Ag-catalyzed synthesis of europium borate Eu(BO2)3 nanowires, growth mechanism and luminescent properties

Eu(BO2)3 nanowires with diameters of 10–20 nm were fabricated through direct sintering Eu(NO3)3·6H2O and H3BO3 with Ag as catalyst. The result of X-ray diffraction (XRD) indicated that the nanowire was single-crystalline with body-centered monoclinic structure. Based on the fact that Ag nanoparticles attached to the tips and middles of nanowires, a vapor–liquid–solid (VLS) growth mechanism of the Eu(BO2)3 nanowires is proposed. Three well-defined stages have been clearly identified during the process: Ag–Eu–B–O cluster process, crystal nucleation, and axial growth. The photoluminescence characteristics under UV excitation were investigated. The dominated Eu3+ orange–red emission corresponding to the magnetic dipole transition 5D0 → 7F1 is centered at 591 nm, indicating that Eu3+ is located at high symmetry crystal field with inversion center.