α-cyclodextrin functionalized CdS nanocrystals for fabrication of 2/3 D assemblies

Different types of cyclodextrins (CDs) have been tested as mediators for the water phase transfer of organic-capped CdS nanocrystals (NCs), and alpha CD has been demonstrated to be the most effective system. The formation of a complex based on alpha CDs and colloidal NCs has been considered to be responsible for the phase transfer process and extensively investigated by optical, structural, and calorimetric measurements, as a function of the experimental parameters (pH and NC and CD concentration). A mechanism for the complexation phenomena has been suggested. The fabrication of 2/ 3 D supramolecular architectures has been proposed according to two different strategies. First, a layer-by-layer procedure has been used to obtain multilayered structures where polyelectrolyte layers have been intercalated with negatively charged alpha CD-CdS NC complexes by exploiting electrostatic interaction between polyelectrolyte and cyclodextrin OH groups. Second, a monolayer of CdS NCs has been deposited onto a self-assembled monolayer of sulfated CDs, thus combining the use of an electrostatic-force-based approach and host-guest chemistry. The important role played by host-guest interactions has then been revealed.