Low temperature investigation of the blue emission in mesoporous silica

The photoluminescence properties of porous silica at low temperature (8 K) are investigated as a function of the porosity of the samples. At 8 K the contribution of the emission at about 2.8 eV with respect to the luminescence at 3.7 eV increases allowing its spectral resolution. The shift of the peak position of the emission at about 2.8 eV at different excitation energies and the non single exponential law of its decay time suggests the presence of two different surface centers.