Investigation of the influence of Eu3+ doping on ZnO: impact on microstructural and optical properties

This study investigated the photoluminescent and photocatalytic performance of europium-doped zinc oxide (ZnO: Eu³⁺) compared with pure zinc oxide. ZnO: Eu³⁺ nanoparticles were successfully synthesized via the co-precipitation method. XRD results confirmed the stabilization of the hexagonal phase without the presence of secondary phases, indicating effective Eu³⁺ doping. Microstructural and morphological modifications were evaluated through X-ray diffraction and scanning electron microscopy. A growth mechanism for the ZnO nanoparticles was proposed, based on a self-organization behavior that led to the formation of 3D microflower-like morphologies. Photoluminescence (PL) measurements of ZnO: Eu³⁺ revealed a strong red emission associated with the electric-dipole ⁵D₀ → ⁷F₂ transition at 615 nm, attributed to the asymmetric environment surrounding the Eu³⁺ ions. The photocatalytic degradation efficiency of the Reactive Red 239 dye was also investigated. The results demonstrated that Eu³⁺ incorporation enhanced the photocatalytic activity relative to pure ZnO, primarily due to the reduced recombination rate of photogenerated charge carriers (e⁻/h⁺). The ZnO:1% Eu³⁺ sample achieved 82% degradation of Reactive Red 239, and under optimized photocatalyst concentration, the degradation efficiency increased to 90%. The results indicate that ZnO: Eu³⁺ is a promising material for optical applications—such as a red phosphor in pc-LEDs and for environmental remediation as an efficient photocatalyst.