doi: 10.17586/2226-1494-2015-15-5-849-855


PERMITTIVITY DISPERSION FEATURES OF A NEMATIC LIQUID CRYSTAL WITH QUANTUM DOTS

D. P. Shcherbinin, E. A. Konshina, M. A. Kurochkina


Read the full article  ';
Article in Russian

For citation: Shcherbinin D.P., Konshina E.A., Kurochkina M.A. Permittivity dispersion features of a nematic liquid crystal with quantum dots. Scientific and Technical Journal of Information Technologies, Mechanics and Optics, 2015, vol. 15, no. 5, pp. 849–855.

Abstract

Subject of Research. The paper deals with research of dielectric properties of suspensions for a nematic liquid crystal (LC) with positive dielectric anisotropy Δε = 10.5, doped with semiconductor quantum dots (QDs) CdSe / ZnS, and dependence on their concentration in the range of 0.05-0.3 wt. %. Methods. The studies were carried out by the method of dielectric spectroscopy. A special flat titanium cell with the distance between the electrodes equal to 250 μm was used for the measurement. The voltage was applied to the electrodes. The dispersion of parallel and normal parts of the real and imaginary components of the dielectric permittivity was measured in the range from 50 Hz to 6.5 MHz at the orienting magnetic field equal to 4 • 105 A / m applied to a cell. Main Results. Deviation of the permittivity spectra of suspensions with QDs concentration growth was observed from a spectrum of the pure LC. It was caused by losses of free ions on the conductivity at frequencies below 103 Hz. The shift of a peak in the suspension spectrum at frequencies above 106 Hz is associated with relaxation of the LC molecules orientation. It has been shown that  lowering in the range of 103 -104 Hz with concentration increasing up to 0.3 wt. % did not exceed 4%. Practical Relevance Obtained results give the possibility to explain the change in macroscopic properties of the liquid crystal as a result of doping.  


Keywords: liquid crystals, quantum dots, dielectric spectroscopy.

Acknowledgements. This work was carried out under financial support by the Ministry of Education and Science of Russia in the framework of the state task project 3.92.2014 / K. The authors express their gratitude to Dobrun L.A., assistant of the Department of Polymer Physics, Saint Petersburg State University, for technical assistance

References
1. Tripathi P., Dixit S., Manohar R. Effect of bridging group on the dielectric properties of liquid crystal. Chemical Rapid Communications, 2013, vol. 1(2), pp. 50–55.
2. Dixit S., Misra Kr., Manohar R., Arora A.K. Enhancement in dielectric properties of nematic liquid crystal by gamma irradiation. Molecular Crystals and Liquid Crystals, 2013, vol. 571, no. 1, pp. 77–85. doi: 10.1080/15421406.2012.744662
3. Manohar R., Manohar S., Chandel V.S. Dielectric behaviour of pure and dye doped nematic liquid crystal BKS/B07. Materials Sciences and Application, 2011, vol. 2, pp. 839–847. doi: 10.4236/msa.2011.27114
4. Bauman D., Haase W. Dielectric measurements of guest-host systems. Molecular Crystals and Liquid Crystals, 1989, vol. 168, pp. 155–168. doi: 10.1080/00268948908045968
5. Manohar R., Pandey K.K., Srivastava A.K., Misra A.K., Yadav S.P. Sign inversion of dielectric anisotropy in nematic liquid crystal by dye doping. Journal of Physica and Chemistry of Solids, 2010, vol. 71, no. 9, pp. 1311–1315. doi: 10.1016/j.jpcs.2010.05.011
6. Yadav S.P., Pandey K.K., Misra A.K., Tripathi P.K., Manohar R. The molecular ordering phenomenon in dye-doped nematic liquid crystals. Physica Scripta, 2011, vol. 83, no. 3, art. 035704. doi: doi: 10.1088/0031-8949/83/03/035704
7. Ouskova E., Buchnev O., Reshetnyak V., Reznikov Yu., Kresse H. Dielectric relaxation spectroscopy of a nematic liquid crystal doped with ferroelectric Sn2P2S6 nanoparticles. Liquid Crystals, 2003, vol. 30, no. 10, pp. 1235–1239. doi: 10.1080/02678290310001601996
8. Kinkead B, Hegmann T. Effects of size, capping agent and concentration of CdSe and CdTe quantum dots doped into a nematic liquid crystal on the optical and electro-optic properties of the final colloidal liquid crystal mixture. Journal of Materials Chemistry, 2010, vol. 20, no. 3, pp. 448–458. doi: 10.1039/b911641a
9. Konshina E.A., Gavrish E.O., Orlova A.O., Artem'ev M.V. Effect of dispersed CdSe/ZnS quantum dots on optical and electrical characteristics of nematic liquid crystal cells. Technical Physics Letters, 2011, vol. 37, no. 11, pp. 1011–1014. doi: 10.1134/S1063785011110071
10. Zhang T., Zhong C., Xu J. CdS-nanoparticle-doped liquid crystal displays showing low threshold voltage. Japanese Journal of Applied Physics, 2009, vol. 48, no. 5, pp. 0550021–05500216. doi: 10.1143/JJAP.48.055002
11. Lee W.-K., Hwang S.J., Cho M.-J., Park H.-G., Han J.-W., Song S., Jang J.H., Seo D.-S., CIS-ZnS quantum dots for self-aligned liquid crystal molecules with superior electro-optic properties. Nanoscale, 2013, vol. 5, no. 1, pp. 193–199. doi: 10.1039/c2nr32458j
12. Kopcansky P., Koval’chuk T., Gornitska O., Vovk V., Tomasovicova N., Koneraeka M., Timko M., Zavisova V., Jadzyn J., Eber N., Studenyak I. Dielectric spectroscopy of liquid crystal doped with Fe3O4 nanoparticles. Physics Procedia, 2010, vol. 9, pp. 36–40. doi: 10.1016/j.phpro.2010.11.010
13. Zakerhamidi M.S., Shoarinejad S., Mohammadpour S. Fe3O4 nanoparticle effect on dielectric and ordering behavior of nematic liquid crystal host. Journal of Molecular Liquids, 2014, vol. 191, pp. 16–19. doi: 10.1016/j.molliq.2013.11.020
14. Tomylko S., Yaroshchuk O., Kovalchuk O., Maschke U., Yamaguchi R. Dielectric properties of nematic liquid crystal modified with diamond nanoparticles. Ukrainian Journal of Physics, 2012, vol. 57, no. 2, pp. 239–243.
15. Lin F.-C, Wu P.-C, Jian B.-R., Lee W. Dopant effect and cell-configuration-dependent dielectric properties of nematic liquid crystals. Advances in Condensed Matter Physics, 2013, vol. 27, art. 271574. doi: 10.1155/2013/271574
16. Tang C.-Y., Huang S.-M., Lee W. Electrical properties of nematic liquid crystals doped with anatase TiO2 nanoparticles. Journal of Physics D: Applied Physics, 2011, vol. 44, no. 35, art. 355102. doi: 10.1088/0022- 3727/44/35/355102
17. Kumar P.K., Tripathi P.K., Misra A.K., Pandey K.K., Manohar R. Study on dielectric and optical properties of ZnO doped nematic liquid crystal in low frequency region. Chemical Rapid Communications, 2013, vol. 1, no. 1, pp. 20–26.
18. Chen W.-T., Chen P.-S., Chao C.-Y. Effect of doped insulating nanoparticles on the electro-optical characteristics of nematic liquid crystals. Japanese Journal of Applied Physics, 2009, vol. 48, no. 1, art. 015006. doi: 10.1143/JJAP.48.015006
19. Haraguchi F., Inoue K.-I., Toshima N., Kobayashi S., Takatoh K. Reduction of the threshold voltages of nematic liquid crystal electrooptical devices by doping inorganic nanoparticles. Japanese Journal of Applied Physics, 2007, vol. 46, no. 33–35, pp. L796–L797. doi: 10.1143/JJAP.46.L796
20. Mottram N.J. A model of dual frequency nematic liquid crystals. Workshop on Modeling of Soft Matter. Cortona, 2005, 30 p.
21. Meier G., Saupe A. Dielectric relaxation in nematic liquid crystals. Molecular Crystals, 1966, vol. 1,pp. 515–525.
22. Blinov L.M. Zhidkie Kristally. Struktura i Svoistva [Liquid Crystals. Structure and Properties]. Moscow, Librokom Publ., 2013, 484 p.


Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Copyright 2001-2022 ©
Scientific and Technical Journal
of Information Technologies, Mechanics and Optics.
All rights reserved.

Яндекс.Метрика