SiO2 nanospheres and tubes obtained by sol–gel method

Multifunctional nanomaterials with one-dimensional structure have become very attractive because of their potential applications in biochemistry (bioseparation and biointeraction), drug delivery, catalysis, nanotechnology (optical sensors). In this work we report on the synthesis of SiO2 nanospheres and tubes, in a solution of tartaric acid (TTA), pure water and absolute ethanol, starting with tetraethyl orthosilicate (TEOS) via the addition of ammonium hydroxide. In order to characterize the obtained material, transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), thermogravimetric and thermodifferential analysis (DTA/TGA), FT-IR spectroscopy and spectroellipsometry (SE) were used. The tubes have an outer diameter of 0.1–0.2 μm and length of some microns containing also spherical nanoparticles. The dimensions of the obtained nanotubes are tunable, their diameter and length depending on the synthesis conditions. In the presence of meso-tartaric acid no hollow tubes but nanospheres are obtained. The SiO2 tubes and nanospheres have similar structure but very different morphologies. The large surface area and the distinctive inner and outer surfaces represent a great advantage of the nanotubes over conventional nanoparticles, making these materials suitable for doping and differential functionalization.