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Nguyen NP, Laird BB. Generation of Amorphous Silica Surfaces with Controlled Roughness. J Phys Chem A 2023; 127:9831-9841. [PMID: 37938899 DOI: 10.1021/acs.jpca.3c04955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
Amorphous silica (a-SiO2) surfaces, when grafted with select metals on the active sites of the functionalized surfaces, can act as useful heterogeneous catalysts. From a molecular modeling perspective, one challenge has been generating a-SiO2 slab models with controllable surface roughness to facilitate the study of the effect of surface morphology on the material properties. Previous computational methods either generate relatively flat surfaces or periodically corrugated surfaces that do not mimic the full range of potential surface roughness of the amorphous silica material. In this work, we present a new method, inspired by the capillary fluctuation theory of interfaces, in which rough silica slabs are generated by cleaving a bulk amorphous sample using a cleaving plane with Fourier components randomly generated from a Gaussian distribution. The width of this Gaussian distribution (and thus the degree of surface roughness) can be tuned by varying the surface roughness parameter α. Using the van Beest, Kramer, and van Santen (BKS) force field, we create a large number of silica slabs using cleaving surfaces of varying roughness (α) and using two different system sizes. These surfaces are then characterized to determine their roughness (mean-squared displacement), density profile, and ring size distribution. This analysis shows a higher concentration of surface defects (under-/overcoordinated atoms and strained rings) as the surface roughness increases. To examine the effect of the roughness on surface reactivity, we re-equilibriate a subset of these slabs using the reactive force field ReaxFF and then expose the slabs to water and observe the formation of surface silanols. We observe that the rougher surfaces exhibit higher silanol concentrations as well as bimodal acidity.
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Affiliation(s)
- Nuong P Nguyen
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
- Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, Kansas 66045, United States
| | - Brian B Laird
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
- Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, Kansas 66045, United States
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2
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Han Y, Slowing II, Evans JW. Surface structure of linear nanopores in amorphous silica: Comparison of properties for different pore generation algorithms. J Chem Phys 2020; 153:124708. [PMID: 33003732 DOI: 10.1063/5.0021317] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
We compare the surface structure of linear nanopores in amorphous silica (a-SiO2) for different versions of "pore drilling" algorithms (where the pores are generated by the removal of atoms from the preformed bulk a-SiO2) and for "cylindrical resist" algorithms (where a-SiO2 is formed around a cylindrical exclusion region). After adding H to non-bridging O, the former often results in a moderate to high density of surface silanol groups, whereas the latter produces a low density. The silanol surface density for pore drilling can be lowered by a final dehydroxylation step, and that for the cylindrical resist approach can be increased by a final hydroxylation step. In this respect, the two classes of algorithms are complementary. We focus on the characterization of the chemical structure of the pore surface, decomposing the total silanol density into components corresponding to isolated and vicinal mono silanols and geminal silanols. The final dehyroxylation and hydroxylation steps can also be tuned to better align some of these populations with the target experimental values.
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Affiliation(s)
- Yong Han
- Division of Chemical and Biological Sciences, Ames Laboratory, USDOE, Iowa State University, Ames, Iowa 50011, USA
| | - Igor I Slowing
- Division of Chemical and Biological Sciences, Ames Laboratory, USDOE, Iowa State University, Ames, Iowa 50011, USA
| | - James W Evans
- Division of Chemical and Biological Sciences, Ames Laboratory, USDOE, Iowa State University, Ames, Iowa 50011, USA
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3
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Zhang M, Jiang B, Chen C, Drummer D, Zhai Z. The Effect of Temperature and Strain Rate on the Interfacial Behavior of Glass Fiber Reinforced Polypropylene Composites: A Molecular Dynamics Study. Polymers (Basel) 2019; 11:E1766. [PMID: 31717858 PMCID: PMC6918261 DOI: 10.3390/polym11111766] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 10/23/2019] [Accepted: 10/25/2019] [Indexed: 11/26/2022] Open
Abstract
To make better use of fiber reinforced polymer composites in automotive applications, a clearer knowledge of its interfacial properties under dynamic and thermal loadings is necessary. In the present study, the interfacial behavior of glass fiber reinforced polypropylene (PP) composites under different loading temperatures and strain rates were investigated via molecular dynamics simulation. The simulation results reveal that PP molecules move easily to fit tensile deformation at higher temperatures, resulting in a lower interfacial strength of glass fiber-PP interface. The interfacial strength is enhanced with increasing strain rate because the atoms do not have enough time to relax at higher strain rates. In addition, the non-bonded interaction energy plays a crucial role during the tensile deformation of composites. The damage evolution of glass fiber-PP interface follows Weibull's distribution. At elevated temperatures, tensile loading is more likely to cause cohesive failure because the mechanical property of PP is lower than that of the glass fiber-PP interface. However, at higher strain rates, the primary failure mode is interfacial failure because the strain rate dependency of PP is more pronounced than that of the glass fiber-PP interface. The relationship between the failure modes and loading conditions obtained by molecular dynamics simulation is consistent with the author's previous experimental studies.
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Affiliation(s)
- Muhan Zhang
- State Key Laboratory of High Performance and Complex Manufacturing, Light Alloy Research Institute, Central South University, Lushan South Road 932, Changsha 410083, China; (M.Z.); (B.J.); (C.C.)
| | - Bingyan Jiang
- State Key Laboratory of High Performance and Complex Manufacturing, Light Alloy Research Institute, Central South University, Lushan South Road 932, Changsha 410083, China; (M.Z.); (B.J.); (C.C.)
| | - Chao Chen
- State Key Laboratory of High Performance and Complex Manufacturing, Light Alloy Research Institute, Central South University, Lushan South Road 932, Changsha 410083, China; (M.Z.); (B.J.); (C.C.)
| | - Dietmar Drummer
- Friedrich-Alexander-University Erlangen-Nürnberg, Institute of Polymer Technology, Am Weichselgarten 9, D-91058 Erlangen, Germany;
| | - Zhanyu Zhai
- State Key Laboratory of High Performance and Complex Manufacturing, Light Alloy Research Institute, Central South University, Lushan South Road 932, Changsha 410083, China; (M.Z.); (B.J.); (C.C.)
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4
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Uddin SMM, Harper RJ, Henry DJ. Contribution of Binary Organic Layers to Soil Water Repellency: A Molecular Level Perspective. J Phys Chem A 2019; 123:7518-7527. [PMID: 31365257 DOI: 10.1021/acs.jpca.9b04033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Soil water repellency (SWR) is an extensively occurring phenomenon on natural and agricultural soils with a severe impact on soil water relations and thus crop yields and ecosystem productivity. It is caused by long chain amphiphilic compounds that originate from plant cuticular waxes. However, the severity of SWR varies with soil physical properties and the concentration of the compounds closely associated with producing hydrophobic coatings on soil surfaces. The induction of SWR by hexadecane, isopropyl tetradecanoate, and palmitic acid (PA), as pure (individual) coatings and as coatings composed of binary mixtures, was investigated by applying a range of loadings on acid-washed sand (AWS) (300-500 μm diameter) and AWS with 5% kaolinite. Molarity of ethanol droplet (MED) tests were conducted to assess the severity of SWR. Palmitic acid was very effective at inducing SWR at loadings of >0.5 × 10-6 mol g-1. Hexadecane and isopropyl tetradecanoate had no effect on SWR when applied as single component coatings. However, when hexadecane was combined with palmitic acid, it enhanced the SWR effect of palmitic acid. In comparison, isopropyl tetradecanoate was found to partially mitigate the SWR caused by palmitic acid. The experimental measurements of SWR were complemented by fully atomistic molecular dynamics simulations that suggested variations of SWR could be explained through molecular level interactions, packing on different soil mineral surfaces and the surface characteristics of the mineral surfaces. In addition, H-donor interactions of PA were found to be instrumental in intermolecular and surface interactions. Furthermore, cohesion and packing of hydrocarbon chains were found to be important parameters favoring surface adhesion, which in turn led to the formation of hydrophobic molecular coatings. The finding that ester derivatives of long chain fatty acids do not induce water repellency suggests that the introduction of chemical or biological processes that promote esterification of fatty acids could be a mechanism for reducing soil water repellency in agricultural soils.
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Affiliation(s)
- S M Mijan Uddin
- College of Science, Health, Engineering and Education , Murdoch University , Murdoch , WA 6150 , Australia.,Institute of Forestry and Environmental Sciences , University of Chittagong , Chittagong 4331 , Bangladesh
| | - Richard J Harper
- College of Science, Health, Engineering and Education , Murdoch University , Murdoch , WA 6150 , Australia
| | - David J Henry
- College of Science, Health, Engineering and Education , Murdoch University , Murdoch , WA 6150 , Australia
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5
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López-Laurrabaquio G, Fernández-García ME, Montejano-Carrizales JM, Morín-Martínez DA, Díaz Torrejón C. Generation and study of a relatively large amorphous silica surface in the liquid phase. MOLECULAR SIMULATION 2019. [DOI: 10.1080/08927022.2019.1569761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Guadalupe López-Laurrabaquio
- Depto. de Física, Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca s/n, Ocoyoacac, Mexico
| | - María E. Fernández-García
- Depto. De Tecnología de Materiales, Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca s/n, Ocoyoacac, Mexico
| | | | - David A Morín-Martínez
- Centro Nacional de Supercomputo, Instituto Potosino de Investigación Científica y Tecnológica, San Luis Potosí, Mexico
| | - Cesar Díaz Torrejón
- Laboratorio Nacional de Supercomputo del Sureste de México, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
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6
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Fossati PCM, Rushton MJD, Lee WE. Atomic-scale description of interfaces in rutile/sodium silicate glass-crystal composites. Phys Chem Chem Phys 2018; 20:17624-17636. [PMID: 29926862 DOI: 10.1039/c8cp00675j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this work interfaces between (Na2O)x(SiO2)1-x glasses (for x = 0.0, 0.1 and 0.2) and TiO2 crystals are simulated using molecular dynamics and empirical potentials. Interfaces are presented for the distinct terminating surfaces of TiO2 with Miller indices ≤2, the properties of which have been investigated using atomistic models. Simulations showed that partially ordered layers had been induced in the glass close to the interfaces, with successive oxygen-rich and cation-rich planes being noted. The first silicate layer in contact with the crystal tended to be highly-structured, with Si ions occupying well-defined positions that depend on the orientation of the crystal at the interface, and showing 2-dimensional ordering depending on glass composition. Finally, interface energies were calculated. These indicated that the interface formation may stabilise a crystal surface in comparison to maintaining a free surface. Results are presented suggesting that the structural flexibility of the glass network allows it to conform to the crystal, thereby providing charge compensation and avoiding large relaxation of the crystal structure close to the interfaces. Such interfacial properties could be crucial to improving phenomenological models of glass-crystal composite properties.
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Affiliation(s)
- Paul C M Fossati
- Department of Materials, Imperial College London, London SW7 2AZ, UK.
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7
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Halbert S, Ispas S, Raynaud C, Eisenstein O. Modelling the surface of amorphous dehydroxylated silica: the influence of the potential on the nature and density of defects. NEW J CHEM 2018. [DOI: 10.1039/c7nj03922k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The nature and density of defects on the amorphous dehydroxylated silica surface are studied by molecular dynamics for information on the silanol groups of pretreated silica.
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Affiliation(s)
| | - Simona Ispas
- Laboratoire Charles Coulomb (L2C)
- UMR 5221
- Univ. Montpellier
- CNRS
- Montpellier
| | | | - Odile Eisenstein
- Institut Charles Gerhardt (ICGM)
- UMR 5253
- Univ. Montpellier
- CNRS
- ENSCM
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8
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Rimsza JM, Jones RE, Criscenti LJ. Surface Structure and Stability of Partially Hydroxylated Silica Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:3882-3891. [PMID: 28375622 DOI: 10.1021/acs.langmuir.7b00041] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Surface energies of silicates influence crack propagation during brittle fracture and decrease with surface relaxation caused by annealing and hydroxylation. Molecular-level simulations are particularly suited for the investigation of surface processes. In this work, classical MD simulations of silica surfaces are performed with two force fields (ClayFF and ReaxFF) to investigate the effect of force field reactivity on surface structure and energy as a function of surface hydroxylation. An unhydroxylated fracture surface energy of 5.1 J/m2 is calculated with the ClayFF force field, and 2.0 J/m2 is calculated for the ReaxFF force field. The ClayFF surface energies are consistent with the experimental results from double cantilever beam fracture tests (4.5 J/m2), whereas ReaxFF underestimated these surface energies. Surface relaxation via annealing and hydroxylation was performed by creating a low-energy equilibrium surface. Annealing condensed neighboring siloxane bonds increased the surface connectivity, and decreased the surface energies by 0.2 J/m2 for ClayFF and 0.8 J/m2 for ReaxFF. Posthydroxylation surface energies decreased further to 4.6 J/m2 with the ClayFF force field and to 0.2 J/m2 with the ReaxFF force field. Experimental equilibrium surface energies are ∼0.35 J/m2, consistent with the ReaxFF force field. Although neither force field was capable of replicating both the fracture and equilibrium surface energies reported from experiment, each was consistent with one of these conditions. Therefore, future computational investigations that rely on accurate surface energy values should consider the surface state of the system and select the appropriate force field.
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Affiliation(s)
- J M Rimsza
- Geochemistry Department, Sandia National Laboratories , Albuquerque, New Mexico 87185, United States
| | - R E Jones
- Science-Based Material Modeling Department, Sandia National Laboratories , Livermore, California 94551, United States
| | - L J Criscenti
- Geochemistry Department, Sandia National Laboratories , Albuquerque, New Mexico 87185, United States
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9
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Kumar S, Parks D, Kamrin K. Mechanistic Origin of the Ultrastrong Adhesion between Graphene and a-SiO2: Beyond van der Waals. ACS NANO 2016; 10:6552-6562. [PMID: 27347793 DOI: 10.1021/acsnano.6b00382] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The origin of the ultrastrong adhesion between graphene and a-SiO2 has remained a mystery. This adhesion is believed to be predominantly van der Waals (vdW) in nature. By rigorously analyzing recently reported blistering and nanoindentation experiments, we show that the ultrastrong adhesion between graphene and a-SiO2 cannot be attributed to vdW forces alone. Our analyses show that the fracture toughness of the graphene/a-SiO2 interface, when the interfacial adhesion is modeled with vdW forces alone, is anomalously weak compared to the measured values. The anomaly is related to an ultrasmall fracture process zone (FPZ): owing to the lack of a third dimension in graphene, the FPZ for the graphene/a-SiO2 interface is extremely small, and the combination of predominantly tensile vdW forces, distributed over such a small area, is bound to result in a correspondingly small interfacial fracture toughness. Through multiscale modeling, combining the results of finite element analysis and molecular dynamics simulations, we show that the adhesion between graphene and a-SiO2 involves two different kinds of interactions: one, a weak, long-range interaction arising from vdW adhesion and, second, discrete, short-range interactions originating from graphene clinging to the undercoordinated Si (≡Si·) and the nonbridging O (≡Si-O·) defects on a-SiO2. A strong resistance to relative opening and sliding provided by the latter mechanism is identified as the operative mechanism responsible for the ultrastrong adhesion between graphene and a-SiO2.
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Affiliation(s)
- Sandeep Kumar
- Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - David Parks
- Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Ken Kamrin
- Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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10
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Kulsing C, Nolvachai Y, Marriott PJ, Boysen RI, Matyska MT, Pesek JJ, Hearn MTW. Insights into the Origin of the Separation Selectivity with Silica Hydride Adsorbents. J Phys Chem B 2015; 119:3063-9. [DOI: 10.1021/jp5103753] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chadin Kulsing
- School
of Chemistry, Monash University, Melbourne, VIC 3800, Australia
| | - Yada Nolvachai
- School
of Chemistry, Monash University, Melbourne, VIC 3800, Australia
- Australian
Centre for Research on Separation Science, School of Chemistry, Monash University, Melbourne, VIC 3800, Australia
| | - Philip J. Marriott
- School
of Chemistry, Monash University, Melbourne, VIC 3800, Australia
- Australian
Centre for Research on Separation Science, School of Chemistry, Monash University, Melbourne, VIC 3800, Australia
| | | | - Maria T. Matyska
- Department
of Chemistry, San Jose State University, San Jose, California 95192, United States
| | - Joseph J. Pesek
- Department
of Chemistry, San Jose State University, San Jose, California 95192, United States
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11
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Yiapanis G, Maclaughlin S, Evans EJ, Yarovsky I. Nanoscale wetting and fouling resistance of functionalized surfaces: a computational approach. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:10617-10625. [PMID: 25141225 DOI: 10.1021/la500114k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A computational modeling methodology has been developed and employed to characterize the nanoscale wettability and antifouling properties of functionalized hard and deformable surfaces, with a specific focus on poly(ethylene glycol) grafted substrates and their resistance to graphitic carbons. Empirical evidence suggests that the antifouling behavior of polyethylene PEG is associated with two main mechanisms: steric repulsions and hydration via formation of a structured water layer. However, there is also little attention paid to the contribution of steric repulsion vs surface hydration. We examine these two mechanisms through a combination of in silico contact angle and force measurements at the nanoscale level. We investigate the properties of the grafted functional chains and the underlying substrate, responsible for resisting surface deposition of graphitic contaminants in aqueous solution. Our results reveal that the fouling-release efficiency is enhanced when PEG chains are grafted onto hard hydrophilic substrates such as silica in contrast to deformable polymer substrates where surface modifications are effectively mitigated during interfacial contact with a hard contaminant. We conclude that the contribution of steric repulsion vs surface hydration to the antifouling ability of surfaces is strongly dependent on the nanoscale structure and deformability of the substrate. This generic method can be applied to examine individual contribution of steric repulsions and surface hydration to antifouling performance of grafted chains.
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Affiliation(s)
- George Yiapanis
- School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University , GPO BOX 2476, Melbourne, Victoria 3001, Australia
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12
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Landers J, Gor GY, Neimark AV. Density functional theory methods for characterization of porous materials. Colloids Surf A Physicochem Eng Asp 2013. [DOI: 10.1016/j.colsurfa.2013.01.007] [Citation(s) in RCA: 768] [Impact Index Per Article: 69.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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13
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Carofalini SH, Melman H. Applications of Molecular Dynamics Simulations to Sol-Gel Processing. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-73-497] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTThe molecular dynamics computer simulation technique has been used to study silicic acid and pyrosilicic acid molecules (H4 SiO4 and H6 Si 2 O7, respectively). The structure of the simulated molecules are compared to those found by molecular orbital calculations as well as structures inferred from silicate hydrates. The potentials used to simulate the molecules were also used in simulations of bulk silicates and compared with experimental data. Results indicate good correlation.
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14
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Levine SM, Garofalini SH. Surface Structure of Silica Glasses by Molecular Dynamics Simulations. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-61-29] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTMolecular dynamics computer simulations were used to study surfaces of pure silica glass. The potentials used here were those previously established to model bulk silica and have been extended to study surface relaxation in a perfect vacuum. A large number of surfaces were made using different starting configurations; system sizes, and cooling procedures. Following “fracture”, many broken bonds rearranged in response to the changes in the net forces in the surface region. After this reconstruction, the simulations showed the expected general features observed experimentally, such as a prevalence of oxygen atoms at the outermost surface, non-bridging oxygens, and strained siloxane bonds. Three fold silicons (similar to e’ centers) were initially present in the “fractured” surfaces but most often were incorporated into the network tetrahedrally after reconstruction. Other defects produced during the reconstruction were five coordinated silicons and more importantly, edge sharing tetrahedra, forming the strained siloxane bonds. Bond angles and bond lengths for each defect were determined, showing good agreement with previously published results as well as providing new information. Finally, estimations for silanol concentrations were made which compare well with experimentally determined coverages. The computer simulation technique used here adequately reproduces many of the structural and dynamic characteristics of silica glass surfaces.
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15
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Abstract
Molecular dynamics simulation of amorphous SiO2 spherical nanoparticles has been carried out in a model with different sizes, 2, 4, and 6 nm, under non-periodic boundary conditions. We use the pair interatomic potentials which have weak Coulomb interaction and Morse type short-range interaction. Models have been obtained by cooling from the melt via molecular dynamics (MD) simulation. Structural properties of amorphous nanoparticles obtained at 350 K have been studied via partial radial distribution functions (PRDFs), mean interatomic distances, coordination numbers, and bond-angle distributions, which are compared with those observed in the bulk. Calculations of the radial density profile in nanoparticles show the tendency of oxygen to concentrate at the surface as observed previously in other amorphous clusters or thin films. Size effects on structure of nanosized models are significant. The calculations show that if the size is larger than 4 nm, amorphous SiO2 nanoparticles have a distorted tetrahedral network structure with the mean coordination number ZSi-O approximately 4.0 and ZO-Si approximately 2.0 like those observed in the bulk. Surface structure, surface energy, and glass transition temperature of SiO2 nanoparticles have been obtained and presented.
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Affiliation(s)
- Vo Van Hoang
- Department of Physics, Institute of Technology, National University of HochiMinh City, 268 Ly Thuong Kiet, District 10, HochiMinh City, Vietnam.
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16
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Robertson JWF, Tiani DJ, Pemberton JE. Underpotential deposition of thallium, lead, and cadmium at silver electrodes modified with self-assembled monolayers of (3-mercaptopropyl)trimethoxysilane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:4651-61. [PMID: 17346068 DOI: 10.1021/la063137x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Investigation of the underpotential deposition (UPD) of three metals-Tl, Pb, and Cd-on Ag surfaces modified with self-assembled monolayers (SAMs) of (3-mercaptopropyl)trimethoxysilane (3MPT) is reported. On the basis of the observation of negative potential shifts for their UPD processes, Tl and Pb undergo UPD directly on the underlying Ag surface by insertion between the Ag-S bond. This process is proposed to occur by penetration of the 3MPT monolayer by hydrated metal ions through spaces in six-membered siloxane rings that form at the terminus of the 3MPT layer after hydrolysis and condensation. In contrast, Cd does not undergo similarly facile UPD at 3MPT-modified Ag electrodes due to a hydrated ion size too large to fit through these openings. The voltammetric evidence that suggests that the hydrated metal cation size, as described by the Stokes diameter, is the primary determinant of Ag electrode accessibility for UPD through the cross-linked 3MPT layer is further supported by molecular mechanics energy minimization computations of six-membered siloxane rings on each of the three low-index faces of Ag. Finally, the 3MPT monolayer is shown to be exceptionally stable to repeated UPD/stripping cycles of Tl and Pb in contrast to SAMs of similar thickness formed from normal alkanethiols.
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Affiliation(s)
- Joseph W F Robertson
- Department of Chemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, USA
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Ravikovitch PI, Neimark AV. Density functional theory model of adsorption on amorphous and microporous silica materials. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:11171-9. [PMID: 17154599 DOI: 10.1021/la0616146] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
We present a novel quenched solid density functional theory (QSDFT) model of adsorption on heterogeneous surfaces and porous solids, which accounts for the effects of surface roughness and microporosity. Within QSDFT, solid atoms are considered as quenched component(s) of the solid-fluid system with given density distribution(s). Solid-fluid intermolecular interactions are split into hard-sphere repulsive and mean-field attractive parts. The former are treated with the multicomponent fundamental measure density functional. Capabilities of QSDFT are demonstrated by drawing on the example of adsorption on amorphous silica materials. We show that, using established intermolecular potentials and a realistic model for silica surfaces, QSDFT quantitatively describes adsorption/desorption isotherms of Ar and Kr on reference MCM-41, SBA-15, and LiChrosphere materials in a wide range of relative pressures. QSDFT offers a systematic approach to the practical problems of characterization of microporous, mesoporous, and amorphous silica materials, including an assessment of microporosity, surface roughness, and adsorption deformation. Predictions for the pore diameter and the extent of pore surface roughness in MCM-41 and SBA-15 materials are in very good agreement with recent X-ray diffraction studies.
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Affiliation(s)
- Peter I Ravikovitch
- Center for Modeling and Characterization of Nanoporous Materials, TRI/Princeton, 601 Prospect Avenue, Princeton, NJ 08540, USA.
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20
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Henry DJ, Evans E, Yarovsky I. Classical Molecular Dynamics Study of [60]Fullerene Interactions with Silica and Polyester Surfaces. J Phys Chem B 2006; 110:15963-72. [PMID: 16898752 DOI: 10.1021/jp0622886] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This study examines the interaction of neutral and charged fullerenes with model silica and polyester surfaces. Molecular dynamics simulations at 298 K indicate that van der Waals forces are sufficiently strong in most cases to cause physisorption of the neutral fullerene particle onto the surfaces. The fullerenes are unable to penetrate the rigid silica surface but are generally able to at least partially infiltrate the flexible polymer surface by opening surface cavities. The introduction of charge to the fullerene generally leads to an increase in both the separation distance and Work of Separation with silica. However, the charged fullerenes generally exhibit significantly closer and stronger interactions with polyester films, with a distinct tendency to absorb into the "bulk" of the polymer. The separation distance and Work of Separation of C60 with each of the surfaces also depend greatly on the sign, magnitude, and localization of the charge on the particle. Cross-linking of the polyester can improve resistance to the neutral fullerene. Functionalization of the polyester surface (F and OH substituents) has been shown to prevent the C60 from approaching as close to the polyester surface. Fluorination leads to improved resistance to positively charged fullerenes, compared to the unmodified polyester. However, hydroxylation generally enables greater adhesion of charged fullerenes to the surface due to H-bonding and electrostatic attraction.
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Affiliation(s)
- David J Henry
- School of Applied Sciences, RMIT University, GPO Box 2476V, Victoria, 3001, Australia
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Chang W, Lee TY. Molecular dynamics simulation of gas permeation phenomena in a microporous silica membrane. Chem Eng Sci 2006. [DOI: 10.1016/j.ces.2006.01.037] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Yang X, Xu Z, Zhang C. Molecular dynamics simulation of dense carbon dioxide fluid on amorphous silica surfaces. J Colloid Interface Sci 2006; 297:38-44. [PMID: 16325840 DOI: 10.1016/j.jcis.2005.10.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Revised: 10/03/2005] [Accepted: 10/03/2005] [Indexed: 11/21/2022]
Abstract
Molecular dynamics (MD) simulations of dense carbon dioxide on the amorphous dehydroxylated silica surfaces have been carried out. The adsorption potential surfaces of the silica solids have been obtained in order to evaluate the characteristics of the amorphous surfaces. The atom density profiles, adsorption free energy profiles, surface orientation order parameters, and radial distribution functions for the CO2 molecules have been presented in order to study the effect of the amorphous surfaces on the microscopic interfacial structure properties of the CO2 molecules. The translational diffusion and orientation rotation at silica surfaces have also been investigated. It was observed that there is marked hindrance of the translational diffusion and orientation rotation of CO2 molecules near amorphous silica surfaces.
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Affiliation(s)
- Xiaoning Yang
- Key Laboratory of Material-Orientated Chemical Engineering of Jiangsu Province, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009, People's Republic of China.
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Vyas S, Dickinson J, Armstrong-Poston E. Towards an understanding of the behavior of silanes on glass: an atomistic simulation study of glass surfaces. MOLECULAR SIMULATION 2006. [DOI: 10.1080/08927020600654637] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Henry DJ, Lukey CA, Evans E, Yarovsky I. Theoretical study of adhesion between graphite, polyester and silica surfaces. MOLECULAR SIMULATION 2005. [DOI: 10.1080/089270412331332712] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Chang W, Lee TY. Observation of adsorption and permeation phenomena in silica membrane system through molecular dynamics simulation. Comput Chem Eng 2004. [DOI: 10.1016/j.compchemeng.2004.07.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Wilson M, Walsh TR. Hydrolysis of the amorphous silica surface. I. Structure and dynamics of the dry surface. J Chem Phys 2000. [DOI: 10.1063/1.1320056] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Walsh TR, Wilson M, Sutton AP. Hydrolysis of the amorphous silica surface. II. Calculation of activation barriers and mechanisms. J Chem Phys 2000. [DOI: 10.1063/1.1320057] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Civalleri B, Ugliengo P. First Principles Calculations of the Adsorption of NH3 on a Periodic Model of the Silica Surface. J Phys Chem B 2000. [DOI: 10.1021/jp002353q] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Bartolomeo Civalleri
- Dipartimento di Chimica IFM, Università di Torino, Via P. Giuria, 7, 10125 Torino, Italy
| | - Piero Ugliengo
- Dipartimento di Chimica IFM, Università di Torino, Via P. Giuria, 7, 10125 Torino, Italy
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Bakaev VA, Steele WA. On the computer simulation of a hydrophobic vitreous silica surface. J Chem Phys 1999. [DOI: 10.1063/1.480317] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Lopez N, Illas F, Pacchioni G. Adsorption of Cu, Pd, and Cs Atoms on Regular and Defect Sites of the SiO2 Surface. J Am Chem Soc 1999. [DOI: 10.1021/ja981753c] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nuria Lopez
- Contribution from the Istituto Nazionale di Fisica della Materia, Dipartimento di Scienza dei Materiali, Università di Milano, via Emanueli, 15, 20126 Milano, Italy, and Departament de Quimica Fisica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona, Spain
| | - Francesc Illas
- Contribution from the Istituto Nazionale di Fisica della Materia, Dipartimento di Scienza dei Materiali, Università di Milano, via Emanueli, 15, 20126 Milano, Italy, and Departament de Quimica Fisica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona, Spain
| | - Gianfranco Pacchioni
- Contribution from the Istituto Nazionale di Fisica della Materia, Dipartimento di Scienza dei Materiali, Università di Milano, via Emanueli, 15, 20126 Milano, Italy, and Departament de Quimica Fisica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona, Spain
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van den Oetelaar LCA, Partridge A, Toussaint SLG, Flipse CFJ, Brongersma HH. A Surface Science Study of Model Catalysts. 2. Metal−Support Interactions in Cu/SiO2 Model Catalysts. J Phys Chem B 1998. [DOI: 10.1021/jp9829997] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- L. C. A. van den Oetelaar
- Faculty of Physics and Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - A. Partridge
- Faculty of Physics and Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - S. L. G. Toussaint
- Faculty of Physics and Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - C. F. J. Flipse
- Faculty of Physics and Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - H. H. Brongersma
- Faculty of Physics and Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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Yablonskii GS, Kundirenko DV, Kulabukhova LA, Barash NY. Modelling structural changes in the near-surface region in amorphous silica. THEOR EXP CHEM+ 1995. [DOI: 10.1007/bf00536136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Plata J, Breton J, Alvira E, Delgado V, Girardet C. Surface effects on the electrodiffusion of alkali-metal ions and protons in quartz. PHYSICAL REVIEW. B, CONDENSED MATTER 1991; 43:5053-5062. [PMID: 9997883 DOI: 10.1103/physrevb.43.5053] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Feuston BP, Garofalini SH. Topological and bonding defects in vitreous silica surfaces. J Chem Phys 1989. [DOI: 10.1063/1.457440] [Citation(s) in RCA: 130] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Levine SM, Garofalini SH. Computer simulation of interactions of model Pt particles and films with the silica surface. J Chem Phys 1988. [DOI: 10.1063/1.454244] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Girard C, Girardet C. Self‐consistent interaction potential for a molecule adsorbed on a dielectric surface: A symmetric top molecule on an ionic crystal. J Chem Phys 1987. [DOI: 10.1063/1.452395] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Interaction between the optical isomers of two samples of α and β quartz - chiral discrimination. Chem Phys 1987. [DOI: 10.1016/0301-0104(87)80005-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Levine SM, Garofalini SH. A structural analysis of the vitreous silica surface via a molecular dynamics computer simulation. J Chem Phys 1987. [DOI: 10.1063/1.452054] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Vega L, Breton J, Girardet C, Galatry L. Interaction potential and chiral discrimination between an alanine molecule and a quartz surface. J Chem Phys 1986. [DOI: 10.1063/1.450670] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kobashi K, Etters RD. Theoretical study of the surface structures and vibrations of solid α‐N2 a). J Chem Phys 1985. [DOI: 10.1063/1.448827] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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