Effects of Transition Metal Doping on the Growth and Properties of Rutile TiO2 Nanoparticles

Rutile TiO2 nanoparticles doped with V, Cr, or Mn ions have been synthesized via a modified Pechini method using polymeric precursors. The final particle sizes range between 20 and 500 nm depending on the selected dopant. The TiO2 rutile phase has been stabilized in the doped nanoparticles at 650 °C. Microstructural analysis shows a good crystallinity and cationic homogeneity of the doped nanoparticles. The cathodoluminescence study of the doped and undoped nanoparticles shows a luminescence signal related to the structural defects of the samples and the presence of dopants. In particular, an intense 1.52 eV emission associated with Ti3+ interstitials dominates the luminescence of undoped nanoparticles, which also exhibit less intense emissions extending from 2 to 3.4 eV. The presence of V, Cr, or Mn in the rutile TiO2 nanoparticles induces variations in the associated cathodoluminescence signal which would be useful in order to achieve a deeper understanding of the doping process and spread future optical applications. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Ti3+ in the near-surface region of the nanoparticles, the concentration of which decreases when doping. The presence of Ti3+ interstitials related states in the band gap is discussed.