Synthesis of single silica nanotubes in the presence of citric acid

Citric acid has been employed as a structural modifier for the first time to synthesize single silica nanotubes via a sol–gel process at room temperature. XRD results reveal the amorphous nature of the silica framework. SEM and TEM images show that the nanotubes were 0.5–20 µm in length, and 50–500 nm in width. TG-DTA and FTIR results indicate that the possible interaction between citric acid molecules and inorganic species should be very weak. The structural direction of ammonium citrate crystals under appropriate synthetic conditions was argued to explain the formation of particular morphologies.