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

• Emil Petrescu Cristina Cirtoaje University Politehnica of Bucharest, Department of Physics, Splaiul Independenţei 313, 060042, Bucharest, Romania 10.3762/bjnano.9.25 Abstract The dynamic behavior of a nematic liquid crystal with added carbon nanotubes (CNTs) in an electric field was analyzed. A

• molecules and align themselves parallel with the long axis of the nematic [12][13][14]. Under the action of an external magnetic or electric field above a critical threshold, nematic molecules collectively change their orientation. This is called the Fréedericksz transition [15][16] and the molecular

• -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

Al₂O₃/TiO₂ inverse opals from electrosprayed self-assembled templates

• Arnau Coll,
• Sandra Bermejo,
• David Hernández and
• Luís Castañer

Beilstein J. Nanotechnol. 2018, 9, 216–223, doi:10.3762/bjnano.9.23

• biased at a high voltage typically between 2 and 10 kV (depending on the needle-to-substrate distance) and the substrate is biased to a voltage between −500 to −1000 V using a high voltage bipolar power source. The high electric field created causes the fluid at the tip of the needle to adopt a cone

• off. In our experiments, the power supply providing the bias to the needle and substrate as well as the nitrogen flow are still switched on. This means that while the remaining liquid dries, the electric field is still on. This electric-field-assisted drying process is believed to be fundamental for

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

• dielectric permittivity of a medium. For a sinusoidal electric field Equation 3 becomes: The real and the imaginary parts are σ′(ω) = σ0 + ωε0ε″(ω) and σ″(ω) = ωε0ε′(ω), respectively. As shown in Figure 11, at medium frequencies (103–105 Hz), the ac conductivity and permittivity spectra are controlled by ion

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

• state where the device becomes transparent (the so called ON state) can be achieved by applying an electric field with adequate magnitude. Under the action of the field, the LC molecules inside each droplet align along the direction of the field, and the ordinary refractive index of the LC becomes equal

• defined as the ratio between the light intensity passing through the sample and the incident light intensity. Figure 11 presents the transmission coefficient versus the ac electric field. An improved characteristic is observed, as compared to the previous similar devices [21][22][28], with a stable “ON

• ” state and a lower required electric field to switch between “OFF” and “ON”, at values of 1–1.5 V/μm. No significant optical hysteresis was observed between the transmission curves obtained when increasing and decreasing the applied voltage. The electro-optical response remained stable when repeating the

Atomic layer deposition and properties of ZrO₂/Fe₂O₃ thin films

• Kristjan Kalam,
• Helina Seemen,
• Peeter Ritslaid,
• Mihkel Rähn,
• Aile Tamm,
• Kaupo Kukli,
• Aarne Kasikov,
• Joosep Link,
• Raivo Stern,
• Salvador Dueñas,
• Helena Castán and
• Héctor García

Beilstein J. Nanotechnol. 2018, 9, 119–128, doi:10.3762/bjnano.9.14

• -centrosymmetric orthorhombic phase of HfO2 stabilized by doping with foreign cations [40], well-defined ferroelectric hysteresis was recorded. For stabilized hafnia [40] the electrical polarization charge clearly tended to saturate upon the incremental increase in the external electric field strength. Along with

• level for polarization was actually not quite achieved at either polarity of the external field, as the polarized charge kept increasing with the voltage. Most probably, the charge (which is responsible for the polarization in the material deposited) was due to the electric field that drifted from an

• layer under certain polarity, and an opposite polarity with increasing, oppositely directed field is required to release the charge from the traps for the subsequent drift towards the counterelectrode. The current density to applied electric field curves are shown in Figure 7 to support the given

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

• rotation of an assembly of TDs. Finally, we show that an external electric field could be used to drag the boojum fingertip towards the interior of the confinement cell. Assemblies of TDs could be exploited as traps for appropriate nanoparticles, opening several opportunities for the development of

• be exploited to form nanowire-type structures [9][13] consisting of NPs. In this contribution we study numerically the effects of geometry and an external electric field on the positions of nematic TDs using the Landau–de Gennes mesoscopic approach. Theoretical Background Of interest is the impact of

• confinement and/or an external electric field on topological defects in a nematic liquid crystal. We use the Landau–de Gennes approach [5] in terms of the tensor order parameter . In its eigenframe it is expressed as , where and λi are the corresponding eigenvectors and eigenvalues, respectively. We consider

Design of photonic microcavities in hexagonal boron nitride

• Sejeong Kim,
• Milos Toth and
• Igor Aharonovich

Beilstein J. Nanotechnol. 2018, 9, 102–108, doi:10.3762/bjnano.9.12

• silicon carbide [19][20]. The hybrid approach is easier from the fabrication point of view but is inherently limited by the fact that the electric field maxima of optical modes are situated within the cavities, and optimal coupling therefore remains a challenge. The optical properties of hBN make it an

• used to increase the Q-factor. Lastly, the number of photonic crystal layers comprising the cavity is denoted by ‘H’ which act as a photonic mirror and the thickness of the hBN slab by ‘t’. The electric field intensity pattern of the L3 cavity calculated using 3D FDTD simulation is shown in Figure 1c

• cavities with a slab thickness of 280 nm. The electric field intensity profiles of L7 and L11 are also shown in the figure (and that of the L3 cavity is shown in Figure 1c). The Q-factor of the fundamental mode increases with effective cavity length. For the L11 cavity, we additionally calculated the

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

• ]. Meanwhile, these gratings can also be used as nanoelectrodes, which allow the LC to be driven by an electric field, enabling a very fast electro-optical effect due to the influence of the adjacent liquid crystal layer on the plasmonic resonance [10]. In all of these effects, the alignment of LC molecules on

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

• 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

• can also compare the simulated optical image in Figure 6a with the photographs shown in Figure 5. The appearance of the homeotropic walls (also shown in Figure 6c) is related to the initial homeotropic alignment with no field and the symmetry of the electric field distribution resulting in zero

• electric field torque above the middle of both the electrodes and the gaps. The simulations show that in the LC volume above the electrodes the LC director field distribution is deformed only partially, which results in reduced optical phase delay and low local transmittance. A useful consequence of the

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

• , one should expect decreasing of the threshold field of the magnetic Fréedericksz transition, which is confirmed by experiment [18][19], as well as a decrease in the electric field of the Fréedericksz transition [11][14][20][21][22]. Along with this, there are experimental studies devoted to the

Electro-optical characteristics of a liquid crystal cell with graphene electrodes

• Nune H. Hakobyan,
• Hakob L. Margaryan,
• Valeri K. Abrahamyan,
• Vladimir M. Aroutiounian,
• Arpi S. Dilanchian Gharghani,
• Amalya B. Kostanyan,
• Timothy D. Wilkinson and
• Nelson Tabirian

Beilstein J. Nanotechnol. 2017, 8, 2802–2806, doi:10.3762/bjnano.8.279

• of a photodetector. When the He–Ne laser beam (632 nm) propagates through the LC cell placed between crossed polarizers (so that the direction of the polarization of the incident beam makes a 45° angle with the LC director), then the influence of an external electric field allows typical oscillations

• unmatched response of the LC molecules to the sharp forced impact of the electric field and the appearance of nonviscous flow (the oscillations fade away due to the strong light scattering). By the end of the pulse action, the system tends towards ordered restoration (restoration of the reorientation

• oscillations). Then the relaxation process takes place only under the influence of the molecular forces of elasticity. The system returns to its original oriented state, similar to relaxation after influence of an electric field. The above-mentioned feature of the reorientation process under the influence of

Thermo- and electro-optical properties of photonic liquid crystal fibers doped with gold nanoparticles

• Agata Siarkowska,
• Miłosz Chychłowski,
• Daniel Budaszewski,
• Bartłomiej Jankiewicz,
• Bartosz Bartosewicz and
• Tomasz R. Woliński

Beilstein J. Nanotechnol. 2017, 8, 2790–2801, doi:10.3762/bjnano.8.278

• are caused by the properties of the infiltration material or due to the setup configuration. The results obtained indicated that with increasing NP doping a significant reduction of the rise time under an external electric field occurs with a simultaneous decrease in the nematic–isotropic phase

• of the response time under an external electric field. In the present research we used a 6CHBT nematic LC [19] and 4 nm diameter, spherical Au NPs (Figure 1a), both synthesized in the Military University of Technology, Warsaw, Poland. Au NPs have been used for applications both in photonics and

• concentrations of gold NPs (0.1, 0.3, 0.5 and 1 wt %) mixed with a 6CHBT nematic LC. These mixtures were tested in LC cells, microcapillaries and PLCFs to observe the influence of the structure geometry on the sample response to external factors such as temperature and electric field. To the best of our

Facile synthesis of silver/silver thiocyanate (Ag@AgSCN) plasmonic nanostructures with enhanced photocatalytic performance

• Xinfu Zhao,
• Dairong Chen,
• Abdul Qayum,
• Bo Chen and
• Xiuling Jiao

Beilstein J. Nanotechnol. 2017, 8, 2781–2789, doi:10.3762/bjnano.8.277

• presence of silver particles not only improves the photocatalytic efficiency, but also enhances the electric field strength around AgSCN due to the surface plasmon resonance, which in turn enhances the optical transition of midgap defect states of AgSCN. All these conditions contribute to the strong

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

• near nanoparticles and the action of a high electric field affect the purification/contamination processes. NPs with smaller size have a larger surface area thereby facilitate purification/contamination processes. Nanoparticles in LCs tend to aggregate. This leads to the reduction of the total number

• imposes restrictions on the concentration of NPs. Several studies [33][34][35] considered the local fields near nanoparticles as a trap of ions. Such a consideration is acceptable for NPs with high polarizability such as graphene or ferroelectric NPs. The next factor is a high electric field. It was shown

• that an electric field higher than 2.5 V/μm induces the desorption of ions [27]. We have studied the impact of TiO2 NPs on nematic LCs with different initial ionic contamination. It has been shown that NPs reduced the ionic density of LCs by two times with an initial contamination of 134.5 × 1012 cm−3

Interactions of low-energy electrons with the FEBID precursor chromium hexacarbonyl (Cr(CO)₆)

• Jusuf M. Khreis,
• João Ameixa,
• Filipe Ferreira da Silva and
• Stephan Denifl

Beilstein J. Nanotechnol. 2017, 8, 2583–2590, doi:10.3762/bjnano.8.258

• (CO)5+ is also formed by the metastable decay of Cr(CO)6+ when flying through the FF2. No other metastable decays are observed for the parent ion as shown in Figure 4. In this case the metastable ion yield was detected in a scan of the electric field E of the electric sector after the FF2. In a

• spectrum of Cr(CO)6+. In CID, a complete loss of CO ligands also occurs, leading to the formation of the bare metal cation, Cr+. Due to the subsequent acceleration of the formed fragments in the cell, CID peaks are slightly shifted to higher electric field values, which is clearly visible for the Cr(CO)5

• electric field was kept constant at electron energies of ca. 70 eV. For the study of dissociative electron attachment, the calibration of the incident electron energy scale was done by measuring the SF6− and F− resonances of SF6. The electron energy resolution was approximately 1 eV (FWHM) [27

Nanoprofilometry study of focal conic domain structures in a liquid crystalline free surface

• Anna N. Bagdinova,
• Evgeny I. Demikhov,
• Nataliya G. Borisenko and
• Sergei M. Tolokonnikov

Beilstein J. Nanotechnol. 2017, 8, 2544–2551, doi:10.3762/bjnano.8.254

• inside of displays when the director field orientation is perpendicular to the display substrate. This configuration is normally unstable and relaxes back after the electric field is switched off. But in some cases, due to the electric properties, the director field can overcome the corresponding energy

Refractive index sensing and surface-enhanced Raman spectroscopy using silver–gold layered bimetallic plasmonic crystals

• Somi Kang,
• Sean E. Lehman,
• Matthew V. Schulmerich,
• An-Phong Le,
• Tae-woo Lee,
• Stephen K. Gray,
• Rohit Bhargava and
• Ralph G. Nuzzo

Beilstein J. Nanotechnol. 2017, 8, 2492–2503, doi:10.3762/bjnano.8.249

• are excited by electromagnetic radiation incident at a metal/dielectric interface. This results in an evanescent decaying electric field that extends from the metal surface for ≈100–200 nm (surface plasmon polaritons), or it can also manifest as a localized surface plasmon resonance at the surface of

• and calculated normal incidence transmission spectra and electric field distributions around the nanoholes for full-3D PCs with Au50 (Figure 2a), Ag50 (Figure 2b), and Ag30Au20 (Figure 2c) mass-coverage metal films. The Al2O3 passivation layer was not included in the calculations as it was found to

• and air stand in good agreement with the characteristic field distribution expected for BW-SPPs. Even so, many of the optical features observed in the transmission spectra are likely the result of complex interactions of light diffraction and concurrent plasmonic modes. The electric field

Strategy to discover full-length amyloid-beta peptide ligands using high-efficiency microarray technology

• Clelia Galati,
• Natalia Spinella,
• Lucio Renna,
• Danilo Milardi,
• Francesco Attanasio,
• Michele Francesco Maria Sciacca and
• Corrado Bongiorno

Beilstein J. Nanotechnol. 2017, 8, 2446–2453, doi:10.3762/bjnano.8.243

• concentrations of peptide are used achieving a relatively inexpensive assay. Here, the HES is a silicon-based substrate able to act as a fluorescence amplifier. The intensity of the fluorescence is increased by exploiting the constructive interference phenomena of the electric field of light in the near-surface

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

• surface [29] was made by first locally depositing Au on the graphene surface from the tip using a high electric field pulse, followed by mechanical annealing similar to [25] over that Au deposit. The authors confirmed that the method improved the topographic contrast of the surface and the quality of the

Fabrication of gold-coated PDMS surfaces with arrayed triangular micro/nanopyramids for use as SERS substrates

• Jingran Zhang,
• Yongda Yan,
• Peng Miao and
• Jianxiong Cai

Beilstein J. Nanotechnol. 2017, 8, 2271–2282, doi:10.3762/bjnano.8.227

• electromagnetic field is the main factor which induces the Raman enhancement for different micro/nanostructures. Compared to a bare surface, the enhanced electric field can be generated by a single pyramid. In addition, the apex of a single pyramid can induce a significant enhancement and an enhanced Raman signal

• in determining the electric field amplitude distribution and the corresponding Raman enhancement factor. The electric field intensity generated by adjacent structures is higher than the electric field intensity generated by dispersed structures [37]. Therefore, compared to the dispersed pyramids, the

• uniformity and stability of the electric field intensity from the molecules adsorbed on the numerous hot spots formed by adjacent pyramids would be significantly enhanced, which agrees well with our experimental results. Figure 8 shows the Raman spectra of R6G molecules on the gold-coated PDMS substrate at a

Dissociative electron attachment to coordination complexes of chromium: chromium(0) hexacarbonyl and benzene-chromium(0) tricarbonyl

• Janina Kopyra,
• Paulina Maciejewska and
• Jelena Maljković

Beilstein J. Nanotechnol. 2017, 8, 2257–2263, doi:10.3762/bjnano.8.225

• mounted at one of the flanges. The generated negative ions were extracted from the reaction area by a small electric field towards the QMA entrance and detected by a single pulse counting technique. The electron energy scale was calibrated by measuring the signal of SF6−, exhibiting an intense resonance

Suppression of low-energy dissociative electron attachment in Fe(CO)₅ upon clustering

• Jozef Lengyel,
• Peter Papp,
• Štefan Matejčík,
• Jaroslav Kočišek,
• Michal Fárník and
• Juraj Fedor

Beilstein J. Nanotechnol. 2017, 8, 2200–2207, doi:10.3762/bjnano.8.219

• decreases the resulting electric field at the target molecule, which reduces its attractive interaction with the incoming electron. This causes the significant cross section drop at very low energies. When such an aggregate is sitting on a much larger argon nanoparticle, the shielding, due to the

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

• , thus leading to improved electrical conductivity. For an electric field applied perpendicular to the film, the conductivity of PEDOT:PSS has been shown to be approximately three orders of magnitude lower when compared to the in-plane case, for thin films [41]. The supposed reason for this is the

Coexistence of strongly buckled germanene phases on Al(111)

• Weimin Wang and
• Roger I. G. Uhrberg

Beilstein J. Nanotechnol. 2017, 8, 1946–1951, doi:10.3762/bjnano.8.195

• might be displaced by the interaction with the STM tip (external electric field applied during scanning). In this paper, we present new data on the Ge/Al(111) system which significantly broadens the view on germanene formation. We show that it is possible to grow well-ordered monolayer Ge at

Spin-dependent transport and functional design in organic ferromagnetic devices

• Guichao Hu,
• Shijie Xie,
• Chuankui Wang and
• Carsten Timm

Beilstein J. Nanotechnol. 2017, 8, 1919–1931, doi:10.3762/bjnano.8.192

• and the lattice structure. If the bias is not too large, a linear treatment is justified [35][36], where we assume that a uniform electric field E = V/[a(N − 1)] along the molecule is induced. Here, N is the total number of carbon atoms in the main chain and a is the lattice constant. Hence, the

• . Wang et al. [45] have found that a polaron moving under an electric field may be trapped near the spin radicals unless the field is stronger than a critical value. The magnitude of the critical field depends on the spin of the polaron, which implies a spin-filtering effect of the polaron transport

• four-state resistive devices have also been reported, where a ferroelectric barrier was introduced between two ferromagnets [48][49][50]. In these designs, both a magnetic field and an electric field are necessary to manipulate both the relative magnetization orientation of the electrodes and the