Effect of light on stability of thiol-capped CdSe/ZnS quantum dots in the presence of albumin

Abstract

The effect of exposure to the green laser light on the photoluminescence (PL) stability of CdSe/ZnS quantum dots (QDs) capped with either mercaptopropionic (MPA) or thioglycolic (TGA) acid was studied in aqueous suspensions and in the presence of bovine serum albumin (BSA). The results of absorbance and luminescence measurements suggest that the capacity of protein to change the coating structure of thiol-capped QDs and the stability of photoluminescence depends on the nature of stabilizing surface ligands. The interaction of BSA molecules with TGA-capped quantum dots increases their PL quantum yield (QY) and makes PL more stable, however, the effect is opposite for MPA-capped QDs. The light exposure instantly increases the PL intensity and the quantum yield of TGA-capped QDs but does not change those of MPA-capped QDs. In the medium with BSA, however, the occurrence of light-induced PL enhancement does not depend on stabilizing thiol ligands of QDs and it lasts for a relatively long period of time.