Наукові публікації кафедри загальної та прикладної фізики
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- ItemMechanism of dimerization of viologens in liquid crystalline medium(Ukr. J. Phys. 2017. Vol. 62, No. 4 294-298, 2017) Bordyuh, HannaThis work presents the analysis of experimental data on electrooptical properties of viologens incorporated into the liquid crystalline medium. These data along with theoretical considerations allow specifying the mechanism, which leads to the double color change in the liquid crystal – viologen samples stipulated by the application of increasing voltage values. Specifically, it is proved that the first color change takes place due to the one-electron reduction of viologen molecules, and the second color change is caused by the dimerization between viologen molecules, which were fully reduced under the action of a voltage applied, and initial viologen molecules.
- ItemElectrooptical and Nonlinear Optical Properties of Lyotropic Liquid Crystals Doped with Electrochromic Viologen(Український фізичний журнал, 2012) Bordyuh, Hanna; Polishchuk, ArkadiyThis work presents the results of experimental studies of the electrooptical and nonlinear optical properties of lyotropic ionic liquid crystals (LILC) with soluted electrochromic admixtures of viologens. It is established that the Smectic A ordering of the LILC of potassium caprylate is not disrupted by the introduction of viologens. Moreover, LILC-viologen composites obtain electrochromic properties inherent to viologens, which produce colored radical cations and dimers, while reducing. The presence of radical cations and dimmers is fixed by the optical absorption spectra. It is found that, under the action of an electric field, the LILC-viologen samples form a bilayer structure consisting of a liquid crystal layer and an absorptive layer of viologen redox products (radical cations and dimers). A dynamic grating recording is realized and studied in bilayer LILC-viologen cells. It is determined that the recording takes place in the colored layer of viologen redox products. A possible mechanism of grating recording in LILC-viologen cells is proposed.
- ItemСтруктурні та електрооптичні властивості електрохромних рідкокристалічних композитів(Національний Авіаційний Університет, 2012) Бордюг, Ганна Борисівна; Поліщук, Аркадій ПетровичНаведено результати структурних та електрооптичних досліджень новостворених композитів на основі ліотропних рідких кристалів каприлату калію та віологенів. Визначено наявність у дослі-джуваних зразках смектичного впорядкування. Описано його основні параметри. Показано, що електрохромні властивості віологенів зберігаються і при розчиненні в рідкокристалічній матриці, що проявляється в забарвленні зразків під дією зовнішнього електричного поля і підтверджується оптичними спектрами поглинання. Проаналізовано процеси, які проходять у композитах ліотропні рідкі кристали – віологен у разі прикладання електричного поля.
- ItemLiquid crystal materials with regulated optical properties(Національний Авіаційний Університет, 2013) Bordyuh, HannaIn this work we present the results of structural and electrooptical investigations of the new-created composites based on lyotropic liquid crystals (LLC) of potassium caprylate and viologens. Provided structural analysis showed the presence of a Smectic ordering in the investigated samples and allowed to determine its main parameters. It was shown that the electrochromic properties of viologens are preserved after their solution in the liquid-crystalline matrix. They reveal themselves as a coloration of the samples under applying of an electric field and are proved by the optical absorption spectra. Also we analyzed the processes taking place in LLC-viologen composites in the case of an electric field applying.
- ItemFast Nolinear Optical Mechanisms in Bi-Layered Cells Composed by Lyotropic Ionic Liquid Crystals with Dye and Viologen Films(Taylor & Francis Group, LLC, Mol. Cryst. Liq. Cryst., Vol. 508, pp. 296[658]–308[670], 2009, 2009) Bordyuh, HannaMechanisms of the fast optical nonlinearity are studied in two types of cells based on lyotropic ionic liquid crystals (LILC) of metal alkanoates. They are (I) bi-layer cell, which consists of a thin dye film covered by LILC, and (II) LILC with electrochromic impurity (viologen). Applying dc electric voltage to the cell II leads to adsorption of viologen redox products with formation of a thin nanosized layer on the cathode. The dynamic holographic technique with pulsed laser radiation of the nanosecond duration was used to investigate nonlinear optical properties in both types of cells. The mechanism of photoconversion of viologen redox products under strong laser radiation is proposed to explain grating recording in the cell II.