Comparison of Size-Dependent Structural and Electronic Properties of Anatase and Rutile Nanoparticles

Abstract

Size-dependent variations in the electronic and structural properties of anatase and rutile nanoparticles have been compared. The anatase nanoparticles of the present study were prepared by hydrothermal ripening of an anatase sol and had diameters in the range 2−130 nm whereas the rutile nanoparticles were prepared by calcination of sol−gel derived rutile and had diameters in the range 3.6−60 nm. The hydrothermally ripened anatase nanoparticles had similar surface structures as deduced from the XANES as previously reported sol−gel anatase materials prepared through calcination (Luca et al., J. Phys. Chem. B 1998, 102, 10650). The optical band gap (Eg) of the anatase nanoparticles as deduced from their electronic absorption spectra showed some variation with size but Eg was not a smooth function of crystallite size, as would be dictated by the effective mass model for both types of anatase nanoparticles. In distinct contrast to the anatase nanoparticles, rutile nanoparticles showed a smooth size dependent ...