Recent highlights in nanoscale and mesoscale friction

• Andrea Vanossi,
• Dirk Dietzel,
• Andre Schirmeisen,
• Ernst Meyer,
• Rémy Pawlak,
• Thilo Glatzel,
• Marcin Kisiel,
• Shigeki Kawai and
• Nicola Manini

Beilstein J. Nanotechnol. 2018, 9, 1995–2014, doi:10.3762/bjnano.9.190

• able to synthesize smart lubricants that can change their lubrication properties on demand. By irradiation with the appropriate wavelength these novel materials might change from a high-friction to a low-friction state. Analogous concepts can be envisaged for friction anisotropy [180] and for adhesion

Synthesis of hafnium nanoparticles and hafnium nanoparticle films by gas condensation and energetic deposition

• Irini Michelakaki,
• Nikos Boukos,
• Dimitrios A. Dragatogiannis,
• Spyros Stathopoulos,
• Costas A. Charitidis and
• Dimitris Tsoukalas

Beilstein J. Nanotechnol. 2018, 9, 1868–1880, doi:10.3762/bjnano.9.179

• demonstrate high catalytic activity during hydrogenation of levulinic acid [17], nickel NPs, which find application as electrochemical sensor [18], and cobalt NPs, which exhibit high magnetic anisotropy [19]. Recently, we have reported that hcp hafnium nanoparticles fabricated by inert-gas condensation, when

Increasing the performance of a superconducting spin valve using a Heusler alloy

• Andrey A. Kamashev,
• Aidar A. Validov,
• Joachim Schumann,
• Vladislav Kataev,
• Bernd Büchner,
• Yakov V. Fominov and
• Ilgiz A. Garifullin

Beilstein J. Nanotechnol. 2018, 9, 1764–1769, doi:10.3762/bjnano.9.167

• samples [15]. Thus, the final design of the SSV structures was set as AFM/F1/N1/F2/N2/S. In this construction the Cu interlayer (N1) decouples magnetizations of the Fe1 (F1) and Fe2 (F2) layers and the antiferromagnetic (AFM) CoOx layer biases the magnetization of the Fe1 layer by anisotropy fields

Magnetic properties of Fe₃O₄ antidot arrays synthesized by AFIR: atomic layer deposition, focused ion beam and thermal reduction

• Juan L. Palma,
• Alejandro Pereira,
• Raquel Álvaro,
• José Miguel García-Martín and
• Juan Escrig

Beilstein J. Nanotechnol. 2018, 9, 1728–1734, doi:10.3762/bjnano.9.164

• of the holes has to be of the same order of magnitude as the domain wall width. Assuming Bloch-type domain walls, the width W is given by where A is the exchange constant and K is the magnetic anisotropy. Taking common values of A = 15.3 × 10−12 J/m [37] and K = 2.1 × 104 J/m3 [38], W = 84 nm is

Photoluminescence of CdSe/ZnS quantum dots in nematic liquid crystals in electric fields

• Margarita A. Kurochkina,
• Elena A. Konshina and
• Daria Khmelevskaia

Beilstein J. Nanotechnol. 2018, 9, 1544–1549, doi:10.3762/bjnano.9.145

• , Russia 10.3762/bjnano.9.145 Abstract We have experimentally investigated the effect of the reorientation of a nematic liquid crystal (LC) in an electric field on the photoluminescence (PL) of CdSe/ZnS semiconductor quantum dots (QDs). To the LC with positive dielectric anisotropy, 1 wt % QDs with a core

• spectral luminescence properties of the nematic LCs with a positive dielectric anisotropy doped with semiconductor CdSe/ZnS quantum dots [18][19][20]. The luminescence quenching of a planar oriented liquid crystal depended not only on the size but also on the concentration of QDs [18]. The PL intensity of

• the director field under the action of an electric field. We have used a nematic liquid crystal with positive dielectric anisotropy as the LC matrix. The liquid crystal doped with QDs was aligned in parallel (a vertical orientation) or perpendicular (a planar orientation) to the electric field vector

Optical near-field mapping of plasmonic nanostructures prepared by nanosphere lithography

• Gitanjali Kolhatkar,
• Alexandre Merlen,
• Jiawei Zhang,
• Chahinez Dab,
• Gregory Q. Wallace,
• François Lagugné-Labarthet and
• Andreas Ruediger

Beilstein J. Nanotechnol. 2018, 9, 1536–1543, doi:10.3762/bjnano.9.144

• periodicity of ≈3 µm−1 in the Fourier (2D reciprocal) space. The anisotropy of this pattern is also reflected in the 2D fast Fourier transform (FFT) of the optical image, presented in Figure 1c. In addition, those patterns vary with the polarization, and with the laser focus. Thus, these oscillation patterns

Robust midgap states in band-inverted junctions under electric and magnetic fields

• Álvaro Díaz-Fernández,
• Natalia del Valle and
• Francisco Domínguez-Adame

Beilstein J. Nanotechnol. 2018, 9, 1405–1413, doi:10.3762/bjnano.9.133

• , v is an interband matrix element having dimensions of velocity and it is assumed scalar, corresponding to isotropic bands around the L point. It is worth mentioning that the bands of IV–VI compounds around the L points are actually anisotropic. Nevertheless, this anisotropy can be absorbed in the

Interplay between pairing and correlations in spin-polarized bound states

• Szczepan Głodzik,
• Aksel Kobiałka,
• Anna Gorczyca-Goraj,
• Andrzej Ptok,
• Grzegorz Górski,
• Maciej M. Maśka and
• Tadeusz Domański

Beilstein J. Nanotechnol. 2018, 9, 1370–1380, doi:10.3762/bjnano.9.129

• angular anisotropy. Our results, presented in Figure 3, clearly indicate the spatial particle–hole oscillations of the YSR states (compare the blue and red lines). Such particle–hole oscillations decay exponentially with r in agreement with previous studies [11][37][38]. The dominant (particle or hole

Disorder-induced suppression of the zero-bias conductance peak splitting in topological superconducting nanowires

• Jun-Tong Ren,
• Hai-Feng Lü,
• Sha-Sha Ke,
• Yong Guo and
• Huai-Wu Zhang

Beilstein J. Nanotechnol. 2018, 9, 1358–1369, doi:10.3762/bjnano.9.128

• -binding model. We introduce three types of disorder into the system, including random fluctuations in the chemical potential, spatially changing in the superconducting pair potential, and the anisotropy of the nearest-neighbor hopping strength through lattice sites. We demonstrated that the disorder could

Formation and development of nanometer-sized cybotactic clusters in bent-core nematic liquid crystalline compounds

• Yuri P. Panarin,
• Sithara P. Sreenilayam,
• Jagdish K. Vij,
• Anne Lehmann and
• Carsten Tschierske

Beilstein J. Nanotechnol. 2018, 9, 1288–1296, doi:10.3762/bjnano.9.121

• . Depending on the frequency and the magnitude of the applied electric field, three types of electro-hydrodynamic instabilities have been observed in the BC nematics with negative dielectric and conductivity anisotropy [60][61]. During this exercise, we checked the effect of an external electric field on a

Field-controlled ultrafast magnetization dynamics in two-dimensional nanoscale ferromagnetic antidot arrays

• Anulekha De,
• Sucheta Mondal,
• Sourav Sahoo,
• Saswati Barman,
• Yoshichika Otani,
• Rajib Kumar Mitra and
• Anjan Barman

Beilstein J. Nanotechnol. 2018, 9, 1123–1134, doi:10.3762/bjnano.9.104

• can be varied to tune the magnonic spectra and magnetization dynamics in ferromagnetic antidot lattices. Several studies have been focused on the engineering of the coercive field, magnetoresistance and anisotropy properties on domain formation and the magnetization reversal mechanism with the change

• strength and orientation of the bias field [6][7][8][19][20][21][22][23][24][25][26]. Intrinsic configurational magnetic anisotropy arising due to the internal field variation can be tuned effectively by varying the antidot lattice symmetry [21][24]. The shape of the antidots is found to control the SW

• mode structures as well as the anisotropy in the frequency spectra [25]. Quantized SW modes have been found to be transformed to propagating ones and vice versa in rhombic antidot lattices with the variation of the in-plane orientation of the bias-magnetic field [26]. A particular study showed the

Magnetic characterization of cobalt nanowires and square nanorings fabricated by focused electron beam induced deposition

• Federico Venturi,
• Gian Carlo Gazzadi,
• Amir H. Tavabi,
• Alberto Rota,
• Rafal E. Dunin-Borkowski and
• Stefano Frabboni

Beilstein J. Nanotechnol. 2018, 9, 1040–1049, doi:10.3762/bjnano.9.97

• noted that Co carbonyl precursor was chosen here because it has been shown to provide high purity deposits with magnetic properties that are close to those of pure Co [13]. It is well known that shape anisotropy has a profound influence on the magnetic properties of nanostructured materials. The NW is a

• basic building block of magnetic nanodevices, as its high aspect ratio (length/width) often results in a single magnetic domain state due to shape anisotropy [14]. In detail, a NW has a stable magnetic state if its width is smaller than 7·Δd, where Δd is the dipolar exchange length [15], which is ca

• monodomain states, with their magnetization aligned along their long axes due to shape anisotropy [13]. Impurities are present on some samples (especially for the 20 s and 40 s depositions at 5 keV), resulting in flux-closure domain states, which deform the dipole-like phase structure locally. These

Effect of ferroelectric BaTiO₃ particles on the threshold voltage of a smectic A liquid crystal

• Abbas R. Imamaliyev,
• Mahammadali A. Ramazanov and
• Shirkhan A. Humbatov

Beilstein J. Nanotechnol. 2018, 9, 824–828, doi:10.3762/bjnano.9.76

• reduce the threshold voltage. The obtained result is explained by two factors: an increase of dielectric anisotropy of the liquid crystals and the formation of a strong electric field near polarized particles of BaTiO3. It was shown that the role of the second factor is dominant. The explanations of some

• ferroelectric BaTiO3 nanoparticles were found to exhibit a nonvolatile electromechanical memory effect in the isotropic phase [9]. Ferroelectric nanoparticles reduce the threshold voltage by enhancing the dielectric anisotropy of the nematic LC and the system becomes sensitive to the sign of the applied

• -decyloxybenzoate and 4-cyano-4′-pentylbiphenyl with a molar ratio of 1:1. The mixture is in the smectic A phase in the temperature range of 32.5–47.0 °C and has positive dielectric anisotropy. BaTiO3 is a ferroelectric material with high spontaneous polarization (0.26 C·m−2 at room temperature) [16][17]. In our

Engineering of oriented carbon nanotubes in composite materials

• Razieh Beigmoradi,
• Abdolreza Samimi and
• Davod Mohebbi-Kalhori

Beilstein J. Nanotechnol. 2018, 9, 415–435, doi:10.3762/bjnano.9.41

• anisotropy, is achieved for the engineering of cardiac [21], muscle [22] and nerve tissues [23]. Finally, CNT properties can be fine-tuned upon chemical functionalization. However, the latter characteristic needs to be well-balanced in order to prevent degradation of the CNT properties [24][25][26]. The

Dynamic behavior of nematic liquid crystal mixtures with quantum dots in electric fields

• Emil Petrescu,
• Cristina Cirtoaje and
• Octavian Danila

Beilstein J. Nanotechnol. 2018, 9, 399–406, doi:10.3762/bjnano.9.39

• quantum dot surface. Dynamic experiments performed in alternating electric fields proved that by adding a small amount of CdSe/ZnS quantum dots in thermotropic nematic liquid crystal with positive dielectric anisotropy, we obtain a decrease of the relaxation time. When an external electric field higher

• -based device parameters. Theoretical Background When a nematic liquid crystal with positive dielectric anisotropy is exposed to an electric field, and if the intensity of the field is higher than the Fréedericksz transition threshold, the molecular director changes its orientation, trying to align in

• , , and electric anisotropy, εa, we use the effective perpendicular permittivity, , and effective anisotropy, εaeff. If a small spherical cavity is considered inside the liquid crystal, a polarisation field on the hole surface appears. According to classical theory developed by Landau and Lifshitz [20

Dynamic behavior of a nematic liquid crystal with added carbon nanotubes in an electric field

• Emil Petrescu and
• Cristina Cirtoaje

Beilstein J. Nanotechnol. 2018, 9, 233–241, doi:10.3762/bjnano.9.25

• -cyano-4’-pentylbiphenyl (5CB) liquid crystal (LC). Theoretical Background When a liquid crystal with positive dielectric anisotropy is exposed to an external electric field higher than the critical Fréedericksz transition threshold, its molecules have a tendency to orient their director parallel to the

• crystal with the electric field (Figure 2) is: where Here is the transverse component of the dielectric permittivity and is the dielectric anisotropy of the liquid crystal. Since D, the electric displacement, is constant, the voltage between the electrodes can be written as: and Equation 7 becomes: If

• time compared to the liquid crystal sample (Figure 4b). If the voltage is applied for a long period of time (at least 1 hour) the nanotubes align parallel to the field, due to their positive anisotropy [18][19][20][21]. When the field is then switched off, the LC molecules return to their original

Liquid-crystalline nanoarchitectures for tissue engineering

• Baeckkyoung Sung and
• Min-Ho Kim

Beilstein J. Nanotechnol. 2018, 9, 205–215, doi:10.3762/bjnano.9.22

• modulus, porosity, surface roughness, and local anisotropy [102]. LC hydrogels and implants in nematic and smectic-A phases LC-ordered anisotropic gels have great potential to be directly applied to regenerative medicine therapeutics, due to their intrinsic tissue compatibility. Thermally or

• applications, the self-assembly of biopolymers in biocompatible ranges of physicochemical factors can be an ideal property, especially for developing scaffolds for cell encapsulation. The local anisotropy of the 3D architecture in the LC scaffolds provides a versatile strategy to dictate guided cell growth and

Humidity-dependent wound sealing in succulent leaves of Delosperma cooperi – An adaptation to seasonal drought stress

• Olga Speck,
• Mark Schlechtendahl,
• Florian Borm,
• Tim Kampowski and
• Thomas Speck

Beilstein J. Nanotechnol. 2018, 9, 175–186, doi:10.3762/bjnano.9.20

• prepared from epidermis samples and from the basal and apical region of the tapered strands and cross-sectional areas were calculated. The epidermis was tested in a longitudinal and in a transversal direction to test possible anisotropy in this tissue layer. To reduce dehydration effects during tensile

Nematic topological defects positionally controlled by geometry and external fields

• Pavlo Kurioz,
• Marko Kralj,
• Bryce S. Murray,
• Charles Rosenblatt and
• Samo Kralj

Beilstein J. Nanotechnol. 2018, 9, 109–118, doi:10.3762/bjnano.9.13

• TDs are various liquid crystal (LC) phases [5]. They are relatively easily accessible to various experimental methods [6] due to their unique combination of optical anisotropy and transparency, fluid character, and mechanical softness. In addition, the diversity of LC phases and structures guarantees

• representative characteristic elastic constant in the single elastic constant approximation, is the external electric field, ε0 is the permittivity of free space, and Δε is the dielectric constant anisotropy. We model conditions at the LC confining boundaries either by [15][16]: or where w is the surface

• departure from the z-axis. We next apply an external electric field along the z-axis and assume that the LC possesses a negative dielectric anisotropy (Δε < 0). In this case the external field favors the negatively uniaxial part of the boojum. Consequently, it becomes elongated on increasing the field

Nematic liquid crystal alignment on subwavelength metal gratings

• Irina V. Kasyanova,
• Artur R. Geivandov,
• Vladimir V. Artemov,
• Maxim V. Gorkunov and
• Serguei P. Palto

Beilstein J. Nanotechnol. 2018, 9, 42–47, doi:10.3762/bjnano.9.6

• transverse magnetic (TM) modes are due to the optical anisotropy of the LC: the TM mode is polarized along the grating wavevector (and across the slits), thus, it deals with the ordinary refractive index, no, whereas the orthogonal TE mode interacts with the extraordinary refractive index, ne. Based on the

Study of the vertically aligned in-plane switching liquid crystal mode in microscale periodic electric fields

• Artur R. Geivandov,
• Mikhail I. Barnik,
• Irina V. Kasyanova and
• Serguei P. Palto

Beilstein J. Nanotechnol. 2018, 9, 11–19, doi:10.3762/bjnano.9.2

• = 3, 6 and 10 μm, respectively. The electrodes were made either of transparent indium tin oxide (ITO) or opaque chromium coating prepared by vacuum sputtering. The LC cells were filled with Merck E7 and ZLI 1957/5 LC mixtures with positive dielectric anisotropy. E7 is almost twice as viscous as ZLI

• 1957/5 and exhibits almost double birefringence (∆n). The larger birefringence of E7 allows for making smaller cells with an equivalent optical retardation. Also, the larger low-frequency dielectric anisotropy of E7 yields a stronger electric field torque, which is favorable for shortening the

• anisotropy. In the mentioned example of the 2 ms driving pulse the maximal switched-on transmittance is about 10%, which is a fifth of the 50% in the ideal case (at 100% optical aperture, ideal polarizers and π-phase delay provided by LC layer; we are also reminding that we define the transmittance with

Magnetic field induced orientational transitions in liquid crystals doped with carbon nanotubes

• Danil A. Petrov,
• Pavel K. Skokov and
• Alexander N. Zakhlevnykh

Beilstein J. Nanotechnol. 2017, 8, 2807–2817, doi:10.3762/bjnano.8.280

• shape (aspect ratios of 102 to 103) and anomalously high anisotropy of the diamagnetic susceptibility ( ≈ 10−5 to 10−4) [8][9][10][11], CNTs are very attractive for the creation of nanocomposites based on LCs with high magneto-orientational response. From experimental data [12][13][14][15][16], it is

• and planar coupling of LC with the CNT surface, then in the absence of a magnetic field . In the case of a positive anisotropy of the diamagnetic susceptibility of the LC χa > 0, applying a magnetic field H = (0,0,H) will lead to the appearance of distortions in the orientational structure of the LC

• . This effect is known as the Fréedericksz transition [32]. CNTs are also oriented by the magnetic field, because they possess an anomalously strong diamagnetism and positive diamagnetic anisotropy [10][33][34][35], so even small concentrations of CNTs in suspension should lead to a decreasing of the

Exploring wear at the nanoscale with circular mode atomic force microscopy

• Olivier Noel,
• Aleksandar Vencl and
• Pierre-Emmanuel Mazeran

Beilstein J. Nanotechnol. 2017, 8, 2662–2668, doi:10.3762/bjnano.8.266

• the probe, if worn during the experiment, is submitted to an isotropic wear; (6) the circular displacement allows for the exploration of wear in all directions of the surface material, which may be of major interest to investigate wear anisotropy; and (7) if wear debris are generated during the wear

Ferrocholesteric–ferronematic transitions induced by shear flow and magnetic field

• Dmitriy V. Makarov,
• Alexander A. Novikov and
• Alexander N. Zakhlevnykh

Beilstein J. Nanotechnol. 2017, 8, 2552–2561, doi:10.3762/bjnano.8.255

• various external influences (mechanical, electromagnetic, acoustic, and temperature fields). It is known [13] that with a positive anisotropy of the magnetic susceptibility χa of a liquid crystal, the director tends to orientate along the magnetic field. The application of a magnetic field perpendicular

• also spirally twisted in space, and in this respect the ferrocholesteric is a liquid crystal analogue of a helicoidal ferromagnet. We apply the magnetic field H = H(cosφH, sinφH, 0) orthogonally to the axis of the ferrocholesteric helix at an angle φH in the shear plane x–y. We assume the anisotropy of

Alternating current magnetic susceptibility of a ferronematic

• Natália Tomašovičová,
• Jozef Kováč,
• Veronika Gdovinová,
• Nándor Éber,
• Tibor Tóth-Katona,
• Jan Jadżyn and
• Peter Kopčanský

Beilstein J. Nanotechnol. 2017, 8, 2515–2520, doi:10.3762/bjnano.8.251

• attention that nematic liquid crystals (LCs) have attracted in recent decades is due to the anisotropy of their physical properties. This anisotropy allows for a realignment of their director (the axis of cylindrical symmetry) by external electrical or magnetic fields, or by shear [1]. In common nematics

• , the threshold voltage of the reorientational response is just a few volts, owing to the relatively large anisotropy of the dielectric permittivity. Analogous effects exist with magnetic fields. However, the threshold magnetic fields are high (B = μ0H ≈ 1 T) as a consequence of the small diamagnetic

• susceptibility anisotropy (χa ≈ 10−6) of liquid crystals. As a way of lowering the required applied magnetic field, doping liquid crystals with magnetic nanoparticles (MNPs) has been proposed [2]. The stable colloidal suspensions of MNPs in nematic LCs are now known as ferronematics (FNs). Following the first