Colloidal Sol-Gel Synthesis and Photocatalytic Activity of Nanoparticulate Nb sub(2)O sub(5) Sols

A detailed study of a novel synthesis via colloidal sol-gel route for obtaining nanoparticulate Nb sub(2)O sub(5) was performed. Parameters such as temperature and H super(+):Nb super(5+) and Nb super(5+):H sub(2)O molar ratios were controlled in order to determine the best conditions of synthesis. Moreover, particle size distribution, zeta potential, structure by X-ray diffraction, and the photocatalytic activity of the particulate sols were also evaluated. The obtained results indicate that the colloidal sol-gel synthesis is a good alternative for obtaining Nb sub(2)O sub(5) either as stable nanoparticulate sol or as a nanosized powder. Nb sub(2)O sub(5) amorphous nanoparticles with an average size of 20 nm were obtained by controlling the synthesis variables. The heat-treatment process allowed the formation of Nb sub(2)O sub(5) with orthorhombic structure that transforms at higher temperatures to monoclinic phase. The highest photocatalytic activity was observed under lambda = 365 nm, the smallest UV energy used in the experimental tests.