Bright visible photoluminescence from silica nanotube flakes prepared by the sol–gel template method

We report macroscopic synthesis of silica nanotubes by the sol–gel template method. A large number of silica nanotubes with small diameters (30–50 nm) were produced and were shaped into flakes successfully. Strong photoluminescence (PL) was observed in both as-grown and annealed nanotube flakes. The PL spectra have maxima at 2.55 and 2.30 eV for the as-grown and annealed samples, respectively; the PL intensity of annealed nanotubes is much higher than that of as-grown nanotubes. The strong emission may be due to the Si–OH complex located on both the inner and outer surfaces of the nanotubes. The nanotube flakes we prepared may have potential applications in future integrated optical devices.