Synthesis and characterization of ultra-long silica nanowires

Large-scale synthesis of amorphous silica nanowires was achieved by using simple physical evaporation of a mixture of Si and Al₂O₃ powders. Scanning electron microscopy observations showed that the silica nanowires have lengths of several mm and diameters of 20–100 nm. X-ray photoelectron spectroscopy revealed that these nanowires consisted of Si and O elements in an atomic ratio of approximately 1:2, consistent with the stoichiometric formula SiO₂. Photoluminescence measurements showed a blue luminescence band in the wavelength range of 400–500 nm with three peaks at 420 nm, 440 nm, and 470 nm, respectively, which also differs from the previous reports of the photoluminescence for oxygen-deficient silica nanowires. This may suggest that the fully oxidized silica nanowires still have many structural defects that contribute to the photoluminescence. PACS 81.05.Ys; 78.55.Et; 78.30.Fs; 52.75.Rx; 81.15.Gh; 64.70.Fx