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

Effect of the fluorination technique on the surface-fluorination patterning of double-walled carbon nanotubes

• Lyubov G. Bulusheva,
• Yuliya V. Fedoseeva,
• Emmanuel Flahaut,
• Jérémy Rio,
• Christopher P. Ewels,
• Victor O. Koroteev,
• Gregory Van Lier,
• Denis V. Vyalikh and
• Alexander V. Okotrub

Beilstein J. Nanotechnol. 2017, 8, 1688–1698, doi:10.3762/bjnano.8.169

• six F neighbors on one tube side (model VII). A shift required for the alignment of the theoretical spectra to the experimental energy scale was evaluated by comparing the spectrum calculated for an outer central fluorine atom of a CNT segment fluorinated on both sides (Figure S1, Supporting

Air–water interface of submerged superhydrophobic surfaces imaged by atomic force microscopy

• Markus Moosmann,
• Thomas Schimmel,
• Wilhelm Barthlott and
• Matthias Mail

Beilstein J. Nanotechnol. 2017, 8, 1671–1679, doi:10.3762/bjnano.8.167

• , the interfaces separating the wetted areas from the air-retaining areas followed exactly the alignment of the micro-pillars. AFM images (a, c) and the corresponding cross-sections (red lines in b, d) of the sample. The image in a) was taken in ambient conditions in tapping mode and confirms the pillar

Process-specific mechanisms of vertically oriented graphene growth in plasmas

• Subrata Ghosh,
• Shyamal R. Polaki,
• Niranjan Kumar,
• Sankarakumar Amirthapandian,
• Mohamed Kamruddin and
• Kostya (Ken) Ostrikov

Beilstein J. Nanotechnol. 2017, 8, 1658–1670, doi:10.3762/bjnano.8.166

• same sp3 content in the film. The effects of the substrate temperature and the electric field in vertical alignment of the graphene sheets are reported. These findings help to develop and optimize the process conditions to produce VGNs tailored for applications including sensing, field emission

Oxidative stabilization of polyacrylonitrile nanofibers and carbon nanofibers containing graphene oxide (GO): a spectroscopic and electrochemical study

• İlknur Gergin,
• Ezgi Ismar and
• A. Sezai Sarac

Beilstein J. Nanotechnol. 2017, 8, 1616–1628, doi:10.3762/bjnano.8.161

• plays an important role in the carbonization. Therefore, a detailed understanding of the mechanism of oxidation has an important part in the success of the production of CNF. Nanofiber webs are produced with different collectors to achieve fiber alignment. The results for webs of aligned and non-aligned

• –strain curve obtained by DMA shows that fiber alignment increases the mechanical properties of the web. A directional orientation of the fibers definitely and expectedly has the effect of increasing modulus and reducing the strain to break [18][28][29]. Aligned nanofibers has a greater modulus than non

• . Conclusion In this paper, CNF webs and GO-containing CNF webs were successfully fabricated. Nanofiber webs were fabricated via electrospinning. Nanofiber alignment was achieved with a rotating collector, which also had the definite and expected effect of increasing modulus and reducing the strain to break of

Development of polycationic amphiphilic cyclodextrin nanoparticles for anticancer drug delivery

• Gamze Varan,
• Juan M. Benito,
• Carmen Ortiz Mellet and
• Erem Bilensoy

Beilstein J. Nanotechnol. 2017, 8, 1457–1468, doi:10.3762/bjnano.8.145

• without the presence of surfactants [21][22][24][32][33][34] due to their favorable self-alignment properties at air–water or oil–water interface [35]. The mean particle size of amphiphilic CD nanoparticles increased linearly with concentration of surfactant. Bilensoy et al. evaluated the effect of the

Adsorption and electronic properties of pentacene on thin dielectric decoupling layers

• Sebastian Koslowski,
• Daniel Rosenblatt,
• Alexander Kabakchiev,
• Klaus Kuhnke,
• Klaus Kern and
• Uta Schlickum

Beilstein J. Nanotechnol. 2017, 8, 1388–1395, doi:10.3762/bjnano.8.140

• conditions, e.g., energy minimization due to best alignment with the hexagonal valley, might hinder additional adsorption geometries. Defects or multiple pentacene molecules adsorbed in the same valley, however, break this scheme and cause adsorptions in alternative geometries. The electronic properties of

Adsorption characteristics of Er₃N@C₈₀on W(110) and Au(111) studied via scanning tunneling microscopy and spectroscopy

• Sebastian Schimmel,
• Zhixiang Sun,
• Danny Baumann,
• Denis Krylov,
• Nataliya Samoylova,
• Alexey Popov,
• Bernd Büchner and
• Christian Hess

Beilstein J. Nanotechnol. 2017, 8, 1127–1134, doi:10.3762/bjnano.8.114

• ), whereby the monolayers can be described as (4 × 4) superstructure [11][12]. Our data reveal a new alignment in addition to this known in-phase orientation of Er3N@C80-monolayer on Au(111). In this case, the monolayer was found to be rotated to form an incommensurate (4 × 4)R30° phase (Figure 3b) with

• temperature range (Tmax ≈ 670 K). On the contrary to W(110), monolayer height molecule islands of hcp structure were formed on Au(111). Those monolayers possess two distinguishable orientations on the Au(111)-surface. Beside the known in-phase (4 × 4) superstructure an out-of-phase alignment (4 × 4)R30° has

Near-field surface plasmon field enhancement induced by rippled surfaces

• Mario D’Acunto,
• Francesco Fuso,
• Ruggero Micheletto,
• Makoto Naruse,
• Francesco Tantussi and
• Maria Allegrini

Beilstein J. Nanotechnol. 2017, 8, 956–967, doi:10.3762/bjnano.8.97

• considered here is composed of the interplay of patterns made of grooves, hills and valleys showing some degree of anisotropy. Alignment effects induced, for example, by the anisotropic ion bombardment can in fact take place, leading to the occurrence of one preferential direction. The surface plasmon

Energy-level alignment at interfaces between manganese phthalocyanine and C₆₀

• Daniel Waas,
• Florian Rückerl,
• Martin Knupfer and
• Bernd Büchner

Beilstein J. Nanotechnol. 2017, 8, 927–932, doi:10.3762/bjnano.8.94

• Daniel Waas Florian Ruckerl Martin Knupfer Bernd Buchner IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany 10.3762/bjnano.8.94 Abstract We have used photoelectron spectroscopy to determine the energy-level alignment at organic heterojunctions made of manganese phthalocyanine (MnPc) and the

• fullerene C60. We show that this energy-level alignment depends upon the preparation sequence, which is explained by different molecular orientations. Moreover, our results demonstrate that MnPc/C60 interfaces are hardly suited for application in organic photovoltaic devices, since the energy difference of

• contribution we present an investigation of the energy level alignment at MnPc/C60 interfaces using photoelectron spectroscopy (PES). We show that this alignment depends on the preparation sequence and that the lowest unoccupied molecular orbitals (LUMOs) of the two molecules lie energetically very close at

Triptycene-terminated thiolate and selenolate monolayers on Au(111)

• Jinxuan Liu,
• Martin Kind,
• Björn Schüpbach,
• Daniel Käfer,
• Stefanie Winkler,
• Wenhua Zhang,
• Andreas Terfort and
• Christof Wöll

Beilstein J. Nanotechnol. 2017, 8, 892–905, doi:10.3762/bjnano.8.91

• . IRRAS can often be used not only to identify the nature of molecular species adsorbed on surfaces but also to gain information on molecular alignment with respect to the surface normal. Due to screening effects, only the transition dipole moment (TDM) vector component perpendicular to the substrate

• , while bands with TDMs (mostly) parallel to the surface will be attenuated or even completely extinguished. Thus, from comparison of relative band intensities in neat substance spectra to those in spectra of monolayers, information can be gained on the alignment of the molecules. With the help of DFT

• ., the intensity of single resonances is strongly dependent on the X-ray incidence angle θ. This points to a uniform alignment of the thiolate and selenolate molecules on the Au(111) surface. A couple of absorption resonances are visible in the NEXAFS spectra, the strongest of which is the C 1s-π1