Phase transfer reaction for the preparation of stable polymer-quantum dot conjugates

Abstract

Polymers are extensively applied to protect fluorescent molecules and nanomaterials against photooxidation. However, the chemical conjugation of nanomaterials such as semiconductor quantum dots to polymers is important for long-term stability, avoiding aggregation, and finding device application of polymer-nanomaterial hybrids. The chemical conjugation of polymers provides quantum dots with superior physical stability than those prepared by physical blending. Here, we report a single step conjugation of an environment-friendly, biocompatible polymer to the surface of CdSe/ZnS core shell quantum dots. The direct conjugation of a polymer to the quantum dot surface helps us to avoid phase segregation of quantum dots and the polymer host, without adversely affecting the photoluminescence properties of quantum dots. Here, N-isopropyl acrylamide-maleic anhydride random copolymer is directly attached to the core-shell quantum dots through the amide linkage. The amino-functionalized quantum dots are employed in the conjugation reaction with maleic anhydride units in the polymer. Quantum dots in the resultant conjugate retain resistance to photooxidation in the solution phase or film state. The properties of the conjugate, including photostability, are studied using fluorescence spectroscopy and microscopy methods.