Measuring adhesion on rough surfaces using atomic force microscopy with a liquid probe

• Juan V. Escobar,
• Cristina Garza and
• Rolando Castillo

Beilstein J. Nanotechnol. 2017, 8, 813–825, doi:10.3762/bjnano.8.84

• and adhesion can be mentioned. Samuel et al. [22] found that when a water drop is retracting from a solid surface, the pull-off force correlates well with the receding contact angle. The pull-off force decreases monotonically as the receding contact angle increases. An important phenomenon that also

• needs to be taken into account is that a drop attached to two flat surfaces can form a liquid bridge that can be compressed and stretched [23][24]; Chen et al. [25] have presented models of the effect of contact angle hysteresis on this phenomenon. Nevertheless, when adhesion is high, the water drop may

• , the differences in roughness are comparatively larger and are enough to explain the wetting differences with mercury as characterized by contact angle measurements [26]. One surface is the original boron-doped microcrystalline diamond film previous to the oxidation described above, with small rugosity

Biological and biomimetic materials and surfaces

• Stanislav Gorb and
• Thomas Speck

Beilstein J. Nanotechnol. 2017, 8, 403–407, doi:10.3762/bjnano.8.42

• advancing and receding contact angles of a liquid drop. The authors additionally applied a three-gradient model for a liquid/vapour system in contact with a complex surface geometry [22]. The authors concluded that the air entrapment is presumably not the main reason for the advancing contact angle

• surface, rather than any simplified parameter, determines the final observed contact angle. Chemical analyses of insect tarsal fluid motivated Speidel et al. to prepare 12 biologically inspired, heterogeneous, synthetic emulsions. The microscopic structure was analysed and adhesive, frictional, and

Functionalized TiO₂ nanoparticles by single-step hydrothermal synthesis: the role of the silane coupling agents

• Antoine R. M. Dalod,
• Lars Henriksen,
• Tor Grande and
• Mari-Ann Einarsrud

Beilstein J. Nanotechnol. 2017, 8, 304–312, doi:10.3762/bjnano.8.33

• ) and chemical bonding (via Ti–O–Si bonds) of silanes onto TiO2 nanoparticles occurred [16]. Later, Zhao et al. detailed the cross-linking and chemical bonding mechanisms of APTMS and 3-isocyanatopropyltrimethoxysilane on TiO2 nanoparticles [15]. A contact angle of about 150° for water was measured

Template-controlled piezoactivity of ZnO thin films grown via a bioinspired approach

• Nina J. Blumenstein,
• Fabian Streb,
• Stefan Walheim,
• Thomas Schimmel,
• Zaklina Burghard and
• Joachim Bill

Beilstein J. Nanotechnol. 2017, 8, 296–303, doi:10.3762/bjnano.8.32

• characterized the structure and hydrophilic character of the templates by atomic force microscopy (AFM) and water contact angle measurements (WCA) prior to mineralization. The AFM images of the PEL and COOH-SAM before mineralization show a smooth surface for both templates (Figure 1). The PEL is slightly

Performance of colloidal CdS sensitized solar cells with ZnO nanorods/nanoparticles

• Anurag Roy,
• Partha Pratim Das,
• Mukta Tathavadekar,
• Sumita Das and
• Parukuttyamma Sujatha Devi

Beilstein J. Nanotechnol. 2017, 8, 210–221, doi:10.3762/bjnano.8.23

• reflectance spectra were measured on a UV–vis–NIR spectrometer (Shimadzu, UV-3600) on the considered films. Contact angle (CA) measurements were performed on a KRUSS Drop Shape Analyser, Germany (DSA-4). The photovoltaic J–V characteristics were measured using a solar simulator (Newport) at 100 mW/cm2 (1 sun

• analysis, as shown in Figure 3b. Further investigation of contact angle (CA) measurements by using CdS dispersions on ZnO-based films justifies the sensitization capability. The reduced CA value of 19.6° for the film fabricated with ZnO-P further ascertains its better CdS affinity whereas a moderate CA

• ) Diffuse reflectance spectrum of the same films compared to bare ZnO and (c) a digital image showing the difference in contact angle for ethanolic solution of N719 dye for ZnO-R and ZnO-P films. (a,b) Microstructural FESEM and TEM bright field images of synthesized ZnO-P and (c,d) ZnO-R. FESEM images of

Flexible photonic crystal membranes with nanoparticle high refractive index layers

• Torben Karrock,
• Moritz Paulsen and
• Martina Gerken

Beilstein J. Nanotechnol. 2017, 8, 203–209, doi:10.3762/bjnano.8.22

• a later water-based fabrication step. The water contact angle of untreated PDMS is 105–115° [19]. To alter the hydrophobic surface of PDMS an O2 plasma treatment is commonly used to temporarily create a hydrophilic surface [17][19]. To prevent damage to the nanostructure we instead add poly

• reorientation of the PEO to the surface–water interface the interfacial free energy is reduced. The modified PDMS surface exhibits a time-dependent water contact angle. It drops rapidly in the first 30 s and is stable after ≈200 s. The contact angle is reduced to 20° at a concentration of about 2% of PEO in the

• from 3M) was added. This results in an even lower contact angle between the solution and the PDMS substrate. The mixture is stirred for 5 min (Figure 6b1). The PDMS membranes are clamped to an appropriate spin coating chuck we designed for the specific geometry of our membranes. To avoid ripples in the

Impact of surface wettability on S-layer recrystallization: a real-time characterization by QCM-D

• Jagoba Iturri,
• Ana C. Vianna,
• Alberto Moreno-Cencerrado,
• Dietmar Pum,
• Uwe B. Sleytr and
• José Luis Toca-Herrera

Beilstein J. Nanotechnol. 2017, 8, 91–98, doi:10.3762/bjnano.8.10

• –substrate interactions, the above mentioned protocol was again followed for silicon dioxide substrates under different wettability conditions: either UV/ozone-treated (hydrophilic, water contact angle Θ < 10°) or vapor-coated with a fluorosilane (Θ = 90°). Figure 4a depicts the time evolution of both Δf and

• is mainly driven by hydrophobic interactions (non-specific). Also, SCWP shows a rather hydrophilic behavior (contact angle Θ < 10°), opposite to that of the fluorosilane. However, and in addition to the transition peak shown in ΔD and the final SbpA mass bound, the rapidity by which the S-layer

• slopes derived, can characterize specifically one type of process and enables the differentiation between them. Contact angle measurements: Sessile-drop experiments were performed with a contact-angle measuring system (Kruss D100, Hamburg, Germany). Millipore water (18.2 MΩ·cm) was used as the liquid

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

• the contact angle, and thus allowing frogs to adhere to even strongly hydrophobic surfaces. Our experiments The whole animal tilting experiments provide direct data about the tree frog’s capabilities on rough surfaces, as the slip and fall angles reflect friction and adhesive forces of the frogs [16

Three-gradient regular solution model for simple liquids wetting complex surface topologies

• Sabine Akerboom,
• Marleen Kamperman and
• Frans A. M. Leermakers

Beilstein J. Nanotechnol. 2016, 7, 1377–1396, doi:10.3762/bjnano.7.129

• (contact angle on a smooth surface θY < 90°) to hydrophobic (effective advancing contact angle θ > 90°). Both the Wenzel wetting state, that is cavities under the liquid are filled, as well as the Cassie–Baxter wetting state, that is air entrapment in the cavities under the liquid, were observed using our

• approach, without a discontinuity in the water front shape or in the water advancing contact angle θ. Therefore, air entrapment cannot be the main reason why the contact angle θ for an advancing water front varies. Rather, the contact line is pinned and curved due to the surface structures, inducing

• curvature perpendicular to the plane in which the contact angle θ is observed, and the contact line does not move in a continuous way, but via depinning transitions. The pinning is not limited to kinks in the surface with angles θkink smaller than the angle θY. Even for θkink > θY, contact line pinning is

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

• , the concentration of oxygen on the CNT surface increases, which decreases the contact angle. The lower contact angle results in an improvement of interfacial interactions and leads to an enhancement of mechanical properties such as tensile strength, modulus and coefficient of friction [123]. Eitan et

Characterization of spherical domains at the polystyrene thin film–water interface

• Khurshid Ahmad,
• Xuezeng Zhao,
• Yunlu Pan and
• Danish Hussain

Beilstein J. Nanotechnol. 2016, 7, 581–590, doi:10.3762/bjnano.7.51

• were studied and characterized using atomic force microscopy (AFM). The study showed that these domains have similar characteristics to micro- and nanobubbles, such as a spherical shape, smaller contact angle, low line tension, and they exhibit phase contrast and the coalescence phenomenon. However

• ][21], and the different characteristics of bubbles have been studied by various research groups [15][16][19][23][24]. Studies have shown that the contact angle of the nanoscale gaseous bubbles is smaller than the macroscopic gaseous bubbles (measured from the air side) [15]. It has also been reported

• that the contact angle of the gaseous bubble increases with the lateral size in each independent size scale [15]. Similarly, increased surface roughness and the influx of gas from the interfacial gas enrichment favors formation of larger gaseous bubbles [15][19]. In addition, other studies have

Rigid multipodal platforms for metal surfaces

• Michal Valášek,
• Marcin Lindner and
• Marcel Mayor

Beilstein J. Nanotechnol. 2016, 7, 374–405, doi:10.3762/bjnano.7.34

• packed self-assembled monolayers (SAMs) on gold [101]. The SAMs were characterized using ellipsometry, contact angle goniometry, polarization modulation-infrared reflection adsorption spectroscopy (PM-IRRAS) and XPS. The data in these fundamental studies were compared with those obtained from SAMs that

• thiol-containing head groups [114]. Ellipsometric measurements of cyclohexyl-based tridental platforms exhibit that the thickness of these SAMs is significantly diminished as compared to alkylthiol SAMs of corresponding chain lengths. The conformational order in these SAMs as determined by the contact

• angle measurements and the PM-IRRAS spectra indicate an overall decreasing trend as follows: C18H37SH >> 22-C13 > 22-C8 > 22-C3. XPS measurements revealed that the sulfur atoms of these alkylated platforms are attached to the gold surface, and perpendicular alkyl tail groups are loosely packed, compared

Chemical bath deposition of textured and compact zinc oxide thin films on vinyl-terminated polystyrene brushes

• Nina J. Blumenstein,
• Caroline G. Hofmeister,
• Peter Lindemann,
• Cheng Huang,
• Johannes Baier,
• Andreas Leineweber,
• Stefan Walheim,
• Christof Wöll,
• Thomas Schimmel and
• Joachim Bill

Beilstein J. Nanotechnol. 2016, 7, 102–110, doi:10.3762/bjnano.7.12

• stronger interaction between the then polar template and polar ZnO crystallites in solution. This may lead to oriented attachment of the crystallites so that the observed (002) texture arises. Characterization of the templates and the resulting ZnO films were performed with ζ-potential and contact angle

• the molecules. Since we measured a thickness of 1–2 nm for our PS films, we can calculate a nominal grafting density of 20–40% (0.164–0.329 molecules per nm2) for our brush system. The polarity of the different surfaces was investigated by ζ-potential and contact angle measurements. The isoelectric

• [38]. This could lead to a smaller difference in the ζ-potential of the SiOx and PS brush in methanol as compared to the results in water. Water contact angle (WCA) measurements confirm the findings of the ζ-potential measurements. The SiOx surface exhibits a high hydrophilicity with a WCA below 4

Nanostructured surfaces by supramolecular self-assembly of linear oligosilsesquioxanes with biocompatible side groups

• Maria Nowacka,
• Anna Kowalewska and
• Tomasz Makowski

Beilstein J. Nanotechnol. 2015, 6, 2377–2387, doi:10.3762/bjnano.6.244

• observed due to the donor–acceptor character of the functional groups. The texture of supramolecular nanostructures formed by the studied materials on mica was analysed with atomic force microscopy and their specific surface energy was estimated by contact angle measurements. Significant differences in the

• ≈1700 cm−1 and emergence of diffuse bands in the formed PSAMs was observed). Surface energy of LPSQ-COOH/X coated on native mica The surface free energy (γS) of each studied PSAM sample was determined by measuring the contact angle of water and glycerol as reference liquids (sessile drop technique and

Self-organization of gold nanoparticles on silanated surfaces

• Htet H. Kyaw,
• Salim H. Al-Harthi,
• Azzouz Sellai and
• Joydeep Dutta

Beilstein J. Nanotechnol. 2015, 6, 2345–2353, doi:10.3762/bjnano.6.242

• -functionalized glass substrates. The as grown monolayers and films annealed in ultrahigh vacuum and air (600 °C) were studied by water contact angle measurements, atomic force microscopy, X-ray photoelectron spectroscopy, UV–visible spectroscopy and ultraviolet photoelectron spectroscopy. Results of this study

• important role to change the surface wetting properties of the glass substrates leading to strong or weak bonding between APTES and metal nanoparticles like Au or Ag [25][26]. Wetting behavior of APTES-functionalized glass substrates Water contact angle (WCA) measurements were performed to study the surface

• important role for interfacing of AuNPs. The deposition and orientation of APTES molecules on glass substrate surface were demonstrated by water contact angle measurements. UPS measurements further proved that different orientations of APTES molecules on glass substrate affect the self-organization of AuNPs

Nanostructured superhydrophobic films synthesized by electrodeposition of fluorinated polyindoles

• Gabriela Ramos Chagas,
• Thierry Darmanin and
• Frédéric Guittard

Beilstein J. Nanotechnol. 2015, 6, 2078–2087, doi:10.3762/bjnano.6.212

• Wenzel equation [36] (cos θ = r·cos θY, where r is a roughness parameter), the surface roughness can increase θ, but only if θY > 90°. Hence, it is possible to have an extremely high θwater, but the contact angle hysteresis (H) is usually high because the surface roughness increases also the solid–liquid

• substrate. The contact angle hysteresis (H) and sliding angle (α) were determined with the tilted-drop method. Here, a 6 µL liquid droplet was put on the substrate and the substrate was inclined until the droplet moving. The maximum inclination angle is α. The advanced (θadv) and receding (θrec) contact

Automatic morphological characterization of nanobubbles with a novel image segmentation method and its application in the study of nanobubble coalescence

• Yuliang Wang,
• Huimin Wang,
• Shusheng Bi and
• Bin Guo

Beilstein J. Nanotechnol. 2015, 6, 952–963, doi:10.3762/bjnano.6.98

• compared. With the modified method, the diameter, contact angle, and radius of curvature were automatically measured for all NBs in AFM images. The influence of the selection of the threshold value on the segmentation result was discussed. Moreover, the morphological change in the NBs was studied in terms

• largest volume at 25 °C [35]. They also found that the contact angle of the NB was a function of its radius of curvature. The NB properties, including diameter, height, contact angle, radius of curvature, density and covered area, are normally studied through morphological characterization from AFM images

• selected cross sections, the NB diameter and height can be directly measured. By fitting the cross sections as arcs, the NB contact angle and radius of curvature can be obtained [36][37][38][39]. The morphological characterization of NBs suffers from several difficulties. First, NB image segmentation is

Morphology control of zinc oxide films via polysaccharide-mediated, low temperature, chemical bath deposition

• Florian Waltz,
• Hans-Christoph Schwarz,
• Andreas M. Schneider,
• Stefanie Eiden and
• Peter Behrens

Beilstein J. Nanotechnol. 2015, 6, 799–808, doi:10.3762/bjnano.6.83

• originating from the amorphous glass (data not shown). FE-SEM also failed to visualize the seeds on the glass slides, probably due to their small size and the strong electric charging of the substrate. However, indirect evidence of a successful seeding was possible. Contact angle measurements showed that the

• slides are slightly more hydrophobic after the seeding process. The contact angle of a seeded glass slide was about 58° in comparison to 46° for a clean glass slide. Furthermore, the UV–vis spectra of seeded glass slides showed an absorption band in the UV range at approximately the energy of the ZnO

• was used for a background correction. The contact angle measurement of the ZnO films was carried out using a Surftens apparatus (OEG GmbH, Frankfurt, Germany). The electrical conductivity measurements were performed with a 2100 Multimeter (Keithley Instruments Inc., Cleveland, USA). For the

Applications of three-dimensional carbon nanotube networks

• Manuela Scarselli,
• Paola Castrucci,
• Francesco De Nicola,
• Ilaria Cacciotti,
• Francesca Nanni,
• Emanuela Gatto,
• Mariano Venanzi and
• Maurizio De Crescenzi

Beilstein J. Nanotechnol. 2015, 6, 792–798, doi:10.3762/bjnano.6.82

• hydrophobicity one can measure the advanced static contact angle at room temperature for water droplets of different volumes ranging from 5 to 20 µL, as shown in Figure 4a. The presence of a composite solid–liquid–air interface explains the high value of the measured contact angle (Θ = 175°), as evaluated in

• Figure 4b, with no observable roll-off angle, even when the substrate is turned upside down, see Figure 5a. Therefore, we infer that the contact angle hysteresis is sufficiently high to pin the water droplet on the MWCNT surface. It is possible to estimate the adhesive force in length units of a surface

• in contact with water from the equation [19]: where γLV denotes the surface tension of the liquid–vapor (LV) interface for water γLV = 72.5 mN/m, and Θ is the measured contact angle (Θ = 175°). The estimated adhesion force of the water droplet (20 µL) reported in Figure 4b, is about 50 µN. Measuring

Self-assembled anchor layers/polysaccharide coatings on titanium surfaces: a study of functionalization and stability

• Ognen Pop-Georgievski,
• Dana Kubies,
• Josef Zemek,
• Neda Neykova,
• Roman Demianchuk,
• Eliška Mázl Chánová,
• Miroslav Šlouf,
• Milan Houska and
• František Rypáček

Beilstein J. Nanotechnol. 2015, 6, 617–631, doi:10.3762/bjnano.6.63

• established continuity of the layers are examined by scanning electron microscopy, surface profilometry and atomic force microscopy. The changes in hydrophilicity after each modification step are further examined by contact angle goniometry. Keywords: alginate; biomimetic surfaces; bisphosphonates

• changes in hydrophilicity after each modification and immersion step are further examined by contact angle goniometry. Results and Discussion Surface analysis of activated titanium surfaces The surface concentration of elements present on pristine, activated and flat titanium surfaces, as determined by

• the successful covalent attachment of ALG chains to neridronate, APTES and PDA anchor layers immobilized on activated titanium surfaces. The formation of the ALG and anchor layer films was investigated utilizing SE, AFM and contact angle goniometry. The IRRAS analysis further evidenced the established

Filling of carbon nanotubes and nanofibres

• Reece D. Gately and
• Marc in het Panhuis

Beilstein J. Nanotechnol. 2015, 6, 508–516, doi:10.3762/bjnano.6.53

• relationship between the TCNS radius, the radius of the nanoscale drop of material used to fill the TCNS, and the contact angle between the filler and the TCNS. This model successfully predicted the capillary absorption of non-wettable nanoparticles [93] and has been employed to achieve filling [94] as well as

Synergic combination of the sol–gel method with dip coating for plasmonic devices

• Cristiana Figus,
• Maddalena Patrini,
• Francesco Floris,
• Lucia Fornasari,
• Paola Pellacani,
• Gerardo Marchesini,
• Andrea Valsesia,
• Flavia Artizzu,
• Daniela Marongiu,
• Michele Saba,
• Franco Marabelli,
• Andrea Mura,
• Giovanni Bongiovanni and
• Francesco Quochi

Beilstein J. Nanotechnol. 2015, 6, 500–507, doi:10.3762/bjnano.6.52

• fine-tuning of the silica layer thickness on the plasmonic structure were studied. Control of the silica coating thickness was achieved through a combined approach involving sol–gel and dip-coating techniques. The silica films were characterized using spectroscopic ellipsometry, contact angle

• hydrophobic property of the surface is an important characteristic from the perspective of biosensing applications since it also allows for altering the surface affinity for specific molecules. The surface of the films prepared from fresh sol of pH ≈4 was further characterized through contact angle

• measurements. As shown in Figure 2, these results highlight that the films are hydrophilic with a contact angle of 65°. This value is independent of the film thickness, but decreases with ethanol dilution up to 34° (inset of Figure 2). This suggests a correlation between the distribution of hydroxy groups

Conformal SiO₂ coating of sub-100 nm diameter channels of polycarbonate etched ion-track channels by atomic layer deposition

• Nicolas Sobel,
• Christian Hess,
• Manuela Lukas,
• Anne Spende,
• Bernd Stühn,
• M. E. Toimil-Molares and
• Christina Trautmann

Beilstein J. Nanotechnol. 2015, 6, 472–479, doi:10.3762/bjnano.6.48

• photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). The hydrophilicity of SiO2-coated PC membranes was tested by contact angle measurements. Experimental Figure 1 displays schematically the three main steps involved in the fabrication of SiO2 coated track-etched membranes. These

• standard Cu-lacey transmission electron microscopy grids. Thickness and homogeneity of the resulting nanotubes were characterized by using a high resolution scanning electron microscope (JEOL JSM-7401F) fitted with a transmitted electron detector (STEM-in-SEM). Contact angle measurements Contact angles

• wettability of uncoated and SiO2-coated track-etched membranes was investigated by contact angle measurements. Figure 6 shows the contact angle as a function of the number of ALD cycles. The contact angle decreases with increasing thickness of the SiO2 layer, evidencing that the membrane surface changes its

Exploiting the hierarchical morphology of single-walled and multi-walled carbon nanotube films for highly hydrophobic coatings

• Francesco De Nicola,
• Paola Castrucci,
• Manuela Scarselli,
• Francesca Nanni,
• Ilaria Cacciotti and
• Maurizio De Crescenzi

Beilstein J. Nanotechnol. 2015, 6, 353–360, doi:10.3762/bjnano.6.34

• investigation of carbon nanotube films through scanning electron microscopy (SEM) reveals the multi-scale hierarchical morphology of the self-assembled carbon nanotube random networks. Moreover, contact angle measurements show that hierarchical SWCNT/MWCNT composite surfaces exhibit a higher hydrophobicity

• depending on the number of coaxially arranged graphite planes. Moreover, owing to their honeycomb lattice, carbon nanotubes are inherently hydrophilic (the contact angle of graphite with water being approx. 86° [22]) but apolar. However, by surface functionalization or textured arrangement it can be

• SWCNT films. Moreover, in Figure 3a and Figure 3b, images of water droplets cast on our SWCNT and MWCNT films are shown, with average contact angle values of θ = 110 ± 3° and θ = 97 ± 8°, respectively. These results can be ascribed to the particular morphology of both the films induced by the inherent

Oxygen-plasma-modified biomimetic nanofibrous scaffolds for enhanced compatibility of cardiovascular implants

• Anna Maria Pappa,
• Varvara Karagkiozaki,
• Silke Krol,
• Spyros Kassavetis,
• Dimitris Konstantinou,
• Charalampos Pitsalidis,
• Lazaros Tzounis,
• Nikos Pliatsikas and
• Stergios Logothetidis

Beilstein J. Nanotechnol. 2015, 6, 254–262, doi:10.3762/bjnano.6.24

• . Goniometry (contact angle measurements), scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) measurements were used to evaluate the morphological and chemical changes induced by the plasma treatment. Moreover, depth-sensing nanoindentation was

• observed from the contact angle measurements presented in Table 1, the untreated PCL scaffold demonstrated a water contact angle of 91.3°. A significant decrease of the contact angle was found for both modified systems with insignificant differences in the measured values (21.4° and 19.8° for P = 20 W and

• not appear to have any additional effect as far as the goniometry analysis is concerned. It is worth noting that the presented data from the contact angle measurements are particularly valid only for comparative purposes as the nanofibrous scaffolds are not smooth and homogeneous solid surfaces but