Energy structure and fluorescence of in ZnS:Eu nanoparticles

(Formula presented)-doped ZnS nanoparticles with an average size of around 3 nm were prepared, and an emission band around 530 nm was observed. By heating in air at 150 °C, this emission decreased, while the typical sharp line emission of (Formula presented) increased. This suggests that the emission around 530 nm is from intraion transition of (Formula presented) In bulk (Formula presented) no intraion transition of (Formula presented) was observed because the excited states of (Formula presented) are degenerate with the continuum of the ZnS conduction band. We show that the band gap in (Formula presented) nanoparticles opens up due to quantum confinement, such that the conduction band of ZnS is higher than the first excited state of (Formula presented) thus enabling the intraion transition of (Formula presented) to occur.