The structural, optical, magnetic and photocatalytic properties of transition metal ions doped TiO_2 nanoparticles

摘要

Metal-ions doped TiO_2 (M-TiO_2) have been synthesized using a hydrothermal method at 100 °C with a post-annealing temperature process at 500 °C, including individual Co~(2+), and Mn~(2+) ions. Furthermore, effects of these doping metals ions on the crystallization and phase transition of the TiO_2 nanoparticles were discussed by XRD, TEM/HRTEM, BET specific surface area (S_(BET)), pore-size distribution by BJH, UV-vis Spectroscopy, photoluminescence (PL), FTIR, VSM as well as photocatalytic measurements. The presence of anatase type structure in TiO_2 nanopowders with high crystallinity and high phase stability even after annealing at 500 °C substantially indicated that the dopants might inhibit densification and crystallite growth in TiO_2 nanophase by providing dissimilar boundaries. Moreover, with a suitable amount (ca. 0.2, 0.3 mol%), the Mn, Co dopants reduces anatase grain size and increases the specific surface area of TiO_2 powders. The band gap energy values of Mn2* and Co~(2+) ions doped nano-TiO_2 were higher than the pure nano-TiO_2 and they showed a blue shift to the visible region. Furthermore, the obtained experimental results revealed that all the samples exhibited the paramagnetic behavior at room temperature. The paramagnetic order was increased with increasing the (Mn, Co) content, whereas the coercivity force H_c was decreased. Photocatalytic degradation of methylene blue (MB) under UV lights indicated that the meso-TiO_2 exhibited enhanced activity under UV lights. However, photodegradation of the MB under UV light was enhanced with the presence of Mn and Co with TiO_2.