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

Experimental techniques for the characterization of carbon nanoparticles – a brief overview

• Wojciech Kempiński,
• Szymon Łoś,
• Mateusz Kempiński and
• Damian Markowski

Beilstein J. Nanotechnol. 2014, 5, 1760–1766, doi:10.3762/bjnano.5.186

• signal of ACFs is the adsorption of molecules at the surface of CNs which comprise the pore walls. The adsorption in ACF pores is of a physical nature (van der Waals forces), without any covalent bond formation. Fully reversible physisorption has been observed with EPR (see Figure 5). The EPR spectrum of

Non-covalent and reversible functionalization of carbon nanotubes

• Antonello Di Crescenzo,
• Valeria Ettorre and
• Antonella Fontana

Beilstein J. Nanotechnol. 2014, 5, 1675–1690, doi:10.3762/bjnano.5.178

• strongly interact with each other through van der Waals forces reaching ~500 eV per μm of CNT’s length [18] and aggregate into bundles and ropes. In order to counteract these forces and favor CNTs manipulability and solubility mainly two strategies have been adopted: i) covalent functionalization through

Probing viscoelastic surfaces with bimodal tapping-mode atomic force microscopy: Underlying physics and observables for a standard linear solid model

• Santiago D. Solares

Beilstein J. Nanotechnol. 2014, 5, 1649–1663, doi:10.3762/bjnano.5.176

• challenging to carry out [43]. Non-viscoelatic dissipative interactions The present work studies an AFM tip that is interacting with a clean SLS surface, so no further interactions are included other than attractive van der Waals forces. However, in practice there can be a number of other interactions that

Hydrophobic interaction governs unspecific adhesion of staphylococci: a single cell force spectroscopy study

• Nicolas Thewes,
• Peter Loskill,
• Philipp Jung,
• Henrik Peisker,
• Markus Bischoff,
• Mathias Herrmann and
• Karin Jacobs

Beilstein J. Nanotechnol. 2014, 5, 1501–1512, doi:10.3762/bjnano.5.163

• bacterium, the surrounding medium, the surface chemistry, and the material composition reflecting the influence of the main interacting forces [12][13]: van der Waals forces, hydrophobic interaction and electrostatic forces. In addition, specific interactions amplify bacterial adhesion whenever

• involved [26]. Since hydrophilic and hydrophobic Si wafers differ in composition only by a 2.6 nm thin OTS-monolayer on the surface, the van der Waals forces are nearly identical [13][27]. Forces due to electrostatic interactions between the negatively charged bacterium and the two types of wafer surfaces

• electrostatic and van der Waals forces by at least an order of magnitude. The main observations are (i) the form of the force/distance curves is characteristic for each bacterium, (ii) this form is independent of the “adhesive history” and (iii) the retraction curves (including the adhesion forces) are

A sonochemical approach to the direct surface functionalization of superparamagnetic iron oxide nanoparticles with (3-aminopropyl)triethoxysilane

• Bashiru Kayode Sodipo and
• Azlan Abdul Aziz

Beilstein J. Nanotechnol. 2014, 5, 1472–1476, doi:10.3762/bjnano.5.160

• ; superparamagnetic iron oxide nanoparticles (SPION); Findings Superparamagnetic iron oxide nanoparticles (SPION) have a wide range of applications in biomedical research and development. The main drawbacks of SPION are a high surface energy, van der Waals forces of attraction and dipole to dipole interactions that

Direct observation of microcavitation in underwater adhesion of mushroom-shaped adhesive microstructure

• Lars Heepe,
• Alexander E. Kovalev and
• Stanislav N. Gorb

Beilstein J. Nanotechnol. 2014, 5, 903–909, doi:10.3762/bjnano.5.103

• vacuum [10][16][17][18], and underwater [19][20]). The origin of the high adhesion capability of the mushroom-shaped adhesive microstructures (MSAMSs) was attributed to the combination of intermolecular van der Waals forces and a particular failure mode at detachment, a consequence of an optimized

• forces [10][16][17][18]. In their recent work Varenberg and Gorb [19] have observed that the pull-off forces measured underwater were significantly higher (about 25%) compared to those measured under ambient conditions. This effect cannot be explained by intermolecular van der Waals forces. The authors

Hairy suckers: the surface microstructure and its possible functional significance in the Octopus vulgaris sucker

• Francesca Tramacere,
• Esther Appel,
• Barbara Mazzolai and
• Stanislav N. Gorb

Beilstein J. Nanotechnol. 2014, 5, 561–565, doi:10.3762/bjnano.5.66

• termini contact elements as well as the presence of water and mucus between hairs and respective substrates suggest that biological structures operating underwater cannot exploit filament-like structures to generate van der Waals forces [3]. We completely agree with this idea and think that under wet

DNA origami deposition on native and passivated molybdenum disulfide substrates

• Xiaoning Zhang,
• Masudur Rahman,
• David Neff and
• Michael L. Norton

Beilstein J. Nanotechnol. 2014, 5, 501–506, doi:10.3762/bjnano.5.58

• to adsorb through van der Waals forces between the four nitrogenous nucleobases and the basal plane of MoS2 [18]. For example, in the report of Maddocks et al. [21], guanine, one of the four DNA bases, was observed, by using scanning tunneling microscopy (STM), to form a stable two-dimensional

• . This is readily understood in the context of a model, in which the pyrenyl group in 1-pyrenemethylamine is bound to the highly planar, polar, and polarizable MoS2 surface by van der Waals forces and forms an adhesion layer. Conversely, the amine group in 1-pyrenemethylamine interacts electrostatically

Morphological characterization of fullerene–androsterone conjugates

• Alberto Ruiz,
• Margarita Suárez,
• Nazario Martin,
• Fernando Albericio and
• Hortensia Rodríguez

Beilstein J. Nanotechnol. 2014, 5, 374–379, doi:10.3762/bjnano.5.43

• representative analysis of each sample, several areas of the grids were observed. The two diastereomeric pairs (Ia,b and IIa,b) showed spherical self-assembly due to the non-covalent interactions present in these compounds, i.e., van der Waals forces, hydrogen bonding, hydrophilic/hydrophobic interactions, π–π

Unlocking higher harmonics in atomic force microscopy with gentle interactions

• Sergio Santos,
• Victor Barcons,
• Josep Font and
• Albert Verdaguer

Beilstein J. Nanotechnol. 2014, 5, 268–277, doi:10.3762/bjnano.5.29

• phase shift calculated as the sums ΣΔ (n = 1–9) are 119.8, 19.3 and 5.4° and decrease with decreasing the variations in peak force, i.e., 29, 8 and 3 pN, respectively. It is also interesting to note that the source of variations in peak force with variations in Hamaker H (Equation 10), i.e., van der

• Waals forces, relates to variations in the distance of minimum approach, dm, with variations in H. To be more specific, dm, increases with increasing H. For example, in the simulations, by varying H from H1 = 0.2 × 10−19 J to H2 = 1.4 × 10−19 J the variation is Δdm ≈ 0.83 nm. This would experimentally

Influence of the adsorption geometry of PTCDA on Ag(111) on the tip–molecule forces in non-contact atomic force microscopy

• Gernot Langewisch,
• Jens Falter,
• André Schirmeisen and
• Harald Fuchs

Beilstein J. Nanotechnol. 2014, 5, 98–104, doi:10.3762/bjnano.5.9

• individually, the evolution of the intramolecular contrast as a function of the distance z is as expected. At larger distances, in the regime of attractive long-range interactions such as van-der-Waals forces, no internal structures can be observed in the horizontal cuts through the 3D force field. The