Red photoluminescence from GeO2-SiO2 gel-glasses prepared by a new sol-gel process

The GeO2-SiO2 gel-glasses were prepared by the sol-gel method with tetraethoxysilane (Si(OC2H5)(4)) and 3-trichlorogermanium propanoic aci (Cl3GeCH2CH2COOH) as starting materials. The gel-glasses show a strong room-temperature photoluminescence with peaks at 575 and 624 nm under the excitation of the 532 nm line of a Nd:YAG laser. The photoluminescence spectra are caused by GeO2 nanoparticles embedded in gel-glasses. The GeO2-SiO2 gel-glasses are characterized by the optical absorption, X-ray diffraction (XRD) and transmission election mecroscopy. The size of GeO2 nanoparticles embedded in gel-glasses becomes larger as the GeO2 content increases, and thus the optical absorption edge of the gel-glass shifts to the lower-energy side. The GeO2 nanoparticle structures are found to be amorphous GeO2 in the gel-glasses by the XRD and the electron diffraction pattern.