Photostimulated control of luminescence quantum yield for colloidal Ag₂S/2-MPA quantum dots

In this paper, we present the results on photoinduced formation of colloidal Ag₂S quantum dots with sizes of 1.5-3 nm passivated by 2-mercaptopropionic acid (Ag₂S/2-MPA) in the presence of ethylene glycol. The synthetized colloidal Ag₂S/2-MPA QDs have NIR recombination luminescence with its maximum near 800 nm. The control of absorption and luminescence properties of the QDs is achieved by photoactivation. It is shown that photoexposure of colloidal solution of Ag₂S/2-MPA QDs leads to an increase in the QD size and monodispersity along side with the growth of the luminescence quantum yield from 1% to 7.9%. Enhancement of the luminescence quantum yield is accompanied by an increase in the average luminescence lifetime up to 190 ns, which is due to the blocking of the nonradiative recombination channel with the radiative recombination rate being (3-5.5) × 10⁵ s^-1. It is shown that the purification of the Ag₂S/2-MPA solution by a dialysis membrane from regenerated cellulose leads to an increase in the sample monodispersity, as well as stops the photoinduced growth of QDs, and also reduces the degradation of their photoluminescence.