Colloidal Ag₂S/SiO₂ core/shell quantum dots with IR luminescence

Abstract

This paper presents the results of studies of the luminescent properties for colloidal Ag 2 S quantum dots, coated with SiO 2 shell, carried out by techniques of transmission electron microscopy, optical absorption and luminescence spectroscopy time correlated single photon counting, quantum yield of luminescence. Various approaches to the formation of SiO 2 shell is analyzed. It is concluded that an increase in the quantum yield of Ag 2 S QDs luminescence in the condition of the formation of a SiO 2 shell on the interfaces provides the passivation of dangling bonds and localization of charge carriers in the nucleus. It is shown that, under the considered conditions for the synthesis of Ag 2 S/SiO 2 core/shell structures in ethylene glycol, the use of TEOS as a precursor for SiO 2 shell provides the formation of a less defective shell, leading to an increase in the quantum yield of luminescence from 1.6% to 8%. On the contrary, the use of sodium metasilicate and high concentrations of MPTMS does not ensure the formation of a dense SiO 2 shell of several monolayers thickness on Ag 2 S interfaces, coated with 2-mercaptopropionic acid.