How Capping Agents Can Impact the Fate of Quantum Dots: Comparing the Effects of Various Capping Agents on the Properties of Zinc Sulfide Quantum Dots

Owing to their unique optoelectrical features and theranostic uses, semiconductor quantum dots (QDs) have been very appealing in nanomedicine. However, surface chemistry and colloidal stability are critical challenges in their biological use. The physicochemical, optical, and biological properties of QDs can be significantly influenced by capping agents used to stabilize their aqueous colloids. Hence, choosing an appropriate capping agent is a critical step in biomedical application of QDs, which requires sufficient knowledge of their effects on QDs features. Here, we investigated the effects of three different capping agents commonly used for stabilization of QDs: mercaptoethanol, mercaptoacetic acid, and cysteamine, on the physicochemical and optical characteristics of ZnS QDs as well as their biological interactions. The capping agents showed considerable impact on the ZnS QDs features and behaviors; therefore, it is recommended that capping agents be selected based on the purpose of the study.