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Abstract: By exciting with synchrotron radiation in the 4–10eV range the emission properties of sol–gel synthesized porous silica at room temperature and at 8K are investigated. The modifications of the ultraviolet emission in the range 3.7–4.2eV excited at different energies (5.64, 6.20, 6.53, and 6.89eV) support the hypothesis of the contribution of two emitting centers. In particular the two emissions are spectrally resolved when exciting at 5.64eV and a blue shift of the emission peak is reported as the excitation energy increases. The analysis of the decay times indicates that the two centers are temporally resolved with the 5.64eV excitation both at room temperature and at 8K and allows to estimate lifetimes of about 3 and 18ns. When exciting at 6.53eV, the larger relative contribution of the 4.0eV band does not allow to efficiently resolve the two decay times and the estimated life time of the 3.8eV band is shortened. [Copyright &y& Elsevier]

Abstract: The photoluminescence properties of type I sol–gel synthesized Rhodamine 6G doped silica samples were investigated in the 1.5×10−4–1.5×10−3 mol/l range of concentration by means of steady-state and time resolved photoluminescence measurements. The emission peak red shifts as the concentration increases. For a fixed concentration, the peak position also red shifts as the excitation wavelength decreases. The observed spectroscopic features, including excitation of photoluminescence and decay time, indicate the formation of fluorescent dimers. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: The photoluminescence properties of sol–gel prepared porous silica in visible and ultraviolet range were studied exciting in the 4–8eV range by means of synchrotron radiation. Two main emissions at 2.8 and 3.7eV were detected and studied as a function of the temperature from 8 up to 300K. The two emission bands displayed different excitation channels: at 5.6 and 6.2eV for the 3.7eV band and at 4.8, 5.2 and 6.0eV for the 2.8eV band. By increasing the temperature the amplitude of the 2.8eV emission decreases with respect to the contribution of the 3.7eV band when excited at 5.6eV. The time decays of the two bands excited at 5.6eV were fitted with two exponential decays with mean life times of about 2.6 and in the range 20–60ns for the 2.8eV emission and 2.6 and 21.8ns for the 3.7eV emission. The analysis of the spectroscopic features suggests the attribution to different emitting surface centers and the presence of at least two contributions for both the emissions. We assign the 3.7eV band to two different species of interacting silanols. [Copyright &y& Elsevier]

Abstract: The optical properties of porous silica were studied by means of synchrotron radiation. We investigated the spectral properties of the blue photoluminescence band as a function of the porosity of the samples. In the whole set of samples the blue band is centered at about 2.8eV, with main excitations at 5.0 and 6.0eV. Time decay analysis indicates the contemporary presence of two contributions of photoluminescence. [Copyright &y& Elsevier]