Facile surface modification of nickel ferrite nanoparticles for inherent multiple fluorescence and catalytic activities

We synthesized biocompatible NiFe2O4 nanoparticles (NPs) with diameters below 10 nm by coating their surface with a tartrate ligand, which interestingly give rise to photoluminescence covering the entire visible region. The analyses with various spectroscopic tools reveal that the reason behind the unique fluorescence properties of functionalized NiFe2O4 NPs is ligand-to-metal charge-transfer transition from the highest occupied energy level of tartrate ligand to the lowest unoccupied energy level of Ni2+ and d–d transitions centered over Ni2+ ions in the NPs. These fluorescent NPs are also found to be suitable for cell imaging. Moreover, the functionalized NiFe2O4 NPs show a good catalytic activity on biologically and environmentally toxic pigments, such as bilirubin and methylene blue which leads to their wide application towards therapeutics and waste water treatment. We believe that the developed multifunctional NiFe2O4 NPs would stimulate the opportunities for advanced biomedical applications.