Tailoring polarization and magnetization of absorbing terahertz metamaterials using a cut-wire sandwich structure

• Hadi Teguh Yudistira,
• Shuo Liu,
• Tie Jun Cui and
• Han Zhang

Beilstein J. Nanotechnol. 2018, 9, 1437–1447, doi:10.3762/bjnano.9.136

• works on metamaterial absorbers have been presented such as split-ring resonators [15], electric-field-coupled (ELC) resonators [16], lossy cut-wire bars [17], and donut-type resonators [18]. Most previous works on the perfect absorber have been explained by interference theory [19][20][21][22][23], for

• relative permeability can be defined as μr = 1 + M / H, where E, H, P, and M are the electric field, magnetic field, polarization, and magnetization [12], respectively. Magnetization and polarization are two factors that can be used to tailor the relative permeability and relative permittivity

• could be explained as follows. The existence of the cut-wire width of the cross-shaped sandwich structure at = 90° reduced the metallic bar length parallel to the external electric field by a few micrometers, thereby, increasing the resonance frequency. Figure 4 shows the simulation result of the

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

• presence of crossed electric and magnetic fields, the electric field being applied along the growth direction of a band-inverted junction. We show that the Dirac cone is robust and persists even if the fields are strong. In addition, we point out that Landau levels of electron states lying in the

• semiconductor bands can be tailored by the electric field. Tunable devices are thus likely to be realizable, exploiting the properties studied herein. Keywords: crystalline topological insulators; electric and magnetic fields; Landau levels; midgap states; Introduction In 1982, Thouless et al. [1] made a

• recently studied band-inverted junctions based on IV–VI compounds using a two-band model when an electric field is applied along the growth direction [25]. We have demonstrated that the Dirac cone of midgap states is robust against moderate values of the electric field but Fermi’s velocity decreases

New 2D graphene hybrid composites as an effective base element of optical nanodevices

• Olga E. Glukhova,
• Igor S. Nefedov,
• Alexander S. Shalin and
• Мichael М. Slepchenkov

Beilstein J. Nanotechnol. 2018, 9, 1321–1327, doi:10.3762/bjnano.9.125

• of the incident wave with respect to the atomic cell of the hybrid nanocomposite. In this case a plane electromagnetic wave with the wave vector k falls on the composite, which lies in the XZ-plane. The angle θ is the angle of incidence, the vectors E and H correspond to the electric field strength

• -known scheme for obtaining the relations between the amplitudes of the incident, refracted and reflected s- and p-polarized waves when passing through the interface based on Maxwell's equations was used [15]. Assuming a value of the amplitude of the electric field equal to 1, one can write for the case

• of a p-polarized wave: where R and T are the reflection and the transmission coefficient, respectively. Due to continuity of the tangent components of the electric field at the composite surface one can write: For the tangent components of the magnetic field at the composite surface one can write

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

• compounds, two relaxation processes are identified and assigned to (i) collective dynamics of molecules in nanometer-sized cybotactic clusters and (ii) individual molecular relaxations, in the ascending order of frequency of the probe field. The temperature and the bias electric field dependence of the

• biaxiality was highly debatable. A major issue arises as to whether the measurable biaxiality in the nematic phase is spontaneous or whether it is entirely induced by the electric field or surface effects [22]. As this issue is unresolved, the topic continues to be highly debated among the scientific LC

• molecules were aligned by surface treatment and one of the short axes was also aligned by the electric field. In more recent studies, the biaxiality of the sample studied was confirmed [3][4][5] by electro-optical switching [23], polarizing infrared spectroscopy (PIR) [24], polarizing optical microscopy

Electro-optical interfacial effects on a graphene/π-conjugated organic semiconductor hybrid system

• Karolline A. S. Araujo,
• Luiz A. Cury,
• Matheus J. S. Matos,
• Thales F. D. Fernandes,
• Luiz G. Cançado and
• Bernardo R. A. Neves

Beilstein J. Nanotechnol. 2018, 9, 963–974, doi:10.3762/bjnano.9.90

• experiments and their results. Initially, a graphite microplate (gray)/RA SAM (orange) sample is electrically connected to the microscope, in which a white LED is mounted and illuminates the sample (Figure 4a). The EFM tip can be biased within the range −6 V < Vtip < 6 V, creating a strong electric field at

Nanoscale mapping of dielectric properties based on surface adhesion force measurements

• Ying Wang,
• Yue Shen,
• Xingya Wang,
• Zhiwei Shen,
• Bin Li,
• Jun Hu and
• Yi Zhang

Beilstein J. Nanotechnol. 2018, 9, 900–906, doi:10.3762/bjnano.9.84

• electric field [33]. At the nanometre scale, EW has also been observed to modify the adhesion force [35][36][37]. The adhesion force between an AFM tip with radius R and a flat surface with liquid absorbed on it can be expressed as [35][36][37][38]: where V is the voltage applied on the AFM tip, γ is the

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

• electric field [10]. The Fréedericksz transition occurs at least in two stages when the BaTiO3 nanoparticles are added to the liquid crystal [11][12]. In colloids of ferroelectric particles in nematic LCs, as a rule, oleic acid is present as a stabilizer, the role of which is to prevent the aggregation of

• the LC. The threshold voltage is defined as the voltage at which the capacitance starts to increase. Results and Discussion The homeotropic-planar transition in a smectic A LC occurs in the form of deformation, destruction and rearrangement of smectic layers under the action of an electric field

Facile synthesis of a ZnO–BiOI p–n nano-heterojunction with excellent visible-light photocatalytic activity

• Mengyuan Zhang,
• Jiaqian Qin,
• Pengfei Yu,
• Bing Zhang,
• Mingzhen Ma,
• Xinyu Zhang and
• Riping Liu

Beilstein J. Nanotechnol. 2018, 9, 789–800, doi:10.3762/bjnano.9.72

• heterojunctions could promote increased photocatalytic activity efficiency. Once the p–n junction has been formed, the inner electric field between the inner surface of two semiconductors will promote the separation efficiency of photoinduced electron–hole pairs [30][31]. Consequently, coupling an n-type metal

• equilibrium state, hence the band bending and the electric field are created consequently [56] and photoinduced electrons are transferred to the conduction band of ZnO and leave the holes in the valence band of BiOI (Figure 7b). This indicates that the separation efficiency of the ZnO/BiOI nanocomposite is

Valley-selective directional emission from a transition-metal dichalcogenide monolayer mediated by a plasmonic nanoantenna

• Haitao Chen,
• Mingkai Liu,
• Lei Xu and
• Dragomir N. Neshev

Beilstein J. Nanotechnol. 2018, 9, 780–788, doi:10.3762/bjnano.9.71

• π/2 phase difference for the electric quadrupole. Thus, there is naturally a π/2 relative phase difference between the electric dipole and quadrupole contribution to the far-field emission, when their corresponding charges oscillate in phase. In this case, the parallel electric field components of

• edges, we model the gold bars having rounded corners with a radius of curvature of 5 nm. The permittivity of the gold in the visible and near-infrared spectral region is modeled based on experimental data from [48]. The intensity of the electric field along X direction (I) and phase information (φ) at

• ), the field induced by the X-oriented point-dipole (Ih) dominates in the wavelength range of 700–750 nm. In contrast, the excited field from the Y-oriented point-dipole (Iv) dominates for the long bar in the same wavelength range (Figure 2d). Importantly, both of the electric field intensities show a

Surface-plasmon-enhanced ultraviolet emission of Au-decorated ZnO structures for gas sensing and photocatalytic devices

• T. Anh Thu Do,
• Truong Giang Ho,
• Thu Hoai Bui,
• Quang Ngan Pham,
• Hong Thai Giang,
• Thi Thu Do,
• Duc Van Nguyen and
• Dai Lam Tran

Beilstein J. Nanotechnol. 2018, 9, 771–779, doi:10.3762/bjnano.9.70

• defect-related emission band of ZnO. The electron–hole (e–h) pairs near the Au NP/ZnO interface generated by the laser source are extracted by the local electric field in the region of the energy barrier of the Au NP/ZnO structure, thus increasing the free carrier density and reducing the energy barrier

Mechanistic insights into plasmonic photocatalysts in utilizing visible light

• Kah Hon Leong,
• Azrina Abd Aziz,
• Lan Ching Sim,
• Pichiah Saravanan,
• Min Jang and
• Detlef Bahnemann

Beilstein J. Nanotechnol. 2018, 9, 628–648, doi:10.3762/bjnano.9.59

• oscillating electric field of the light. The photon frequency is designed to match with the natural frequency of the noble metal throughout the oscillation. This reduces the field on one side of the electron while increasing it on the other side of the noble metal. The development of this nonequilibrium

• condition results in the rearrangement of the charge density and builds an opposing electric field within the noble metal NPs. This further leads to the establishment of a coulombic restoring force and the noble metal NP electrons then experience harmonic oscillation [1][5][13][14]. These oscillating

• charges trigger the LSPR effects when the excited surface electric field frequency is sufficient, and the noble metal resonance leads to dynamic utilisation of visible light. A schematic representation of the phenomenon is illustrated in Figure 2. Hence, it is clear that absorption of photons emitted by

Facile phase transfer of gold nanorods and nanospheres stabilized with block copolymers

• Yaroslav I. Derikov,
• Georgiy A. Shandryuk,
• Raisa V. Talroze,
• Alexander A. Ezhov and
• Yaroslav V. Kudryavtsev

Beilstein J. Nanotechnol. 2018, 9, 616–627, doi:10.3762/bjnano.9.58

• polarized light wave with the electric field set parallel (TM) or perpendicular (TE) to the cylinder long axis. The obtained spectra were averaged for all possible nanorod orientations. The aim of the simulations was twofold: (i) to confirm that, both in water and in an organic medium, Au nanorods exist as

High-contrast and reversible scattering switching via hybrid metal-dielectric metasurfaces

• Jonathan Ward,
• Khosro Zangeneh Kamali,
• Lei Xu,
• Guoquan Zhang,
• Andrey E. Miroshnichenko and
• Mohsen Rahmani

Beilstein J. Nanotechnol. 2018, 9, 460–467, doi:10.3762/bjnano.9.44

• emergence of the Fano-like resonance during the heating process, strong field localization and enhancement inside the silicon disk occurs as a result of the excitation and interferences between optically-induced electric and magnetic multipoles (see Figure 3a and 3b). The enhancement of the electric field

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

• are produced by applying a suitable electric field to a piezoelectric material such as LiNbO3. One set of metallic interdigital transducers (IDTs) intercalated on the piezoelectric surface introduces the electric field, generating a SAW displacement amplitude on the order of 10 Å. A solution of CNTs

• electric field which moves the CNTs, the magnetic field only reorients them. This method is not limited to CNTs and can be used to align any carbon fiber. Figure 19 indicates the SEM image of the arranged CNTs in ethanol. In this study, the magnetic field magnitude was 10 T [108]. Although magnetic field

• nanofibers containing MWCNTs were successfully fabricated by a magnetic field [110]. Electric field The alignment and orientation of CNTs by an electric field is applied in two ways: as electrophoresis (EP) and dielectrophoresis (DEP). EP is the transport of charged particles through a medium enforced by a

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

• CdSe/ZnS quantum dots in electric fields was theoretically studied. The model was based on elastic continuum theory considering the interaction of the nematic molecules with the surrounding molecules, with the quantum dots and with the electric field. Experimental data obtained by dynamic measurements

• nanoparticles [6], quantum dots (QDs) [7][8][9][10][11][12] or other nanomaterials [13][14][15][16][17] that can be effectively used in electro-optical devices. When added to liquid crystals, quantum dots may seriously influence their behavior under an electric field due to the anchoring forces acting on the

• 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

Electron interaction with copper(II) carboxylate compounds

• Michal Lacko,
• Peter Papp,
• Iwona B. Szymańska,
• Edward Szłyk and
• Štefan Matejčík

Beilstein J. Nanotechnol. 2018, 9, 384–398, doi:10.3762/bjnano.9.38

• main reaction chamber by small capillary, which creates a molecular beam that perpendicularly collides with the electron beam. Ionic products are then forced by a weak electric field into the ion optics of the quadrupole mass spectrometer. After separation of the products with different mass-to-charge

Periodic structures on liquid-phase smectic A, nematic and isotropic free surfaces

• Anna N. Bagdinova,
• Evgeny I. Demikhov,
• Nataliya G. Borisenko,
• Sergei M. Tolokonnikov,
• Gennadii V. Mishakov and
• Andrei V. Sharkov

Beilstein J. Nanotechnol. 2018, 9, 342–352, doi:10.3762/bjnano.9.34

• near-field optical microscope (SNOM). The SNOM has a sharpened optical fiber probe with an aperture much smaller than the wavelength. The probe detects (or excites) the so-called "evanescent" ("vanishing") component of the alternating electric field of the optical signal, which rapidly decays at short

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

• easily reachable by applying of a low frequency a.c. electric field. Spontaneous quantities The temperature dependences of the spontaneous polarization Ps and of the tilt angle θs (angle of (in-layer) molecular director with respect to the smectic layer normal) are shown in Figure 2a,b, respectively. The

• for KL 4/4 (see Figure 2a). It is a well-known fact that the measured θs values involve at least two components, namely the real spontaneous tilt angle existing without applied electric field and the field-induced tilt angle existing due to the electro-clinic effect [51]. However, the field-induced

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

• Si. SiC is a wide bandgap (2.4–3.3 eV) semiconductor with a bulk Young’s modulus of 400–500 GPa [136] and high thermal conductivity on the order of 330 W∙m−1∙K−1 for bulk 3C–SiC [137], a larger than 1 MV cm−1 breakdown electric field as well as a high melting temperature. Regarding its elastic

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