Selective adsorption of alkyl thiols on gold in different geometries

Schapotschnikow, Philipp; Pool, René; Vlugt, Thijs J. H.

doi:10.1016/j.cpc.2007.02.028

Cited by 25 publications

(38 citation statements)

References 10 publications

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“…We compute adsorption isotherms to understand the thermodynamics and structural properties involved in the formation of SAMs and capping layers. We will also extend our preliminary simulations 32 for the adsorption selectivities of binary mixtures of alkyl thiols that differ in tail length to larger NCs. An important aspect in these simulations is the influence of the solvent, which we simulate explicitly.…”

Section: Introductionmentioning

confidence: 99%

Solvent Effects in the Adsorption of Alkyl Thiols on Gold Structures: A Molecular Simulation Study

2007

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We carried out Monte Carlo simulations of gold nanocrystals (NCs) and (111) slabs covered with alkyl thiols, with and without explicit solvent (n-hexane), at T ) 300 K. Adsorption isotherms for propane-and octanethiol showed a phase behavior measured previously in experiments. Comparison of the adsorption isotherm of octanethiol in hexane on a (111) slab with experimental data suggests that, in this system, no thiolate bond was formed. The geometry of a gold surface strongly influences the formation and structure of the capping monolayer. On a (111) surface, attractive interactions between carbon chains are more pronounced than on a NC. This leads to a stronger penetration of the capping layer by the solvent. Adsorption selectivity for binary alkyl thiol mixtures is stronger in vacuum than in solution. The convex shape of the NCs also reduces the adsorption selectivity of binary thiol mixtures. This result shows that the solvent cannot be ignored in simulations.

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Section: Introductionmentioning

confidence: 99%

Solvent Effects in the Adsorption of Alkyl Thiols on Gold Structures: A Molecular Simulation Study

2007

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“…The binding of thiol headgroups to Au surfaces is better understood than for other NC-surfactant systems. 16 Several models have been successfully applied to describe the structure and thermodynamics of alkyl thiol monolayers on flat Au͑111͒-surfaces [17][18][19] and Au-NCs. [18][19][20][21] It is important to note that the effective NC-NC interactions in a solvent are very different from the ones in vacuum due to solvent-capping layer interactions.…”

Section: Introductionmentioning

confidence: 99%

“…16 Several models have been successfully applied to describe the structure and thermodynamics of alkyl thiol monolayers on flat Au͑111͒-surfaces [17][18][19] and Au-NCs. [18][19][20][21] It is important to note that the effective NC-NC interactions in a solvent are very different from the ones in vacuum due to solvent-capping layer interactions. The work of Patel and Egorov 22 focused on the PMF for very small capped NC cores ͑Au 38 ͒ for varying solvent quality, and it was found that the PMF can be tuned from strongly attractive to fully repulsive.…”

Section: Introductionmentioning

confidence: 99%

Understanding interactions between capped nanocrystals: Three-body and chain packing effects

Schapotschnikow

Vlugt

2009

The Journal of Chemical Physics

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154

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Self-assembly of capped nanocrystals ͑NC͒ attracted a lot of attention over the past decade. Despite progress in manufacturing of NC superstructures, the current understanding of their mechanical and thermodynamic stability is still limited. For further applications, it is crucial to find the origin and the magnitude of the interactions that keep self-assembled NCs together, and it is desirable to find a way to rationally manipulate these interactions. We report on molecular simulations of interacting gold NCs protected by capping molecules. We computed the potential of mean force for pairs and triplets of NCs of different size ͑1.8-3.7 nm͒ with varying ligand length ͑ethanethiol-dodecanethiol͒ in vacuum. Pair interactions are strongly attractive due to attractive van der Waals interactions between ligand molecules. Three-body interaction results in an energy penalty when the capping layers overlap pairwise. This effect contributes up to 20% to the total energy for short ligands. For longer ligands, the three-body effects are so large that formation of NC chains becomes energetically more favorable than close packing of capped NCs at low concentrations, in line with experimental observations. To explain the equilibrium distance for two or more NCs, the overlap cone model is introduced. This model is based on relatively simple ligand packing arguments. In particular, it can correctly explain why the equilibrium distance for a pair of capped NCs is always Ϸ1.25 times the core diameter independently on the ligand length, as found in our previous work ͓Schapotschnikow, R. Pool, and T. J. H. Vlugt, Nano Lett. 8, 2930 ͑2008͔͒. We make predictions for which ligands capped NCs self-assemble into highly stable three-dimensional structures, and for which they form high-quality monolayers.

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“…Since adsorption in nanopores can be studied on the basis of effective pair potentials 3,[5][6][7][8][9] , it is obversely possible to fit model parameters to adsorption isotherms 10 . The present study follows the line of research, suggested by WERDER et al 11 , of adjusting unlike parameters to contact angle measurements.…”

Section: Introductionmentioning

confidence: 99%

“…In principle, the Lorentz-Berthelot rule can be applied for effective pair potentials acting between the fluid particles and the atoms of a solid wall 2,3 , based on size and energy parameters derived from properties of the solid and the fluid. However, while using combination rules to extrapolate from homogeneous bulk solid and fluid properties to interfacial phenomena can lead to a good agreement with the actual behavior 2 , this approach has only shaky theoretical foundations 4 .…”

Section: Introductionmentioning

confidence: 99%

Contact Angle Dependence on the Fluid−Wall Dispersive Energy

et al. 2010

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Vapor-liquid menisci of the truncated and shifted Lennard-Jones fluid between parallel planar walls are investigated by molecular dynamics simulation. Thereby, the characteristic energy of the unlike dispersive interaction between fluid molecules and wall atoms is systematically varied to determine its influence on the contact angle. The temperature is varied as * To whom correspondence should be addressed † University of Paderborn

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Selective adsorption of alkyl thiols on gold in different geometries

Cited by 25 publications

References 10 publications

Solvent Effects in the Adsorption of Alkyl Thiols on Gold Structures: A Molecular Simulation Study

Solvent Effects in the Adsorption of Alkyl Thiols on Gold Structures: A Molecular Simulation Study

Understanding interactions between capped nanocrystals: Three-body and chain packing effects

Contact Angle Dependence on the Fluid−Wall Dispersive Energy

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