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<p>In this study, a natural dye extracted from walnut leaves was used to modify titanium dioxide (TiO<sub>2</sub>) thin films via the sol–gel method. TiO<sub>2</sub> films with 0.1, 0.2, and 0.3 vol% dye were structurally and optically characterized. The amorphous structure of the undoped TiO<sub>2</sub> thin films was identified by the X-ray diffraction (XRD) technique. Field emission-scanning electron microscopy (FE-SEM) showed uniform nanoparticles (~ 20&#xa0;nm) and a film thickness of ~ 80.5&#xa0;nm. Raman spectroscopy confirmed dye–TiO<sub>2</sub> interactions, with redshifts linked to phenol and quinone groups. UV–Vis analysis revealed a redshift in the absorption edge, reducing the TiO<sub>2</sub> bandgap from 3.22&#xa0;eV (undoped) to 1.93&#xa0;eV (highest dye), enhancing visible-light absorption. Energy dispersive X-rays (EDX) confirmed compositional purity. Dielectric spectroscopy showed increased real and imaginary dielectric constants, indicating stronger photon–molecule interactions. These results demonstrate that walnut dye-doped TiO<sub>2</sub> films are a sustainable, low-cost material with improved optical and dielectric properties.</p>

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Optical and structural properties of bio-derived walnut dye-doped TiO2 synthesized via sol–gel method

  • 期刊论文

  • 发表日期：

    2025年11月4日

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  • Majida A. Ameen,
  • Muhammad A. Saeed,
  • Peshawa O. Amin,
  • Rebar T. Abdulwahid,
  • Shujahadeen B. Aziz

摘要

In this study, a natural dye extracted from walnut leaves was used to modify titanium dioxide (TiO2) thin films via the sol–gel method. TiO2 films with 0.1, 0.2, and 0.3 vol% dye were structurally and optically characterized. The amorphous structure of the undoped TiO2 thin films was identified by the X-ray diffraction (XRD) technique. Field emission-scanning electron microscopy (FE-SEM) showed uniform nanoparticles (~ 20 nm) and a film thickness of ~ 80.5 nm. Raman spectroscopy confirmed dye–TiO2 interactions, with redshifts linked to phenol and quinone groups. UV–Vis analysis revealed a redshift in the absorption edge, reducing the TiO2 bandgap from 3.22 eV (undoped) to 1.93 eV (highest dye), enhancing visible-light absorption. Energy dispersive X-rays (EDX) confirmed compositional purity. Dielectric spectroscopy showed increased real and imaginary dielectric constants, indicating stronger photon–molecule interactions. These results demonstrate that walnut dye-doped TiO2 films are a sustainable, low-cost material with improved optical and dielectric properties.