Enhancing the physical properties and photocatalytic activity of TiO₂ nanoparticles via cobalt doping

Cobalt-doped TiO₂-based diluted magnetic semiconductors were successfully synthesized using a co-precipitation method. The X-ray diffraction study of all the samples showed good crystallinity, matching the standard tetragonal anatase phase. The X-ray diffraction peaks of the cobalt-doped sample slightly shifted towards a lower angle showing the decrease in particle size and distortion in the unit cell due to cobalt incorporation in the lattice of TiO₂. Transmission electron microscopy showed the spherical morphology of the TiO₂ nanoparticles, which decreased with Co-doping. The optical characteristics and band gap investigation revealed that defects and oxygen vacancies resulted in lower band gap energy and maximum absorption in the visible region. Dielectric measurements showed enhancement in the dielectric constant and AC conductivity, while the dielectric loss decreased. The enhancement in the dielectric properties was attributed to interfacial polarization and charge carrier hopping between Co and Ti ions. The magnetic properties displayed that pure TiO₂ was diamagnetic, while Co-doped TiO₂ showed a ferromagnetic response at 300 K. The visible light-driven photocatalytic activity showed an improvement for Co-doped TiO₂. Our results demonstrate that Co-doping can be used to tune the physical properties and photocatalytic activity of TiO₂ for possible spin-based electronics, optoelectronics, and photo-degradation applications.