Molecular Dynamics Simulation of a Binary Hydrocarbon Mixture near an Adsorbing Wall:  Benzene/<i>n</i>-Heptane on Graphite

Fodi, B.; Hentschke, Reinhard

doi:10.1021/la9706983

Cited by 6 publications

(6 citation statements)

References 52 publications

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“…However, we cannot discount that favorable interactions between defects and the tripod could account for slowing down its surface mobility. The value obtained here is also at least 3 orders of magnitude lower than that computationally predicted in vacuum for adsorbed aromatics, , although this discrepancy can be explained by the lack of description of ion and solvent displacement in such theoretical treatments. Intuitively, the obtained value fits well a middle region between diffusion in solution and in solids.…”

Section: Resultscontrasting

confidence: 74%

Quantification of the Surface Diffusion of Tripodal Binding Motifs on Graphene Using Scanning Electrochemical Microscopy

et al. 2012

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The surface diffusion of a cobalt bis-terpyridine, Co(tpy)(2)-containing tripodal compound (1·2PF(6)), designed to noncovalently adsorb to graphene through three pyrene moieties, has been studied by scanning electrochemical microscopy (SECM) on single-layer graphene (SLG). An initial boundary approach was designed in which picoliter droplets (radii ~15-50 μm) of the tripodal compound were deposited on an SLG electrode, yielding microspots in which a monolayer of the tripodal molecules is initially confined. The time evolution of the electrochemical activity of these spots was detected at the aqueous phosphate buffer/SLG interface by SECM, in both generation/collection (G/C) and feedback modes. The tripodal compound microspots exhibit differential reactivity with respect to the underlying graphene substrate in two different electrochemical processes. For example, during the oxygen reduction reaction, adsorbed 1·2PF(6) tripodal molecules generate more H(2)O(2) than the bare graphene surface. This product was detected with spatial and temporal resolution using the SECM tip. The tripodal compound also mediates the oxidation of a Fe(II) species, generated at the SECM tip, under conditions in which SLG shows slow interfacial charge transfer. In each case, SECM images, obtained at increasing times, show a gradual decrease in the electrochemical response due to radial diffusion of the adsorbed molecules outward from the microspots onto the unfunctionalized areas of the SLG surface. This response was fit to a simple surface diffusion model, which yielded excellent agreement between the two experiments for the effective diffusion coefficients: D(eff) = 1.6 (±0.9) × 10(-9) cm(2)/s and D(eff) = 1.5 (±0.6) × 10(-9) cm(2)/s for G/C and feedback modes, respectively. Control experiments ruled out alternative explanations for the observed behavior, such as deactivation of the Co(II/III) species or of the SLG, and verified that the molecules do not diffuse when confined to obstructed areas. The noncovalent nature of the surface functionalization, together with the surface reactivity and mobility of these molecules, provides a means to couple the superior electronic properties of graphene to compounds with enhanced electrochemical performance, a key step toward developing dynamic electrode surfaces for sensing, electrocatalysis, and electronic applications.

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Section: Resultscontrasting

confidence: 74%

Quantification of the Surface Diffusion of Tripodal Binding Motifs on Graphene Using Scanning Electrochemical Microscopy

et al. 2012

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“…The second-order dependence of O 2 reduction on the coverage of Cu(phen C ), best observed at positive potentials, is distinct from the first-order dependence on Cu coverage determined by Anson et al for Cu(phen P ) on edge-plane graphite . We have confirmed the Anson result at 0 mV vs NHE and have previously reported that there is no rate-limiting step for electrocatalytic O 2 reduction by Cu(phen P ) subsequent to O 2 binding. , In the physisorbed case, the expected high surface lateral mobility of Cu(phen P ) will ensure that, once one Cu(phen P ) coordinates O 2 , another Cu(phen P ) will be able to combine rapidly in an unconstrained manner to form a Cu 2 O 2 (phen P ) 2 complex. This would lead to the observed first-order dependence on the Cu coverage if all reduction and protonation steps beyond the peroxide level intermediate are fast.…”

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confidence: 85%

Electrocatalytic O₂ Reduction by Covalently Immobilized Mononuclear Copper(I) Complexes: Evidence for a Binuclear Cu₂O₂ Intermediate

et al. 2011

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A Cu I complex of 3-ethynyl-phenanthroline covalently immobilized to an azide-modified glassy carbon surface is an active electrocatalyst for the 4-electron reduction of O 2 to H 2 O. The rate of O 2 reduction is 2 nd order in Cu coverage at moderate overpotential, suggesting that two Cu I species are necessary for efficient 4-electron reduction of O 2 . Mechanisms for O 2 reduction are proposed that are consistent with the observations for this covalently immobilized system and previously reported results for a similar physisorbed Cu I system. Discrete copper complexes are potential catalysts for the 4-electron reduction of O 2 to water in ambient temperature fuel cells as evidenced by Cu-containing fungal laccase enzymes that rapidly reduce O 2 directly to water at a trinuclear Cu active site at remarkably positive potentials. [1][2][3][4][5] Several groups have studied molecular Cu complexes immobilized onto electrode surfaces as an entry into the study of 4-electron O 2 reduction. [6][7][8][9][10][11][12][13][14][15][16][17][18][19] In particular, physisorbed Cu I (1,10-phenanthroline), Cu(phen P ), reduces O 2 quantitatively by 4 electrons and 4 protons to water. [8][9][10] Anson, et al., determined that this reaction was 1 st order in Cu coverage, suggestive of a mononuclear Cu site as the active catalyst. 8,10 In the present study, similar Cu I complexes are covalently attached to a modified glassycarbon electrode surface to form a species denoted Cu(phen C ), and the effect of Cu coverage on the kinetics of electrocatalytic O 2 reduction is investigated. At low overpotentials, we observe a 2 nd order dependence of the O 2 -reduction rate on the coverage of Cu(phen C ), from which we infer that two physically proximal Cu(phen C ) bind O 2 to form a binuclear Cu 2 O 2 species required for 4-electron reduction. We suggest that a similar binuclear species also forms in the case of Cu(phen P ) 8,10 but that rate-limiting binding of O 2 to the first Cu(phen P ) NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript followed by rapid surface diffusion of a second Cu(phen P ) has, until now, obscured the binuclear nature of the reaction.The covalent attachment of 3-ethynyl-1,10-phenanthroline to an azide-modified glassy carbon electrode to form Cu(phen C ) relies on the Cu I -catalyzed cycloaddition of azide and ethynyl groups to form a triazole linker, commonly referred to as the click reaction. 20,21 The electrode is azide terminated by treating a roughly-ground, heat-treated glassy carbon surface with a solution of IN 3 in hexanes, a procedure modified from that first described by Devadoss and Chidsey. 22 An XPS survey of the azide-modified surface shows two N 1s peaks at 399 eV and 403 eV in a 2:1 ratio attributable to the azide nitrogens. [22][23][24] Upon exposure to 3-ethynyl-1,10-phenanthroline under the click reaction conditions 25 , the 403-eV peak disappears and the 399-eV peak broadens, consistent with the formation of the 1,2,3-triazole linker. 22,24 XPS peaks at 934 and ...

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“…Even though an early united-atom model MD study by Xia and Landman showed preferential adsorption of n -hexadecane from an equal weight mixture with n -hexane on a Au(001) surface taking place within 1 ns of cooling the mixture down, modeling approaches to date have not explored the spontaneous adsorption further . Fodi and Hentschke showed that reparametrization of standard force fields is likely necessary to obtain reasonable adsorption energies for benzene and n -heptane mixtures on graphite . Often, modeling is used to assess the relative energies of proposed alternative surface arrangements, and starts from ordered structures based on scanning tunneling microscopy (STM) pictures, allowing relaxation in short (<1 ns) MD runs. , A number of studies using MD or Monte Carlo techniques addressed the surface layer structure and diffusion of alkanes, but no study addresses the simulation of the whole process, including adsorption and surface reorganization up to the formation of an ordered monolayer.…”

Section: Introductionmentioning

confidence: 99%

MARTINI Model for Physisorption of Organic Molecules on Graphite

et al. 2013

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An extension to the MARTINI coarse-grained model is presented to describe the adsorption of organic molecules on graphite surfaces. The model allows the study of the dynamics of the preferential adsorption of long-chain organic molecules from solvent and the formation of ordered structures on the surface through self-assembly on the microsecond time scale. It was found that the MARTINI model, developed for self-assembling biomolecular systems in solution, could be extended to include two-dimensional selfassembly on a solid surface using a single recipe to determine the interactions of the existing bead-types with the new representation of graphite. The model was parametrized on adsorption enthalpies of small molecules from the gas phase and on wetting enthalpies of pure compounds. Three wetting enthalpies were determined experimentally to extend the range of chemical functionalities parametrized against. The model reproduces order− disorder transitions of hexadecane and hexadecanol and preferential adsorption of long-chain organic compounds from organic solvents, including the formation of lamellar arrangements on the surface.

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Molecular Dynamics Simulation of a Binary Hydrocarbon Mixture near an Adsorbing Wall: Benzene/n-Heptane on Graphite

Cited by 6 publications

References 52 publications

Quantification of the Surface Diffusion of Tripodal Binding Motifs on Graphene Using Scanning Electrochemical Microscopy

Quantification of the Surface Diffusion of Tripodal Binding Motifs on Graphene Using Scanning Electrochemical Microscopy

Electrocatalytic O₂ Reduction by Covalently Immobilized Mononuclear Copper(I) Complexes: Evidence for a Binuclear Cu₂O₂ Intermediate

MARTINI Model for Physisorption of Organic Molecules on Graphite

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Molecular Dynamics Simulation of a Binary Hydrocarbon Mixture near an Adsorbing Wall: Benzene/n-Heptane on Graphite

Cited by 6 publications

References 52 publications

Quantification of the Surface Diffusion of Tripodal Binding Motifs on Graphene Using Scanning Electrochemical Microscopy

Quantification of the Surface Diffusion of Tripodal Binding Motifs on Graphene Using Scanning Electrochemical Microscopy

Electrocatalytic O2 Reduction by Covalently Immobilized Mononuclear Copper(I) Complexes: Evidence for a Binuclear Cu2O2 Intermediate

MARTINI Model for Physisorption of Organic Molecules on Graphite

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Product

Resources

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Electrocatalytic O₂ Reduction by Covalently Immobilized Mononuclear Copper(I) Complexes: Evidence for a Binuclear Cu₂O₂ Intermediate