Photostability of luminescence of Ag$_2$S quantum dots and Ag$_2$S/SiO$_2$ core/shell structures

The paper presents regularities that demonstrate the effect of passivating ligands formation of thioglycolic acid and L-cysteine (TGA, L-Cys) and dielectric shells (SiO$_2$) on Ag$_2$S nanocrystals interface on the photostability of their IR luminescence. Using FTIR absorption spectroscopy, the interaction manifestations of passivating ligands molecules of TGA and L-Cys with Ag$_2$S nanocrystals, as well as the formation of SiO$_2$ shell due to the process of replacing organic ligands with a silica ligand (MPTMS) (“ligand exchange”), were found. In the case of replacing TGA with MPTMS, an increase in the luminescence quantum yield of Ag$_2$S quantum dots (QDs) and its resistance to long-term exposure to exciting radiation was found. In the case of replacing L-Cys with MPTMS, the formation of a fragmentary SiO$_2$/L-Cys shell on Ag$_2$S nanocrystals was observed due to the partial replacement of L-Cys with MPTMS, which contributes to the reverse photodegradation of KT Ag$_2$S luminescence of as a result of SiO$_2$/L-Cys shell photodestruction.