An ion adsorption-diffusion process for preparing YVO4:Eu3+@SiO2 core-shell nanoparticles with strong luminescence

In this work, YVO4:Eu3+@SiO2 core-shell nanoparticles with strong luminescence were successfully prepared using an ion adsorption-diffusion process. Undoped YVO4 nanoparticles with a size about 7 nm were synthesized using a solvothermal method, and they were then coated with SiO2 shell using a facile sol-gel method to form the YVO4@SiO2 core-shell nanoparticles with a size about 10 nm. Eu3+ ions were adsorbed onto the YVO4@SiO2 nanoparticles to prepare the YVO4:Eu3+@SiO2 core-shell nanoparticles. For the same Eu3+ concentration in the ion-exchange solution, luminescence of the as-prepared YVO4:Eu3+@SiO2 nanoparticles decreased with the amount of SiO2. For the same amount of SiO2, luminescence of the as-prepared YVO4:Eu3+@SiO2 nanoparticles increased with the Eu3+ concentration before a quenching concentration was reached. Upon thermal annealing, the adsorbed Eu3+ ions were doped into the YVO4 matrix via diffusion to form the annealed YVO4:Eu3+@SiO2 core-shell nanoparticles with a size about 11 nm. It was found that luminscence of the YVO4:Eu3+@SiO2 core-shell nanoparticles can be considerably enhanced by annealing. The effect of the SiO2 shell, Eu3+ concentration and annealing temperature on the luminescence of the YVO4:Eu3+@SiO2 nanoparticles was investigated in detail.