In-situ heating study on the structural change of surfactant-templated germanium oxide mesostructure

Mesostructured germanium oxide has been well-synthesized by using a surfactant-templated approach under basic hydrothermal conditions. The cationic surfactant cetyltrimethylammonium bromide (CTAB) has formed nanotubes with uniform diameter of about 3.2 nm. Blanket-like morphology of the as-prepared sample has been observed with transmission electron microscopy (TEM). High-resolution TEM image reveals that the nanotubes are connected with inorganic germanium oxide and have self-assembled into periodic mesostructure. In-situ heating X-ray diffraction (XRD) patterns confirm that the germanium oxide is in amorphous phase in the temperature range from room temperature (RT) to 700 degrees C. In-situ heating small-angle X-ray scattering (SAXS) presents the mesostructural change with temperature. The local atomic structures around germanium atom have been obtained with in-situ heating X-ray adsorption fine structure (XAFS) techniques. The stability of this mesostructure has been determined to be correlated with the cationic surfactant CTAB. The structural evolution from the GeO 2/NaOH aqueous solution, the as-prepared sample to the sample heated at 700 degrees C, has been described, and the formation mechanism of mesostructured germanium oxide has been discussed.