Optically stimulated persistent luminescence of europium-doped LaAlO3 nanocrystals.

Optically stimulated persistent luminescence was investigated for europium-doped LaAlO3 nanocrystals. This system shows conventional luminescence of both the Eu(3+) line emission and the weak broad-band emission of Eu(2+) upon UV excitation. The persistent luminescence is predominantly associated with the Eu(3+) emission, and can be amplified significantly through irradiation with IR at 975 nm. The conventional luminescence from Eu(3+) is strongly enhanced when the material is excited simultaneously with both UV and IR radiation. The enhancement of persistent luminescence is accompanied by increased persistent photoconductivity. The charge transfer band of the LaAlO3:Eu(3+) nanocrystals in the UV excitation spectra significantly weakens with increasing IR excitation power, also correlating well with the enhancement of persistent luminescence. Finally, a mechanism is presented for the optically stimulated and persistent luminescence in this Eu(2+)- and Eu(3+)-doped LaAlO3 material.