We present the implementation of a three-dimensional mapping routine for probing solid-liquid interfaces using frequency modulation atomic force microscopy. Our implementation enables fast and flexible data acquisition of up to 20 channels simultaneously. The acquired data can be directly synchronized with commercial atomic force microscope controllers, making our routine easily extendable for related techniques that require additional data channels, e.g., Kelvin probe force microscopy. Moreover, the closest approach of the tip to the sample is limited by a user-defined threshold, providing the possibility to prevent potential damage to the tip. The performance of our setup is demonstrated by visualizing the hydration structure above the calcite (10.4) surface in water.

Control of molecular self-assembly at solid− liquid interfaces is challenging due to the complex interplay between molecule−molecule, molecule−surface, molecule− solvent, surface−solvent, and solvent−solvent interactions. Here, we use in-situ dynamic atomic force microscopy to study the self-assembly of Benzopurpurine 4B into oblong islands with a highly ordered inner structure yet incommensurate with the underlying calcite (10.4) surface. Molecular dynamics and free energy calculations provide insights by showing that Benzopurpurine 4B molecules do not anchor to the surface directly but instead assemble on top of the second hydration layer. This seemingly peculiar behavior was then rationalized by considering that hydrophobic molecules placed atop the second water layer cause the least distortion to the existing hydration structure. Further experiments for the adsorption of Benzopurpurine 4B on other minerals indicate that the specific interfacial water structure on calcite is decisive for rationalizing the self-assembly of Benzopurpurine 4B in this system.

In this work, we present the stabilization of polar step edges along the [010] direction of calcite (10.4) by the presence of a water-soluble organic molecule, namely Congo Red. While characteristic etch pits are observed on the surface in the absence of the additive, no etch pits can be found in the presence of the additive. Using atomic force microscopy, we can directly follow the restructuring of the surface. Upon addition of Congo Red, the charge-neutral step edges confining the characteristic etch pits vanish, while polar step edges along the [010] direction appear on the surface, which are entirely decorated by well-ordered molecular islands of the additive. After the restructuring has taken place, the surface exclusively exhibits these polar step edges. Our results give direct evidence of the fact that these polar step edges become thermodynamically favored when Congo Red is present.

We study the influence of Alizarin Red S deprotonation on molecular self-assembly at the solid-liquid interface of the natural cleavage plane of calcite immersed in aqueous solution. To elucidate the adsorption details, we perform pH dependent high-resolution atomic force microscopy measurements.When Alizarin Red S is deposited onto calcite(10.4) in a liquid environment at an acidic pH of 5, weakly bound, ordered islands with a (3 Â 3) superstructure are observed. A sharp structural transition is revealed when increasing the pH above 8. Above this pH, stable needle-like structures oriented along the [01.0] direction form on the surface. Comparing these results with potentiometric titration data allows for unambiguously assigning the two molecular structures to the single and two-fold deprotonated moieties of Alizarin Red S. Our work, thus, illustrates the decisive impact of the protonation state on molecular self-assembly.

This study describes the deposition and recording of surface charges on polyimide with a scanning Kelvin probe microscope. The apparatus used here works with a needle tip whose movements and oscillations are controlled and driven by an electromechanical system. To deposit charges the probe tip touches down to the insulator surface and with an external voltage the contact charging is performed. After the charge deposition the same system works as a vibrating scanning Kelvin probe to measure the charged surface area. This Kelvin probe system has the advantage of a controlled tip oscillation compared to a conventional AFM probe with a free oscillating cantilever. Electrostatic forces cannot stick the tip to the surface. In an additional experiment the charges deposited around an electrode as known from Lichtenberg figures are detected.

Organophosphonates are well-known to strongly interact with the surfaces of various minerals, such as brucite, gypsum, and barite. In this work, we study the influence of six systematically varied organophosphonate molecules (tetraphosphonates and diphosphonates) on the dissolution process of the (10.4) surface of calcite. In order to pursue a systematic study, we have selected organophosphonates that exhibit similar structural features, but also systematic architectural differences. The effect of this class of additives on the dissolution process of the calcite (10.4) surface is evaluated using in situ dynamic atomic force microscopy. For all of the six organophosphonate derivatives, we observe a pronounced restructuring of the (10.4) cleavage plane of calcite, demonstrated by the formation of characteristically shaped etch pits. To elucidate their specific influence on the dissolution process of calcite (10.4), we vary systematically the number of functional end groups (two for the tetraphosphonates and one for the diphosphonates), the spacing between the functional ends through separating methylene groups (2, 6, and 12), as well as the pH of the solution (ranging from 2.6 up to 11.7). For each of the two groups of the organophosphonate derivatives, we observe the very same formation of etch pits (olive-shaped for the tetraphosphonate and triangular-shaped for the diphosphonate molecules), respectively. This finding indicates that the number of functional ends decisively determines the resulting calcite (10.4) surface morphology, whereas the size of the organophosphonate molecule within one group seems not to play any important role. For all of the molecules, the restructuring process of calcite (10.4) is qualitatively independent of the pH of the solution and, therefore, independent of the protonation/deprotonation states of the molecules. Our results reveal a general property of organophosphonate derivatives to induce surface restructuring of the calcite (10.4), which seems to be very robust against variations in both, different molecular structures and different protonation/deprotonation states.

Closures such as buttons, clasps, zippers, and hook‐and‐loops find widespread use in daily life, and all work by mechanical interlocking. However, these traditional closures are often rigid, lose performance with age, and can produce a harsh sound during use. Here high strength (>50 N cm−2), reusable, and nearly silent closure devices are fabricated based on recently developed fibril‐less gecko‐inspired adhesives. Guided by a reversible adhesion scaling law, the closure force capacity is tuned by modifying the closure materials and geometry. A simple analytical model is presented which accurately predicts system performance, based on the reversible adhesion scaling parameter. The force capacity of these adhesive closures is measured and compared to commercially‐available hook‐and‐loop closures, and it is found that the adhesive closures sustain forces that are 4.4 times greater for comparable geometry. The sound of release is also quantified and shown to be minimal for adhesive closures. This work provides motivation to develop new high strength, reusable closures for commercial and industrial applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1783–1790

Organic additives are known to alter the mineral-water interface in various ways. On the one hand, organic molecules can selfassemble into ordered structures wetting the surface. On the other hand, their presence can affect the interfacial morphology, referred to as surface restructuring. Here, we investigate the impact of a class of calciumcomplexing azo dyes on the dissolution of calcite (10.4) using high-resolution atomic force microscopy operated in aqueous solution, with a focus on the two constitutional isomers Eriochrome Black T and Eriochrome Black A. A very pronounced surface restructuring is observed in the presence of the dye solution, irrespective of the specific dye used and independent of the pH. This surface restructuring is obtained by the stabilization of both the nonpolar acute and the polar [010] step edges, resulting in a greatly altered, characteristic interface morphology. In sharp contrast to the prevalence of the surface restructuring, an ordered molecular structure on the crystal terraces is observed only under very specific conditions. This formation of an ordered stripe-like molecular structure is obtained from Eriochrome Black A only and limited to a very narrow pH window at a pH value of around 3.6. Our results indicate that such molecular self-assembly requires a rather precise adjustment of the molecular properties including control of the conformation and deprotonation state. This is in sharp contrast to the additive-induced surface restructuring, which appears to be far more robust against both pH changes and variations in the molecular conformation.