Mert YILDIRIM, Özge TÜZÜN ÖZMEN, Gülnur ÖNSAL, Gülsüm KOCAKÜLAH, Oğuz KÖYSAL

Dielectric and Performance Analysis of CdTe Quantum Dots Doped Nematic Liquid Crystal

Bu çalışmada çekirdek tipi kadmiyum tellür kuantum noktaları (CdTe QDs) ağırlıkça % 0,05 oranında 5CB (4pentil-4'-siyanobifenil) nematik sıvı kristale (LC) katkılanmış ve dielektrik özellikleri 100 Hz-10 MHz frekans aralığında empedans ölçümleri kullanılarak araştırılmıştır. CdTe kuantum noktaların 5CB nematik sıvı kristal yapıda gösterdiği etkiyi belirlemek için dielektrik anizotropi (??), geçiş frekansı (fgeçiş), kritik frekans (fkritik), dielektrik sabiti (?' ve ?") değerleri saf ve CdTe katkılı LC için deneysel veriler kullanılarak elde edilmiştir. Ayrıca, eşik voltajı (Vth) ve eğilme elastik sabiti (K11) hesaplanmıştır. CdTe katkılanmasıyla eşik voltajı (Vth) ve eğilme elastik sabitinin (K11) önemli ölçüde azaldığı görülmüştür

CdTe Kuantum Nokta Katkılı Nematik Sıvı Kristalin Dielektrik ve Performans Analizi

In this work, cadmium telluride core type quantum dots (CdTe QDs) were dispersed in 4-pentyl-4′cyanobiphenyl (5CB) nematic liquid crystal (LC) with a concentration of 0.05 % wt/wt; and dielectric properties were investigated by using admittance measurements in the frequency range of 100 Hz - 10 MHz. In order to determine the effects of CdTe QDs in 5CB nematic LC, dielectric anisotropy (∆ε), crossover frequency (fcrossover), critical frequency (fcritical), real and imaginary parts of permittivity (ε' and ε") of neat LC and CdTe QDs dispersed LC composites were obtained using the experimental data. Moreover, threshold voltage (Vth), splay elastic constant (K11) were also calculated. It was found that Vth and K11 of QDs dispersed LC are significantly decreased due to the existence of CdTe QDs

PDF

___

V. REFERENCES
[1] U. B. Singh, R. Dhar, A. S. Pandey, S. Kumar, R. Dabrowski, and M. B. Pandey, “Electrooptical and dielectric properties of CdSe quantum dots and 6CHBT liquid crystals composites, ” AIP Advances, vol. 4, no. 11, pp. 117112-1 - 117112-9, 2014.
[2] P. Malik, A. Chaudhary, R. Mehra, and K. K. Raina, “Electrooptic and dielectric studies in cadmium sulphide nanorods/ferroelectric liquid crystal mixtures,” Advances in Condensed Matter Physics, vol. 2012, pp. 1-8, 2012.
[3] E. A. Konshina, E. O. Gavrish, A. O. Orlova, and M. V. Artem’ev, “Effect of dispersed CdSe/ZnS quantum dots on optical and electrical characteristics of nematic liquid crystal cells,” Tecnical Physics Letters, vol. 37, no. 11, pp. 1011-1014, 2011. 261
[4] M. Yıldırım, A. Allı, G. Önsal, N. Gök, and O. Köysal, “Synthesis & chemical and dielectric characterization of poly (linoleic acid)-g-poly (dimethylaminoethyl methacrylate): A novel high-κ graft copolymer,” Composites: Part B, vol. 117, pp. 43-48, 2017
[5] M. Gökçen and O. Köysal, “Effect of frequency on dielectric properties of liquid crystal doped with side-chain liquid crystalline polymer,” Materials Chemistry and Physics, vol. 129, pp. 1142- 1145, 2011.
[6] M. Yıldırım, O. Köysal, G. Önsal, and E. Gümüş,“Effect of iron phthalocyanine (FePc) concentration on electrical and dielectric properties of the nematic liquid crystal composites,” Journal of Molecular Liquids, vol. 223, pp. 868-872, 2016.
[7] R. Basu and G. S. Iannacchione, “Evidence for directed self-assembly of quantum dots in a nematic liquid crystal,” Physical Review E, vol. 80, pp. 010701(R)-1 – 010701(R)-4, 2009.
[8] O. Köysal, “Conductivity and dielectric properties of cholesteric liquid crystal doped with single wall carbon nanotube,” Synthetic Metals, vol. 160, 1097-1100, 2010.
[9] J. Mirzaei, M. Reznikov, and T. Hegmann, “Quantum dots as liquid crystal dopants,” Journal of Materials Chemistry, vol. 22, pp. 22350-22365, 2012.
[10] R. K. Shukla, Y. G. Galyametdinov, R. R. Shamilov, and W. Haase, “Effect of CdSe quantum dots doping on the switching time, localised electric field and dielectric parameters of ferroelectric liquid crystal,” Liquid Crystals, vol. 41, no. 12, pp. 1889-1896, 2014.
[11] A. Kumar and A. M. Biradar, “Effect of cadmium telluride quantum dots on the dielectric and electro-optical properties of ferroelectric liquid crystals,” Physical Review E, vol. 83, pp. 041708-1 ˗ 041708-8, 2011.
[12] P. K. Tripathi, A. Kr Misra, K. Kr Pandey, and R. Manohar, “Study on dielectric and optical properties of ZnO doped nematic liquid crystal in low frequency region,” Chemical Rapid Communications, vol. 1, no. 1, pp. 20-26, 2013.
[13] J. Kumar, R. K. Gupta, S. Kumar, and V. Manjuladevi, “Electro-optic and dielectric studies on quantum dot doped nematic liquid crystal,” Macromolecular Symposia, vol. 357, pp. 47-51, 2015.
[14] S. K. Gupta, S. Pandey, D. P. Singh, T. Vimal, S. Manohar, and R. Manohar, “Quantum dot doped ferroelectric liquid crystal system: Investigation of electro-optical parameters and relaxation behavior,” Molecular Crystals and Liquid Crystals, vol. 610, pp. 227-234, 2015.
[15] P. K. Tripathi, B. Joshi, and S. Singh, “Pristine and quantum dots dispersed nematic liquid crystal: Impact of dispersion and applied voltage on dielectric and electro-optical properties,” Optical Materials, vol. 69, pp. 61-66, 2017.
[16] F. Al-Hazmi, A. A. Al-Ghamdi, N. Al-Senany, F. Alnowaiser, and F. Yakuphanoglu, “Dielectric anisotropy and electrical properties of the copper phthalocyanine (CuPc): 4–4’-nHeptylcyanobiphenyl (7CB) composite liquid crystals,” Composites: Part B, vol. 56, pp. 15-19, 2014. 262
[17] J. Mirzaei, M. Urbanski, H. S. Kitzerow, and T. Hegmann, “Hydrophobic gold nanoparticles via silane conjugation: chemically and thermally robust nanoparticles as dopants for nematic liquid crystals,” Philosophical Transactions of the Royal Society A, vol. 371, pp. 20120256-1 – 20120256- 18, 2013.