Synthesis and characterization of hierarchically structured La ₂O₂M@C:Eu³⁺ (M = S, Se) microflowers by a single-step RAPET method

Hierarchically structured La₂O₂M@C:Eu³⁺ (M = S, Se) microflowers have been successfully prepared by a facile one-pot synthesis at a low temperature of 950 °C by the reaction under autogenic pressure at elevated temperature (RAPET) technique. The X-ray diffraction patterns reveal the single-phase formation of hexagonally structured La ₂O₂M and La₂O₂M:Eu³⁺ (M = S, Se) microstructures. The optimization of reaction parameters, such as temperature and the molar concentrations of the precursors, for the preparation ofmonophasic La₂O₂M was evaluated by XRD measurements. Raman spectroscopy measurements allowed for the elucidation of the formation of La₂O₂M (M = S, Se) through examination of the active vibrational modes, and also proved the presence of carbon in the compounds. The field emission scanning electron microscopy (FESEM) and TEM images clearly show the micron-sized rose-like morphology, as well as the nanoflake-like structure of the final products. The high resolution transmission electron microscopy (HRTEM) images reveal well-defined lattice fringes indicating the highly crystalline nature of the products. The selected area electron diffraction (SAED) pattern indicates the single- and polycrystalline nature of the products. The optical properties of the materials have been studied by UV/Vis spectroscopy.