Size-tunable synthesis of SiO₂ nanotubes via a simple in situ templatelike process

SiO₂ nanotubes with tunable diameters and lengths have been successfully synthesized via a simple in situ templatelike process by thermal evaporation of SiO, ZnS, and GaN in a vertical induction furnace. The structure and morphologies were systematically investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectrometry. Studies found that both the diameters and lengths of the SiO₂ nanotubes can be effectively tuned by simply changing the reaction temperatures. The range of changes was from 30 nm (diameter) and several hundred micrometers (length) at 1450°C to 100 nm (diameter) and 2-10 micrometers (length) at 1300°C. Varying some other experimental parameters results in the formation of additional SiO ₂-based nanostructures, such as core-shell ZnS-SiO₂ nanocables, ZnS nanoparticle filled SiO₂ nanotubes, and fluffy SiO₂ spheres. Based on the observations, an in situ templatelike process was proposed to explain the possible growth mechanism.