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

Abstract

SiO2 glass doped with Ni2+ and Mn2+ 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 SiO2 glass and about 160 times of that of ZnS nanocrystallites) from the SiO2 glass doped with Ni2+ and Mn2+ has been observed. The emission wavelength of Ni2+-doped, Mn2+-doped, and undoped glass samples is about 450 nm. However, the co-doping of Ni2+ and Mn2+ shifts the emission wavelength to 420 nm. The sol–gel SiO2 glass is a porous phosphor material. Very strong photoluminescence of the sol–gel SiO2 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 SiO2 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 Ni2+- and Mn2+-doped samples. Because the emission wavelength of Ni2+ and Mn2+ luminescent centers in the sol–gel silica glass is almost the same as that of undoped sample, the fluorescence intensities of Ni2+- and Mn2+-doped samples are higher than those of the co-doped samples.