Effect of Ag2S/SiO2 QDs surface structure on luminescence photostability

The paper presents regularities that demonstrate the formation effect of passivating ligands of thioglycolic acid, L-cysteine (TGA, L-Cys), and dielectric shells (SiO2) on the Ag2S nanocrystals' surface on the their IR luminescence photostability. Manifestations of the interaction between passivating ligand molecules of TGA and L-Cys with Ag2S nanocrystals, as well as SiO2 shell formation due to the replacement process of organic ligands with a silica ligand (MPTMS) ("ligand exchange"), were established, using FTIR absorption spectroscopy. In the case of replacing TGA with MPTMS, an increase in the luminescence quantum yield of formed Ag2S quantum dots (QDs) and its resistance to long-term exposure to exciting light was found. In the case of replacing L-Cys with MPTMS, the formation of a fragmentary SiO2/L-Cys shell on Ag2S nanocrystals due to the partial replacement of L-Cys with MPTMS was found. It contributes to the non-reversible photodegradation of Ag2S QDs luminescence as a result of SiO2/L-Cys shell photodestruction.