Defects and Photoluminescence of Ni2+ and Mn2+-Doped Sol–Gel SiO2 Glass

Abstract SiO 2 glass doped with Ni 2+ and Mn 2+ has been prepared by the sol–gel process. Very strong visible light (its fluorescence efficiency is about 4 times of that of undoped sol–gel SiO 2 glass and about 160 times of that of ZnS nanocrystallites) from the SiO 2 glass doped with Ni 2+ and Mn 2+ has been observed. The emission wavelength of Ni 2+ -doped, Mn 2+ -doped, and undoped glass samples is about 450 nm. However, the co-doping of Ni 2+ and Mn 2+ shifts the emission wavelength to 420 nm. The sol–gel SiO 2 glass is a porous phosphor material. Very strong photoluminescence of the sol–gel SiO 2 glass mainly comes from structural defects. Because the doped samples contain more Si dangling bonds, nonbridging oxygen, and oxygen vacancy in its structure and surface defects inside the nanometer-scale hole in the sol–gel SiO 2 glass than undoped glass sample, the fluorescence efficiency of doped samples has been remarkably increased. Because the doped ions affect the band gap structure of the host materials, the emission wavelength of the co-doped samples is different from that of Ni 2+ - and Mn 2+ -doped samples. Because the emission wavelength of Ni 2+ and Mn 2+ luminescent centers in the sol–gel silica glass is almost the same as that of undoped sample, the fluorescence intensities of Ni 2+ - and Mn 2+ -doped samples are higher than those of the co-doped samples.