Preparation and characterization of TiO2 and V2O5 nanoparticles produced by ball-milling

We studied the crystalline and electronic structure of TiO2 and V2O5 nanoparticles produced by ball-milling. The experimental techniques used here were X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD diagrams show that ball-milling preserves the crystalline structure of the bulk TiO2 and V2O5 materials. The particle size estimated with the Scherrer formula after 24 h of ball-milling is 6 nm for TiO2 and 13 nm for V2O5. The XPS spectra exclude the possibility of impurity contamination and confirm the composition of the nanoparticles. A chemical shift in the Ti 2p XPS spectrum indicates a slight reduction of the Ti ions in the TiO2 nanoparticles. The analysis of the Ti 2p satellites shows that the O 2p-Ti 3d covalence decreases in the TiO, nanoparticles. These effects are attributed to a reduced O coordination of the Ti ions at the surface of the TiO2 nanoparticles. The effects are less evident in the case of the larger V2O5 nanoparticles because the surface/volume ratio is smaller.