Effects of surface modification on photoluminescence properties of LaPO₄:Ce,Tb nano-phosphor synthesized by solvotliernial reaction

The transparent colloidal solution of LaPO₄:Ce,Tb nano-phosphor is synthesized from lanthanum acetate, cerium acetate, terbium acetate and trimethyl phosphate by the solvothermal reaction at 140°C in the mixture of water and methanol. The green photoluminescence (PL) due to the f-f transition of Tb³⁺ is observed by exciting the d-f transition of Ce ³⁺, followed by the energy transfer from Ce³⁺ to Tb ³⁺. The surface modification of LaPO₄:Ce,Tb nano-phosphor powder by lauryl phosphate increases the PL intensity by a factor of 18. The surface modification is effective for LaPO₄:Ce, but not for LaPO ₄:Tb. These results suggest that the surface-passivation plays a significant role in the suppression of energy loss and the higher site-symmetry around Ce³⁺.