Synthesis, novel luminescence properties, and surface-enhanced Raman scattering of Au/Y2O3:Eu3+ composite nanotubes

Abstract

Y(OH)₃:Eu³⁺ nanotubes were synthesized by a facile hydrothermal method first, and then Au particles were grown on the surface of Y₂O₃:Eu³⁺ nanotubes by combining the vacuum extraction method and the annealing process. The composite nanotubes were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The effects of the Au content on the photoluminescence properties of the Au/Y₂O₃:Eu³⁺ composite nanotubes were investigated in detail. In the excitation spectra of Au/Y₂O₃:Eu³⁺ monitored at 614 nm, the ⁷F₀→⁵H₃ transition from Eu³⁺ increased with increasing Au content, while the other sharp lines originating from Eu³⁺ f–f electron transitions almost vanished. In the emission spectra, the spectral configurations of Eu³⁺ in Au/Y₂O₃:Eu³⁺ composite nanotubes varied with the excitation wavelengths. When the excitation wavelength was 256 nm, the ⁵D₄→⁷F₀, ⁵D₇→⁷F₀, ⁵G₂→⁷F₀, ⁵L₆→⁷F₀, ⁵D₀→⁷F₀, ⁵D₀→⁷F₁, ⁵D₀→⁷F₂, ⁵D₀→⁷F₃, and ⁵D₀→⁷F₄ transitions from Eu³⁺ ions in Au/Y₂O₃:Eu³⁺ were observed. When the excitation wavelength was 378 nm, the plasmon resonance peak from Au nanoparticles was observed. In addition, 4-ATP was chosen as the model molecule to examine the performance of the Au/Y₂O₃:Eu³⁺ composite nanotubes as SERS substrates. The relative intensities of the SERS spectra enhanced with the increase of Au⁺ : Ln³⁺ ratio.