Preparation and characterisation of nanoscale Vb-metal oxides M2O5 (M = V, Nb, Ta)

Nanoscale Vb-metal oxides M2O5 (M = V, Nb, Ta), about 10 to 200 nm in diameter are prepared via a polyol-mediated synthesis. The preparation is performed by a controlled hydrolysis of the alcoholates VO(i-OC3H7)(3), Nb(OC2H5)(5) and Ta(OC2H5)(5) at 180 degreesC in diethylene glycol (DEG). The monodisperse morphology as well as the colloidal stability of the nanoscale particles in DEG and H2O prove the surface-active role of diethylene glycol regarding particle growth and particle agglomeration. Based on thermal analysis and a determination of B.E.T.-surfaces, ail almost monomolecular coverage of the M2O5 nanoparticles with DEG molecules can be concluded. According to electron and X-ray diffraction images, the as-prepared nanoscale particles are amorphous. However, a treatment at moderate temperatures results in a significantly increased crystallinity.