Characterization of α-Fe2O3 nanoparticles by X-ray absorption at the oxygen K edge

alpha - Fe2O3 nanoparticles were chosen to study nanostructured materials by using X - ray absorption near edge structure (XANES) technique. It shows that oxygen K - edgy XANES spectra of all alpha - Fe2O3 nanoparticles of different sizes (3 nm, 10 nm and 55 nm) are different from that of commercial alpha - Fe2O3 coarse particles. The key feature with alpha - Fe2O3 nanoparticles is the occurrence of a new absorption peak labeled B in this paper. It reveals that peak B is attributed to the new states formed by the 2p states of grain boundary oxygen hybridized with iron 4s and 4p states. Further studies suggest that hybridization of oxygen 2p states with 3d metal states, mainly e(g) orbital, increases as alpha - Fe2O3 nanoparticles decrease in their size, resulting in a bigger distortion of oxygen octahedrally local symmetry around the iron. Finally, we obtained both oxygen K - edge XANES spectra by making alpha - Fe2O3 nanoparticles (3 nm) directly for the experiment and making the same size nanoparticles after grinding. It proves that there is a special coordination force existing in nanostructured alpha - Fe2O3.