Hydrothermal control, characterization, growth mechanism, and photoluminescence properties of highly crystalline 1D Eu(OH)3 nanostructures

Abstract

Six types of 1D Eu(OH)₃ nanostructures with typical morphologies, including short hexagonal prism, long hexagonal prism, coiling rod, short rod, long rod, and nanobunch, were synthesized via the hydrothermal route using EuCl₃ and NaOH as raw materials. The morphologies, sizes, structures, and compositions of the as-prepared products were characterized by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction, and Fourier transform infrared spectroscopy. The effects of different reaction conditions on the morphology and size of the products were also investigated, and the relevant growth mechanism was assessed. Results showed that the geometric features of Eu(OH)₃ are affected by the precursor pH and reaction time and temperature; among these factors, precursor pH played a key role in controlling the morphologies of the resulting Eu(OH)₃ nanostructures. The fluorescence properties of the six Eu(OH)₃ nanostructures were analyzed, and typical photoluminescence emission peaks due to the ⁵D₀–⁷F_J (J = 1–4) transition of Eu³⁺ were noted. Moreover, the intensity of the emission peak of the products at 616 nm was slightly weaker than that at 592 nm. This finding reflects the high site symmetry of Eu³⁺ in the Eu(OH)₃ nanostructures.