Dielectric and electrical properties of nematic liquid crystals 6CB doped with iron oxide nanoparticles. The combined effect of nanodopant concentration and cell thickness

Dispersing nanomaterials in liquid crystals has emerged as a very promising non-synthetic way to produce advanced multifunctional and tunable materials. As a rule, dielectric and electrical characterization of such materials is performed using cells of single thickness. As a result, the published reports vary even for similar systems. Confusion still exists as to the effects of nanodopants and cell thickness on the dielectric and electrical properties of liquid crystals. This factor hinders a widespread use of liquid crystals – nanoparticles systems in modern tech products. In this paper, we report systematic experimental studies of the combined effect of the cell thickness and iron oxide nanoparticle concentration on the electrical and dielectric properties of nematic liquid crystals 6CB. The measured dielectric spectra can be divided into three distinct regions corresponding to a low frequency (<10 Hz) dispersion, dispersion free range (102 - 104 Hz (electrical conductivity) and 102 - 105 (dielectric permittivity)), and high frequency dispersion (104 - 106 Hz (electrical conductivity) and 105 - 106 Hz (dielectric permittivity)). The real part of the dielectric permittivity is not affected by the cell thickness and its value can be tuned by changing the concentration of nanoparticles. At the same time, the electrical conductivity depends on both cell thickness and nanoparticle concentration. At intermediate frequencies (102 - 104 Hz) the electrical conductivity obeys the Jonscher power law and is dependent on the cell thickness because of ion-releasing and ioncapturing effects caused by nanoparticles and substrates of the cell. In addition, its value is affected by the electronic conductivity due to iron oxide nanoparticles and their nanoclusters. At higher frequencies (104 - 106 Hz) the electrical conductivity follows a super linear power law and is nearly independent of the cell thickness and nanoparticle concentration

Peculiarities of nonadditive changes in conductivity of nano-PDLC under influence of magnetite and single-wall carbon nanotubes

Studied in this work has been the effect of nanoparticles – magnetite and single-wall carbon nanotubes – separately and together on the conductivity of nematic liquid crystal 6CHBTdispersed in polyvinyl alcohol. Morphology of these films was analyzed using an electron microscope. When using selected technology of homogenizing the mixture components, there takes place formation of liquid crystals dispersed in the polymer matrix with the average sizes of liquid-crystal droplets close to 500 nm (nano-PDLC). It has been found that simultaneous introduction of magnetite and nanotubes results in lowering the conductivity of nano-PDLC as compared to the total conductivity of nano-PDLC with each kind of nanoparticles separately. It has been suggested that the main mechanism of this effect lies in formation of deep centers for electron capture by complexes with different types of nanoparticles, which leads to a decrease in electronic conductivity through the polymer matrix

Congenital trichinellosis ? Case report

A large trichinellosis outbreak in the Slovak Republic caused by the species Trichinella britovi and affecting 336 people also affected a pregnant woman. The mother was infected in the 10thth week of pregnancy and was treated with mebendazole. On her own request abortion was performed in the 22nd week of pregnancy. Medium lgM and high lgG anti-Trichinella antibody titres were found. The placenta, body cavities liquid, tissues and organs of the foetus contained 0.02 - 30 larvae per gram of tissue, measuring 0.68 ± 0.05 - 1.17 ± 0.07 mm, with blurred inner structure. Immunocytochemical examination identified Trichinella larvae that infected the foetus in the early stage of development

Congenital trichinellosis ? Case report

A large trichinellosis outbreak in the Slovak Republic caused by the species Trichinella britovi and affecting 336 people also affected a pregnant woman. The mother was infected in the 10thth week of pregnancy and was treated with mebendazole. On her own request abortion was performed in the 22nd week of pregnancy. Medium lgM and high lgG anti-Trichinella antibody titres were found. The placenta, body cavities liquid, tissues and organs of the foetus contained 0.02 - 30 larvae per gram of tissue, measuring 0.68 ± 0.05 - 1.17 ± 0.07 mm, with blurred inner structure. Immunocytochemical examination identified Trichinella larvae that infected the foetus in the early stage of development

Magnetic-Field Induced Isotropic-Nematic Phase Transition in PDLC Doped with Magnetic Nanoparticles

The paper presents a study of the polymer dispersed liquid crystals that consist of liquid crystal 4-trans-4'-n-hexyl-cyclohexyl-isothiocyanatobenzene (6CHBT) microdroplets dispersed in polyvinyl alcohol and doped with various kinds of magnetic particles. As magnetic nanoparticles there were used single walled carbon nanotubes and magnetite labeled single walled carbon nanotubes. The volume concentration of the particles was 2 × $10^{-3}$. Magnetic properties were investigated by a SQUID magnetometer. The higher saturation magnetization has been achieved in sample polymer dispersed liquid crystal doped with magnetite labeled single walled carbon nanotubes. The phase transition temperature from isotropic to nematic phase at the external magnetic field 0 T and 12 T was monitored by precise capacitance measurements in the capacitance cell filled with prepared sample. The significant shift of the phase transition temperature (0.2°C) at the external magnetic field 12 T has been observed in sample polymer dispersed liquid crystal doped with magnetite labeled single walled carbon nanotubes

Sensitivity of 6CHBT Liquid Crystal Doped with Ferroelectric or Magnetic Particles to Electric and Magnetic Fields

Introduction of ferroelectric or magnetic nanoparticles into nematic liquid crystal is a promising method for the improvement of the electro-optic or magneto-optic properties of different nematic liquid crystals by non-chemical way. This work is devoted to the study of composite systems of liquid crystal with spherical ferroelectric or magnetic particles with the aim to study their sensitivity to electric and magnetic fields. The nematic 4-(trans-4'-n-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT) liquid crystal was doped with SbSI ferroelectric particles or with $Fe_{3}O_{4}$ magnetic particles. The structural transitions in ferronematic samples were indicated by capacitance measurements in a capacitor made of ITO-coated glass electrodes in combined electric and magnetic fields. The obtained results showed the increase of the shift in critical voltage with increasing magnetic field in both kinds of samples

Вплив суперіонних наночастинок Cu6PS5I на діелектричні властивості нематичного рідкого кристала 6СНВТ

Within the frequency range 10…106 Hz, the influence of Cu6PS5І nano-particles on the dielectric properties of planar oriented liquid crystal 6СНВТ has been studied. It has been shown that nanoparticles lead to an increase in conductivity, but the conductivity dependence on concentration is non-monotonic function. It has been suggested that the reason of non-monotonic dependence of conductivity of 6СНВТ on the concentration of nanoparticles is significant influence of ion adsorption on the nanoparticle surface and increase in the viscosity of liquid crystal when introducing nanoparticles