Studies of the photostability of CdSe/CdS dot-in-rod nanoparticles

Fluorescent CdSe/CdS dot-in-rod nanoparticles have attracted considerable interest for fundamental research and potential applications in bioscience and physical science. In this work, we investigated photoinduced phenomena in CdSe/CdS dot-in-rods using time-resolved photoluminescence (PL). Our experimental results show that photopassivation, photooxidation, and photoinduced defect/surface states occur in CdSe/CdS dot-in-rods, and these processes depend on the irradiation amount. The thickness of the CdS shell plays an important role for photostability. Photopassivation was found to initially result in an increase of PL intensity when fluence is low. Photooxidation was found to cause a spectral blue shift due to shrinkage of the core. We also found that a thick shell of CdS can effectively suppress photooxidation and hinder the diffusion of oxygen into the core. Irradiation could generate defect/surface states predominantly in the shell and also on the interface between the core and the shell. A weak PL shoulder in the blue side was observed in heavily irradiated samples as a result of photoinduced rupture of encapsulation.