Magnetism and Afterglow United: Synthesis of Novel Double Core–Shell Eu(2+)‐Doped Bifunctional Nanoparticles

Afterglow–magnetic nanoparticles (NPs) offer enormous potential for bioimaging applications, as they can be manipulated by a magnetic field, as well as emitting light after irradiation with an excitation source, thus distinguishing themselves from fluorescent living cells. In this work, a novel double core–shell strategy is presented, uniting co‐precipitation with combustion synthesis routes to combine an Fe(3)O(4) magnetic core (≈15 nm) with an afterglow SrAl(2)O(4):Eu(2+),Dy(3+) outer coat (≈10 nm), and applying a SiO(2) protective middle layer (≈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 attributed to the 4f(6)5d(1)→4f(7)((8)S(7/2)) transition of Eu(2+) under UV radiation and for a few seconds afterwards. This bifunctional nanocomposite can potentially be applied for the detection and separation of cells or diagnostically relevant molecules.