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<p>We report here an eco-friendly route to tune the physical properties of a highly birefringent nematic liquid crystal (NLC, LC-PD40300, Δε = +16.8) with wide nematic temperature range by doping of green zinc oxide nanoparticles (ZnO NPs). ZnO NPs (diameter: 5.9 ± 1.2&#xa0;nm) were hydrothermally synthesized using <i>Justicia adhatoda</i> (Vasaka) leaf extract which acted as both reducing and capping agent. FTIR and XRD confirm ligand-assisted formation of phase-pure wurtzite ZnO, while UV-Vis shows a quantum-confined excitonic edge at 355&#xa0;nm (E<sub>g</sub> = 2.75&#xa0;eV). Afterwards, these NPs were dispersed (concentration: 0.05, 0.1 and 0.5 wt %) in the NLC matrix, producing green ZnO/NLC composites. Optical textures reveal the uniform and stable dispersion of ZnO NPs in the NLC matrix. The dielectric spectroscopy and voltage dependent optical transmission studies show the tunable dielectric parameters (permittivity, loss, and loss factor), electrical conductivity and display parameters (threshold voltage, birefringence and contrast ratio) of NLC by the dopant ZnO NPs. Out of three ZnO NPs-NLC composites, the lowest concentration composite i.e., 0.05wt% showed the promising results as compared pure NLC and other two composites. For instance, in 0.05 wt% composite, the real dielectric permittivity (ε′, 1&#xa0;kHz) increasedby 38%, the low-frequency loss tangent is suppresse by 42%, and ionic conductivity doubled, indicating effective interfacial polarisation without ion trapping. Voltage dependent optical transmission measurements reveled 22% reduction in threshold voltage and 1.5-fold gain in contrast ratio, corroborated well with optical textures showing improved molecular alignment. We believe that our work introduces a green strategy for simultaneously lowering driving voltage and boosting electro-optical contrast in advanced ZnO NPs-NLC composites for sustainable dielectric additives for next-generation displays, adaptive optics, and low-power photonic components.</p> Graphical Abstract <p></p>

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Tunable optical, dielectric, electrical and electro-optical features of green ZnO nanoparticles doped nematic liquid crystal composites

  • 期刊论文

  • 发表日期：

    2026年2月16日

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  • Geetika Jangid,
  • Gautam Singh,
  • Pankaj Kumar,
  • Vandna Sharma,
  • Praveen Malik,
  • Dharmendra Pratap Singh,
  • Kasim Sakran Abass,
  • Sanjeev Kumar,
  • Rabia Pandit,
  • Supreet

摘要

We report here an eco-friendly route to tune the physical properties of a highly birefringent nematic liquid crystal (NLC, LC-PD40300, Δε = +16.8) with wide nematic temperature range by doping of green zinc oxide nanoparticles (ZnO NPs). ZnO NPs (diameter: 5.9 ± 1.2 nm) were hydrothermally synthesized using Justicia adhatoda (Vasaka) leaf extract which acted as both reducing and capping agent. FTIR and XRD confirm ligand-assisted formation of phase-pure wurtzite ZnO, while UV-Vis shows a quantum-confined excitonic edge at 355 nm (Eg = 2.75 eV). Afterwards, these NPs were dispersed (concentration: 0.05, 0.1 and 0.5 wt %) in the NLC matrix, producing green ZnO/NLC composites. Optical textures reveal the uniform and stable dispersion of ZnO NPs in the NLC matrix. The dielectric spectroscopy and voltage dependent optical transmission studies show the tunable dielectric parameters (permittivity, loss, and loss factor), electrical conductivity and display parameters (threshold voltage, birefringence and contrast ratio) of NLC by the dopant ZnO NPs. Out of three ZnO NPs-NLC composites, the lowest concentration composite i.e., 0.05wt% showed the promising results as compared pure NLC and other two composites. For instance, in 0.05 wt% composite, the real dielectric permittivity (ε′, 1 kHz) increasedby 38%, the low-frequency loss tangent is suppresse by 42%, and ionic conductivity doubled, indicating effective interfacial polarisation without ion trapping. Voltage dependent optical transmission measurements reveled 22% reduction in threshold voltage and 1.5-fold gain in contrast ratio, corroborated well with optical textures showing improved molecular alignment. We believe that our work introduces a green strategy for simultaneously lowering driving voltage and boosting electro-optical contrast in advanced ZnO NPs-NLC composites for sustainable dielectric additives for next-generation displays, adaptive optics, and low-power photonic components.

Graphical Abstract