Lanthanide Luminescence Enhancement of Core-Shell Magnetite-SiO2Nanoparticles Covered with Chain-Structured Helical Eu/Tb Complexes

Abstract

Oligomeric-brush chains of helical lanthanide (Ln) complexes retain their structural and luminescent behavior after coating onto magnetic nanoparticles (MNPs) consisting of Fe3O4 covered with silicate. It is one of the type of bifunctional NPs exhibiting luminescence of Ln and superparamagnetism of Fe3O4. In comparison to a simple monolayer of complexes adsorbed on a modified surface, a layer made of luminescent chains allowed us to obtain a more intensive red/green luminescence originating from Eu3+/Tb3+ ions, and at the same time, no visible increase in particle size (compared to Fe3O4@silica particles) was observed. The luminescent properties of the Tb3+ complex were altered by MNPs; the decrease of the luminescence was not as large as expected, the excitation spectrum changed significantly, and the average luminescence lifetime was much longer at room temperature. Surprisingly, this phenomenon was not observed at 77 K and also did not occur for the Eu3+ complexes. The possibility to stack building blocks in a chain using complexes of different lanthanide ions can be used to design novel multifunctional nanosystems.