Longin. Lisetski

Longin. Lisetski
National Academy of Sciences of Ukraine | ISP · Molecular and Heterostructured Materials Department

D.Sc. (Phys.-Math.), Professor

About

131
Publications
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1,101
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Publications

Publications (131)
Preprint
Full-text available
We present the newly synthesized chiral dopant 2-[(2-isopropyl-5-methylcyclohexyl)oxy]-2-oxoethyl 4-{(E)-[4-(decyloxy)phenyl]diazenyl}benzoate (ChD-3501), consisting of azo- and aliphatic fragments together with a chiral center based on l-menthol as a reversible light-controllable chiral dopant. To assess the effects of UV/VIS irradiation and tempe...
Chapter
The structure and properties of soft colloidal systems filled by nano-disks of Laponite® (Lap) are critically reviewed. The known Lap grades, chemical structure and physical properties are described. Various phases formed by exfoliated surface-charged Lap discs in aqueous media are analyzed, accounting for the kinetics of phase transformations and...
Article
The organic substance quercetin, when added to liquid crystal (LC) systems as non-mesogenic dopant significantly affects properties of the LC host. The microphotographs of cholesteric (M5) and nematic (5CB) LC textures evidenced about presence of aggregation quercetin molecules in LC hosts. These results are in agreement with literature data on que...
Article
Lyotropic phases of hydrated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) are generally considered as models of biological membranes. Effects of lauric acid (LA) and fenspiride (FS) on DPPC membrane were studied by differential scanning calorimetry and fluorescence spectroscopy with environment-sensitive probe PH7 (2-(2'-hydroxy-phenyl)-phena...
Article
In mixtures of nematic liquid crystals with opposite signs of dielectric anisotropy (alkylcyanobiphenyls and azoxybenzenes), a possibility of photoinduced Freedericks-type transition was realized, which could be observed both by optical transmission in a standard geometry and by changes in electric conductivity. UV irradiation leads to lowering of...
Article
Calcium and cerium chlorides, as well as cerium nitrate and cerium ammonium nitrate were examined in model lipid membranes of hydrated L‑α‑dipalmitoylphosphatidylcholine (DPPC) by means of differential scanning calorimetry (DSC). The shift of main transition temperature of DPPC membrane (ΔTm) was chosen as a measure of the ion-membrane effects resu...
Article
Monte Carlo model for simulation of light transmission in anisotropic suspensions filled by absorbing cylindrical particles with anisotropic shape was developed. Aspect ratio of the cylinders (i.e., ratio of length and diameter) was varied between r = 0 (infinitely thin disks) and r → ∞ (infinitely thin rods). The cooperative filling model was used...
Article
Phase transitions of multibilayer structures of hydrated L-α-dipalmitoyl- and L-α-dimyristoylphosphatidylcholine (DPPC and DMPC) were studied by differential scanning calorimetry. For the main phase transition, thermodynamic parameters (temperature, enthalpy, half-width and cooperative domain size, CN) were determined in a broad range of scanning r...
Article
Branched dextran-graft-polyacrylamide copolymers with different surface properties (charged and uncharged, pure and loaded by Ag or Au nanoparticles) were created in order to drug delivery usage. By means of differential scanning calorimetry, membranotropic action of the polymers was revealed in a set of model lipid membranes, both charged and unch...
Article
Individual and joint action of two water-soluble drugs, DMSO and tilorone, on model L-α-dipalmitoylphosphatidylcholine (DPPC) membranes were studied in equilibrium and kinetic regimes by differential scanning calorimetry (DSC). For equilibrium experiments, the drugs were introduced during preparation of the model membrane. In kinetic studies, one o...
Article
This article based on the archival documents and scientific periodicals, for the first time reveals a discoverer of so called transitional phase of the substance from the solid state to liquid - the liquid crystals. This fundamental discovery has been made by the Austrian scientist Julius Planer at the Lviv University in 1861.
Article
The nematic (5CB) and cholesteric (the mixture of 5CB with chiral M5) liquid crystals (LC) doped with organo-modified inorganic platelets Laponite® (LO) were studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD), microscopic image analysis, and optical density measurements. Cetyl-trimethylammonium-bromide (CTAB) was used as an...
Article
Full-text available
A comparative study of the effects of the active pharmaceutical ingredients of amixin, aspirin, metronidazole, phenibut, and fenspiride, as well as corresponding pharmaceuticals on lipid membranes was carried out. Lipid membranes of L-α-dipalmitoylphosphatidylcholine and native carp spermatozoa were used as models. A decrease in the melting tempera...
Article
The question of the activation energy of phase transitions in lyotropic liquid crystal phases of model phospholipid membranes was considered. In our experiments, we obtained DSC thermograms of hydrated DPPC and DMPC at different scanning rates, and activation energy values were determined by a modification of Kissinger non-isothermal kinetics metho...
Article
Optical transmission and selective reflection data are reported for suspensions of single-walled carbon nanotubes (CNTs) in photoactive nematic material ZhK-440 with a mesogenic chiral dopant M5. At small concentrations of CNTs (C ≈ 0.01–0.05%), the preferential localisation of CNTs at oily sticks (cholesteric topological defects) and suppression o...
Article
Model multibilayer membranes based on L-α-dimyristoylphosphatidylcholine containing nitrates of silver, sodium, potassium, and copper as AgNO3–NaNO3, AgNO3–KNO3, and AgNO3–Cu(NO3)2 pairs were investigated. In each system studied the molar fraction of nitrates relative to the lipid was kept unchanged at 0.35, whereas the molar fraction of silver nit...
Article
The optical density, microstructure and electrical conductivity in nematic (ZhK440, 5CB and their mixtures) and cholesteric (the mixtures of ZhK440, 5CB with chiral M5) colloids with single-walled carbon nanotubes (CNTs) were studied. The azoxy nematic ZhK440 is photoactive, and the effects of UV-irradiation and restoring irradiation were also inve...
Article
Full-text available
Effect of guests molecules on phase transitions of model lipid membranes was studied by differential scanning calorimetry. Membranotropic action of guest molecules was estimated from the shift of “gel – liquid crystal” phase transition temperature of lipid membranes. Relationships between membranotropic action and molecular parameters of guest mole...
Article
Full-text available
Intermolecular interactions between decamethoxinum (DEC) and acetylsalicylic acid (ASА) have been studied in the phospholipid-containing systems of escalating complexity levels. The host media for these substances were solvents, L-α-dipalmitoylphosphatidylcholine (DPPC) membranes, and samples of human erythrocytes. Peculiar effects caused by DEC-AS...
Article
Full-text available
Thermotropic mesogens of different chemical nature - 4-pentyl-4′-cyanobiphenyl (5CB), azoxy nematic ZhK-440, and cholesteryl oleyl carbonate (COC) were introduced as dopants to hydrated DPPC, with their effects on phase transitions recorded by DSC. When mesogen pairs (5CB + ZhK-440 and 5CB + COC) were added at constant total concentration, dependen...
Article
Full-text available
We focus on investigating the dielectric behaviors and the low-frequency texture transitions in a cholesteric liquid crystal (CLC) doped with graphene nanoplatelets (GNPs) by means of dielectric spectroscopy and measurements of electro-optical responses. The experimental results indicate that incorporating GNPs at a content of 0.5 wt% into the CLC...
Article
Full-text available
Aim. To determine the effect of the oxyethylated glycerol cryoprotectants (OEG n) with polymerization degrees n = 5, 25, 30 on the phase states and phase transitions of dipalmitoylphosphatidylcholine (DPPC)-based model membranes. Methods. Differential scanning calorimetry. Results. Model lipid membranes on water/OEG n and water/glycerol subphases w...
Article
Full-text available
Multilamellar structures formed in DPPC/water/glycerol and DPPC/water/oxyethylated glycerol systems are studied by small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) methods. The effects of glycerol, oxyethylated glycerol, and other membranotropic agents (MTAs) on the lamellar repeat distance 𝐷 are compared in gel, ripp...
Article
Full-text available
Multibilayer structures of hydrated phospholipids, often considered as model biological membranes, are, from the physical viewpoint, lyotropic liquid crystalline systems undergoing temperature-induced mesomorphic phase transitions. Effects of silver nitrate and urocanic acid on lyotropic phase states of hydrated L-a-dipalmitoylphosphatidylcholine (...
Article
Full-text available
To investigate the effects of silver nitrate (AgNO3) on model lipid membranes, we studied multibilayer membranes based on L-α-dipalmitoylphosphatidylcholine (DPPC) and AgNO3 aqueous solutions in a wide concentration range (up to 30 wt %) using differential scanning calorimetry. It was shown that the presence of AgNO3 leads to both an increase in th...
Chapter
Full-text available
The structure and properties of liquid crystalline suspensions filled by carbon nanotubes (CNTs) are critically reviewed.Special attention is paid to interactions between CNTs and molecules of the liquid crystals( LC), which lead to formation of ordered supramolecular structures.These structures, in turn,determine unique physical properties of LC+CN...
Article
Full-text available
Optical transmission and selective reflection data are reported for dispersions of single-walled carbon nanotubes (SWCNT) in cholesteric liquid crystals comprising a mixture of cholesterol esters and azoxy nematic ZhK-440. The optical density was shown to be essentially non-linear with SWCNT concentration, with a minimum ascribed to formation of "s...
Article
Full-text available
A model molecular biosystem of hydrated dipalmitoylphosphatidylcholine (DPPC) bilayers that mimics cell biomembranes is used to probe combined membranotropic effects of drugs by instrumental techniques of molecular biophysics. Differential scanning calorimetry reveals that doping of the DPPC model membrane with individual bisquaternary ammonium com...
Article
Full-text available
Comparative studies of optical transmission of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), dispersed in nematic liquid crystal matrix 5CB, were carried out. The data evidence violations of Beer-Lambert-Bouguer (BLB) law both in cell thickness and concentration dependencies. The most striking is the fact that...
Article
Full-text available
Comparative studies have been carried out of multi-walled and single-walled carbon nanotubes (CNT) dispersed in nematic liquid crystal matrix. Under strictly similar experimental conditions (5CB nematic host, the same supplier of CNTs, the same 50 μm thick cell for optical and dielectric measurements, the same CNT concentration range, identical pro...
Article
Full-text available
We report an experimental evidence that molecules of anthraquinone dye aggregate in an anisotropic solvent, a nematic liquid crystal (NLC). We observe strong nonlinear dependencies of the dielectric permittivity and anisotropy of light absorption on the dye concentration c. Moreover, the data suggest that the aggregates are linear, but, in contrast...
Conference Paper
Microstructure and electrooptical properties of multiwalled carbon nanotubes (NTs), dispersed in the cholesteric liquid crystal (cholesteryl oleyl carbonate, COC), nematic 5CB and their mixtures, were studied at the fixed temperature of 298 K. The relative concentration X=COC(COC + 5CB) was varied within 0.0-1.0, the concentration C of NTs was vari...
Article
By means of differential scanning calorimetry, effects of systematic series of Group I and VII ions on the phase state of model multibilayer dimyristoylphosphatidylcholine (di(14:0)PC) membranes have been studied at a lipid/ion molar ratio of 3/1. The sign-changing correlations between the ionic radii of cations and temperature shifts of di(14:0)PC...
Article
Full-text available
The effects of urocanic acid (UA) on thermodynamic parameters of model dipalmitoylphosphatidylcholine (DPPC) lipid membrane have been studied by means of differential scanning calorimetry (DSC). The observed ordering effect of UA on the lipid bilayer is reflected in the increase in both the main phase transition temperature and cooperative unit siz...
Article
Full-text available
Liquid crystalline (LC) mixtures of cholesteryl oleyl carbonate (COC) and 4-pentyl-4'-cyanobiphenyl (5CB), as well as dispersions of single-walled carbon nanotubes (NTs) in these mixtures, were studied by means of selective reflection measurements, differential scanning calorimetry (DSC) and optical microscopy. The relative mass of COC in a mixture...
Article
Full-text available
Microstructure, phase transitions, electrical conductivity, and optical and electrooptical properties of multiwalled carbon nanotubes (NTs), dispersed in the cholesteric liquid crystal (cholesteryl oleyl carbonate, COC), nematic 5CB and their mixtures, were studied in the temperature range between 255 K and 363 K. The relative concentration X=COC/(...
Article
Full-text available
Fine complex light structure, optical singularities and electroconductivty of nematic 5CB doped by multi-walled carbon nanotubes (MWCNTs) were investigated. MWCNTs gather spontaneously to system of micro scale clusters with random fractal borders at small enough concentration. They are surrounded by the striped micro scale cladding which creates op...
Article
Full-text available
For cholesteric liquid crystal systems containing photosensitive nematic ZhK-440 and a mixture of cholesterol derivatives, changes in helical twisting induced by UV radiation were studied. The UV-induced shift of selective reflection maximum λmax was shown to depend upon concentration of the nematic component. For low concentrations of ZhK-440, λma...
Article
Full-text available
For liquid crystal dispersions of carbon nanotubes (CNT), experimental data on time stability of their characteristics were obtained by three different methods (optical trans-mission vs. temperature, electric conductivity vs. time, and electric conductivity vs. voltage in conditions of Freedericksz transition). The results clearly suggest that indu...
Article
Full-text available
Aim. To compare effects of vitamin D (VitD), provitamin D (ProD) and its photo- and thermoisomerization products on thermodynamical parameters of hydrated dipalmitoylphoshpatidylcholine (DPPC) multilayers. Methods. Differential scanning calorimetry, UV spectroscopy. Results. A regular decrease was established in the melting temperature accompanied...
Article
Full-text available
For cholesteric liquid crystal systems containing photosensitive nematic ZhK-440 and a mixture of cholesterol derivatives, the changes in helical twisting induced by UV radiation are studied. The UV-induced shift of the selective reflection maximum λmax is shown to depend on the concentration of the nematic component. For low concentrations of ZhK-...
Article
Full-text available
Comparative studies were carried out of cholesteric liquid crystal dispersions of anisotropic nanoparticles of different types, namely, essentially rod-like carbon nanotubes (CNT) and plate-like exfoliated particles of organo-modified Laponite and montmorillonite clays. The characteristic properties under study were selective reflection spectra of...
Article
Full-text available
The phase transitions in smectogenic liquid crystal BBBA (4-butoxybenzylidene-4′-butylaniline) doped by multi-walled carbon nanotubes (NTs) were studied by methods of optical transmission, differential scanning calorimetry (DSC), measurement of electrical conductivity and analysis of microscopic images. The concentration of NTs was varied within 0–...
Article
Full-text available
The incubation process of self-aggregated 5CB-MWCNT composites followed by nonlinear evolution of their optical, electroconductivity and thermodynamic characteristics were investigated and discussed for the first time. Induced optical singularities, the interfacial LC layers around the aggregates of nanotubes and inversion walls generated between t...
Article
Helical pitch vs. temperature measurements were carried out for cholesteric liquid crystal matrices of different types doped with a set of banana-shaped compounds. The effects of these dopants on the helical pitch were found to be essentially different for systems based on cholesterol esters and for induced cholesterics based on twisted nematics. I...
Article
Full-text available
A new method of lasing frequency phototuning was studied for dye-doped cholesteric liquid crystal (CLC) mixtures of azoxy-nematic ZhK-440 and cholesterol derivatives by variation of their helical pitch under irradiation by light of different wavelengths. For most lasing dyes introduced into CLC systems the fluorescence quantum yield becomes substan...
Article
Aggregation of carbon nanotubes dispersed in nematic liquid crystalline medium is discussed. A model assuming that the aggregates consist of a "skeleton" formed by stochastically arranged nanotubes and a "shell" ("coat") of incorporated and adjacent nematic molecules is proposed. The aggregates of this type can be considered as large quasi-macrosco...
Article
Full-text available
The lyotropic Lα-phase of hydrated dipalmitoylphosphatidylcholine has been proposed as a solvent medium for modeling the effects of membranotropic agents upon cell membranes, including interactions between different agents inside the membrane. For quasibinary systems containing bisquaternary ammonium compounds decamethoxinum or aethonium and 2,5-di...
Article
Full-text available
For cholesteric liquid crystals (CLC) based on azoxy nematic ZhK-440 and cholesterol esters, variation of selective reflection band maximum with temperature and under irradiation by light of different wavelengths were studied. In these materials, lasing is hindered because fluorescence quantum yield of most lasing dyes falls sharply at concentratio...
Article
Full-text available
The nonocomposites on the base of long (5-10 $\mu$m, ${o}$-MWCNTs) and short (2 $\mu$m, ${m}$-MWCNTs) multi-walled carbon nanotubes (MWCNTs) hosted by nematic 5CB were investigated in details by means of polarizing microscopy, studies of electrical conductivity and electro-optical behaviour. The spontaneous self-organization of MWCNTs was observed...
Article
Full-text available
Aggregation of carbon nanotubes dispersed in nematic liquid crystalline medium is discussed. A model is proposed, which assumes that the aggregates consist of a "skeleton" formed by stochastically arranged nanotubes and a "shell" ("coat") of incorporated and adjacent nematic molecules. The aggregates of this type can be considered as large quasi-ma...
Article
This work reports a study on microstructure, electrical conductivity and phase transitions of 5CB(4-pentyl-4′-cyanobiphenyl) + multi-walled carbon nanotubes (MWCNTs) composite materials. The concentration of MWCNTs was varied within 0.025 and 1 wt.%. The unmodified (o) and modified (m) MWCNTs were used. The mild milling was applied for shortening l...
Article
Full-text available
Comparative studies were carried out of aggregate formation by carbon nanotubes (CNT) of different geometry dispersed in nematic liquid crystal 5CB. The picture of aggregation was found to be essentially similar for multi-walled and single-walled nanotubes (MWCNTs and SWCNTs), apparently not affected by the difference in aspect ratios, while for "s...
Article
Full-text available
Aim. To study membranotropic activity modulation of bisquaternary ammonium compounds (BQAC) decamethoxinum and aethonium determined by their interaction with dihydroxybenzoic acid (DHB) organic anion. Methods. Differential scanning calorimetry, mass spectrometry. Results. Doping phospholipid membranes with individual BQAC or DHB leads to a consider...
Article
Investigations of electrophysical properties of nematic liquid crystals (LC) based on cyanobiphenyls under the frequency of 106-1010 GHz with applied electric and magnetic static fields are presented. The obtained results are interpreted in terms of molecular models. Possibilities of LC implementation into various electronic devices are also discus...
Article
Tuning of resonator characteristics by control of electrophysical properties of cyanobiphenyl-based nematic liquid crystals (LC) is investigated theoretically and experimentally. The LC properties are changed by external electric and magnetic fields.
Article
It is known that dielectric non-linearity of liquid crystals (LC) is based on reorientation of their molecules (which are characterized by geometric anisometry, accompanied by anisotropy of dielectric permittivity ε and magnetic susceptibility χ) under external electroand magnetostatic fields. The effective values of ε measured in specific experime...
Article
Full-text available
Formation of aggregates of multiwalled carbon nanotubes dispersed in nematic 5CB was studied using different methods (microscopy, optical transmission, electric conductivity, differential scanning calorimetry, and methods of singular optics). Monitoring of the aggregate formation on the time scale of several hours has been realized, and a physical...
Article
In 1861 Julius Planner published a paper in which he described his observations of selective light reflection in monotropic cholesteric liquid crystal phase of cholesteryl chloride that he synthesized We repeat his experiments and report in modern interpretation what indeed was observed by Planer at that time
Article
Full-text available
Cholesteric liquid crystal mixtures containing nematic ZhK-440 (comprising alkyl- and alkoxy azoxybenzenes) and cholesterol esters were studied as examples of UV-sensitive systems based on a photoactive nematic hosts and non-photoactive chiral components (ChC). The ChC concentration was varied within 35-90 %, resulting in selective reflection with...