New emerging magnetic, optical and photocatalytic properties of Tb doped TiO2 interfaced with CoFe2O4 nanoparticles

The CoFe2O4/TiO2:Tb composite nanoparticles were prepared by a two-stage chemical route. The composites were characterized by using X-Ray Diffraction, Transmission Electron Microscopy, X-ray and UV Photoelectron Spectroscopies, FT-IR, Raman and UV-Vis spectroscopies. There is a polarized spin transfer at the interface between the cobalt ferrite into the TiO2 conduction band. As a result, the magnetic moments of oxygen vacancies in TiO2 becomes (ferro) magnetically ordered. The magnetic moments sublattice of Tb ions may have an either ferro or antifero coupling depending on the dopant concentration. The magnetic semiconductor intensifies the optical absorption in the visible. There is a band-to band absorption assisted by single-occupied oxygen vacancies coupled to some local crystal lattice relaxations. The lifetime of the photoexcited electrons in the conduction band increases due to their coupling with magnetically ordered interface transferred states. Also, the trapping of electrons into multiplet states of Tb3+ reduces the recombination rate. The photocatalytic efficiency of the magnetically ordered titania increases with respect to bare TiO2. The reactive oxygen species produced at the solid-liquid interface of TiO2 were identified by Electron Spin Resonance coupled with spin-trapping technique. The results were correlated to the presence of the magnetic order inside the titania.

Automated summary

In this study, CoFe2O4/TiO2:Tb composite nanoparticles were synthesized by a chemical method, and it was found that there was a spin transfer between TiO2 and cobalt ferrite, resulting in ordered magnetic moments of oxygen vacancies in TiO2. The magnetic moments of Tb ions could have different coupling states depending on the dopant concentration, and the magnetically ordered interface transferred states helped increase the lifetime of photoexcited electrons.