Emission properties of Ln (Eu, Tb, Dy, Er)-doped Y2O3 nanoparticles synthesized by surfactant-assembly and their applications in visible color-tuning

Abstract

We have prepared lanthanoid (Ln = Eu, Tb, Dy, and Er)-doped Y2O3 nanoparticles (YNPs) for producing nanomaterials showing emission in the visible region. YNPs were fabricated by means of surfactant assembly, and they had a diameter of 500 ± 200 nm. Under UV excitation, Ln-doped YNPs showed sharp emission spectra due to the 4f–4f transitions of Ln3+ in the YNP environment. The photoexcitation spectra of Ln-doped YNP comprised 4f–4f transitions and Ln3+ 4f–5d transitions, or charge transfer from the Y2O3 matrix to Ln3+; the bands in the latter case were broad. By appropriate choice of the excitation wavelength (λex), either Eu3+ or Tb3+ could be dominantly excited in the Eu3+ and Tb3+ co-doped YNP. At an appropriate λex, the co-doped YNP showed emission in the orange and green regions due to Eu3+ and Tb3+, respectively; alternatively, an intermediate color resulted because of additive color-tuning of the resources. The emission color can also be varied by changing the Eu–Tb doping ratio in the YNP, under a fixed λex. It was demonstrated that Eu3+ and Tb3+ emit almost independently, which makes such a color-tuning process feasible.