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

• CNT growth, while in the latter, the CNTs are initially grown in random orientation and the arrangement is then achieved during the device integration process. As the ex situ techniques are free from growth restrictions and more flexible in terms of controlling the alignment and sorting of the CNTs

• , they are considered by some as the preferred technique for engineering of oriented CNTs. This review focuses on recent progress in the improvement of the orientation and alignment of CNTs in composite materials. Moreover, the advantages and disadvantages of the processes are discussed as well as their

• future outlook. Keywords: arrangement and alignment; carbon nanotubes; composite materials; orientation; Review Introduction Carbon is one of the most abundant elements comprising the world around us. Before 1985 graphite and diamond were the only known structural forms of carbon [1]. In 1991, Iijima

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

• dots. Basu and co-workers [7] proposed a different model of a quantum dot dispersion in a nematic liquid crystal. According to this model, dots are gathering together forming long chains around which liquid crystal molecules are homogeneously aligned. Such an alignment could not explain the decrease of

• the relaxation time when the field is switched on because the anchoring forces on quantum dots surface will slow down the molecular movement. A possible explanation for this behavior might be given considering a homeotropic alignment of the LC molecules on the QD surface [12]. Thus, if the applied

Temperature-tunable lasing from dye-doped chiral microdroplets encapsulated in a thin polymeric film

• Gia Petriashvili,
• Mauro Daniel Luigi Bruno,
• Maria Penelope De Santo and
• Riccardo Barberi

Beilstein J. Nanotechnol. 2018, 9, 379–383, doi:10.3762/bjnano.9.37

• the coalescence of droplets and to induce the planar alignment of the liquid-crystal molecules at the interface. Inside the droplets, the cholesteric helices arrange in a radial configuration, with the cholesteric layers bent in concentric spherical surfaces. In order to study laser emission from

Design of polar self-assembling lactic acid derivatives possessing submicrometre helical pitch

• Alexej Bubnov,
• Cyril Vacek,
• Michał Czerwiński,
• Terezia Vojtylová,
• Wiktor Piecek and
• Věra Hamplová

Beilstein J. Nanotechnol. 2018, 9, 333–341, doi:10.3762/bjnano.9.33

• and the same length of non-chiral terminal chain. For all compounds the SmC* phase remains quite stable also at its supercooled state, i.e., below the melting point; the crystallisation does not occur even under an applied electric field. Moreover, the uniform alignment of the SmC* phase texture is

• applying an electric field, it is possible to reach uniform alignment which remains very stable with time. Their most exciting property, namely the helical pitch length of 120–320 nm, makes the materials from the KL n/m series potentially applicable for the design of advanced functional multicomponent

• filled into glass cells (Military University of Technology, cell gap of 12 μm, homogeneous alignment) with indium tin oxide transparent electrodes and polyimide layers rubbed unidirectional, which ensured a planar geometry supporting an induction of bookshelf-like smectic structures. The alignment was

Review: Electrostatically actuated nanobeam-based nanoelectromechanical switches – materials solutions and operational conditions

• Liga Jasulaneca,
• Jelena Kosmaca,
• Raimonds Meija,
• Jana Andzane and
• Donats Erts

Beilstein J. Nanotechnol. 2018, 9, 271–300, doi:10.3762/bjnano.9.29

• nanomanipulation approaches. The top-down approach involves lithography, etching and coating technologies to fabricate device structures from bulk materials or thin films [7][19][23][39][47][48][49][50]. The combined approach of fabricating NEM switches requires subsequent transfer and alignment of synthesized

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

• Dierking and co-workers [13][14] proved an alignment of CNTs parallel to the liquid crystal molecules, so we may assume that the anchoring angle α is neglectable. Thus, Equation 11 becomes: When exposed to an external electric field higher than the critical Fréedericksz transition threshold the molecules

• the nanotubes surface and a homogeneous alignment of the cell was considered. Thus, in the absence of any external fields, the nematic director and carbon nanotubes axis are parallel to the x-axis. When the electric field is applied on a LC + SWCNT cell, the molecules change their orientation tending

• aligned along the x-axis. In this case the relaxation time will be smaller than that of a pure nematic because the interaction forces between nematic molecules and carbon nanotubes pull the molecules back to a planar alignment. The free energy density results from Equation 22 in which the applied voltage

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

• less parallel to one another. The mean direction of this long-range orientational order is called the director. If the constituent rods have intrinsic chirality, the cholesteric phase (also termed as chiral nematic phase) is induced by continuously twisting the nematic alignment, which can be

• alignment of ECM fibers is known to control the cell shape and motion [53]. During development, growth, and proliferation, the 2D/3D topography of ECM affects the cell spreading, focal adhesion strength, and intercellular mechanical signaling [54]. For example, the guided migration of cells in the ECM was

• production of physiologically functional tissue replicas of nerves by controlling 3D cell alignment and growth direction. When cardiomyocytes are embedded in the anisotropic gel scaffolds, the guided cell growth parallel to the major axis of the bundle structure enables the long-range propagation of action

Dielectric properties of a bisimidazolium salt with dodecyl sulfate anion doped with carbon nanotubes

• Doina Manaila Maximean,
• Viorel Cîrcu and
• Constantin Paul Ganea

Beilstein J. Nanotechnol. 2018, 9, 164–174, doi:10.3762/bjnano.9.19

• imposed on the CNTs in such a way that the alignment axis of the CNTs is driven by the LC reorientation controlled by an electric field [37]. The concentration and the spatial distribution of charges in the LC matrix will be affected by the presence of CNTs and, hence, the conductivity will be changed [38

Electrical properties of a liquid crystal dispersed in an electrospun cellulose acetate network

• Doina Manaila Maximean,
• Octavian Danila,
• Pedro L. Almeida and
• Constantin Paul Ganea

Beilstein J. Nanotechnol. 2018, 9, 155–163, doi:10.3762/bjnano.9.18

• there is no uniform direction of alignment of the LC director between different droplets, the optical path of the incident light travelling through a PDLC is different from point to point, due to the mismatch between the effective refractive index of the LC and the refractive index of the polymer. The

Combined scanning probe electronic and thermal characterization of an indium arsenide nanowire

• Tino Wagner,
• Fabian Menges,
• Heike Riel,
• Bernd Gotsmann and
• Andreas Stemmer

Beilstein J. Nanotechnol. 2018, 9, 129–136, doi:10.3762/bjnano.9.15

• = 2 mΩ·cm) silicon wafers coated with a 100 nm thick thermal oxide. Electrical contact pads and alignment marks for e-beam alignment and localization of the NWs where defined and fabricated using an ultraviolet lithography process. The InAs NWs were transferred from a growth substrate onto the pre

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

• , Russia 10.3762/bjnano.9.6 Abstract We have studied the alignment of a nematic liquid crystal (LC) material on aluminum subwavelength nanogratings as a function of the period, p, and the slit width to period ratio, w/p. A method, based on Fourier analysis of the transmittance spectra of the LC grating

• system, has been applied. We show that the gratings provide stable planar alignment only for shorter periods and narrower slits (p < 400 nm, w/p < 2/3). As these parameters increase, the homogeneous surface alignment changes to domains with different tilt angles or to spatially modulated alignment. We

• have also obtained a 90° twisted LC director distribution, implying sufficiently strong azimuthal LC anchoring at the grating surface. Keywords: alignment; Fourier analysis; nematic liquid crystal; subwavelength metal grating; Introduction In the age of nanotechnology, various nanostructured

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

• experimental measurements. Keywords: electrooptics; in-plane switching; liquid crystals; vertical alignment; Introduction In 1997, Lee and co-workers discovered a new LC switching mode and called it vertically aligned in-plane switching (VA-IPS) mode [1]. At that time researchers were looking for LC modes

• electrodes to the opposite substrate [6]. Said approach requires a precise alignment of in-plane electrodes at the opposite substrates, while the resultant benefit from the use of additional electrodes remains questionable. In our opinion, decreasing the characteristic size of LC deformation is the key to

• index of the E7 LC material, which results in stronger reflections at LC–alignment layer–glass boundaries. The second reason is associated with a higher spectral dispersion of the optical phase delay, which is due to the higher birefringence of the E7 LC. The higher dispersion provides a narrower

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

• reentrant transitions occur only for weak coupling of CNTs with the LC matrix. A magnetic field directed perpendicularly to the CNTs makes the initial alignment of tubes energetically unfavorable, so that they begin to rotate in the field direction minimizing the contribution F3 in Equation 1. The LC

• quadrupole response to the magnetic field applied perpendicularly to the initial alignment of the magnetic subsystems. They exhibit a threshold Fréedericksz transition from the initial compensated phase (planar phase) to the non-uniform angular phase, like the CNT suspensions. For weak coupling of magnetic

Impact of titanium dioxide nanoparticles on purification and contamination of nematic liquid crystals

• Dmitrii Pavlovich Shcherbinin and
• Elena A. Konshina

Beilstein J. Nanotechnol. 2017, 8, 2766–2770, doi:10.3762/bjnano.8.275

• addition, nanoparticles can induce other new functions in liquid crystals, including improved response time [14][15], surface plasmon resonance [16], and improvements in alignment [17]. The ionic contamination of LCs remains one of the challenges to LC technology. Ionic conductivity negatively affects LC

Dry adhesives from carbon nanofibers grown in an open ethanol flame

• Christian Lutz,
• Julia Syurik,
• C. N. Shyam Kumar,
• Christian Kübel,
• Michael Bruns and
• Hendrik Hölscher

Beilstein J. Nanotechnol. 2017, 8, 2719–2728, doi:10.3762/bjnano.8.271

• demonstrated possible alignment during growth with an external electric [6] or magnetic field [9]. Surprisingly, these alternative growth methods for 1D-CNs did not receive much attention so far. One among many promising applications of carbon nanotubes are dense arrays that feature interesting adhesion

Patterning of supported gold monolayers via chemical lift-off lithography

• Liane S. Slaughter,
• Kevin M. Cheung,
• Sami Kaappa,
• Huan H. Cao,
• Qing Yang,
• Thomas D. Young,
• Andrew C. Serino,
• Sami Malola,
• Jana M. Olson,
• Stephan Link,
• Hannu Häkkinen,
• Anne M. Andrews and
• Paul S. Weiss

Beilstein J. Nanotechnol. 2017, 8, 2648–2661, doi:10.3762/bjnano.8.265

• measured by electron diffraction [55][56]. At molecular resolution, scanning probe measurements have revealed the rearrangement of Au surface atoms [57][58][59], diffusion and alignment of adatom–adsorbate complexes [50][60], and phase separation of SAMs composed of molecules with different backbones or

The role of ligands in coinage-metal nanoparticles for electronics

• Ioannis Kanelidis and
• Tobias Kraus

Beilstein J. Nanotechnol. 2017, 8, 2625–2639, doi:10.3762/bjnano.8.263

• [83]. Copper nanoparticles in a polypyrrole matrix altered the morphology of the unfilled polymer and changed electrical conductivities from 0.012 S/cm to 0.208 S/cm. Annealing increased the conductivities of both materials; the authors suggest alignment of the polymeric chains and an increase of the

Inelastic electron tunneling spectroscopy of difurylethene-based photochromic single-molecule junctions

• Youngsang Kim,
• Safa G. Bahoosh,
• Dmytro Sysoiev,
• Thomas Huhn,
• Fabian Pauly and
• Elke Scheer

Beilstein J. Nanotechnol. 2017, 8, 2606–2614, doi:10.3762/bjnano.8.261

• located around 0.2 eV below EF. The pinning of the HOMO level at EF for the closed form may lead to enhanced uncertainties with regard to the description of the level alignment in this molecular state with its extended conjugated electron system as compared to the open form with its interrupted π system

• . Although the DFT+Σ method applied here is supposed to reduce level-alignment and band-gap errors, they might not be completely lifted in the closed form. Another important uncertainty, this time on the experimental side, stems from the interpretation of particular peaks in the conductance histograms. We

Localized growth of carbon nanotubes via lithographic fabrication of metallic deposits

• Fan Tu,
• Martin Drost,
• Imre Szenti,
• Janos Kiss,
• Zoltan Kónya and
• Hubertus Marbach

Beilstein J. Nanotechnol. 2017, 8, 2592–2605, doi:10.3762/bjnano.8.260

• ], nanoscale actuators [38], and on-chip coolers [5]. A CNT forest is defined as CNTs grown with high density and vertical alignment. Therefore, it is necessary to increase the number of the CNTs grown per surface area. Corresponding attempts on the native oxide surface on Si(100) used for the results

• enlarged to 10 µm (Figure 7a). Correspondingly Figure 7b,c depicts the results of CNT growth via CVD at two different temperatures: 1073 K and 1133 K. At the lower CVD temperature of 1073 K, CNTs were obtained, apparently with high yield but not with a consistently vertical alignment. However, after growth

• as evidenced via TEM. Additionally, CNTs patterned in high density with vertical alignment, referred to as CNT forests, were produced on Fe deposits fabricated on an Al2O3 substrate. It can be stated that the Al2O3 supports the growth and enhances the yield of CNTs, given that a lower temperature was

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

• magnetic field and a shear flow. Both influences are able to induce the ferrocholesteric–ferronematic transition independently; however, the differences between the magnetic field orientation and the flow alignment direction lead to a competition between magnetic and hydrodynamic mechanisms of influence on

• alignment area of a CLC with a magnetic admixture. This enables the shear flow to unwind the spiral structure of ferrocholesterics with the reactive parameter λ < 1. We have obtained the dependence of the FC helix pitch of the orientational structure on the magnetic field strength and the gradient of the

Dynamic behavior of a nematic liquid crystal mixed with CoFe₂O₄ ferromagnetic nanoparticles in a magnetic field

• Emil Petrescu,
• Cristina Cirtoaje and
• Cristina Stan

Beilstein J. Nanotechnol. 2017, 8, 2467–2473, doi:10.3762/bjnano.8.246

• field intensity of 790 kA/m and a coercive field of 239 kA/m. The cell thickness was set by a pair of 180 micrometer Mylar sheets and planar alignment was obtained by coating the glass plates with a solution of 0.1% PVA and rubbing them with a soft cloth. The experimental setup used for the measurement

• , the relaxation time τoff does not depend on the applied field as long as it is higher than the Fréedericksz transition threshold. As it can be observed from Table 1, when ferro-particles are added, the relaxation time decreases with increase of the applied field. Conclusion A new alignment was

Au nanostructure fabrication by pulsed laser deposition in open air: Influence of the deposition geometry

• Rumen G. Nikov,
• Anna Og. Dikovska,
• Nikolay N. Nedyalkov,
• Georgi V. Avdeev and
• Petar A. Atanasov

Beilstein J. Nanotechnol. 2017, 8, 2438–2445, doi:10.3762/bjnano.8.242

• are arranged along the (111) reflection plane of Au, which possesses the lowest surface-free energy. This crystallite alignment leads to the chain-like nanostructure formation on the substrate, as shown in Figure 1b. The XPS analysis of the as-deposited Au nanostructure is presented in Figure 3. The

Robust procedure for creating and characterizing the atomic structure of scanning tunneling microscope tips

• Sumit Tewari,
• Koen M. Bastiaans,
• Milan P. Allan and
• Jan M. van Ruitenbeek

Beilstein J. Nanotechnol. 2017, 8, 2389–2395, doi:10.3762/bjnano.8.238

• simulations [25], the mechanical annealing cycles lead to a more regular atomic packing at both sides of the junction. The smooth evolution of this alignment observed here suggests that the process evolves through gradual shifts in packing and orientation of the layers farther away from the apex atom. Based

High-stress study of bioinspired multifunctional PEDOT:PSS/nanoclay nanocomposites using AFM, SEM and numerical simulation

• Alfredo J. Diaz,
• Hanaul Noh,
• Tobias Meier and
• Santiago D. Solares

Beilstein J. Nanotechnol. 2017, 8, 2069–2082, doi:10.3762/bjnano.8.207

• free amplitude of the higher eigenmode (i.e., lowest and highest applied force). The models used were specifically developed for polymer/nanoclay composites with unidirectional alignment, thus the resemblance with the experimental results is consistent with the expectation that the coating contains

Identifying the nature of surface chemical modification for directed self-assembly of block copolymers

• Laura Evangelio,
• Federico Gramazio,
• Matteo Lorenzoni,
• Michaela Gorgoi,
• Francisco Miguel Espinosa,
• Ricardo García,
• Francesc Pérez-Murano and
• Jordi Fraxedas

Beilstein J. Nanotechnol. 2017, 8, 1972–1981, doi:10.3762/bjnano.8.198

• becomes evident that when the brush cooling is performed in nitrogen rather than in air, the polymer has the proper surface free energy to induce the alignment of the BCP after the lithography and BCP spin-coating. In order to understand the origin of the influence of the DSA process, we have performed

• Figure 2), there will be enough chemical contrast to guide the alignment of the BCP. We thus conclude that such a small increase in hydroxyl bonding is sufficient to disable the alignment capabilities of the PS–OH brush layer (see Figure 2a,b). Once the favourable cooling conditions for the preparation

• corrugation is not enough to induce the alignment of the BCP. This is confirmed by the results shown in Figure 2a,b. Finally, we investigate the interfacial affinity between the PMMA block and both modified (oxygen plasma) and unmodified brush layers. For this matter ≈20 nm thick PMMA films have been