Eu3+ as a marker for formation of core-shell system: YVO4:SiO2

- Preparation of highly crystalline YVO4 nanoparticles covered with SiO2 at low temperature.
- Luminescence technique could prove the core-shell formation of YVO4 covered by SiO2.
- There are fairly energy transfer both core and core-shell nanoparticles.

Eu3+ doped in core and shell (YVO4:SiO2) nanoparticles show luminescence peaks corresponding to magnetic and electric dipole transitions of Eu3+. When Eu3+ ions occupy Y3+ sites, Eu3+ ions are surrounded by eight O2− ions, which is highly asymmetric (D2d). This asymmetric environment can be used to see amount of Eu3+ ions present in Y3+ sites. When Eu3+ ions are present in shell (SiO2), luminescence intensity is very weak. On further annealing, luminescence intensity increases due to diffusion of Eu3+ ions towards to YVO4 core through pores of SiO2. Distribution of Eu3+ in core and shell are supported by lifetime studies.

Decay for 5D0 level of Eu3+ in core (YVO4-Eu) and core:shell (YVO4-Eu:SiO2, YVO4:SiO2-Eu) annealed at 900 °C. Inset shows their lifetime values along with 500 °C heated sample.177