When the going gets rough – studying the effect of surface roughness on the adhesive abilities of tree frogs

• Niall Crawford,
• Thomas Endlein,
• Jonathan T. Pham,
• Mathis Riehle and
• W. Jon P. Barnes

Beilstein J. Nanotechnol. 2016, 7, 2116–2131, doi:10.3762/bjnano.7.201

• situation where capillary forces would be absent. Additionally, since toe pads make close contact to surfaces, a role for van der Waals forces cannot be excluded [3]. However, little evidence was found for such forces in a recent AFM study of the toe pads of Litoria [24]. Capillary forces are highest when

Solvent-mediated conductance increase of dodecanethiol-stabilized gold nanoparticle monolayers

• Patrick A. Reissner,
• Jean-Nicolas Tisserant,
• Antoni Sánchez-Ferrer,
• Raffaele Mezzenga and
• Andreas Stemmer

Beilstein J. Nanotechnol. 2016, 7, 2057–2064, doi:10.3762/bjnano.7.196

• dependence can be expected if the decrease in lattice constant is driven by an energy minimization process. Attractive van-der-Waals forces between adjacent nanoparticles can cause agglomeration of nanoparticles, which we observed after removing the alkane ligands by UV/ozone treatment. However, van-der

• -Waals forces rather decrease slightly in a liquid medium in comparison to air. A slow compaction of the nanoparticle monolayer as we observed may be caused either by a collapse of alkyl tails or by partial interdigitation of alkyl tails between nanoparticles. The good solubility of 1-dodecanethiol in

Morphology of SiO₂ films as a key factor in alignment of liquid crystals with negative dielectric anisotropy

• Volodymyr Tkachenko,
• Antigone Marino,
• Eva Otón,
• Noureddine Bennis and
• Josè Manuel Otón

Beilstein J. Nanotechnol. 2016, 7, 1743–1748, doi:10.3762/bjnano.7.167

• homeotropically, respectively. Such behavior can be explained by induced dipole–dipole interaction between LC and a smoothed oxide surface derived from van der Waals forces [3][8]. When α increases from 60° to 85°, the preferred orientation of LC with positive Δε switches from orthogonal to parallel to the plane

Filled and empty states of Zn-TPP films deposited on Fe(001)-p(1×1)O

• Gianlorenzo Bussetti,
• Alberto Calloni,
• Rossella Yivlialin,
• Andrea Picone,
• Federico Bottegoni and
• Marco Finazzi

Beilstein J. Nanotechnol. 2016, 7, 1527–1531, doi:10.3762/bjnano.7.146

• limited to weak van der Waals forces [11]. Consequently, changes in the energy position of the different spectroscopic features of the 1 ML film with respect to the reference layer are usually interpreted in terms of intensity strength of the molecule–substrate interaction. In Figure 2, we report the

Surface roughness rather than surface chemistry essentially affects insect adhesion

• Matt W. England,
• Tomoya Sato,
• Makoto Yagihashi,
• Atsushi Hozumi,
• Stanislav N. Gorb and
• Elena V. Gorb

Beilstein J. Nanotechnol. 2016, 7, 1471–1479, doi:10.3762/bjnano.7.139

• (Figure 4a,b). In the latter case, it is presumably due to wetting reduction by the pad fluid (Figure 4c,d). Additionally, at the sites of solid–solid contact between insect pads and substrates, the true contact area and contribution of van der Waals forces are believed to be effectively reduced for both

Influence of ambient humidity on the attachment ability of ladybird beetles (Coccinella septempunctata)

• Lars Heepe,
• Jonas O. Wolff and
• Stanislav N. Gorb

Beilstein J. Nanotechnol. 2016, 7, 1322–1329, doi:10.3762/bjnano.7.123

• [14], and geckos, revealed in measurements with living animals [11] and with isolated setae [10]. This is particularly interesting since both types of adhesive systems (wet and dry) are supposed to be based on different physical interactions (capillarity versus van der Waals forces). For the dry

Reasons and remedies for the agglomeration of multilayered graphene and carbon nanotubes in polymers

• Rasheed Atif and
• Fawad Inam

Beilstein J. Nanotechnol. 2016, 7, 1174–1196, doi:10.3762/bjnano.7.109

• dispersion state of filler as multilayered graphene (MLG) and carbon nanotubes (CNTs) tend to agglomerate due to van der Waals forces. The agglomeration can be avoided by using organic solvents, selecting suitable dispersion and production methods, and functionalizing the fillers. Another proposed method is

• nanocomposites and to gain knowledge about their biocompatibility and performance in living organisms. One of the main issues in the production of polymer nanocomposites is the dispersion state of fillers, because MLG and CNTs tend to agglomerate due to van der Waals forces. The agglomeration can be avoided by

• about 1 TPa (more than steel by factor of 5) [2]. MWNTs comprise a number of concentric graphene cylinders, which is known as “Russian doll” structure. There are van der Waals forces between adjacent graphene layers [40]. MWNTs have diameters and lengths in the ranges of 10–20 nm and of 10–50 μm

Nanoscale effects in the characterization of viscoelastic materials with atomic force microscopy: coupling of a quasi-three-dimensional standard linear solid model with in-plane surface interactions

• Santiago D. Solares

Beilstein J. Nanotechnol. 2016, 7, 554–571, doi:10.3762/bjnano.7.49

• or dispersion (van der Waals) forces exerted by the probe, thus leading to a situation in which the sample is influenced by the measurement itself. One could continue extending the list of phenomena that preclude an ideal measurement by considering other issues such as limitations of the measurement

• of the Q3D force curve of Figure 7 (note that the model does not currently include other types of forces, besides the force due to the viscoelastic elements and the van der Waals forces). Since the Q3D model is based on individual 1D SLS elements, it also exhibits the qualitatively correct behavior

• far only linear elastic. A fourth, related, limitation is that the model assumes uniform material relaxation in the subsurface, which cannot be guaranteed even in one dimension. Adhesion forces other than attractive van der Waals forces are also not considered, although these can be important and may

Influence of calcium on ceramide-1-phosphate monolayers

• Joana S. L. Oliveira,
• Gerald Brezesinski,
• Alexandra Hill and
• Arne Gericke

Beilstein J. Nanotechnol. 2016, 7, 236–245, doi:10.3762/bjnano.7.22

• negatively charged head groups are responsible for the larger areas per molecule and larger tilt angles. Upon compression, the strong van der Waals forces between the acyl chains and the screening effect of sodium ions surpass the electrostatic repulsions allowing C1P to transform into the untilted state. On

• liquid-expanded phase (LE) due to repulsive forces between the negatively charged phosphate head groups. At pH 4, the C1P head groups are either one-fold deprotonated or neutral (most probably a mixture of protonation states). The strong van der Waals forces between the chains allow the system to be in a

• attractive van der Waals forces). This result supports the calcium-mediated interaction of C1P with the C2 domain of cPLa2α (effector protein). Since C1P is involved in many biological functions, its interaction with other ions could also be of interest. Furthermore, the potential to form solid-like domains

Synthesis and applications of carbon nanomaterials for energy generation and storage

• Marco Notarianni,
• Jinzhang Liu,
• Kristy Vernon and
• Nunzio Motta

Beilstein J. Nanotechnol. 2016, 7, 149–196, doi:10.3762/bjnano.7.17

• acid [53]. In both the arc discharge and laser ablation methods, bundles of MWNTs and SWNTs held together by van der Waals forces are generated by the condensation of carbon atoms generated from the evaporation of solid carbon sources. The third method, chemical vapor deposition (CVD), involves the

• and can thus only be considered for research purposes. Chemical exfoliation. It is well known that the van der Waals forces that bond together the graphene sheets to form graphite are particularly weak and can be broken by external mechanical force. A common example of this can be seen with the usage

A simple and efficient quasi 3-dimensional viscoelastic model and software for simulation of tapping-mode atomic force microscopy

• Santiago D. Solares

Beilstein J. Nanotechnol. 2015, 6, 2233–2241, doi:10.3762/bjnano.6.229

• amplitude. The total tip–sample force term Fts consists of the repulsive forces generated by the Q3D model (these are calculated numerically since there does not exist an analytical expression to calculate them [10]) plus attractive van der Waals forces, which are included for each area element in the Q3D

• model via an equation similar to the Hamaker equation [12]. Thus, the contribution to the van der Waals forces for area element j is where V is a van der Waals ‘strength’ parameter in the code (see c-file in Supporting Information File 1) that adjusts the magnitude of the van der Waals interaction

• of force curve for bimodal AFM, showing a double impact. The blue arrows indicate in each case the position where the tip first reaches the sample, and the red arrows indicate the position where the tip leaves the sample. Van der Waals forces have been included in the attractive (noncontact) region

Kelvin probe force microscopy for local characterisation of active nanoelectronic devices

• Tino Wagner,
• Hannes Beyer,
• Patrick Reissner,
• Philipp Mensch,
• Heike Riel,
• Bernd Gotsmann and
• Andreas Stemmer

Beilstein J. Nanotechnol. 2015, 6, 2193–2206, doi:10.3762/bjnano.6.225

• subsequently to retrace the scanned line at a small distance, Δz, above the surface to perform KFM measurements. This enables tuning the ac modulation frequency for KFM to resonance to enhance the signal, and, at the same time, to reduce the contribution of van der Waals forces to the total force measured and

Atomic force microscopy as analytical tool to study physico-mechanical properties of intestinal cells

• Christa Schimpel,
• Oliver Werzer,
• Eleonore Fröhlich,
• Gerd Leitinger,
• Markus Absenger-Novak,
• Birgit Teubl,
• Andreas Zimmer and
• Eva Roblegg

Beilstein J. Nanotechnol. 2015, 6, 1457–1466, doi:10.3762/bjnano.6.151

• the cantilever got in contact with the sample. Due to strong adhesion forces (van der Waals forces), the tip snapped in contact with the cell membrane. When retracting the tip, adhesion was maintained until the cantilever-force overcame the pull-off force (also referred as adhesion force) [51]. Lowest

Nano-contact microscopy of supracrystals

• Adam Sweetman,
• Nicolas Goubet,
• Ioannis Lekkas,
• Marie Paule Pileni and
• Philip Moriarty

Beilstein J. Nanotechnol. 2015, 6, 1229–1236, doi:10.3762/bjnano.6.126

• strong forces applied to the sample, the supracrystal remains stable, most likely due to the high cohesive energy arising both from the integrated van der Waals forces and ligand interdigitation. The question of where to define the contact point is, of course, a notoriously vexed issue, as Smith et al

Synthesis of boron nitride nanotubes and their applications

• Saban Kalay,
• Zehra Yilmaz,
• Ozlem Sen,
• Melis Emanet,
• Emine Kazanc and
• Mustafa Çulha

Beilstein J. Nanotechnol. 2015, 6, 84–102, doi:10.3762/bjnano.6.9

• the BNNTs via a targeting protein could generate smart and selective nanocarriers to be used in nanomedicine [67]. Physical modifications For these types of modifications, weak interactions such as π–π, hydrophobic, and van der Waals forces are utilized to coat the BNNTs with mostly a polymeric

Mammalian cell growth on gold nanoparticle-decorated substrates is influenced by the nanoparticle coating

• Christina Rosman,
• Sebastien Pierrat,
• Marco Tarantola,
• David Schneider,
• Eva Sunnick,
• Andreas Janshoff and
• Carsten Sönnichsen

Beilstein J. Nanotechnol. 2014, 5, 2479–2488, doi:10.3762/bjnano.5.257

• adsorption of nanoparticles onto the substrate. Once the nanoparticles are near the glass surface, they remain attached by van der Waals forces even in the absence of salt. Optical dark field microscopy was used to quantify the nanoparticle density on the substrate. In this technique, only scattered light

• work, gold nanorods were purposely immobilized to the substrate using a salt solution, resulting in an attachment by van der Waals forces. This attachment could obviously not be reversed by the cells. We investigated three different stabilizing agents present on the particle surface regarding their

• substrate, it is assumed that the interaction between the cell membrane and the nanoparticles was not strong enough to overcome the van der Waals forces keeping the particles attached to the substrate. The other stabilizer investigated, PEG, is considered to be biocompatible [23]. This biocompatibility

Aquatic versus terrestrial attachment: Water makes a difference

• Petra Ditsche and
• Adam P. Summers

Beilstein J. Nanotechnol. 2014, 5, 2424–2439, doi:10.3762/bjnano.5.252

• , lock, clamp and spacer) significant differences have to be considered under water. For example, the main principles of dry adhesion, van der Waals forces and chemical bonding, which make a gecko stick to the ceiling, are weak under submerged conditions. Capillary forces are very important for wet

• ) diffusion, (iv) chemical bonding as ionic, covalent or hydrogen bonds, and (v) dispersive or van der Waals forces. While the first three mechanisms of adhesion presumably contribute just a minor part to general adhesion, the latter two are generally accepted as the primary mechanisms in many systems [19

• forces and chemical bonding van der Waals forces are the sum of attractive forces between molecules that have regions of slightly negative and slightly positive charges. These forces are only effective over a very small distance, less than one nanometer [41]. Therefore, these forces are considerably

Nanobioarchitectures based on chlorophyll photopigment, artificial lipid bilayers and carbon nanotubes

• Marcela Elisabeta Barbinta-Patrascu,
• Stefan Marian Iordache,
• Ana Maria Iordache,
• Nicoleta Badea and
• Camelia Ungureanu

Beilstein J. Nanotechnol. 2014, 5, 2316–2325, doi:10.3762/bjnano.5.240

• biomedical field is complicated as they are completely insoluble in all solvents and are present as bundles. Thus, they have a tendency to aggregate due to van der Waals forces, π–π stacking and hydrophobic interactions among individual CNTs, making them difficult for characterization, handling, and

Spectroscopic mapping and selective electronic tuning of molecular orbitals in phosphorescent organometallic complexes – a new strategy for OLED materials

• Pascal R. Ewen,
• Jan Sanning,
• Tobias Koch,
• Nikos L. Doltsinis,
• Cristian A. Strassert and
• Daniel Wegner

Beilstein J. Nanotechnol. 2014, 5, 2248–2258, doi:10.3762/bjnano.5.234

• . TLs of neighboring molecules as well as the pyridine AL of complex C1 seem to be packed in a steric fashion. However, we attribute the different patterns of C2 to additional van der Waals forces between the amyl chains [38][39]. We note that an additional molecular structure is evident in the third

• substituents do not show any influence on the measured structures. We suggest that only weak lateral interactions, most likely van der Waals forces (especially between neighboring amyl groups), and steric effects drive the self-assembly, similar to the situation of complex C2. For C3, one may think that

• additional role of van der Waals forces between neighboring R3 alkyl chains for the self-assembly. (a) Energy and LDOS of calculated orbitals for C1 in the gas phase. Here, a work function of 5.1 eV was assumed. This value results from minimizing the energy differences between calculated and measured

Two-dimensional and tubular structures of misfit compounds: Structural and electronic properties

• Tommy Lorenz,
• Jan-Ole Joswig and
• Gotthard Seifert

Beilstein J. Nanotechnol. 2014, 5, 2171–2178, doi:10.3762/bjnano.5.226

• shown in Figure 1b. In these cases, the TMX2 layers are held together by van der Waals forces, whereas the interaction between MX and TMX2 layers is based on van der Waals interaction and a charge transfer (CT) from MX to TMX2 [12]. Thus, misfit compounds do not only differ by stoichiometry, difference

Modeling viscoelasticity through spring–dashpot models in intermittent-contact atomic force microscopy

• Enrique A. López-Guerra and
• Santiago D. Solares

Beilstein J. Nanotechnol. 2014, 5, 2149–2163, doi:10.3762/bjnano.5.224

• SLS is the simplest model that is able to describe stress relaxation and creep, and the DMT is a widely used model in contact mechanics that is typically used in the context of AFM. We include both DMT contact forces and long-range van der Waals forces [6][32]. where H is the Hammaker constant, R is

Modification of a single-molecule AFM probe with highly defined surface functionality

• Fei Long,
• Bin Cao,
• Ashok Khanal,
• Shiyue Fang and
• Reza Shahbazian-Yassar

Beilstein J. Nanotechnol. 2014, 5, 2122–2128, doi:10.3762/bjnano.5.221

• , such as hydrogen bonds, and non-specific interactions, such as van der Waals forces, where Fav is the total average adhesion force, nav is the average number of specific interactions, which is hydrogen bonding in our case, Fi is the magnitude of the specific interaction, and F0 is non-specific

Carbon nano-onions (multi-layer fullerenes): chemistry and applications

• Juergen Bartelmess and
• Silvia Giordani

Beilstein J. Nanotechnol. 2014, 5, 1980–1998, doi:10.3762/bjnano.5.207

• . Analogous to carbon nanotubes, CNOs display poor solubility in both aqueous and organic solvents. This is due to aggregation, promoted by strong intermolecular interactions such as van-der-Waals forces. To overcome this tendency to aggregate, functionalization of the surface of the carbon materials is the

Carbon-based smart nanomaterials in biomedicine and neuroengineering

• Antonina M. Monaco and
• Michele Giugliano

Beilstein J. Nanotechnol. 2014, 5, 1849–1863, doi:10.3762/bjnano.5.196

• integrate with biological systems is a consequence of their interactions with cells and membranes occurring at the subcellular level. However, due to their chemically inert surface and van der Waals forces occurring at the surface, carbon-based nanomaterials, particularly pristine CNTs, tend to agglomerate

• control conditions. The improved neuronal adhesion on graphene, compared to the bare plastic polymeric dish, was ascribed by the authors to van der Waals forces between cell membranes and graphene. Similarly to NDs [140], surface charges can influence adhesion and outgrowth of neuronal cells on graphene

Biocompatibility of cerium dioxide and silicon dioxide nanoparticles with endothelial cells

• Claudia Strobel,
• Martin Förster and
• Ingrid Hilger

Beilstein J. Nanotechnol. 2014, 5, 1795–1807, doi:10.3762/bjnano.5.190

• -potentials were neither positively nor negatively charged enough to prevent agglomeration by van der Waals forces [29]. Interestingly, the smaller nanoparticles (sample #A) exhibited a tendency towards an increasing negative charge with increasing serum content, while the larger nanoparticles (sample #B