The optical studies of SiO2 mesoporous materials with hierarchical tubules-within-tubule structure have been investigated by photoluminescence and Fourier-transform infrared transmittance (FTIR). Our results suggest that the radiative intensity can be strongly enhanced by annealing the samples in N2 environment. From the FTIR spectra, we have pointed out that the origin responsible for the strong emission is Si–OH complexes located on nanotube surface. It has been observed that after turning off the pumping laser, the photoluminescence signal of SiO2 nanotubes can persist for several seconds, which is much longer than that of most materials performed under similar conditions. We have found that the decay of the photoluminescence signal is due to the quantum tunneling process. These are triplet and singlet states of Si–OH complexes that are responsible for the observed persistent photoluminescence.

No abstract

The mesoporous silica submicron-spheres (80–200 nm) with a small dispersion in diameter (< 10%) as the building blocks of the artificial mesoporous silica opals have been synthesized using quaternary ammonium surfactant as template in an aqueous solution of suitable polarity at near neutral condition of pH = 7.0–9.0.

No abstract

The effect of laser illumination on the luminescent properties of MCM-41 was investigated by photoluminescence (PL) measurements. It was found that PL peak energy, PL intensity, and PL degradation of MCM-41 can be manipulated by controlling the laser illumination time. Laser illumination on MCM-41 gave at least a 2.5 times increase in PL intensity and an improvement in PL degrading phenomena. Possible mechanisms were proposed to explain our experimental results in a consistent way. The results presented here are expected to be useful for clarifying the nature of light emission from MCM-41 materials and to be of practical use for its possible applications in optical devices.