Magnetic Field-Dependent Photoluminescence of Tartrate-Functionalized Gadolinium-Doped Manganese Ferrite Nanoparticles: A Potential Therapeutic Agent for Hyperbilirubinemia Treatment

Herein, we report a magneto-photoluminescence study of transition metal oxide, in particular, Gd-doped (x = 0, 0.03, 0.10, and 0.15) MnFe2O4 (MnGdxFe2-xO4) magnetic nanoparticles (NPs) of average diameter 10 nm on surface functionalization by a small organic ligand, disodium tartrate dihydrate (T). In marked contrast to MnGdxFe2-xO4 NPs, the blue emission band at around 417 nm of T-MnGd0.10Fe1.90O4 NPs occurs due to energy transfer transition from the highest occupied molecular orbital of the T ligand to the lowest unoccupied molecular orbital of surface magnetic ions (Mn2+, Fe3+, and Gd3+) in MnGd0.10Fe1.90O4 NPs. Interestingly, the ligand-to-metal charge transfer increases significantly upon application of an external magnetic field (B) on T-MnGd0.10Fe1.90O4 NPs. The time-dependent photoluminescence spectra of T-MnGd0.10Fe1.90O4 NPs show better intensity under discontinuous B than continuous B. This outcome is further verified through the study of B-dependent RGB fluorescence micrographs. The comparative magneto-photoluminescence study of T-MnGd0.10Fe1.90O4 and T-MnFe2O4 NPs reveals that sp-d coupling strength between the T ligand and Gd+3 magnetic ions plays the most prominent role for the development of magneto-photoluminescence in T-MnGd0.10Fe1.90O4 NPs instead of Mn2+ and Fe3+ magnetic ions. Finally, an in vitro and bilirubin degradation study using our developed superparamagnetic and multicolor fluorescent T-MnGd0.10Fe1.90O4 NPs reveals their nontoxicity and potential activity as a therapeutic agent for hyperbilirubinemia treatment.