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<p>Cobalt-doped zinc oxide (ZnO:Co) thin films with varying Co concentrations (0–4 at%) were synthesized via a low-cost sol-gel spin-coating technique to systematically evaluate their structural, optical, magnetic, and photocatalytic properties for water remediation applications. X-ray diffraction (XRD) and FTIR analyses confirmed that lower dopant levels successfully preserve the host hexagonal wurtzite framework with induced lattice strain, while minor traces of a secondary Co<sub>3</sub>O<sub>4</sub> phase emerge. Transmission spectra revealed a noticeable drop in transparency alongside characteristic sub-band gap d–d crystal field transitions, confirming the effective substitution of Co<sup>2+</sup> ions and the narrowing of the optical band gap. Room-temperature magnetic measurements indicated a transition from host diamagnetism to weak ferromagnetism upon doping. The saturation and remanent magnetization parameters demonstrated a controlled concentration dependence, which becomes suppressed at 4 at% Co due to antiferromagnetic secondary-phase contributions that simultaneously introduce loop asymmetry via exchange bias effects. Under visible-light irradiation, the ZnO:Co films exhibited a significantly enhanced photocatalytic degradation rate against methylene blue (MB) dye compared to undoped ZnO. This performance improvement is driven by a synergistic defect-mediated charge separation mechanism and expanded visible absorption. Overall, these findings highlight the potential of tuning the electronic-structural configurations in ZnO:Co thin films for integrated spintronic and environmental applications.</p>

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Study of structural, optical, and magnetic properties of ZnO:Co thin films prepared by spin-coating method for photocatalytic applications

  • 期刊论文

  • 发表日期：

    2026年8月4日

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  • Abdelkader Mohammedi,
  • Nafissa Megag,
  • Lotfi khezami,
  • Mamoun Fellah

摘要

Cobalt-doped zinc oxide (ZnO:Co) thin films with varying Co concentrations (0–4 at%) were synthesized via a low-cost sol-gel spin-coating technique to systematically evaluate their structural, optical, magnetic, and photocatalytic properties for water remediation applications. X-ray diffraction (XRD) and FTIR analyses confirmed that lower dopant levels successfully preserve the host hexagonal wurtzite framework with induced lattice strain, while minor traces of a secondary Co3O4 phase emerge. Transmission spectra revealed a noticeable drop in transparency alongside characteristic sub-band gap d–d crystal field transitions, confirming the effective substitution of Co2+ ions and the narrowing of the optical band gap. Room-temperature magnetic measurements indicated a transition from host diamagnetism to weak ferromagnetism upon doping. The saturation and remanent magnetization parameters demonstrated a controlled concentration dependence, which becomes suppressed at 4 at% Co due to antiferromagnetic secondary-phase contributions that simultaneously introduce loop asymmetry via exchange bias effects. Under visible-light irradiation, the ZnO:Co films exhibited a significantly enhanced photocatalytic degradation rate against methylene blue (MB) dye compared to undoped ZnO. This performance improvement is driven by a synergistic defect-mediated charge separation mechanism and expanded visible absorption. Overall, these findings highlight the potential of tuning the electronic-structural configurations in ZnO:Co thin films for integrated spintronic and environmental applications.