Upconversion (UC) process in rare earth nanomaterials has attracted great research interest for its extensive applications in light converter, lasers and vitro and in vivo biological imaging, benefiting from the near-infrared light excitation.  In this work, we show that core/shell structure is designed to modify the upconversion emission behavior of sodium rare earth fluorides. For NaYF4:Yb,Er/Tm@CaF2 nanoparticles (NPs), the shell is epitaxial growth over the core, and exhibits a good way to isolate the emitters from the surface quenching sites, thus enhancing the upconversion emission from Er3+ or Tm3+ in the visible and ultraviolet range. The shell is also benefit from suppressing the rare earth ions release from sodium rare earth fluorides. Intriguing with the application request of multi-wavelength emission and excitation, multi-shell is designed to not only support multifunction, but also tuning the emission from visible to near infrared and shift the excitation to a wavelength with less water absorption. With a shell doped with Nd and Yb simultaneously, which Nd3+ ions act as new NIR absorbers and sensitizers for the conventional Yb3+-doped UCNPs, the excitation spectrum of UC is extended to shorter wavelengths. Nd3+?Yb3+ energy transfer was demonstrated, and its effect on cascade energy transfer for Yb3+ activated upconversion emission is developed.

New insight into rare earth nanostructure design toward application

248th National Meeting (2014)

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