Morphology-controlled facile surfactant-free synthesis of 3D flower-like BiOI:Eu3+ or Tb3+ microarchitectures and their photoluminescence properties

Abstract

Three-dimensional (3D) flower-like bismuth oxyiodide (BiOI) and Eu³⁺ or Tb³⁺ ions single-doped BiOI microarchitectures were successfully synthesized by a facile and eco-friendly wet chemical method in an ethylene glycol solvent. The solvent played a significant role in the formation of the 3D flower-like BiOI microarchitectures with respect to temperature and time. The phase formation of the synthesized BiOI samples was examined by X-ray diffraction analysis, which confirmed a characteristic tetragonal crystal structure with the space group of P4/nmm. The growth mechanism was discussed based on the field-emission scanning electron microscope images obtained for the samples at different growth temperatures and growth times. The crystallinity of the BiOI sample was confirmed by field-emission transmission electron microscope images. The photoluminescence (PL) properties were analyzed for the Eu³⁺ or Tb³⁺ single-doped BiOI 3D flower-like microarchitectures. The PL emission spectra of BiOI:Eu³⁺ samples showed intense red emission peak at 616 nm due to the ⁵D₀ → ⁷F₂ electronic transition of Eu³⁺ ions under 255 nm excitation. Similarly, under 253 nm (f → d transition) excitation, the PL emission spectra of BiOI:Tb³⁺ samples exhibited intense green emission peak at 545 nm corresponding to the f → f transitions of Tb³⁺ ions. Additionally, the temperature-dependent PL emission spectra were studied for the optimized BiOI:0.07Eu³⁺ and BiOI:0.02Tb³⁺ samples, indicating good thermal stability. The Commission Internationale de l'Eclairage chromaticity coordinates were calculated for the optimized samples, which showed values close to those of commercial red- and green-emitting phosphors.