Ag–Y2O3:Eu3+ composite nanotubes: synthesis, tunable photoluminescence and surface-enhanced Raman scattering

Abstract

Ag–Y₂O₃:Eu³⁺ composite nanotubes were synthesized by growing Ag nanoparticles on the surface of Y₂O₃:Eu³⁺ nanotubes. The effects of the Ag content on the photoluminescence properties of the Ag–Y₂O₃:Eu³⁺ composite nanotubes were investigated in detail. In addition to the charge transfer from the 2p orbital of O²⁻ to the 4f orbital of Eu³⁺, several sharp lines corresponding to the f–f transitions of Eu³⁺ were also observed in the excitation spectra of the Y₂O₃:Eu³⁺ nanotubes monitored at different emission wavelengths. However, only one excitation band centered at 535 nm was observed in the excitation spectrum of Ag–Y₂O₃:Eu³⁺ monitored at 590 nm, which is different from that monitored at 614 nm. We suggest that the change in the excitation spectra between Y₂O₃:Eu³⁺ and Ag–Y₂O₃:Eu³⁺ is attributed to the interaction between Ag and Ag–Y₂O₃:Eu³⁺. In particular, the inhomogeneous linewidth of the ⁵D₀ → ⁷F₁ transition from Ag–Y₂O₃:Eu³⁺ was observed to broaden when the excitation wavelength was set at 535 nm. Decay dynamics were performed to study the photoluminescence of the Ag–Y₂O₃:Eu³⁺ composite nanotubes, and the decay curve can be well fitted with a second order exponential decay function. Moreover, the surface-enhanced Raman scattering effect of the Ag aggregates was evaluated by using 4-aminothiophenol as a Raman probe molecule. It was demonstrated that a high SERS signal can be observed by increasing the Ag : Ln³⁺ ratios in the Ag–Y₂O₃:Eu³⁺ composite nanotubes.