Hybrid synthesis (biosynthesis-hydrothermal) of yttrium hydroxide doped with Eu ³⁺

Abstract Structural and photoluminescence properties of undoped and Eu 3+ doped yttrium hydroxide (Y(OH) 3 :Eu 3+ ) particles synthesized via conventional hydrothermal and hybrid (biosynthesis–hydrothermal) methods are reported. The hybrid route employs Camellia sinensis extract and two precursors: yttrium nitrate and yttrium acetate. X-ray diffraction analysis revealed the formation of hexagonal Y(OH) 3 (space group P6₃/m) together with secondary phases depending on the synthesis conditions, particularly in samples prepared without the extract. Rietveld refinement indicated that the hybrid method promotes improved phase formation within a reduced reaction time (4 h), compared to conventional hydrothermal processes typically requiring longer durations. Scanning electron microscopy revealed distinct morphologies, including urchin-like, ovoid, and needle-like structures, with particle sizes ranging from 3 to 25 µ m. However, the hybrid method also led to increased morphological heterogeneity and compositional variations. XPS and EDS analyses suggest that biomolecules from the Camellia sinensis extract interact with Eu 3+ ions, limiting their incorporation into the Y(OH)₃ lattice. As a result, while strong red photoluminescence was observed in Y(OH)₃:Eu 3+ synthesized via the conventional hydrothermal method, no detectable emission was obtained for hybrid-synthesized samples under the same conditions. This behavior is attributed to inefficient Eu 3+ incorporation. These findings demonstrate that the hybrid approach is effective in reducing synthesis time and influencing phase formation, but also significantly impacts dopant incorporation, morphology, and optical properties.