patel AJ. Protein Hydration Waters Are Susceptible to Unfavorable Perturbations. J Am Chem Soc 2019; 141:2080-2086. [DOI: 10.1021/jacs.8b11448] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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14
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Antunes LF, Simon DA, Fiorio R, Francisquetti E. Effects of polyether siloxane surfactant on the hydrophilic capacity of polypropylene films. POLIMEROS 2019. [DOI: 10.1590/0104-1428.06518] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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15
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Ojaghlou N, Tafreshi HV, Bratko D, Luzar A. Dynamical insights into the mechanism of a droplet detachment from a fiber. SOFT MATTER 2018; 14:8924-8934. [PMID: 30232489 DOI: 10.1039/c8sm01257a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Quantifying the detachment behavior of a droplet from a fiber is important in many applications such as fog harvesting, oil-water separation, or water management in fuel cells. When the droplets are forcibly removed from hydrophilic fibers, the ease of detachment strongly depends on droplet volume and the rate of the process controlled by the applied force. Experiments, conducted on a ferrofluid under magnetic force, as well as continuum level calculations from fluid mechanics have so far been unable to resolve the time-dependent dynamics of droplet detachment and, most importantly, to assess the role of the applied force as the key determinant of the volume of the droplet residue remaining on the fiber after detachment. In the present work, we study the mechanism of water droplet detachment and retention of residual water on smooth hydrophilic fibers using nonequilibrium molecular dynamics simulations. We investigate how the applied force affects the breakup of a droplet and how the minimal detaching force per unit mass decreases with droplet size. We extract scaling relations that allow extrapolation of our findings to larger length scales that are not directly accessible by molecular models. We find that the volume of the residue on a fiber varies nonmonotonically with the detaching force, reaching the maximal size at an intermediate force and associated detachment time. The strength of this force decreases with the size of the drop, while the maximal residue increases with the droplet volume, V, sub-linearly, in proportion to the V2/3.
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Affiliation(s)
- Neda Ojaghlou
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, USA.
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16
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Computational discovery of chemically patterned surfaces that effect unique hydration water dynamics. Proc Natl Acad Sci U S A 2018; 115:8093-8098. [PMID: 30038028 DOI: 10.1073/pnas.1807208115] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The interactions of water with solid surfaces govern their apparent hydrophobicity/hydrophilicity, influenced at the molecular scale by surface coverage of chemical groups of varied nonpolar/polar character. Recently, it has become clear that the precise patterning of surface groups, and not simply average surface coverage, has a significant impact on the structure and thermodynamics of hydration layer water, and, in turn, on macroscopic interfacial properties. Here we show that patterning also controls the dynamics of hydration water, a behavior frequently thought to be leveraged by biomolecules to influence functional dynamics, but yet to be generalized. To uncover the role of surface heterogeneities, we couple a genetic algorithm to iterative molecular dynamics simulations to design the patterning of surface functional groups, at fixed coverage, to either minimize or maximize proximal water diffusivity. Optimized surface configurations reveal that clustering of hydrophilic groups increases hydration water mobility, while dispersing them decreases it, but only if hydrophilic moieties interact with water through directional, hydrogen-bonding interactions. Remarkably, we find that, across different surfaces, coverages, and patterns, both the chemical potential for inserting a methane-sized hydrophobe near the interface and, in particular, the hydration water orientational entropy serve as strong predictors for hydration water diffusivity, suggesting that these simple thermodynamic quantities encode the way surfaces control water dynamics. These results suggest a deep and intriguing connection between hydration water thermodynamics and dynamics, demonstrating that subnanometer chemical surface patterning is an important design parameter for engineering solid-water interfaces with applications spanning separations to catalysis.
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Jabes BS, Bratko D, Luzar A. Curvature dependence of the effect of ionic functionalization on the attraction among nanoparticles in dispersion. J Chem Phys 2018; 148:222815. [DOI: 10.1063/1.5017525] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Affiliation(s)
- B. Shadrack Jabes
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, USA
| | - Dusan Bratko
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, USA
| | - Alenka Luzar
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, USA
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18
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Xi E, Marks SM, Fialoke S, Patel AJ. Sparse sampling of water density fluctuations near liquid-vapor coexistence. MOLECULAR SIMULATION 2018. [DOI: 10.1080/08927022.2018.1457218] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Erte Xi
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania , Philadelphia, PA, USA
| | - Sean M. Marks
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania , Philadelphia, PA, USA
| | - Suruchi Fialoke
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania , Philadelphia, PA, USA
| | - Amish J. Patel
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania , Philadelphia, PA, USA
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Abstract
The behavior of water confined at the nanoscale plays a fundamental role in biological processes and technological applications, including protein folding, translocation of water across membranes, and filtration and desalination. Remarkably, nanoscale confinement drastically alters the properties of water. Using molecular dynamics simulations, we determine the phase diagram of water confined by graphene sheets in slab geometry, at T = 300 K and for a wide range of pressures. We find that, depending on the confining dimension D and density σ, water can exist in liquid and vapor phases, or crystallize into monolayer and bilayer square ices, as observed in experiments. Interestingly, depending on D and σ, the crystal-liquid transformation can be a first-order phase transition, or smooth, reminiscent of a supercritical liquid-gas transformation. We also focus on the limit of stability of the liquid relative to the vapor and obtain the cavitation pressure perpendicular to the graphene sheets. Perpendicular cavitation pressure varies non-monotonically with increasing D and exhibits a maximum at D ≈ 0.90 nm (equivalent to three water layers). The effect of nanoconfinement on the cavitation pressure can have an impact on water transport in technological and biological systems. Our study emphasizes the rich and apparently unpredictable behavior of nanoconfined water, which is complex even for graphene.
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20
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Jabes BS, Bratko D, Luzar A. Extent of Surface Force Additivity on Chemically Heterogeneous Substrates at Varied Orientations. J Phys Chem B 2018; 122:3596-3603. [PMID: 29185778 DOI: 10.1021/acs.jpcb.7b10790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Surface interactions between chemically mixed surfaces, as well as those among dissolved biomolecules, comprise distinct contributions from polar and hydrophobic moieties. These contributions are often context dependent. Approximate compliance to the Cassie additivity equation for the wetting free energies on mixed surfaces in water is, however, indicative of similarly additive forces between individual surface elements, suggesting a quadratic interpolation model for total force from the forces between pure surfaces. We use molecular dynamics/umbrella sampling simulations of parallel and nonparallel mixed surfaces with demonstrable Cassie-like behavior to verify how well the total surface force between the heterogeneous, molecularly rough surfaces can be approximated as a combination of forces among the homogeneous ones. When accounting for dissimilar distances of approach between functional groups of different types, our results for graphene surfaces with mixed methyl and nitrile coating show such a superposition to provide a reasonable first order approximation of interactions between the platelets. Deviations from additivity are more prominent in parallel-plate configurations, at high content of hydrophobic groups, and small separations. The inclusion of water polarizability does not visibly alter the observed behavior regardless of platelet orientations. The outcome of this study determines the necessary molecular conditions for observing force additivity that emphasize the context dependence of hydrophobic interaction in the presence of polar groups. This notion provides guidelines for the syntheses of new, chemically heterogeneous materials with tailored function-oriented properties in aqueous media.
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Affiliation(s)
- B Shadrack Jabes
- Department of Chemistry , Virginia Commonwealth University , Richmond , Virginia 23284 , United States
| | - Dusan Bratko
- Department of Chemistry , Virginia Commonwealth University , Richmond , Virginia 23284 , United States
| | - Alenka Luzar
- Department of Chemistry , Virginia Commonwealth University , Richmond , Virginia 23284 , United States
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21
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Remsing RC, Xi E, Patel AJ. Protein Hydration Thermodynamics: The Influence of Flexibility and Salt on Hydrophobin II Hydration. J Phys Chem B 2018; 122:3635-3646. [DOI: 10.1021/acs.jpcb.7b12060] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Richard C. Remsing
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
- Institute for Computational Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Erte Xi
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Amish J. Patel
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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22
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Hydrophobicity of proteins and nanostructured solutes is governed by topographical and chemical context. Proc Natl Acad Sci U S A 2017; 114:13345-13350. [PMID: 29158409 DOI: 10.1073/pnas.1700092114] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Hydrophobic interactions drive many important biomolecular self-assembly phenomena. However, characterizing hydrophobicity at the nanoscale has remained a challenge due to its nontrivial dependence on the chemistry and topography of biomolecular surfaces. Here we use molecular simulations coupled with enhanced sampling methods to systematically displace water molecules from the hydration shells of nanostructured solutes and calculate the free energetics of interfacial water density fluctuations, which quantify the extent of solute-water adhesion, and therefore solute hydrophobicity. In particular, we characterize the hydrophobicity of curved graphene sheets, self-assembled monolayers (SAMs) with chemical patterns, and mutants of the protein hydrophobin-II. We find that water density fluctuations are enhanced near concave nonpolar surfaces compared with those near flat or convex ones, suggesting that concave surfaces are more hydrophobic. We also find that patterned SAMs and protein mutants, having the same number of nonpolar and polar sites but different geometrical arrangements, can display significantly different strengths of adhesion with water. Specifically, hydroxyl groups reduce the hydrophobicity of methyl-terminated SAMs most effectively not when they are clustered together but when they are separated by one methyl group. Hydrophobin-II mutants show that a charged amino acid reduces the hydrophobicity of a large nonpolar patch when placed at its center, rather than at its edge. Our results highlight the power of water density fluctuations-based measures to characterize the hydrophobicity of nanoscale surfaces and caution against the use of additive approximations, such as the commonly used surface area models or hydropathy scales for characterizing biomolecular hydrophobicity and the associated driving forces of assembly.
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23
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Bakli C, P D SH, Chakraborty S. Mimicking wettability alterations using temperature gradients for water nanodroplets. NANOSCALE 2017; 9:12509-12515. [PMID: 28819670 DOI: 10.1039/c7nr03320f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A sessile droplet or a film usually moves from hotter regions to colder regions, due to variations in interfacial tension. This, known as the so-called Marangoni effect, is true for most pure liquids like water for which the surface tension decreases with an increase in temperature. In stark contrast to this existing understanding, we bring forth the coupled effect of wettability and temperature gradients on the dynamics of the three-phase contact line. By simultaneously tracking the dynamic evolution of the three-phase contact line due to the evaporation and diffusion of molecules through molecular dynamics simulations, we explore the coterminous effects of the change of surface tension coefficients and wetting parameters with temperature on sessile droplets residing on surfaces with different wettabilities. We demonstrate, for the very first time, that the inverse Marangoni effect, which is believed to be exclusively observed in mixtures and self-rewetting fluids, is feasible in pure water at scales where inertial effects are negligible. The results of the study find application in electronic chip cooling where by the combined tuning of surface characteristics and Marangoni forces, droplets can be passively transported to warmer regions for efficient thermal management.
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Affiliation(s)
- Chirodeep Bakli
- Department of Mechanical Engineering, Indian Institute of Technology Ropar, Rupanagar 140001, India
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24
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Lundy R, Byrne C, Bogan J, Nolan K, Collins MN, Dalton E, Enright R. Exploring the Role of Adsorption and Surface State on the Hydrophobicity of Rare Earth Oxides. ACS APPLIED MATERIALS & INTERFACES 2017; 9:13751-13760. [PMID: 28383896 DOI: 10.1021/acsami.7b01515] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Rare earth oxides (REOs) are attracting attention for use as cost-effective, high-performance dropwise condensers because of their favorable thermal properties and robust nature. However, to engineer a suitable surface for industrial applications, the mechanism governing wetting must be first fully elucidated. Recent studies exploring the water-wetting state of REOs have suggested that these oxides are intrinsically hydrophobic owing to the unique electronic structure of the lanthanide series. These claims have been countered with evidence that they are inherently hydrophilic and that adsorption of contaminants from the environment is responsible for the apparent hydrophobic nature of these surfaces. Here, using X-ray photoelectron spectroscopy and dynamic water contact angle measurements, we provide further evidence to show that REOs are intrinsically hydrophilic, with ceria demonstrating advancing water contact angles of ≈6° in a clean surface state and similar surface energies to two transition metal oxides (≳72 mJ/m2). Using two model volatile species, it is shown that an adsorption mechanism is responsible for the apparent hydrophobic property observed in REOs as well as in transition metal oxides and silica. This is correlated with the screening of the polar surface energy contribution of the underlying oxide with apparent surface energies reduced to <40 mJ/m2 for the case of nonane adsorption. Moreover, we show that the degree of surface hydroxylation plays an important role in the observed contact angle hysteresis with the receding contact angle of ceria increasing from ∼10° to 45° following thermal annealing in an inert atmosphere. Our findings suggest that high atomic number metal oxides capable of strongly adsorbing volatile species may represent a viable paradigm toward realizing robust surface coating for industrial condensers if certain challenges can be overcome.
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Affiliation(s)
- Ross Lundy
- Thermal Management Research Group, Efficient Energy Transfer (ηET) Department, Bell Labs Ireland, Nokia , Blanchardstown Business & Technology Park, Snugborough Rd, Dublin 15, Ireland
- Stokes Laboratories, University of Limerick , County Limerick V94 T9PX, Ireland
| | - Conor Byrne
- School of Physical Sciences, Dublin City University , Glasnevin, Dublin 9, Ireland
| | - Justin Bogan
- School of Physical Sciences, Dublin City University , Glasnevin, Dublin 9, Ireland
| | - Kevin Nolan
- Thermal Management Research Group, Efficient Energy Transfer (ηET) Department, Bell Labs Ireland, Nokia , Blanchardstown Business & Technology Park, Snugborough Rd, Dublin 15, Ireland
| | - Maurice N Collins
- Stokes Laboratories, University of Limerick , County Limerick V94 T9PX, Ireland
| | - Eric Dalton
- Stokes Laboratories, University of Limerick , County Limerick V94 T9PX, Ireland
| | - Ryan Enright
- Thermal Management Research Group, Efficient Energy Transfer (ηET) Department, Bell Labs Ireland, Nokia , Blanchardstown Business & Technology Park, Snugborough Rd, Dublin 15, Ireland
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25
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Sosso GC, Caravati S, Rotskoff G, Vaikuntanathan S, Hassanali A. On the Role of Nonspherical Cavities in Short Length-Scale Density Fluctuations in Water. J Phys Chem A 2016; 121:370-380. [PMID: 27935707 DOI: 10.1021/acs.jpca.6b11168] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Density fluctuations in liquid water are at the heart of numerous phenomena associated with hydrophobic effects such as protein folding and the interaction between biomolecules. One of the most fundamental processes in this regard is the solvation of hydrophobic solutes in water. The vast majority of theoretical and numerical studies examine density fluctuations at the short length scale focusing exclusively on spherical cavities. In this work, we use both first-principles and classical molecular dynamics simulations to demonstrate that density fluctuations in liquid water can deviate significantly from the canonical spherical shapes. We show that regions of empty space are frequently characterized by exotic, highly asymmetric shapes that can be quite delocalized over the hydrogen bond network. Interestingly, density fluctuations of these shapes are characterized by Gaussian statistics with larger fluctuations. An important consequence of this is that the work required to create non spherical cavities can be substantially smaller than that of spheres. This feature is also qualitatively captured by the Lum-Chandler-Weeks theory. The scaling behavior of the free energy as a function of the volume at short length scales is qualitatively different for the nonspherical entities. We also demonstrate that nonspherical density fluctuations are important for accommodating the hydrophobic amino acid alanine and are thus likely to have significant implications when it comes to solvating highly asymmetrical species such as alkanes, polymers, or biomolecules.
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Affiliation(s)
- Gabriele Cesare Sosso
- Thomas Young Centre, London Centre for Nanotechnology and Department of Physics and Astronomy, University College London , Gower Street, London WC1E 6BT, United Kingdom
| | - Sebastiano Caravati
- Department of Chemistry, University of Zurich , Winterhurerstrasse 190, Zurich CH-8057, Switzerland
| | - Grant Rotskoff
- Biophysics Graduate Group, University of California , Berkeley, California 94720, United States
| | | | - Ali Hassanali
- Condensed Matter and Statistical Physics Section, The Abdus Salam International Centre for Theoretical Physics , I-34151 Trieste, Italy
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26
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Włoch J, Terzyk AP, Gauden PA, Wesołowski R, Kowalczyk P. Water nanodroplet on a graphene surface-a new old system. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:495002. [PMID: 27736807 DOI: 10.1088/0953-8984/28/49/495002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The major subject of our study is the accuracy of contact angle calculations. Reporting new simulation data for graphene-water systems, we show that the majority of previously reported data should be treated with caution, since the proper contact angle can be recorded only after a sufficiently long simulation time. It has been proven that-if one wants to gain accuracy greater than 0.1°-long calculations (exceeding 50 ns) are required. Finally, we also show, using both a Groningen Machine for Chemical Simulations (GROMACS) package and our new molecular dynamics (MD) code, that the changes in the contact angle, caused by graphene bottom layer rotation, are within the range of calculation error. We also propose a novel definition of the bottom of the droplet as the height where the density is half the density of liquid water. This new definition is applied in the method of the contact angle calculation from the MD simulation data.
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Affiliation(s)
- Jerzy Włoch
- Faculty of Chemistry, Synthesis and Modification of Carbon Materials Research Group, Nicolaus Copernicus University in Toruń, Gagarin Street 7, 87-100 Toruń, Poland
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27
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Choudhuri JR, Vanzo D, Madden PA, Salanne M, Bratko D, Luzar A. Dynamic Response in Nanoelectrowetting on a Dielectric. ACS NANO 2016; 10:8536-8544. [PMID: 27556934 DOI: 10.1021/acsnano.6b03753] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Droplet spreading at an applied voltage underlies the function of tunable optical devices including adjustable lenses and matrix display elements. Faster response and the enhanced resolution motivate research toward miniaturization of these devices to nanoscale dimensions. The response of an aqueous nanodroplet to an applied field can differ significantly from macroscopic predictions. Understanding these differences requires characterization at the molecular level. We describe the equilibrium and nonequilibrium molecular dynamics simulations of nanosized aqueous droplets on a hydrophobic surface with the embedded concentric electrodes. Constant electrode potential is enforced by a rigorous account of the metal polarization. We demonstrate that the reduction of the equilibrium contact angle is commensurate to, and adjusts reversibly with, the voltage change. For a droplet with O(10) nm diameter, a typical response time to the imposition of the field is of O(10(2)) ps. Drop relaxation is about twice as fast when the field is switched off. The friction coefficient obtained from the rate of the drop relaxation on the nonuniform surface, decreases when the droplet approaches equilibrium from either direction, that is, by spreading or receding. The strong dependence of the friction on the surface hydrophilicity points to the dominance of the liquid-surface friction at the drop's perimeter as described in the molecular kinetic theory. This approach enables correct predictions of trends in dynamic responses associated with varied voltage or substrate material.
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Affiliation(s)
- Jyoti Roy Choudhuri
- Department of Chemistry, Virginia Commonwealth University , Richmond, Virginia 23284, United States
| | - Davide Vanzo
- Department of Chemistry, Virginia Commonwealth University , Richmond, Virginia 23284, United States
| | - Paul Anthony Madden
- Department of Material Science, Oxford University , Park Road, Oxford OX1 3PH, United Kingdom
| | - Mathieu Salanne
- Sorbonne Universités, UPMC Université Paris 06, CNRS, UMR 8234 PHENIX , 75005 Paris, France
- Maison de la Simulation, CEA, CNRS, Université Paris-Sud, UVSQ, Université Paris-Saclay , F-91191 Gif-sur-Yvette, France
| | - Dusan Bratko
- Department of Chemistry, Virginia Commonwealth University , Richmond, Virginia 23284, United States
| | - Alenka Luzar
- Department of Chemistry, Virginia Commonwealth University , Richmond, Virginia 23284, United States
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28
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Jabes BS, Bratko D, Luzar A. Universal Repulsive Contribution to the Solvent-Induced Interaction Between Sizable, Curved Hydrophobes. J Phys Chem Lett 2016; 7:3158-3163. [PMID: 27463998 DOI: 10.1021/acs.jpclett.6b01442] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In addition to the direct attraction, sizable hydrophobes in water experience an attractive force mediated by interfacial water. Using simple geometric arguments, we identify the conditions at which the water-induced interaction between curved hydrocarbon surfaces becomes repulsive. The repulsive contribution arises from the thermodynamic penalty due to the emergence of the liquid/vapor boundary created as water gets expelled between curved hydrophobes. By augmenting the mean field approach with atomistic simulations of pristine and alkyl-coated graphitic nanoparticles in three distinct geometries, spherical, cylindrical and planar, immersed in water, we show the macroscopic thermodynamics remarkably works down to the molecular scale. The new insights improve the prediction and control of wetting and dispersion properties for a broad class of nonpolar nanoparticles.
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Affiliation(s)
- B Shadrack Jabes
- Department of Chemistry, Virginia Commonwealth University , Richmond, Virginia 23284, United States
| | - Dusan Bratko
- Department of Chemistry, Virginia Commonwealth University , Richmond, Virginia 23284, United States
| | - Alenka Luzar
- Department of Chemistry, Virginia Commonwealth University , Richmond, Virginia 23284, United States
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29
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Martin L, Bilek MM, Weiss AS, Kuyucak S. Force fields for simulating the interaction of surfaces with biological molecules. Interface Focus 2016; 6:20150045. [PMID: 26855748 PMCID: PMC4686237 DOI: 10.1098/rsfs.2015.0045] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The interaction of biomolecules with solid interfaces is of fundamental importance to several emerging biotechnologies such as medical implants, anti-fouling coatings and novel diagnostic devices. Many of these technologies rely on the binding of peptides to a solid surface, but a full understanding of the mechanism of binding, as well as the effect on the conformation of adsorbed peptides, is beyond the resolution of current experimental techniques. Nanoscale simulations using molecular mechanics offer potential insights into these processes. However, most models at this scale have been developed for aqueous peptide and protein simulation, and there are no proven models for describing biointerfaces. In this review, we detail the current research towards developing a non-polarizable molecular model for peptide-surface interactions, with a particular focus on fitting the model parameters as well as validation by choice of appropriate experimental data.
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Affiliation(s)
- Lewis Martin
- Department of Applied Physics, University of Sydney, Sydney, New South Wales, Australia
| | - Marcela M. Bilek
- Department of Applied Physics, University of Sydney, Sydney, New South Wales, Australia
| | - Anthony S. Weiss
- Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia
- Department of Molecular Bioscience, University of Sydney, Sydney, New South Wales, Australia
- Bosch Institute, University of Sydney, Sydney, New South Wales, Australia
| | - Serdar Kuyucak
- Department of Applied Physics, University of Sydney, Sydney, New South Wales, Australia
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30
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Xi E, Remsing RC, Patel AJ. Sparse Sampling of Water Density Fluctuations in Interfacial Environments. J Chem Theory Comput 2016; 12:706-13. [DOI: 10.1021/acs.jctc.5b01037] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Erte Xi
- Department of Chemical and
Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Richard C. Remsing
- Department of Chemical and
Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Amish J. Patel
- Department of Chemical and
Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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31
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Wan R, Wang C, Lei X, Zhou G, Fang H. Enhancement of Water Evaporation on Solid Surfaces with Nanoscale Hydrophobic-Hydrophilic Patterns. PHYSICAL REVIEW LETTERS 2015; 115:195901. [PMID: 26588399 DOI: 10.1103/physrevlett.115.195901] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Indexed: 05/13/2023]
Abstract
Using molecular dynamics simulations, we show that the evaporation of nanoscale water on hydrophobic-hydrophilic patterned surfaces is unexpectedly faster than that on any surfaces with uniform wettability. The key to this phenomenon is that, on the patterned surface, the evaporation rate from the hydrophilic region only slightly decreases due to the correspondingly increased water thickness; meanwhile, a considerable number of water molecules evaporate from the hydrophobic region despite the lack of water film. Most of the evaporated water from the hydrophobic region originates from the hydrophilic region by diffusing across the contact lines. Further analysis shows that the evaporation rate from the hydrophobic region is approximately proportional to the total length of the contact lines.
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Affiliation(s)
- Rongzheng Wan
- Division of Interfacial Water and Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai 201800, China
| | - Chunlei Wang
- Division of Interfacial Water and Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai 201800, China
| | - Xiaoling Lei
- Division of Interfacial Water and Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai 201800, China
| | - Guoquan Zhou
- School of Sciences, Zhejiang A & F University, Lin'an 311300, P. R. China
| | - Haiping Fang
- Division of Interfacial Water and Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai 201800, China
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32
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Zhang J, Müller-Plathe F, Leroy F. Pinning of the Contact Line during Evaporation on Heterogeneous Surfaces: Slowdown or Temporary Immobilization? Insights from a Nanoscale Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:7544-7552. [PMID: 26090782 DOI: 10.1021/acs.langmuir.5b01097] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The question of the effect of surface heterogeneities on the evaporation of liquid droplets from solid surfaces is addressed through nonequilibrium molecular dynamics simulations. The mechanism behind contact line pinning which is still unclear is discussed in detail on the nanoscale. Model systems with the Lennard-Jones interaction potential were employed to study the evaporation of nanometer-sized cylindrical droplets from a flat surface. The heterogeneity of the surface was modeled through alternating stripes of equal width but two chemical types. The first type leads to a contact angle of 67°, and the other leads to a contact angle of 115°. The stripe width was varied between 2 and 20 liquid-particle diameters. On the surface with the narrowest stripes, evaporation occurred at constant contact angle as if the surface was homogeneous, with a value of the contact angle as predicted by the regular Cassie-Baxter equation. When the width was increased, the contact angle oscillated during evaporation between two boundaries whose values depend on the stripe width. The evaporation behavior was thus found to be a direct signature of the typical size of the surface heterogeneity domains. The contact angle both at equilibrium and during evaporation could be predicted from a local Cassie-Baxter equation in which the surface composition within a distance of seven fluid-particle diameters around the contact line was considered, confirming the local nature of the interactions that drive the wetting behavior of droplets. More importantly, we propose a nanoscale explanation of pinning during evaporation. Pinning should be interpreted as a drastic slowdown of the contact line dynamics rather than a complete immobilization of it during a transition between two contact angle boundaries.
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Affiliation(s)
- Jianguo Zhang
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 4, D-64287 Darmstadt, Germany
| | - Florian Müller-Plathe
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 4, 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 4, D-64287 Darmstadt, Germany
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33
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Ou SC, Cui D, Wezowicz M, Taufer M, Patel S. Free energetics of carbon nanotube association in aqueous inorganic NaI salt solutions: Temperature effects using all-atom molecular dynamics simulations. J Comput Chem 2015; 36:1196-212. [PMID: 25868455 PMCID: PMC4445429 DOI: 10.1002/jcc.23906] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Revised: 01/22/2015] [Accepted: 02/21/2015] [Indexed: 11/06/2022]
Abstract
In this study, we examine the temperature dependence of free energetics of nanotube association using graphical processing unit-enabled all-atom molecular dynamics simulations (FEN ZI) with two (10,10) single-walled carbon nanotubes in 3 m NaI aqueous salt solution. Results suggest that the free energy, enthalpy and entropy changes for the association process are all reduced at the high temperature, in agreement with previous investigations using other hydrophobes. Via the decomposition of free energy into individual components, we found that solvent contribution (including water, anion, and cation contributions) is correlated with the spatial distribution of the corresponding species and is influenced distinctly by the temperature. We studied the spatial distribution and the structure of the solvent in different regions: intertube, intratube and the bulk solvent. By calculating the fluctuation of coarse-grained tube-solvent surfaces, we found that tube-water interfacial fluctuation exhibits the strongest temperature dependence. By taking ions to be a solvent-like medium in the absence of water, tube-anion interfacial fluctuation shows similar but weaker dependence on temperature, while tube-cation interfacial fluctuation shows no dependence in general. These characteristics are discussed via the malleability of their corresponding solvation shells relative to the nanotube surface. Hydrogen bonding profiles and tetrahedrality of water arrangement are also computed to compare the structure of solvent in the solvent bulk and intertube region. The hydrophobic confinement induces a relatively lower concentration environment in the intertube region, therefore causing different intertube solvent structures which depend on the tube separation. This study is relevant in the continuing discourse on hydrophobic interactions (as they impact generally a broad class of phenomena in biology, biochemistry, and materials science and soft condensed matter research), and interpretations of hydrophobicity in terms of alternative but parallel signatures such as interfacial fluctuations, dewetting transitions, and enhanced fluctuation probabilities at interfaces.
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Affiliation(s)
- Shu-Ching Ou
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
| | - Di Cui
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
| | - Matthew Wezowicz
- Department of Computer and Information Sciences, University of Delaware, Newark, Delaware 19716, USA
| | - Michela Taufer
- Department of Computer and Information Sciences, University of Delaware, Newark, Delaware 19716, USA
| | - Sandeep Patel
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
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34
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Zhang J, Zhong J, Li W, Wang M, Liu B, Li Z, Yan Y. Molecular insight into the dynamical adsorption behavior of nanoscale water droplets on a heterogeneous surface. RSC Adv 2015. [DOI: 10.1039/c5ra09296e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
A heterogeneous surface is constructed by adding one hydrophilic patch at the center of a hydrophobic surface, and the dynamical adsorption process of nanoscale water droplets is investigated adopting molecular dynamics simulations.
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Affiliation(s)
- Jun Zhang
- College of Science
- China University of Petroleum
- 266580 Qingdao
- People’s Republic of China
- Key Laboratory of New Energy Physics & Materials Science in Universities of Shandong
| | - Jie Zhong
- College of Science
- China University of Petroleum
- 266580 Qingdao
- People’s Republic of China
- Key Laboratory of New Energy Physics & Materials Science in Universities of Shandong
| | - Wen Li
- College of Science
- China University of Petroleum
- 266580 Qingdao
- People’s Republic of China
- Key Laboratory of New Energy Physics & Materials Science in Universities of Shandong
| | - Muhan Wang
- College of Science
- China University of Petroleum
- 266580 Qingdao
- People’s Republic of China
- Key Laboratory of New Energy Physics & Materials Science in Universities of Shandong
| | - Bing Liu
- College of Science
- China University of Petroleum
- 266580 Qingdao
- People’s Republic of China
- Key Laboratory of New Energy Physics & Materials Science in Universities of Shandong
| | - Zhen Li
- College of Science
- China University of Petroleum
- 266580 Qingdao
- People’s Republic of China
- Key Laboratory of New Energy Physics & Materials Science in Universities of Shandong
| | - Youguo Yan
- College of Science
- China University of Petroleum
- 266580 Qingdao
- People’s Republic of China
- Key Laboratory of New Energy Physics & Materials Science in Universities of Shandong
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35
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Driskill J, Vanzo D, Bratko D, Luzar A. Wetting transparency of graphene in water. J Chem Phys 2014; 141:18C517. [DOI: 10.1063/1.4895541] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Affiliation(s)
- Joshua Driskill
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284-2006, USA
| | - Davide Vanzo
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284-2006, USA
| | - Dusan Bratko
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284-2006, USA
| | - Alenka Luzar
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284-2006, USA
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36
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Zhang B, Wang J, Liu Z, Zhang X. Beyond Cassie equation: local structure of heterogeneous surfaces determines the contact angles of microdroplets. Sci Rep 2014; 4:5822. [PMID: 25059292 PMCID: PMC5376047 DOI: 10.1038/srep05822] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Accepted: 06/30/2014] [Indexed: 11/09/2022] Open
Abstract
The application of Cassie equation to microscopic droplets is recently under intense debate because the microdroplet dimension is often of the same order of magnitude as the characteristic size of substrate heterogeneities, and the mechanism to describe the contact angle of microdroplets is not clear. By representing real surfaces statistically as an ensemble of patterned surfaces with randomly or regularly distributed heterogeneities (patches), lattice Boltzmann simulations here show that the contact angle of microdroplets has a wide distribution, either continuous or discrete, depending on the patch size. The origin of multiple contact angles observed is ascribed to the contact line pinning effect induced by substrate heterogeneities. We demonstrate that the local feature of substrate structure near the contact line determines the range of contact angles that can be stabilized, while the certain contact angle observed is closely related to the contact line width.
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Affiliation(s)
- Bo Zhang
- State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, P. R. China
| | - Jianjun Wang
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Zhiping Liu
- State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, P. R. China
| | - Xianren Zhang
- State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, P. R. China
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37
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Lee K, Kim QH, An S, An J, Kim J, Kim B, Jhe W. Superwetting of TiO2 by light-induced water-layer growth via delocalized surface electrons. Proc Natl Acad Sci U S A 2014; 111:5784-9. [PMID: 24711400 PMCID: PMC4000815 DOI: 10.1073/pnas.1319001111] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Titania, which exhibits superwetting under light illumination, has been widely used as an ideal material for environmental solution such as self-cleaning, water-air purification, and antifogging. There have been various studies to understand such superhydrophilic conversion. The origin of superwetting has not been clarified in a unified mechanism yet, which requires direct experimental investigation of the dynamic processes of water-layer growth. We report in situ measurements of the growth rate and height of the photo-adsorbed water layers by tip-based dynamic force microscopy. For nanocrystalline anatase and rutile TiO2 we observe light-induced enhancement of the rate and height, which decrease after O2 annealing. The results lead us to confirm that the long-range attraction between water molecules and TiO2, which is mediated by delocalized electrons in the shallow traps associated with O2 vacancies, produces photo-adsorption of water on the surface. In addition, molecular dynamics simulations clearly show that such photo-adsorbed water is critical to the zero contact angle of a water droplet spreading on it. Therefore, we conclude that this "water wets water" mechanism acting on the photo-adsorbed water layers is responsible for the light-induced superwetting of TiO2. Similar mechanism may be applied for better understanding of the hydrophilic conversion of doped TiO2 or other photo-catalytic oxides.
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Affiliation(s)
- Kunyoung Lee
- Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 151-747, Korea; and
| | - QHwan Kim
- Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 151-747, Korea; and
| | - Sangmin An
- Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 151-747, Korea; and
| | - JeongHoon An
- Park Systems, Iui-Dong 906-10, Suwon 443-270, Korea
| | - Jongwoo Kim
- Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 151-747, Korea; and
| | - Bongsu Kim
- Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 151-747, Korea; and
| | - Wonho Jhe
- Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 151-747, Korea; and
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38
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Vasumathi V, Cordeiro MND. Molecular dynamics study of mixed alkanethiols covering a gold surface at three different arrangements. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.03.064] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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39
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Patel AJ, Garde S. Efficient Method To Characterize the Context-Dependent Hydrophobicity of Proteins. J Phys Chem B 2014; 118:1564-73. [DOI: 10.1021/jp4081977] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Amish J. Patel
- Department
of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Shekhar Garde
- Howard P. Isermann Department of Chemical & Biological Engineering, and Center for Biotechnology & Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
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40
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Samuel AZ, Ramakrishnan S. Self-adapting peripherally heterofunctionalized hyperbranched polymers: formation of Janus and tripodal structures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:1245-1257. [PMID: 23308366 DOI: 10.1021/la304146r] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A peripherally clickable hyperbranched polyester carrying numerous propargyl terminal groups was prepared by a simple melt transesterification polycondensation of a suitably designed AB(2) monomer; this clickable hyperscaffold was then transformed into a variety of different derivatives by using the Cu-catalyzed azide-yne click reaction. Functionalization of the periphery with equimolar quantities of mutually immiscible segments, such as hydrocarbon, fluorocarbon, and PEG, yielded frustrated molecular systems that readapt and form structures wherein the immiscible segments appear to self-segregate to generate either Janus structures (when two immiscible segments are present) or tripodal structures (when three immiscible segments are present). Evidence for such self-segregation was obtained from a variety of studies, such as differential scanning calorimetry, Langmuir isotherms, AFM imaging, and small-angle X-ray scattering measurements. Crystallization of one or more of the peripheral segments reinforced this self-segregation; the weight-fraction-normalized enthalpies of melting associated with the different domains revealed a competition between the segments to optimize their crystalline organization. When one or more of the segments are amorphous, the remaining segments crystallize more effectively and consequently exhibit a higher melting enthalpy. AFM images of monolayers, transferred from the Langmuir trough, revealed that the thickness matches the expected values; furthermore, contact angle measurements clearly demonstrated that the monolayer films are fairly hydrophobic, and in the case of the tripodal hybramers, the presence of domains of hydrocarbon and fluorocarbon appears to impart nanoscale chemical heterogeneity that is reflected in the strong hysteresis in the advancing and receding contact angles.
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Affiliation(s)
- Ashok Zachariah Samuel
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India
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41
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Vanzo D, Bratko D, Luzar A. Wettability of pristine and alkyl-functionalized graphane. J Chem Phys 2012; 137:034707. [DOI: 10.1063/1.4732520] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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42
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Giovambattista N, Rossky P, Debenedetti P. Computational Studies of Pressure, Temperature, and Surface Effects on the Structure and Thermodynamics of Confined Water. Annu Rev Phys Chem 2012; 63:179-200. [DOI: 10.1146/annurev-physchem-032811-112007] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- N. Giovambattista
- Department of Physics, Brooklyn College of the City University of New York, Brooklyn, New York 11210;
| | - P.J. Rossky
- Institute for Computational Engineering and Sciences, Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712;
| | - P.G. Debenedetti
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544-5263;
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43
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Leroy F, Müller-Plathe F. Can Continuum Thermodynamics Characterize Wenzel Wetting States of Water at the Nanometer Scale? J Chem Theory Comput 2012; 8:3724-32. [PMID: 26593016 DOI: 10.1021/ct300089j] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We address the question of how solid-liquid surface free energy is affected by nanometer scale roughness. We proceed through molecular dynamics calculations of the solid-liquid surface free energy of water in a collapsed wetting state on rough nonpolar surfaces characterized by an array of parallel linear grooves. We establish a continuum equation based on Wenzel and Cassie-Baxter approaches to predict the solid-liquid surface free energy variations of systems, where the vertical and horizontal surfaces of the groove have different interactions with water and where the groove geometry can be varied. We show that the molecular simulations results agree with the prediction of the continuum equation under the condition that the groove is wider than three water molecular diameters and deeper than one molecular diameter.
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Affiliation(s)
- Frédéric Leroy
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt , Petersenstrasse 22, 64287 Darmstadt, Germany
| | - Florian Müller-Plathe
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt , Petersenstrasse 22, 64287 Darmstadt, Germany
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44
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Milne AJB, Amirfazli A. The Cassie equation: how it is meant to be used. Adv Colloid Interface Sci 2012; 170:48-55. [PMID: 22257682 DOI: 10.1016/j.cis.2011.12.001] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Revised: 12/06/2011] [Accepted: 12/06/2011] [Indexed: 11/28/2022]
Abstract
A review of literature shows that the majority of papers cite a potentially incorrect form of the Cassie and Cassie-Baxter equations to interpret or predict contact angle data. We show that for surfaces wet with a composite interface, the commonly used form of the Cassie-Baxter equation, cosθ(c)=f(1)cosθ-(1-f), is only correct for the case of flat topped pillar geometry without any penetration of the liquid. In general, the original form of the Cassie-Baxter equation, cosθ(c)=f(1)cosθ(1)-f(2), with f(1)+f(2)≥1, should be used. The differences between the two equations are discussed and the errors involved in using the incorrect equation are estimated to be between ~3° and 13° for superhydrophobic surfaces. The discrepancies between the two equations are also discussed for the case of a liquid undergoing partial, but increasing, levels of penetration. Finally, a general equation is presented for the transition/stability criterion between the Cassie-Baxter and Wenzel modes of wetting.
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Affiliation(s)
- A J B Milne
- Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2G8
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45
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Steinacher A, Soyer OS. Evolutionary principles underlying structure and response dynamics of cellular networks. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 751:225-47. [PMID: 22821461 DOI: 10.1007/978-1-4614-3567-9_11] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The network view in systems biology, in conjunction with the continuing development of experimental technologies, is providing us with the key structural and dynamical features of both cell-wide and pathway-level regulatory, signaling and metabolic systems. These include for example modularity and presence of hub proteins at the structural level and ultrasensitivity and feedback control at the level of dynamics. The uncovering of such features, and the seeming commonality of some of them, makes many systems biologists believe that these could represent design principles that underpin cellular systems across organisms. Here, we argue that such claims on any observed feature requires an understanding of how it has emerged in evolution and how it can shape subsequent evolution. We review recent and past studies that aim to achieve such evolutionary understanding for observed features of cellular networks. We argue that this evolutionary framework could lead to deciphering evolutionary origin and relevance of proposed design principles, thereby allowing to predict their presence or absence in an organism based on its environment and biochemistry and their effect on its future evolution.
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Affiliation(s)
- Arno Steinacher
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK.
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46
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47
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Acharya H, Mozdzierz NJ, Keblinski P, Garde S. How Chemistry, Nanoscale Roughness, and the Direction of Heat Flow Affect Thermal Conductance of Solid–Water Interfaces. Ind Eng Chem Res 2011. [DOI: 10.1021/ie2010274] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hari Acharya
- Howard P. Isermann Department of Chemical and Biological Engineering, and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Nicholas J. Mozdzierz
- Howard P. Isermann Department of Chemical and Biological Engineering, and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Pawel Keblinski
- Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Shekhar Garde
- Howard P. Isermann Department of Chemical and Biological Engineering, and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
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48
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Yang S, Pelton R. Nanoparticle flotation collectors II: the role of nanoparticle hydrophobicity. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:11409-11415. [PMID: 21830818 DOI: 10.1021/la202751y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The ability of polystyrene nanoparticles to facilitate the froth flotation of glass beads was correlated to the hydrophobicity of the nanoparticles. Contact angle measurements were used to probe the hydrophobicity of hydrophilic glass surfaces decorated with hydrophobic nanoparticles. Both sessile water drop advancing angles, θ(a), and attached air bubble receding angle measurements, θ(r), were performed. For glass surfaces saturated with adsorbed nanoparticles, flotation recovery, a measure of flotation efficiency, increased with increasing values of each type of contact angle. As expected, the advancing water contact angle on nanoparticle-decorated, dry glass surfaces increased with surface coverage, the area fraction of glass covered with nanoparticles. However, the nanoparticles were far more effective at raising the contact angle than the Cassie-Baxter prediction, suggesting that with higher nanoparticle coverages the water did not completely wet the glass surfaces between the nanoparticles. A series of polystyrene nanoparticles was prepared to cover a range of surface energies. Water contact angle measurements, θ(np), on smooth polymer films formed from organic solutions of dissolved nanoparticles were used to rank the nanoparticles in terms of hydrophobicity. Glass spheres were saturated with adsorbed nanoparticles and were isolated by flotation. The minimum nanoparticle water contact angle to give high flotation recovery was in the range of 51° < θ(np(min)) ≤ 85°.
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Affiliation(s)
- Songtao Yang
- Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7
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49
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Daub CD, Bratko D, Luzar A. Nanoscale Wetting Under Electric Field from Molecular Simulations. MULTISCALE MOLECULAR METHODS IN APPLIED CHEMISTRY 2011; 307:155-79. [DOI: 10.1007/128_2011_188] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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50
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Wang J, Kudesia S, Bratko D, Luzar A. Computational probe of cavitation events in protein systems. Phys Chem Chem Phys 2011; 13:19902-10. [PMID: 21922115 DOI: 10.1039/c1cp22082a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Jihang Wang
- Department of Chemistry, Virginia Commonwealth University, Richmond, VA 23284-2006, USA
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