Dual light-emitting nanoparticles: Second harmonic generation combined with rare-earth photoluminescence

Dual light emitting KTP@LaPO₄:Eu nanoparticles have been synthesized and characterized. These core@shell heterostructures consisting of a KTP (KTiOPO₄) single-crystal core and a Eu³⁺-doped LaPO₄ shell were synthesized by a coprecipitation method and controlled heterogeneous nucleation of LaPO₄:Eu around the KTP nanocrystals. These nanoparticles exhibit both the SHG (second harmonic generation) signal of the KTP core and the PL (photoluminescence) emission of the doping europium ions of the shell. The orientation-dependent signal of SHG in contrast to the PL emission has been demonstrated through a detailed optical study at the single particle level. This property makes these dual emitting systems original nanoprobes for studying dynamic systems in biology. The versatility of the developed method can be straightforwardly adapted to other lanthanide ions to develop new multifunctional nanoprobes.