Plane-polarized Light Research Articles

Photochemistry with Plane-Polarized Light: Controlling Selectivity of a Photochemical Rearrangement.

Over the past 50 years, a principal approach to controlling conventional photochemical reactions has relied on imposing geometric constraints on reactant or transition state via conducting photochemistry in the organized or constraining media. Herein, we describe a fundamentally different approach to affect the course of photochemical reactions (photochemical rearrangements) by utilizing spatially selective excitation of specific electronic transitions with plane-polarized light in the reactant molecules uniformly aligned in the nematic liquid crystal phase. In particular, we focused on the Type B enone rearrangement of 4,4-diarylcyclohexenones -one of the most common photochemical rearrangements. We demonstrated that the aryl migratory aptitude in this reaction was attenuated in response to changing an angle between the polarization plane of the incident light and the alignment direction of nematic liquid crystal, with the enhanced aryl migration achieved when the polarization plane coincided with the transition dipole moment leading to the excited state responsible for this migration. The spatially-selective initial excitation therefore was overruling the electronic factors responsible for the relative ratio of the two alternative photoproducts. The experimental findings were further supported by the results of a computational study. This work showcases a new fundamental paradigm in controlling photochemical reactivity and selectivity of photoreactions.

Markwelchite, TlPbSbS3, a new Tl–Pb sulfosalt from the hydrothermal deposit of Jas Roux, Hautes-Alpes, France

AbstractMarkwelchite, ideally TlPbSbS3, is a new mineral from the hydrothermal deposit of Jas Roux, Hautes-Alpes, France. It occurs as a black anhedral crystal associated closely with protochabournéite. Microhardness measurements (VHN15) gave a mean value of 197 kg/mm2 corresponding to a Mohs hardness of ~3–4. In plane-polarised incident light, markwelchite is grey in colour. Under crossed polars, it is distinctly anisotropic with greyish white to bluish rotation tints, with bright red internal reflections. Reflectance percentages (Rmin and Rmax) are: 28.5, 31.5 (471.1 nm); 28.3, 30.7 (548.3 nm); 27.9, 30.3 (586.6 nm); and 27.6, 29.8 (652.3 nm). The mean of 5 electron microprobe spot analyses gave Tl 34.67(45), Pb 31.86(25), Sb 15.06(15), As 2.37(5), S 15.35(20), total 99.31 wt.%, corresponding, on the basis of a total of 6 atoms per formula unit and structural results, to Tl1.063Pb0.964(Sb0.775As0.198)Σ0.973S3.000. Single-crystal X-ray diffraction studies revealed that markwelchite is isotypic with richardsollyite, TlPbAsS3. It is monoclinic, space group P21/c, with the following unit-cell parameters: a = 8.9144(3), b = 8.4513(3), c = 8.6511(3) Å, β = 108.723(4)°, V = 617.27(4) Å3 and Z = 4. The five strongest observed powder-diffraction lines [d in Å (Irel)(hkl)] are: 3.88 (100)($\bar{2}$11); 3.78 (90)(210); 3.29 (90)(102); 2.73 (85)($\bar{1}$13); and 2.93 (75)(022). The crystal structure can be described as formed by (100) [Me2(SbS3)]– layers sandwiching the Me1+ cations. The Me1 site has a seven-fold coordination, whereas the Me2 site has an 6+2 coordination corresponding to a distorted, bicapped trigonal prismatic coordination, and the Sb site displays a trigonal pyramidal coordination with three S atoms and Sb at the apex.The name markwelchite honours Dr Mark D. Welch of the Natural History Museum, London, UK.The new mineral has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2024–001). A discussion on the relationships between markwelchite and synthetic TlPbSbS3 is also provided.

Polycations as Aptamer-Binding Modulators for Sensitive Fluorescence Anisotropy Assay of Aflatoxin B1.

Fluorescence induced by the excitation of a fluorophore with plane-polarized light has a different polarization depending on the size of the fluorophore-containing reagent and the rate of its rotation. Based on this effect, many analytical systems have been implemented in which an analyte contained in a sample and labeled with a fluorophore (usually fluorescein) competes to bind to antibodies. Replacing antibodies in such assays with aptamers, low-cost and stable oligonucleotide receptors, is complicated because binding a fluorophore to them causes a less significant change in the polarization of emissions. This work proposes and characterizes the compounds of the reaction medium that improve analyte binding and reduce the mobility of the aptamer-fluorophore complex, providing a higher analytical signal and a lower detection limit. This study was conducted on aflatoxin B1 (AFB1), a ubiquitous toxicant contaminating foods of plant origins. Eight aptamers specific to AFB1 with the same binding site and different regions stabilizing their structures were compared for affinity, based on which the aptamer with 38 nucleotides in length was selected. The polymers that interact reversibly with oligonucleotides, such as poly-L-lysine and polyethylene glycol, were tested. It was found that they provide the desired reduction in the depolarization of emitted light as well as high concentrations of magnesium cations. In the selected optimal medium, AFB1 detection reached a limit of 1 ng/mL, which was 12 times lower than in the tris buffer commonly used for anti-AFB1 aptamers. The assay time was 30 min. This method is suitable for controlling almond samples according to the maximum permissible levels of their contamination by AFB1. The proposed approach could be applied to improve other aptamer-based analytical systems.

Dead-zone-free atomic magnetometer based on hybrid Poincaré beams

In this paper, we present the experiment and the theory scheme of light-atom interaction in atomic magnetometers by using a hybrid Poincaré beam (HPB) to solve an annoying problem, named “dead zone.” This kind of magnetometer can be sensitive to arbitrary directions of external magnetic fields. The HPB has a complex polarization distribution, consisting of a vector radially polarized beam and a scalar circularly polarized beam in our experiment. These two kinds of beams have different directions of dead zones of external magnetic fields; thereby, the atomic magnetometer with an HPB can avoid the non-signal area when the direction of the external magnetic field is in the plane perpendicular to the light polarization plane. Furthermore, the optical magnetic resonance (OMR) signal using an HPB still has no dead zones even when the direction of the external magnetic field is in the plane parallel to the polarization plane in our scheme. Our work has the potential to simplify and optimize dead-zone-free atomic magnetometers.

(Invited) Photoluminescence-Based Circular Polarization Convertors for Multiplexing of Optical Information

Polarized light has a great potential to provide a variety of optical information at once such as light intensity (brightness), wavelength (color), and polarization. In particular, circularly polarized (CP) light is expected to be used not only for 3D display but also for optical data encryption and anti-counterfeiting, because the polarization plane of CP light rotates during light propagation resulting in no angular dependence on information transmission. The previously reported approaches for creating CP light from unpolarized light can be roughly classified into the filtration using a circular polarizer, the selective reflection by chiral liquid crystals, and the circularly polarized luminescence (CPL) from chiral luminophores. Meanwhile, we have recently proposed a new approach for creating highly-pure CP light by converting linearly polarized luminescence (LPL) using luminescence-based CP convertor (Figure 1a).[1] The unique advantage of the luminescence-based CP convertor lies in the spectral conversion properties of the LPL films which allows multiplexing of optical information by simply laminating LPL films. In this presentation, we introduce the multilayer-type luminescence-based CP convertors (Figure 1b) fabricated by using two or three LPL films showing different PL wavelength.In this study, we selected quantum rods (QRs) and π-conjugated luminescent polymers as one-dimensional (1D) luminophores. As a stretchable transparent polymer, poly(ethylene-co-vinyl acetate) (EVA) was used. LPL films were prepared by uniaxial stretching of the luminophore/EVA composite films. When yellow-, orange-, and red-color-emissive QRs were used as a luminophore, yellow-, orange-, and red-LPL were obtained as shown in Figures 1c-e. By laminating LPL film on the quarter-wave film with the angles between polarization plane of LPL and fast-axis of quarter-wave film were -45˚, 0˚, and +45˚, left-handed (LH-), parallel LP, and right-handed (RH-) CP light were produced, respectively. When the yellow-, orange-, and red-LPL films were laminated at three different angles (-45˚, 0˚, and +45˚) against the fast axis of the quarter-wave film, 3×3×3=27 different pieces of optical information were produced as shown in Figure 1f. Furthermore, time information on CP light can also be multiplexed theoretically by laminating several LPL films showing different fluorescence lifetimes. In this presentation, we will also discuss about time-multiplexing of optical information by multilayer-type luminescence-based CP light convertor consisting of multiple LPL films showing different PL lifetimes.[1] Y. Okazaki et. al., J. Mater. Chem. C, 2022. DOI: 10.1039/d2tc03955a. Figure 1

Geometric phase and photonic spin Hall effect in thin films with architected columnar morphology

We have detected spin-dependent splitting of light, the signature of the photonic spin Hall effect (PSHE), via quantum weak measurements on two types of thin films with architected columnar morphology. Specifically, we fabricated columnar thin films comprising parallel tilted nanocolumns and chiral sculptured thin films comprising parallel upright nanohelices by resistively heating zinc selenide (ZnSe) in a low-pressure chamber and collecting the collimated vapor flux of ZnSe on planar substrates with dynamically varying orientation. The architected columnar morphology creates a spin-dependent geometric Pancharatnam–Berry (PB) phase corresponding to the evolution of polarization states on the Poincaré sphere. Morphology-controlled anisotropy and spatial inhomogeneity result in the depolarization and optical rotation of incident plane-polarized light, and intrinsic spin-precession coupling with the propagation vector, contributing to the efficient generation and two-dimensional manipulation of both in-plane and out-of-plane spin splitting and steering the PB phase in the propagation process. The first experimental observations of widely tailorable PSHE and PB phase in thin films with architected columnar morphology may lead to new applications ranging from spin-controlled nanophotonics to optoelectronic devices for quantum information processing and optical communication.

Nickelalumite, ideally NiAl4(SO4)(OH)12(H2O)3, a new-old mineral from the Kara-Tangi uranium deposit, Kyrgyzstan

Nickelalumite, ideally NiAl4(SO4)(OH)12(H2O)3, is a newly approved mineral from the Batken region, Kyrgyzstan, where it occurs in the Kara-Tangi and Kara-Chagyr uranium deposits. It formed in a zone of hydrothermal alteration of U–V-bearing carbonaceous siliceous schists, in association with quartz, calcite, alumohydrocalcite, allophane, crandallite, kyrgyzstanite, ankinovichite and an unknown Al–OH-mineral. It occurs as aggregates of colourless to pistachio-green radiating bladed crystals from 0.05 to 0.50 mm long. It is vitreous to transparent in thin flakes, has a white streak, and shows no fluorescence under long-wave or short-wave ultraviolet light. Cleavage is perfect parallel to {001} and no parting was observed. Mohs hardness is 2, it is brittle and has a splintery fracture. The calculated mass density is 2.231 g cm–3. In transmitted plane-polarized white light, nickelalumite is non-pleochroic, biaxial, α = 1.542(2), γ = 1.533(2), β could not be measured due to the almost negligible thickness of the flakes. EPMA chemical analysis gave Al2O3 39.94, SiO2 0.17, SO3 15.20, V2O3 0.29, FeO 0.15, NiO 8.00, ZnO 6.21, (H2O)calc. 31.87, total 101.83 wt%, H2O was determined by crystal-structure analysis, and the empirical formula is as follows: (Ni0.55Zn0.39V0.02Fe0.01)Σ0.97(Al3.99Si0.01)Σ4.00 (SO4)(OH)12(H2O)3 based on 4 (Al + Si) cations. There is considerable variation in substitution of Zn, Cu, Fe and V3+ for Ni and V5+ for S6+. Nickelalumite is monoclinic, P21/n, a = 10.2567(5), b = 8.8815(4), c = 17.0989(8) Å, β = 95.548(1)°, V = 1550.3(2) Å3, Z = 4. The crystal structure of nickelalumite was refined to an R1 index of 5.66% and consists of interrupted [NiAl4(OH)12] sheets intercalated with layers of {(SO4)2(H2O)3}; nickelalumite is a member of the chalcoalumite group.

Enantiomeric discrimination by chiral electromagnetic resonance enhancement.

Circularly polarized light interacts preferentially with the biomolecules to generate spectral fingerprints reflecting their primary and secondary structure in the ultraviolet region of the electromagnetic spectrum. The spectral features can be transferred to the visible and near-infrared regions by coupling the biomolecules with plasmonic assemblies made of noble metals. Nanoscale gold tetrahelices were used to detect the presence of chiral objects that are 40 times smaller in size by using plane-polarized light of 550 nm wavelength. The emergence of chiral hotspots in the gaps between 80 nm long tetrahelices differentiate between weakly scattering S- vs R-molecules with optical constants similar to that of organic solvents. Simulations map the spatial distribution of the scattered field to reveal enantiomeric discrimination with selectivity up to 0.54.

Formation of calcium oxalates and carbonates due to water stress in “nopalitos”

The “nopalitos” (Opuntia ficus-indica L. Miller) is an essential source of calcium in the human diet; however, the bioavailability and viability of the mineral are limited by precipitating in the form of calcium oxalate (CaC2O4) when the plant is exposed to water stress. The objective of this study was to quantify calcium oxalates and carbonates in cactus subjected to water differentials of 10, 30 and 60% of available water (AW) through photomicrographic analysis. The micro mosaics are composed of sequential images of a 10x amplitude, taken in a petrographic microscope with different light sources, plane-polarized light (LPP), cross-polarized light (LPC), and light compensated (LPC). High spectral resolution mosaics were produced using geospatial operators (ArcGIS v.10.1 and ERDAS Imagine, 2014v®). The CaC2O4 and CaCO3 were identified by spectral signature or brightness degrees in RGB format images, quantifying the minerals and surface they occupy in the cladode. The quantification of minerals in situ in nopal cladodes at different water stresses showed significant differences (p<0.05) in the area occupied by oxalates at 10% water stress and calcium carbonates at 60% within the vegetal structures of nopal vegetables. Consequently, using high-resolution mosaics and spatial operators allows the identification and quantification of mineral biomarkers in plant tissues in situ. Therefore, using image overlay, the proposed method is an alternative to the in situ quantification of minerals in plant tissues.

Linear photogalvanic effect in surface states of topological insulators

The theory of the linear photogalvanic effect is developed for direct optical transitions between surface states of three-dimensional topological insulators. The photocurrent governed by the orientation of the polarization plane of light and caused by the warping of the energy dispersion of two-dimensional carriers is calculated. It is shown that both the shift contribution caused by coordinate shifts of the particle wave packets during the optical transitions and the ballistic contribution caused by interference of the optical absorption and scattering by disorder have generally the same order of magnitude. The ballistic contribution is present owing to electron-hole asymmetry of topological surface states and has a frequency dependence in contrast to the shift photocurrent. In the nonlinear-in-the-light-intensity regime appearing due to saturation of the direct optical transitions, the ballistic contribution dominates. The nontrivial dependence of the photocurrent on the polarization plane orientation in the nonlinear regime appears solely due to the ballistic contribution. Our findings allow separating the ballistic and shift contributions to the Linear photogalvanic current in experiments.

Measurements of large optical rotary dispersion in the adipose eyelid of Atlantic mackerel (Scomber scombrus).

Collagen is the most prevalent of Nature's structural proteins, and is found in the extracellular matrices of animals. The structures of collagen molecules and aggregates are chiral, which leads to the rotation of transmitted, plane-polarized light. Here, it is shown that the concentrations of chiral molecules and aggregates in the optically transparent, adipose eyelid of Atlantic mackerel (Scomber scombrus) can be so high, that plane-polarized light in the visible spectrum is rotated by tens to hundreds of degrees, depending on wavelength (the optical rotatory dispersion (ORD)). This gives rise to intensely coloured images of eyelid samples when illuminated with white light and viewed between crossed polarizers. The ORD in the visible spectrum is measured with monochromatic light sources, and using this dispersion, the variation of optical thickness within a sample (proportional to collagen concentration and path length) is determined. The agreement between observed and simulated white-light images is almost perfect. While collagen provides vital mechanical rigidity to animal tissue, it might also possess optical properties that are useful for vision and camouflage.

PETROGRAPHIC FEATURES AND MODELLING OF SOME WATERFALL ROCKS IN KENYIR LAKE, TERENGGANU: A MICROSCOPIC PERSPECTIVE APPROACH IN SUSTAINABLE GEOTOURISM

Waterfalls around Kenyir Lake, Terengganu, naturally serve as an iconic symbol of amazing rock bounded formation amidst the wilderness, which stores a hidden story for millions of years. The waterfalls feeding Kenyir Lake have become tourists’ main attractions since they are located separately on different islands. There are three naturally picturesque waterfalls worth sight-seeing in the study area, namely Sungai Buweh Waterfall, Lasir Waterfall and Saok Waterfall, which are made up of granitic rock bodies that emerged in the Eastern Belt during the Late Triassic. To date, the waterfall landscape displayed in any area concerning geotourism focuses more on outcrop architecture and geomorphological features but with limited accessibility to the rock records. Thus, this study is carried out to evaluate the geo-heritage features of the waterfall landscape and its rock-forming minerals. Four rock samples were carefully collected from the waterfalls and subsequently prepared for optical thin section petrography analysis using a polarised light microscope. The petrographic analysis will determine the precise mineral compositions, fabrics and microstructures under plane polarised light (PPL) and cross-polarised light (XPL) at different magnifications. In addition, petrographic modelling was constructed using integrated software Autodesk 3ds Max and Debrismaker 2.0 from optical microscopic data to help identify a microscopic mineral in detail so that the mineral becomes clear to both geologists and the public at large. Generally, this modelling will enlighten the public on the material embedded in the rocks, illustrate the importance of learning about a rock-forming mineral and bring this futuristic idea with Sustainable Development Goal 15 (SDG). Besides making geology an interesting field for young geologists and the public, this mineral affirms the beautiful scenery of waterfalls for tourism, thereby connecting the interrelationship between geotourism and nature. In this regard, the current study was carried out to evaluate the geo heritage features and use an interactive learning platform for interpreting rock-forming minerals and their function towards sustainable geo-tourism.

Ferro-ferri-katophorite, a new clinoamphibole from the silicocarbonatite dykes in Sierra de Maz, La Rioja, Argentina

AbstractFerro-ferri-katophorite (IMA2016–008), ideally Na(NaCa)(Fe2+4Fe3+)(Si7Al)O22(OH)2, was found as xenocrysts up to 3 cm long and replacement rims around aegirine–augite in silicocarbonatite dykes cropping out in the Sierra de Maz, La Rioja province, NW Argentina. Ferro-ferri-katophorite is black and has vitreous lustre and a pale green streak. The new mineral is brittle, with perfect {110} cleavage and has a Mohs hardness of 6. The measured density is 3.32(1) g/cm3. In plane-polarised light it is strongly pleochroic, X = light greenish brown, Y = dark greyish brown and Z = dark greyish olive green. Absorption (very strong) is Z > Y > X. The orientation is: Z ∥ b, and X forms a small angle with [001]. Ferro-ferri-katophorite is biaxial (–), with α = 1.688(3), β = 1.697(3), γ = 1.698(3) and 2V(calc) = 36.7°. It is monoclinic, space group C2/m, a = 9.8270(7), b = 18.0300(8), c = 5.316(4) Å, β = 104.626(4)°, V = 911.4(6) Å3 and Z = 2. The strongest five lines in the powder X-ray diffraction pattern [d in Å (I)(hkl)] are: 8.416(100)(110), 3.135(50)(310), 2.815(26)(330), 2.720(18)(151) and 1.4422(15)($\bar{6}$61). The chemical composition is SiO2 43.08, TiO2 2.76, ZrO2 0.15, Al2O3 8.76, V2O3 0.07, Fe2O3 9.28, FeO 13.85, MnO 0.43, MgO 6.88, CaO 6.58, ZnO 0.06, Na2O 5.55, K2O 1.18, Cl 0.01, H2O calc 1.36, total 99.95 wt.%. The formula unit (confirmed by single-crystal structural analysis) is (Na0.74K0.23)Σ0.97(Ca1.08Na0.91Mn0.01)Σ2.00(Fe2+1.78Mg1.57Fe3+1.07Ti4+0.32Al0.19Mn2+0.04Zr0.01V3+0.01Zn0.01)Σ5.00(Si6.61Al1.39)Σ8.00O22(OH1.59O0.61)Σ2.00. Aluminium is strongly ordered at the T(1) site. Ferro-ferri-katophorite is the 9th species carrying the katophorite root name and is related to katophorite by the Fe2+ + Fe3+ → Mg2+ + Al3+ substitution. Type material was deposited at the Museo de Mineralogía “Stelzner”, Universidad Nacional de Córdoba, Argentina, under catalogue number MS003341.

Эффект Фарадея в знакопеременном магнитном поле: математическая модель

When creating magnetic focusing systems, for example, for traveling wave lamps, there are known problems associated with the need to adjust the electron flow moving in a given direction along the axis of the device, that is, to align its axis with the magnetic axis of the focusing system. The ideal adjustment of the device is very difficult to achieve due to many influencing factors, therefore, it becomes necessary to create automated complexes for simulating the alignment of the electron beam in the magnetic field formation system for focusing systems. The alignment problems can be solved using magneto-optical methods, since it is known that when exposed to a magnetic field, the light exhibits a number of similar properties (reaction). The aim of the work is to create a mathematical model for the passage of a light beam through an alternating magnetic system based on the Faraday effect. As a result, a mathematical model has been obtained, that should allow modeling the change in the plane of light polarization during the passage (movement of the magneto-optical sensor) along the axis of the magnetic system. The simulation of the passage of light according to the Faraday effect through a magnetic system of one and five magnets is considered.

Polysynthetic Twinning of Diopsides in the Niewang and Tatliksu Nephrite Deposits, Xinjiang, China

Diopside, an important component of the crustal and upper mantle, plays an important role in the formation of nephrite. Polysynthetic twinning in natural diopside, especially from skarns, has rarely been systematically researched. Here, the polysynthetic twinning of natural diopside was investigated in two skarn-type nephrite deposits (Niewang and Tatliksu) in Qiemo, Xinjiang, China. Petrographic observations revealed periodic alternations of dark–light lamellae under cross-polarized light and parallel striations under plane-polarized light, whereas backscattered electron images indicated high homogeneity, which suggested a type of mechanical polysynthetic twinning. According to the optical indicatrix, twins were predominantly oriented as a (100)[100] system. Raman spectra and chemical data show that pyroxenes in nephrite are close to the Di end-member with 0.90–1.04 a.p.f.u. Mg and 0.98–1.05 a.p.f.u. Ca. Both diopside and tremolite from Tatliksu contain slightly higher Fe than those from Niewang. Given the seismic origin of mechanical clinopyroxenes twins, twins of studied diopsides are likely to be attributed to Paleozoic-Mesozoic paleoearthquakes in the Altyn Mountain. A shear stress ≥ 140 MPa and a differential stress greater than 280 MPa are suggested as conditions linked to generation of the twinning of diopsides in the nephrite deposits. The replacement of diopside by tremolite along its twin planes highlights the potential gemological implications, as such replacement by tremolite probably facilitated the formation of dense, fine fibre textures in the nephrites.

Practice of the Visual Determination of the Direction of the Rotation of the Light Polarization Plane in Gyrotropic Uniaxial Single Crystals

Practice of the Visual Determination of the Direction of the Rotation of the Light Polarization Plane in Gyrotropic Uniaxial Single Crystals

Quantification analysis of geometric characteristics of micro crack network on fault rock surface

Faults are common water conduits in coal mines, with variable permeability based upon the extent of cracks along the fault plane. In this study, three samples from a fault were obtained from a mining area in Southwest Shandong, China to determine the geometric characteristics, including crack density, fractal dimension, and crack connectivity. For microstructural analysis of fault rock specimens, scanning electron microscopy (SEM), x-ray diffraction (XRD), and plane-polarized light microscopy tests were used, and the geometric characteristics were calculated. A nonuniformity coefficient that considers the mineral composition is proposed to describe the micro-crack network of fault rocks. The results show that there is a significant positive correlation among three geometric characteristic parameters, and the nonuniformity coefficient is positively correlated with those parameters of the crack network. The crack extension forms of the three fault rock samples are different, which is related to the different fracture toughness of the mineral particles. The optical photomicrographs and SEM images show that crack networks are most developed in the samples with the least clay content. There is a negative correlation between clay content and the geometric parameters of the crack network, which may be related to the friction coefficient of clay.

Practice of the visual determination of the direction of light polarization plane rotation in the gyrotropic uniaxial single crystals

When studying and applying crystals of the middle category, it is necessary to take into account the manifestations of anisotropy of their properties, in particular, optical anisotropy. One of the manifestations of optical anisotropy is the rotation of the polarization plane (gyrotropy effect), which is observed in the direction of the optical axis of such crystals. The plane of polarization of light can rotate clockwise and counterclockwise. To determine the direction of rotation of the polarization plane, simple visual methods can be used based on studies of samples in converging polarized light – observations of conoscopic figures. In general, the type of conoscopic figures depends on the relative position of the polarizers, the wavelength of light in the system, the cut of the single crystal perpendicular to which the light propagates, the thickness of the sample and the birefringence. The direction of rotation of the polarization plane can be determined by еру change of the type of conoscopic figure of a sample of a gyrotropic crystal cut perpendicular to the optical axis: change of the central spot color during the analyzer rotation; the extinction of the central spot when observing a conoscopic figure using light filters; the direction of movement of the rings in monochromatic light; observation of Airy patterns. According to the experience of working in our laboratory “Single crystals and Stocke on their Base”, the simplest, most operational and unambiguous visual method for determining the direction of rotation of the polarization plane is the observation of Airy figures. A conoscopic pattern in the form of Airy figures (a four-way spiral) occurs when observing in converging polarized light a combination of two superimposed samples of gyrotropic crystals cut perpendicular to the optical axis, rotating the plane of polarization of light in opposite directions. To use this method, a well-known sample of a gyrotropic crystal cut perpendicular to the optical axis is required.

Photoinduced Split of the Cavity Mode in Photonic Crystals Based on Porous Silicon Filled with Photochromic Azobenzene-Containing Substances

Phototunable photonic structures based on electrochemically etched silicon filled with four photochromic azobenzene-containing compounds, a bent-shaped low-molar-mass substance and side-chain polymethacrylates and a copolyacrylate, were prepared, and their photo-optical properties were studied. It was found that irradiation of these composites with polarized blue light results in spectral changes in the photonic band gap (split of the cavity mode) associated with cooperative photo-orientation of azobenzene moieties inside silicon pores in the direction perpendicular to the polarization plane of the incident light. Kinetics of the photoinduced split is studied. The observed photoinduced split is completely reversible, and heating of the composites to temperatures above isotropization or glass transitions fully recovers the initial spectral shape of the photonic band gap. Thermal and temporal stabilities of the obtained photoinduced split were comparatively studied, and it was found that for composites with a bent-shaped substance and polymethacrylate shape of the reflectance spectra do not change over time at room temperature. The prepared composites have a high potential for the different applications in photonics.

The study of the optical activity of some S-derivatives 4-R-5-((((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1, 2,4-triazole-3-thiols

About half of the drugs currently produced are chiral compounds, and about 90 % of these compounds are sold as racemates, consisting of an equimolar mixture of two enantiomers. Although they have the same chemical structure, most of the optical isomers of chiral substances show marked differences in biological activity. It is known that the presence of a single asymmetric atom has become almost an integral part of advanced drug design. The aim of this work was to determine the angle of rotation of the polarization plane of solutions of some S-derivatives of 4-R-5-((((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl))-4H-1,2,4-triazole-3-thiols and the establishment of regularities between the structure of the studied molecules and their optical activity. Materials and methods. The subject of the study was 2-[5-R1-4R2-1,2,4-triazole-3-ylthio]-1-aryletanols. The study of the angle of rotation of the plane of polarization of solutions of newly synthesized compounds was carried out using an Atago AP-300 polarimeter and the DFU 2.2.7 physical-chemical analysis method “Optical rotation”. Results. The results of the physical-chemical analysis were carried out that the studied compounds exhibit optical activity. The compound 1-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio)methyl)-4H-1,2,4-triazole-3-yl)thio)-2-phenylethan-1-ol (+43° [deg∙g/cm3∙dm]). The only levorotatory substance was 1-(4-fluorophenyl)-2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl)thio))methyl)-4H-1,2,4-triazole-3-yl)thio)ethan-1-ol with specific rotation [α]D20 = -43° [deg∙g/cm3∙dm]. Conclusions. Studies had shown that 1-(4-fluorophenyl)-2-((4-methyl-5-(((3-(pyridin-4-yl)-1H-1,2,4-triazole-5-yl))thio)methyl)-4H-1,2,4-triazole-3-yl)thio)ethan-1-ol was able to rotate the light polarization plane to the left, which was evidence of the advantage of the S-enantiomer in the racemic mixture, and therefore this compound was considerable interest for further preclinical research. Also, all other analyzed compounds behave as optical isomers.