Investigation of the Dielectric Behavior of Nematic Liquid Crystals Doped with Phosphorus-Based Nanostructures: An Experimental and DFT-Based Study

Öz

Nematic liquid crystals containing nanoscopic fillers provide a versatile platform for regulating interfacial polarization and charge dynamics. In this study, the effects of crystalline black phosphorus (BP), amorphous red phosphorus (RP), and BP–multi-walled carbon nanotube (BP–MWCNT) hybrid nanostructures on the dielectric properties of nematic 5CB (4-cyano-4′-pentylbiphenyl) are investigated using broadband dielectric spectroscopy and density functional theory (DFT) calculations. BP exhibits pronounced low-frequency permittivity enhancement due to Maxwell–Wagner–Sillars interfacial polarization arising from its layered and anisotropic electronic structure, while RP provides limited improvement accompanied by increased dielectric losses. The BP–MWCNT hybrid combines elevated ε′ values with reduced dielectric loss through cooperative dipole formation and charge-balancing interactions, yielding a balanced dielectric response. DFT calculations reveal that BP possesses a pronounced dielectric anisotropy (εxx > εyy >> εzz) and that the BP–5CB adsorption energy of approximately −2.98 eV supports the formation of stable interfacial dipoles through strong interfacial electronic coupling. Under an applied DC field, BP-doped composites exhibit asymmetric relaxation behavior, indicating localized symmetry breaking driven by interfacial anisotropy within the nematic phase. These findings demonstrate that phosphorus-based nanofillers offer a powerful engineering strategy for tuning interfacial polarization, dielectric symmetry, and field-responsive behavior in nematic liquid crystals.

Anahtar Kelimeler

• Nematic liquid crystals
• Black phosphorus
• Interfacial polarization
• Dielectric properties
• DFT calculations

Destekleyen Kurum

Kocaeli University Scientific Research Projects Unit

Proje Numarası

FKA-2024-3938 ve FKA-2024-4063

Etik Beyan

The authors declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this paper.

Teşekkür

We gratefully acknowledge the support provided by the Kocaeli University Scientific Research Projects Unit through the projects numbered FKA-2024-3938 and FKA-2024-4063

Fosfor Tabanlı Katkılanmış Nanoyapılarla Nematik Sıvı Kristallerin Dielektrik Davranışının İncelenmesi: Deneysel ve DFT Tabanlı Bir Çalışma

Öz

Nanoskopik dolgular içeren nematik sıvı kristaller, arayüzey polarizasyonunu ve yük dinamiklerini düzenlemek için çok yönlü bir platform sunmaktadır. Bu çalışmada, kristal yapılı siyah fosfor (Black Phosphorus, BP), amorf kırmızı fosfor (Red Phosphorus, RP) ve BP–çok duvarlı karbon nanotüp (BP–MWCNT) gibi hibrit ve fosfor temelli nanoyapıların nematik 5CB’nin (4-siyano-4′-pentilbifenil) dielektrik özellikleri üzerindeki etkileri, geniş bant dielektrik spektroskopisi ve yoğunluk fonksiyonel teorisi (DFT) hesaplamalarıyla incelenmiştir. BP, tabakalı ve belirgin anizotropik elektronik yapısından kaynaklanan Maxwell–Wagner–Sillars arayüzey polarizasyonu sayesinde düşük frekanslarda en belirgin dielektrik geçirgenliği artışını göstermektedir. Kristal düzeni bulunmayan RP ise sınırlı bir dielektrik geçirgenliği iyileşmesi sağlamakta ve buna yüksek dielektrik kayıplar eşlik etmektedir. BP–MWCNT hibriti, işbirlikçi dipol oluşumu ve yük dengeleme etkileşimleri sayesinde yükselmiş ε′ değerini düşük dielektrik kayıpla birleştirerek daha dengeli bir dielektrik yanıt sunmaktadır. DFT hesaplamaları, BP’nin belirgin bir dielektrik anizotropiye (εxx > εyy >> εzz) sahip olduğunu ve yaklaşık −2,98 eV düzeyindeki BP–5CB adsorpsiyon enerjisinin güçlü arayüzey elektronik etkileşimler yoluyla kararlı arayüzey dipollerinin oluşumunu desteklediğini göstermektedir. DC alan altında BP katkılı kompozitlerde gözlenen asimetrik gevşeme davranışı, arayüzey anizotropisi kaynaklı yerelleşmiş simetri kırılmasına işaret etmektedir. Bu sonuçlar, fosfor bazlı nanodolguların nematik sıvı kristallerde dielektrik yanıtın etkin biçimde mühendisliğinde güçlü bir yaklaşım sunduğunu ortaya koymaktadır.

Anahtar Kelimeler

• Nematik sıvı kristaller
• Siyah fosfor
• Arayüzey polarizasyonu
• Dielektrik gevşeme
• DFT hesaplamaları

Destekleyen Kurum

Kocaeli Üniversitesi Bilimsel Araştırma Projeleri Birimi

Proje Numarası

FKA-2024-3938 ve FKA-2024-4063

Etik Beyan

Bu makalenin yazarları çalışmalarında kullandıkları materyal ve yöntemlerin etik kurul izni ve/veya yasalözel bir izin gerektirmediğini beyan ederler.

Teşekkür

FKA-2024-3938 ve FKA-2024-4063 numaralı projeler ile vermiş oldukları destekten dolayı Kocaeli Üniversitesi Bilimsel Araştırma Projeleri Birimi’ne teşekkür ederiz.

Kaynakça

1. [1] Dierking I., Scalia G., Morales P., LeClere D., “Aligning and reorienting carbon nanotubes with nematic liquid crystals”, Advanced Materials, 16: 865–869, (2004).
2. [2] Önsal G., “Investigation of dielectric properties of MBBA-5CB nematic liquid crystal structures”, Mugla Journal of Science and Technology, 8: 49–53, (2022).
3. [3] Chen H. Y., Lee W., “Suppression of field screening in nematic liquid crystals by carbon nanotubes”, Applied Physics Letters, 88: 1–3, (2006).
4. [4] Ocaya R. O. et al., “Impact of TiO₂, ZnO, and methylene blue doping on the dielectric anisotropy of planar 8CB nematic liquid crystal”, Optical Materials, 150: 115320, (2024).
5. [5] Seidalilir Z., Taher S. A., “Enhanced electro-chemical characteristics and superior electro-optical switching performance of nematic liquid crystal doped with MgO nanoparticles”, Optical and Quantum Electronics, 56: 1–26, (2024).
6. [6] Dehghani Z., Madani A., “Enhanced electro-optical properties of nematic liquid crystal doped with nitrogen-doped graphene quantum dots”, Optik, 286: 171015, (2023).
7. [7] Basu R., Iannacchione G. S., “Nematic anchoring on carbon nanotubes”, Applied Physics Letters, 95: 1–3, (2009).
8. [8] Jayalakshmi V., Prasad S. K., “Understanding the observation of large electrical conductivity in liquid crystal–carbon nanotube composites”, Applied Physics Letters, 94: 1–3, (2009).

9. [9] Van Der Schoot P., Popa-Nita V., Kralj S., “Alignment of carbon nanotubes in nematic liquid crystals”, Journal of Physical Chemistry B, 112: 4512–4518, (2008).
10. [10] Okutan M., Yeşilot G., Haring Bolivar P., “Contribution of multiwalled carbon nanotubes to dielectric and elastic properties in E7 nematic liquid crystal”, Journal of Molecular Liquids, 368: 120662, (2022).
11. [11] San S. E., Okutan M., Köysal O., Yerli Y., “Carbon nanoparticles in nematic liquid crystals”, Chinese Physics Letters, 25: 212–215, (2008).
12. [12] Singh B. P., Sikarwar S., Pandey K. K., Manohar R., Depriester M., Singh D. P., “Carbon nanotubes blended nematic liquid crystal for display and electro-optical applications”, Electronic Materials, 2: 466–481, (2021).
13. [13] Samet M., Kallel A., Serghei A., “Maxwell–Wagner–Sillars interfacial polarization in dielectric spectra of composite materials: Scaling laws and applications”, Journal of Composite Materials, 56: 3197–3217, (2022).
14. [14] Tran V., Soklaski R., Liang Y., Yang L., “Layer-controlled band gap and anisotropic excitons in few-layer black phosphorus”, Physical Review B, 89: 235319, (2014).
15. [15] Yang B. et al., “Liquid crystal behaviors of micron and submicron-sized black phosphorus nanosheets”, Journal of Luminescence, 251: 119172, (2022).
16. [16] Pedersen S. V., Muramutsa F., Wood J. D., Husko C., Estrada D., Jaques B. J., “Mechanochemical conversion kinetics of red to black phosphorus and scaling parameters for high-volume synthesis”, npj 2D Materials and Applications, 4: 1–8, (2020).
17. [17] Li R., Shang Y., Xing H., Wang X., Sun M., Qiu W., “Orientation identification of black phosphorus with different thickness based on B2g mode using micro-Raman spectroscopy”, Materials, 13: 1–12, (2020).
18. [18] Liu X. et al., “Black phosphorus-based field effect transistors with near-ideal subthreshold swing and high hole mobility”, Scientific Reports, 6: 1–8, (2016).
19. [19] Shen Z., Sun S., Wang W., Liu J., Liu Z., Yu J. C., “A black/red phosphorus heterostructure for efficient visible-light-driven photocatalysis”, Journal of Materials Chemistry, 22: 1–3, (2012).
20. [20] Doke S., Ganguly P., Mahamuni S., “Dielectric and electro-optical studies of Au/SnO₂ core/shell nanocrystals incorporated ferroelectric liquid crystal”, Liquid Crystals, 47: 1–8, (2020).
21. [21] Singh D., Singh U. B., Pandey M. B., Dhar R., “Dielectric and electro-optic behaviour of nematic–SWCNT nanocomposites under applied bias field”, Liquid Crystals, 46: 1389–1395, (2019).
22. [22] Ben Ishai P., Talary M. S., Caduff A., Levy E., Feldman Y., “Electrode polarization in dielectric measurements: A review”, Measurement Science and Technology, 24: 102001, (2013).
23. [23] Cîrtoaje C., Petrescu E., Stoian V., “Electrical Freedericksz transitions in nematic liquid crystals containing ferroelectric nanoparticles”, Physica E: Low-Dimensional Systems and Nanostructures, 67: 23–27, (2015).
24. [24] De Paula J. L. et al., “Non-Debye relaxation in the dielectric response of nematic liquid crystals: Surface and memory effects in the adsorption–desorption process of ionic impurities”, Physical Review E, 86: 051705, (2012).
25. [25] Yadav G., Katiyar R., Pathak G., Manohar R., “Effect of ion trapping behavior of TiO₂ nanoparticles on weakly polar nematic liquid crystals”, Journal of Theoretical and Applied Physics, 12: 191–198, (2018).
26. [26] Mishra S., Sontakke A. M., Gupta R. K., Kumar S., Manjuladevi V., “Dielectric spectroscopy studies of silver nanorod doped nematic liquid crystal”, Materials Today: Proceedings, 50: 2587–2591, (2022).
27. [27] Abdullah L. A., Khalid F. G., Ibrahim R. K., Mahmood A. I., Rashad A. A., Jber N. R., “The influence of gold nanoparticles on electro-optical properties of nematic liquid crystal”, Journal of Optics (India), 53: 997–1002, (2024).
28. [28] Al-Zangana S., Iliut M., Turner M., Vijayaraghavan A., Dierking I., “Properties of a thermotropic nematic liquid crystal doped with graphene oxide”, Advanced Optical Materials, 4: 1541–1548, (2016).
29. [29] Dierking I., Scalia G., Morales P., “Liquid crystal–carbon nanotube dispersions”, Journal of Applied Physics, 97: 1–3, (2005).
30. [30] De Paula J. L. et al., “Non-Debye relaxation in the dielectric response of nematic liquid crystals: Surface and memory effects”, Physical Review E, 86: 051705, (2012).
31. [31] Yadav G., Katiyar R., Pathak G., Manohar R., “Effect of ion trapping behavior of TiO₂ nanoparticles on different parameters of weakly polar nematic liquid crystal”, Journal of Theoretical and Applied Physics, 12: 191–198, (2018).