Experimental and theoretical study of optical properties and quantum size phenomena in the BiVO₄/TiO₂ nanostructures

Novel BiVO₄/3DOM TiO₂ nanostructure has been synthesized by hydrothermal method. BiVO₄ nanoparticles and TiO₂ inverse opal structure have also been prepared as reference. The prepared samples were characterized by Diffuse reflectance UV-Visible and photoluminescence (PL) spectroscopy. The absorption spectra of BiVO₄/TiO₂ nanocomposite samples show an absorption edge in the visible region, suggesting the potential application of this composite as an active visible-light driven photocatalysts. Theoretically quantum confinement phenomena and size dependent optical properties of BiVO₄ quantum dots have been also studied. Using the effective mass approximation model, we computed the optical properties for spherical BiVO₄ nanoparticles incorporated in TiO₂ matrix. The size dependent of charge carrier's energies were calculated. The result shows that the confinement energy decreases with increase the size of BiVO₄ nanoparticles. Dielectric properties of the BiVO₄ nanoparticles were investigated and it was found that the dielectric constant decreases significantly as the size is reduced as a result the exciton energy decreases. It has been also found that the radiative recombination lifetime is concurrently enhanced with decreasing BiVO₄ QDs size.