Magnetism and Afterglow United: Synthesis of Novel Double Core‐Shell Eu2+‐doped Bifunctional Nanoparticles

Afterglow-magnetic nanoparticles (NPs) offer an enormous potential for bioimaging applications, since they can be manipulated by a magnetic field, besides emitting light after the irradiation with an excitation source, distinguishing themselves from fluorescent living cells. In this work, we present a novel double core-shell strategy uniting co-precipitation with combustion synthesis routes in order to combine a Fe 3 O 4 magnetic core (ca. 15 nm) with an afterglow SrAl 2 O 4 :Eu 2+ ,Dy 3+ outer coat (ca. 10 nm), applying a SiO 2 protective middle layer (ca. 16 nm) to reduce the luminescence quenching caused by the Fe core ions. The resulting Fe 3 O 4 @SiO 2 @SrAl 2 O 4 :Eu 2+ ,Dy 3+ NPs emit green light due to the 4f 6 5d 1 -->4f 7 ( 8 S 7/2 ) transition of Eu 2+ under UV radiation and few seconds afterwards. In general, this bifunctional nanocomposite can be potentially applied for detecting and separating cells or diagnostically relevant molecules.