Photostability of the Oleic Acid-Encapsulated Water-Soluble Cd(x)Se(y)Zn(1–x)S(1–y) Gradient Core–Shell Quantum Dots

[Image: see text] Composite systems where quantum dots (QDs) are combined with other nanomaterials (e.g., gold nanorods) in aqueous solutions have attracted broad attention—both for their potential in applications and for studies of fundamental processes. However, high-quality QDs are typically prepared in organic solvents, and the transfer of QDs to an aqueous phase is needed to create the desired QD composites. Photostability of the transferred QDs—both the steady-state and photo-induced dynamic properties—is essential for studying the processes in the composites and for their applications. We present a detailed study of the photostability of aqueous Cd(x)Se(y)Zn(1–x)S(1–y) gradient core–shell QDs obtained by various approaches using linker exchange and surfactant encapsulation. Beside the steady-state photoluminescence (PL) emission stability, we also study changes in the PL decay. From the variety of the studied samples, the water-soluble QDs encapsulated by a double layer of oleic acid show superior properties, that is, stable PL emission and PL decay under continuous light or pulsed-laser light irradiation. We demonstrate that the double-layer encapsulation of QDs can be used to create QDs–metal nanoparticle composites.