Role of water in atomic resolution AFM in solutions

Watkins, Matthew; Berkowitz, Max L.; Shluger, Alexander L.

doi:10.1039/c1cp21021a

Cited by 54 publications

(89 citation statements)

References 58 publications

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“…Similar conclusions were found in previous molecular dynamics simulations based on density functional theory, suggesting the preference for an associative rather than dissociative adsorption of water molecules [3,75].…”

Section: A Interface With Explicit Water Moleculessupporting

confidence: 78%

“…To properly emulate an aqueous environment, the inclusion of at least three to four water layers is required to account for several solvation shells. Even for strongly charged interfaces, water molecules lose their ordered layered structure after roughly 2-3 solvation layers [28,75]. With this large amount of water molecules in our simulation cell, most of the local minima are conformers with slightly different packing of the solvent.…”

Section: Adsorption Energiesmentioning

confidence: 99%

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Surface reconstruction of fluorites in vacuum and aqueous environment

Fisicaro

Sicher

Amsler

et al. 2017

Phys. Rev. Materials

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Surfaces and interfaces of bulk materials with liquids are of importance for a wide range of chemical processes.In this work, we systematically explore reconstructions on the (100) surface of calcium fluoride (CaF 2 ) and other fluorites (MF 2 ), M = {Sr,Cd,Ba} by sampling the configurational space with the minima hopping structure prediction method in conjunction with density functional theory calculations. We find a large variety of structures that are energetically very close to each other and are connected by very low barriers, resulting in a high mobility of the topmost surface anions. This high density of configurational states makes the CaF 2 (100) surface a very dynamic system. The majority of the surface reconstructions found in CaF 2 are also present in SrF 2 , CdF 2 , and BaF 2 . Furthermore, we investigate in detail the influence of these reconstructions on the crystal growth of CaF 2 in solvents by modeling the fluorite-water interface and its wetting properties. We perform a global structural search both by explicitly including water molecules and by employing a recently developed soft-sphere solvation model to simulate an implicit aqueous environment. The implicit approach correctly reproduces both our findings with the explicit-water model and the experimentally reported contact angles for the partial-hydrophobic (111) and hydrophilic (100) surfaces. Our simulations show that the high anion mobility and the low coordination of the (100) surface atoms strongly favors the adsorption of water molecules over the (111) surface. The aqueous environment makes terminations with low-coordination surface atoms more stable, promoting (100) growth instead of the (111).

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Section: A Interface With Explicit Water Moleculessupporting

confidence: 78%

Section: Adsorption Energiesmentioning

confidence: 99%

Surface reconstruction of fluorites in vacuum and aqueous environment

Fisicaro

Sicher

Amsler

et al. 2017

Phys. Rev. Materials

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“…Obtaining the F distributions requires free energy calculations due to the importance of the entropic contributions from the water molecules in the hydration layers of both tip and substrate [23,29,30]. Until now, only individual F profiles over several ionic surfaces in water have been published [23,[29][30][31][32][33][34], which is mainly due to the increased computational complexity involved when constructing a full 3D F image from atomistic simulations. These individual F profiles do not allow for good comparison with experiment, as the identity of the surface atoms over which the experimental profiles are obtained is unknown-only a 3D F map allows for an unambiguous comparison.…”

Section: Published By the American Physical Society Under The Terms Omentioning

confidence: 99%

Mechanism of atomic force microscopy imaging of three-dimensional hydration structures at a solid-liquid interface

et al. 2015

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Here we present both subnanometer imaging of three-dimensional (3D) hydration structures using atomic force microscopy (AFM) and molecular dynamics simulations of the calcite-water interface. In AFM, by scanning the 3D interfacial space in pure water and recording the force on the tip, a 3D force image can be produced, which can then be directly compared to the simulated 3D water density and forces on a model tip. Analyzing in depth the resemblance between experiment and simulation as a function of the tip-sample distance allowed us to clarify the contrast mechanism in the force images and the reason for their agreement with water density distributions. This work aims to form the theoretical basis for AFM imaging of hydration structures and enables its application to future studies on important interfacial processes at the molecular scale.

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“…Thus, the theoretical basis for atomistic molecular dynamics (MD) simulation of the fluorite-water interface was relatively well-established. Therefore, some of the early simulation studies on the imaging mechanism of atomic-resolution liquid-environment AFM were performed with a model of this interface [22,47,48]. To compare the results obtained by simulation and experiments, we previously performed systematic AFM experiments at this interface with different CaF 2 concentration and pH [49].…”

Section: Introductionmentioning

confidence: 99%

Influence of ions on two-dimensional and three-dimensional atomic force microscopy at fluorite–water interfaces

et al. 2017

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Abstract. Recent advancement in liquid-environment atomic force microscopy (AFM) has enabled us to visualize three-dimensional (3D) hydration structures as well as two-dimensional (2D) surface structures with subnanometer-scale resolution at solid-water interfaces. However, the influence of ions present in solution on the 2D-and 3D-AFM measurements has not been well understood. In this study, we perform atomic-scale 2D-and 3D-AFM measurements at fluorite-water interfaces in pure water and supersaturated solution of fluorite. The images obtained in these two environments are compared to understand the influence of the ions in solution on these measurements. In the 2D images, we found clear difference in the nanoscale structures but no significant difference in the atomic-scale contrasts. However, the 3D force images show clear difference in the subnanometer-scale contrasts. The force contrasts measured in pure water largely agree with those expected from the molecular dynamics simulation and the solvent tip approximation model. In the supersaturated solution, an additional force peak is observed over the negatively charged fluorine ion site. This location suggests that the observed force peak may originate from cations adsorbed on the fluorite surface. These results demonstrate that the ions can significantly alter the subnanometer-scale force contrasts in the 3D-AFM images.

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Role of water in atomic resolution AFM in solutions

Cited by 54 publications

References 58 publications

Surface reconstruction of fluorites in vacuum and aqueous environment

Surface reconstruction of fluorites in vacuum and aqueous environment

Mechanism of atomic force microscopy imaging of three-dimensional hydration structures at a solid-liquid interface

Influence of ions on two-dimensional and three-dimensional atomic force microscopy at fluorite–water interfaces

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