The optical studies of SiO2 mesoporous materials with hierarchical tubules-
within-tubule structure have been investigated by photoluminescence and Fou
rier-transform infrared transmittance (FTIR). Our results suggest that the
radiative intensity can be strongly enhanced by annealing the samples in N-
2 environment. From the FTIR spectra, we have pointed out that the origin r
esponsible for the strong emission is Si-OH complexes located on nanotube s
urface. 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 c
onditions. We have round 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 photolu
minescence. (C) 2001 American Institute of Physics.