Photodegradation of IR luminescence of Ag$_2$Se colloidal quantum dots

Photodegradation of exciton and trap-state luminescence, in bands with maxima at 705 and 905 nm respectively,.of hydrophilic Ag$_2$Se colloidal quantum dots (QD), passivated with 2-mercaptopropionic acid molecules (Ag$_2$Se/2MPA) was established. Herewith, the exciton band is characterized by complete quenching of luminescence of Ag$_2$Se/2MPA QD as the sample gets exposed. Trap-state luminescence experiences quenching by 40–60%.The quenching of trap-state luminescence is accompanied by an acceleration of luminescence kinetics and a decrease in the decay time from 280 to 210 ns. In this case, photodegradation of luminescence in this band is reversible. After 24 h of storage of the exposed colloidal solution of Ag$_2$Se/2MPA QDs, a long-wave shift of the recombination luminescence band to the region of 960–1200 nm occurs, with an even greater decrease in its decay time to 170 ns. The regularities gained are explained by the formation of core/shell systems Ag$_2$Se/SeO$_2$ with a type I heterojunction.