Enhancement of upconversion luminescence of Er and Yb co-doped Y2O3 nanoparticle by Ag half-shell

• Enhancement of upconversion PL of Er doped Y2O3 nanoparticles with Ag half shells.
• Upconversion PL of individual particles with different shell thicknesses is studied.
• Upconversion PL and light scattering of individual particles are compared.

Upconversion photoluminescence (PL) properties of single Y2O3 nanoparticles doped with Yb and Er (Y2O3:Yb,Er) with a Ag over-layer is studied. We traced the PL and light scattering images of individual nanoparticles by changing the thickness of a Ag over-layer. When the Ag thickness is relatively small and only the upper part of a nanoparticle is covered by Ag (Ag half-shell), the PL is strongly enhanced. On the other hand, when the Ag thickness is increased and a continuous Ag over layer is formed, the enhancement factor decreases. From the correlation between the enhancement factors of the upconversion PL and scattering intensities as well as the change of the PL lifetime, the mechanism of the PL enhancement is discussed.