Ultraviolet photoluminescence from nonbridging oxygen hole centers in porous silica

In this letter, we report the observation of an ultraviolet (UV) photolumin escence (PL) emission at around 330 nm in porous silica prepared by the sol -gel process. Upon a posttreatment which leads to OH adsorption, the intens ity of the observed UV PL emission increases significantly. It is shown tha t this behavior is associated with the increase of OH groups adsorbed on th e surface of porous silica. We suggest that the observed UV PL emission ori ginates from the nonbridging oxygen hole centers generated from surface hyd roxyls. The mechanism of the UV PL emission is expressed tentatively by com bining the nonbridging oxygen centers charge modification model and the vib rative absorption of a SiO2 network containing water. (C) 2001 American Ins titute of Physics.