The size effect on the energy transfer in Bi3+–Eu3+ co-doped GdVO4 nanocrystals
Nanocrystals of GdVO4 co-doped with various concentrations of Bi3+ and a constant concentration of Eu3+ ions (5 mol%) were synthesized by Pechini's method and annealed in the range of temperature from 750 °C to 900 °C in order to obtain different sizes of individual crystallites. Upon the excitation of near-UV light, an intense red/orange-red luminescence of Eu3+ was observed. Shifting of the maximum and broadening of the excitation band with increasing Bi3+ concentration were also observed. In particular, the influence of the size effect on the energy transfer in the chain: (O2−–V5+) charge transfer → (Bi3+–V5+) charge transfer → Eu3+ ions was determined and analysed.