Luminescence enhancement in bromine and samarium co-doped TiO2 semiconductor nanocrystalline powders

In this paper, TiO2:Sm3+ (0.75 mol%) nanoparticles doped with different amounts of Br− were prepared by an improved sol-gel method and were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), VG ESCALAB MKIIX-ray photoelectron spectrometer (XPS) and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS). Their photoluminescence (PL) properties were investigated at room temperature. The emissions of 4G5/2-6HJ (J=5/2, 7/2, 9/2) transitions of Sm3+ ions were observed under the excitation wavelength at 350 nm and the emission intensity depended strongly on the doping amount of Br−. TiO2:Sm3+ (0.75 mol%) nanoparticles doped with 1 mol% of Br− calcined at 700 °C exhibit highest intensity of luminescence, which is nearly three times than the undoped one. The mechanism of photoluminescence in the co-doped system was discussed.