Recombination Dynamics of Colloidal Nanocrystals in Functionalized-Poly-Methylmethacrylate Nanocomposites

Two colloidal methods, namely one pot and two steps approaches, have been exploited to synthesize light emitting CdSe/ZnS core-shell nanocrystals, differing in growth process of the inorganic ZnS shell and, therefore in the resulting surface chemistry of the two types of nanocrystals. The synthesized nanocrystals have been incorporated, by using an "ex situ" procedure, in different thermoplastic PMMA-based polymers, including PMMA co-polymer specifically functionalized by means of groups having high chemical affinity to nanocrystal surface, and the resulting nanocomposites have been processed in thin films. Spectroscopic steady state and time-resolved investigations, carried out both on nanocomposite solution and thin film samples, indicate as a change in the optical properties of the two steps nanocrystals is observed upon incorporation in polymers, especially in PMMA homopolymer, where significant aggregation of inorganic nanostructures occurs. On the contrary, the one pot CdSe/ZnS nanocrystals preserve in all investigated samples their long-lived radiative emission. Such nanocrystals result homogeneously dispersed in the polymers, providing high quality films and thus representing ideal candidates for future optical applications.