Accelerated Photostability Studies of Colloidal Quantum Dots

Photostability of colloidal quantum dots (QDs) is one of the major criteria determining their long-term applicability in energy and chemical technologies. Yet, photostability studies of QDs are extremely sensitive to experimental conditions, lack a detailed mechanistic understanding, and are time-, material-, and labor-intensive. Herein, an automated microfluidic platform for accelerated photostability studies of colloidal QDs is introduced, 3.5x faster and 100x more material efficient than the conventional flask-based studies. The developed microfluidic strategy provides real-time in situ access to the optical properties of QDs throughout the photostability experiments. Specifically, the material-efficient microfluidic platform is used to study the mechanism and kinetics of CdSe QDs' photodegradation. The studies suggest that a generation of singlet oxygen via triplet energy transfer from colloidal CdSe QDs can initiate photo-oxidation of CdSe QDs. Furthermore, the presence of at least one additional photodegradation pathway of CdSe QDs parallel to the photo-oxidation pathway is unveiled. The systematic photostability experiments reveal how the incident photon flux and the starting average diameters of CdSe QDs affect their photodegradation rates. This work sheds light on the complex and multifaceted photodegradation phenomena of colloidal CdSe QDs and illustrates the unique characteristics of microfluidic strategies to improve and accelerate photostability studies of QDs.