Defect-induced luminescence in Co(II)-doped anatase TiO2 prepared by the sol-gel method

The defect luminescence properties of titania sol-gel materials doped with Co2+ ions are reported. The laser irradiation of Co-doped titania samples produces a fluorescence, which is reduced as the continuous irradiation time is increased. The fluorescence decay depends on irradiation time as a double exponential function; the characteristic times involved for the luminescence quenching are in the range of seconds. We have associated the suppression of luminescence to the effect of the local heating produced by the laser beam on the reduction of physical defects such as grain boundaries, surface states and chemical defects originating from oxygen vacancies.