Threshold voltage decrease in a thermotropic nematic liquid crystal doped with graphene oxide flakes

• Mateusz Mrukiewicz,
• Krystian Kowiorski,
• Paweł Perkowski,
• Rafał Mazur and
• Małgorzata Djas

Beilstein J. Nanotechnol. 2019, 10, 71–78, doi:10.3762/bjnano.10.7

• dielectric spectroscopy measurements. The effect is related to the disrupted planar alignment due to the strong π–π stacking between the 5CB’s benzene rings and the graphene oxide’s structure. Additionally, we present the GO concentration dependence on the isotropic–nematic phase transition temperature

• presence of the electric field was discussed. Keywords: graphene oxide; liquid crystal; nematic phase; switching; threshold voltage; Introduction Liquid crystals (LCs) are classified as a type of soft matter which are characterized by anisotropic molecules and a liquid-like fluidity behavior. Of all LC

• phases, special attention is paid to the nematic liquid crystal (NLC) phase because is widely used in many electro-optical applications [1][2]. In the uniaxial nematic phase, the direction of the optical axis is described by the director n, which is the unit vector along the molecular axis. An applied

Induced smectic phase in binary mixtures of twist-bend nematogens

• Anamarija Knežević,
• Irena Dokli,
• Marin Sapunar,
• Suzana Šegota,
• Ute Baumeister and
• Andreja Lesac

Beilstein J. Nanotechnol. 2018, 9, 1297–1307, doi:10.3762/bjnano.9.122

• recent discovery of the twist-bend nematic phase (NTB) has sparked great interest in the scientific community, not only from a fundamental viewpoint, but also due to its potential for innovative applications. Here we report on the unexpected phase behaviour of a binary mixture of twist-bend nematogens. A

• binary phase diagram for mixtures of imino-linked cyanobiphenyl (CBI) dimer and imino-linked benzoyloxy-benzylidene (BB) dimer shows two distinct domains. While mixtures containing less than 35 mol % of BB possess a wide temperature range twist-bend nematic phase, the mixtures containing 55–80 mol % of

• BB exhibit a smectic phase despite that both pure compounds display a Iso–N–NTB–Cr phase sequence. The phase diagram shows that the addition of BB of up to 30 mol % significantly extends the temperature range of the NTB phase, maintaining the temperature range of the nematic phase. The periodicity

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

• dielectric strength and relaxation frequency for these processes are shown to give rise to sharpness in cluster boundaries, increased size and volume fraction in the LC nematic phase. The effect of the bias field on the LC cell is similar to reducing its temperature; both variables increase the cluster size

• and volume fraction and give rise to sharp cluster boundaries. The findings confirm that dielectric spectroscopy is a powerful and an extremely useful technique to provide a deeper understanding of the mechanism of cybotactic cluster formation in the isotropic liquid and the nematic phase of LCs as a

• -range translational order. The optical switching by rotation around the long molecular axes is much faster and easier than switching by rotation around the short axes. In 1970, Freiser predicted that the long and flat LC molecules could form a biaxial nematic phase (Nb), and furthermore, a second-order

Synthesis and characterization of two new TiO₂-containing benzothiazole-based imine composites for organic device applications

• Anna Różycka,
• Agnieszka Iwan,
• Krzysztof Artur Bogdanowicz,
• Michal Filapek,
• Natalia Górska,
• Damian Pociecha,
• Marek Malinowski,
• Patryk Fryń,
• Agnieszka Hreniak,
• Jakub Rysz,
• Paweł Dąbczyński and
• Monika Marzec

Beilstein J. Nanotechnol. 2018, 9, 721–739, doi:10.3762/bjnano.9.67

• synthesized compounds – aromatic Schiff bases – are known as thermally stable, and second, thanks to the plane structure, they will tend to adopt a column-like structure. In the case of the asymmetric molecule (SP2), it was expected to obtain a columnar structure in low-ordered mesophase, such as a nematic

• phase. Whereas, for the symmetric structure (SP1), an additional linkage between two benzothiazole units would cause some distortions and formation of a more ordered phase. Moreover, due to a significant number of donor heteroatoms, an interesting interaction with TiO2 was also expected. In order to

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

• directly after the stripe formation. Generally, the stripe texture becomes smoother. Figure 8 shows the stripe formation on the free surface of the nematic phase at T = 38 °C. Directly after heating to 38 °С, the surface structure is homogeneous. Shortly after, a periodic striped structure perpendicular to

• the tip motion is formed on the nematic phase free boundary, similar to the SmA phase. The periodicity of stripes in the nematic phase is approximately ten times larger than in the SmA phase and the amplitude of film thickness modulation is ten times smaller than in the SmA phase at room temperature

• . Figure 9 shows the stripe structure formation on the surface of the isotropic liquid, 8CB, at 46 °С. The contrast of this stripe texture is weaker than in the SmA phase. The stripe periodicity in the isotropic liquid is approximately the same as in the nematic phase. Discussion The comparison of optical

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

• columnar hexagonal phase (380–670 mg/mL) to the crystalline phase. The isotropic phase is the solution at a low rod concentration and lacks orientational and positional orders. In the nematic phase, orientational order is introduced by volume exclusion effects, in a way that the rods are aligned more or

• 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

• smectic-A phase can be obtained from concentrated DNA solutions [34]. In the smectic-A phase, translational symmetry is broken along the director of the nematic phase, so that the rods that form a multilayer organization are oriented perpendicular or oblique to the layers, and are in a liquid-like order

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

• sample with LC. In the temperature range between 293 K and 350 K, where the DS measurements were performed, the pure liquid crystal E7 exhibits an anomalous behavior of the nematic phase around 305 K [26]. This behavior cannot be seen from the results presented here, since the CA component of the

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

• droplets appeared in the sample. Figure 4 shows the behavior of undoped and Au-doped (0.5 wt % and 1 wt %) LC cells at a temperature near the phase transition. For the MCs the N–I phase transition temperature was defined as the temperature where the nematic phase begins to become distorted and slowly

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

• of a magnetic field and a shear flow was theoretically investigated in [21], where it is shown that the competing effects of a magnetic field and a shear flow lead to the appearance of reentrant nematic–cholesteric–nematic phase transitions under the rotation of the magnetic field in the plane of

• Discussion Let us analyze the combined effect of the shear flow and the magnetic field on the spiral structure of a ferrocholesteric for various orientations of the magnetic field in the shear plane (Figure 1). In the untwisted (i.e., nematic) phase, in the presence of a magnetic field and a shear flow the

• obtained from Equation 15. In the untwisted (nematic) phase dφ/dζ = 0, hence Substituting Cc in Equation 17, we obtain the condition which together with Equation 14 determines the critical values uc and hc, under which the spiral structure of the ferrocholesteric is unwound. In the absence of magnetic

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

• measured by ISSA at T = 43 °C. The surface is smooth and possesses no peculiarities. The thickness of the LC layer in the top part of the droplet was 109 μm. Figure 1b demonstrates the structure of the free surface in the nematic phase at T = 37 °C. It looks similar with an isotropic phase and does not

• with twist grain boundary (TGB)-like structures [18][19][20] because of some interdomain regions, which can explain the holes in the FCD-structured surface. We could expect some pattern formation starting from the nematic phase. The surface of the isotropic liquid and the nematic phase of 8CB revealed

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

• , that in the isotropic phase of a ferronematic, a weak dc bias magnetic field of a few oersteds increases the ac magnetic susceptibility. This increment vanishes irreversibly if the substance is cooled down to the nematic phase, but can be reinduced by applying the dc bias field again in the isotropic

• crystal and the magnetic field. Experiments have proved that MNPs can alter the threshold fields for structural (e.g., Fréedericksz) transitions [9][10][11]; unexpected magneto-optical [12][13] and magneto-dielectric effects [14] have been found and shifts in the isotropic-to-nematic phase-transition

• -nematic phase transition on cooling (unless the bias field is applied again in the isotropic phase). A phenomenological explanation of the experimental results related this behavior to defect-mediated aggregation and magnetic-field-assisted disaggregation of MNPs [27]. In principle, the effect can provide

Reorientation of single-wall carbon nanotubes in negative anisotropy liquid crystals by an electric field

• Amanda García-García,
• Ricardo Vergaz,
• José F. Algorri,
• Gianluigi Zito,
• Teresa Cacace,
• Antigone Marino,
• José M. Otón and
• Morten A. Geday

Beilstein J. Nanotechnol. 2016, 7, 825–833, doi:10.3762/bjnano.7.74

• cells. Impedance magnitude and phase variation at different frequencies as a function of applied driving voltage, Vp. The LC is in a nematic phase. Raman Intensity evolution of the G’-band and LC peaks with voltage. The SWCNT threshold voltage is visible between 2Vp and 2.5Vp. Acknowledgements This

Electrical response of liquid crystal cells doped with multi-walled carbon nanotubes

• Amanda García-García,
• Ricardo Vergaz,
• José F. Algorri,
• Xabier Quintana and
• José M. Otón

Beilstein J. Nanotechnol. 2015, 6, 396–403, doi:10.3762/bjnano.6.39

• is a well-known positive dielectric nematic mixture that has been used in low-end LC displays. Its main features are a kinematic viscosity of 20 mm2·s−1 at 20 °C and an optical birefringence (Δn) of 0.120 at 588 nm. The material shows a wide nematic phase range above and below room temperature. The