Tailoring the Design of a Lanthanide Complex/Magnetic Ferrite Nanocomposite for Efficient Photoluminescence and Magnetic Hyperthermia Performance.

In this work, we have designed a magnetoluminescent nanocomposite as a single platform for optical imaging and safe magnetic hyperthermia therapy by optimizing the composition of magnetic nanoparticles and controlling the conjugation strategy of the luminescent lanthanide complex. We have synthesized CoxMn1-xFe2O4 nanoferrites, with x = 0 to 1 in 0.25 steps, from soft (MnFe2O4) to hard (CoFe2O4) ferrites of size (∼20 nm) following a one-pot oxidative hydrolysis method. We have performed the induction heating study with an aqueous dispersion of nanoferrites using an alternating magnetic field (AMF) of 12 kAm-1, 335 kHz. This shows an enhancement of heating efficiency with the increment of manganese content and attains the highest intrinsic loss power (ILP) of 6.47 nHm2 kg-1 for MnFe2O4 nanoparticles. We have then fabricated a magnetoluminescent nanocomposite employing MnFe2O4 nanoparticles as it shows outstanding heating performance within the threshold limit of AMF (≤5 × 109 Am-1 s-1). A layer-by-layer coating strategy is followed, where a pure silica coating of thickness ∼10 nm on MnFe2O4 nanoparticles is achieved before encapsulation of the luminescent complex of europium(III), 2-thenoyltrifluoroacetone, and 1,10-phenanthroline in the second layer of silica. This is to ensure the optimal distance between the magnetic core and Eu(III)-complex to pertain significant luminescence in the composite (Eu-MnFe2O4). The photoluminescence spectra of an aqueous dispersion of Eu-MnFe2O4 by excitation in the UV region show a narrow and strong emission at 612 nm, which is stable even after 72 h. The induction heating study of an aqueous dispersion of Eu-MnFe2O4 in 12 kAm-1, 335 kHz AMF shows an ILP as 4.02 nHm2 kg-1, which is remarkably higher than the hyperthermia efficiency of reported magnetoluminescent nanoparticles.