Luminescent properties of colloidal Ag-=SUB=-2-=/SUB=-S quantum dots for photocatalytic applications

Abstract

The structural and optical properties of colloidal Ag2S quantum dots in various environments are investigated. With the help of transmission electron microscopy, X-ray diffraction and energy-dispersive X-ray analysis the formation of colloidal Ag2S quantum dots with an average size of 2-3 nm with a monoclinic crystal lattice, and Ag2S/SiO2 core-shell systems based on them, has been established. The change in the luminescence quantum yield of quantum dots with the change of the surface environment state is shown. The decoration of TiO2 nanoparticles of 10-15 nm in size with Ag2S quantum dots was performed and the influence of the structure of the interfaces of quantum dots and their environment (2-mercaptopropionic acid, water, ethylene glycol, SiO2 dielectric shell with a thickness of 0.6 nm and 2.0 nm) on the formation of TiO2-Ag2S heterosystems was analyzed. For Ag2S quantum dots passivated with 2-mercaptopropionic acid, signs of charge phototransfer after adsorption on TiO2 nanoparticles surface have been established. Signs of reactive oxygen species appearance due to charge phototransfer in heterosystem are enstablished, based on methylene blue photobleaching under excitation of heterosystem outside of TiO2 fundamental absorption region, Keywords: Quantum dots, photocatalysis, luminescence, titanium dioxide, silver sulfide.