Size-dependent optical and dielectric properties of BiVO4 nanocrystals

Optical and dielectric properties of BiVO4 nanocrystals with different particle sizes have been investigated. BiVO4 nanocrystals with different particle sizes were synthesized through a solid-state reaction method followed by mechanical ball milling for different time durations. The samples were characterized by X-ray diffraction, UV–Vis spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and photoluminescence spectroscopy. Direct and indirect band gap energies were found to vary in the range 4.04–4.16 eV and 3.51–3.67 eV respectively, for different particle sizes. The band gap energies are higher with respect to their values in the bulk BiVO4 due to quantum confinement effects. Dielectric properties of the BiVO4 nanocrystals were investigated and it was found that the dielectric constant increased from 32 to 41 for the reduction of particle size from 29 to 7 nm.