Poly(ethylene oxide) and Polystyrene Encapsulated Quantum Dots: Highly Fluorescent, Functionalizable, and Ultrastable in Aqueous Media

The polymer encapsulation of quantum dots via seeded emulsion polymerization is a powerful method for the preparation of extraordinarily stable fluorescent particles and furthermore allows simple and straightforward in situ functionalization of the polymeric shell. Both features are inevitable for the application of quantum dots as targetable fluorescent probes in advanced biomedical studies. In particular, polymer encapsulated quantum dots showed only marginal loss of quantum yields when exposed to Cu 2+ ions, which under nonoptimized conditions completely quenched quantum dot fluorescence. This will allow the application of copper-catalyzed click chemistry. Furthermore, by simple addition of functional surfactants or functional monomers during the seeded emulsion polymerization process, a broad range of in situ functionalized polymer-coated quantum dots were obtained. This was demonstrated by purposeful modulation of the zeta potential encapsulated of quantum dots and conjugation of dyestuff. Successful functionalization was unequivocally proven by total reflection X-ray fluorescence.