Fluorescent Nanocrystal−Polymer Composites from Aqueous Nanocrystals:  Methods without Ligand Exchange

Fluorescent nanocrystal−polymer composites were prepared from aqueous CdTe nanocrystals via two related routes. Route 1 was summarized as CFP (coating followed by polymerization), coating CdTe nanocrystals with polymerizable surfactant of octadecyl-p-vinylbenzyldimethylammonium chloride (OVDAC), followed by the copolymerization of OVDAC-coated CdTe with radical monomers to achieve nanocrystal−polymer bulk composites. Route 2 was summarized as PFC (polymerization followed by coating), coating CdTe directly with the copolymers of OVDAC and styrene to achieve processable nanocrystal−polymer composites. Both of these two methods avoided the exchange of surface ligands of nanocrystals. Photoluminescence (PL) quenching from free radicals was observed in the CFP method, which depended strongly on both the size of the nanocrystals and the species of the thiol stabilizers. We attributed it to the distinct surface composition of each nanocrystal sample. With control of the surface composition of the nanocrystals, this PL quenching could be effectively avoided. The PFC method obviated handling nanocrystals in the polymerization process and thus the maximum PL was retained.