RARE-EARTH IONS ADSORBED ONTO POROUS-GLASS - LUMINESCENCE AS A CHARACTERIZING TOOL

The luminescence properties of some rare-earth (Ln) ions adsorbed on porous vycor glass (PVG) are reported. The results are used to characterize this system. Vibronic sidebands of the Gd3+ 6P7/2 →8S7/2 emission due to coupling with vibrations of the water molecule and of silica are observed. This observation indicates that the Ln ions are bound to the surface of the pores of PVG and that they are coordinated on the other side by water molecules. From the decay time of Eu3+ on PVG, the number of coordinating water molecules is determined by using Horrocks’ formula. This number is approximately 4. The energy transfer from Ce3+ to Tb3+ and from Gd3+ to Tb3+ is studied. From the dependence of the transfer efficiency on the acceptor concentration, an estimation of the mean distance between two adsorbed in Ln ions is made. This distance is about 7 Å. Ce3+ and Eu3+ are observed to quench each other’s luminescence. The maximum quenching distance is determined to be about 14 Å. © 1990, American Chemical Society. All rights reserved.