Luminescence and photophysical properties of colloidal ZnS nanoparticles

Abstract

ZnS nanoparticles were successfully prepared by a reverse micelle method with AOT(bis(2-ethylhexyl) sulfosuccinate, disodium salt) as surfactant. The photophysical properties of two colloidal systems, ZnS/AOT − and ZnS/pyridine/AOT −, have been investigated. The absorption spectra of the ZnS nanoparticles with different size and with different surface modification demonstrated the effects of quantum confinement and dielectric confinement on the band gap of colloidal ZnS nanoparticles. Photoluminescence measurements were carried out to investigate the energetic positions of the surface state, shallow trap and deep trap in band gap. The peaks in photoluminescence emission spectrum of ZnS/AOT − in heptane, located at 405 and 420 nm, were identified to be due to the electron–hole recombination from surface and internal vacancies for Zn and S atoms, respectively, while the peak at 385 nm was ascribed to the dangling bond of AOT − linked with the surface of ZnS nanoparticles. The study provides a method of differentiating deep trap, shallow trap and surface state in the band gap.