Luminescent and structural behaviour of Tb+3 ions doped TiO2 nanoparticles synthesized by facile sol-gel method

Terbium doped titania (Tb–TiO2) nanoparticles with different concentration of Tb+3 ions were synthesized by sol-gel method. The crystallite size of nanoparticles decreased with increasing the Tb+3 ions concentration suggesting the inhibition of growth of TiO2 nanoparticles while the phase of nanoparticles was not affected by doping of Tb+3 ions. A marginal red shift in absorption and a decrement in the band gap from ⁓3.18 eV–3.06 eV after doping of Tb+3 ions were observed. The radiative transitions of Tb+3 ions were observed at 489 nm, 542 nm, 495 nm, and 654 nm corresponding to 5D4-7F6, 5D4-7F5, 5D4-7F4, and 5D4-7F3 transitions respectively in PL spectra. The PL intensity of these transitions first increases and then decreases with increasing Tb+3 concentration. The enhancement in PL intensity is due to more Tb+3 ions, and further addition of Tb+3 ions leads to the cluster formation which results in the loss of PL intensity.