Photoacoustic Study on the Co-luminescence Effect of Lanthanide Complexes with Aromatic Acid in Silica Gels

In this study, lanthanide complexes Tb(o-HBA)(3) center dot H2O and Ln(o-HBA)(3)center dot H2O (o-HBA: o-hydroxy benzoic acid; Ln(3+):Y3+ or Er3+) co-doped silica samples have been prepared via a sol-gel method. The photoacoustic (PA) intensity of the ligand decreases with the addition of the Y3+ complex, and increases remarkably with the addition of the Er3+ complex. Different PA intensities of the samples are interpreted by comparison with their luminescence spectra. The luminescence quantum yields, which are accurate within 10%, have been determined to be 26 %, 22 %, and 6.9% for the silica samples doped with Tb3+-Y3+ complexes, Tb3+ complex, and Tb3+-Er3+ complexes, respectively. A possible mechanism for the co-luminescence phenomena is proposed.