Radiative and non radiative recombinations study in the novel nanocomposites BiVO4/3DOM-TiO2, ZnO/3DOM-TiO2 and BiVO4/3DOM-ZnO: Application to the photocatalysis

Abstract

A theoretical investigation of optical proprieties of three nanostructures such as BiOV4/3DOM TiO2, ZnO/3DOM TiO2 and BiOV4/3DOM ZnO has been presented and discussed. The study based on a one band effective mass approximation model was developed to calculate the charge carrier energies on various parameters of nanostructures including their size. We computed the optical properties for both spherical BiVO4 and ZnO nanoparticles incorporated in the three dimensionally ordered macroporous inverse opal TiO2 nanocomposites (3DOM-TiO2). At first and by solving a three dimension Schrödinger equation we calculated the dependence of charge carriers energies on the size of nanoparticles. Then we investigated the variation of the excitonic energy of BiOV4/3DOM-TiO2, ZnO/3DOM-TiO2 and BiOV4/3DOM-ZnO as function of the radius of these nanostructures into taken account the effects of dielectric and coulomb interaction between charge carriers. We showed that the radiative recombination lifetime is enhanced with decreasing BiVO4 and ZnO quantum dots (QDs) size. It was found that as the size of the dot is reduced the confinement of charge carriers and the optical gap are increased. The optical gap of the ZnO/3DOM-TiO2 is larger than both BiOV4/3DOM-TiO2 and BiOV4/3DOM-ZnO especially for small radius. It was also found that radiative life time in the BiOV4/3DOM-TiO2, ZnO/3DOM-TiO2 and BiOV4/3DOM-ZnO increased by increasing the radius of these nanostructures. In addition, we have also showed that, the radiative lifetime in the ZnO/3DOM-TiO2 nanostructure is less than both BiOV4/3DOM-TiO2 and BiOV4/3DOM-ZnO nanostructures. Finally, we have studied and discussed the Auger process in BiOV4/3DOM-TiO2, ZnO/3DOM-TiO2 and BiOV4/3DOM-ZnO nanostructures. At first, we have showed that the auger process is important when the radiuses of nanostructures are less than 2 nm. Then we have also showed that this process is more important for ZnO/3DOM-TiO2 compared to the other nanostructures.