Nanoassemblies designed from semiconductor quantum dots and molecular arrays

The formation of nanoassemblies of CdSe/ZnS quantum dots (D) and pyridyl-substituted free-base porphyrin (H2P) molecules has been spectroscopically identified by static and time-resolved techniques. The formation of nanoassemblies has been engineered by controlling the type and geometry of the H2P molecules. Pyridyl functionalization gives rise to a strong complex formation accompanied by QD photoluminescence (PL) quenching. For some of the systems, this quenching is partly related to fluorescence resonance energy transfer (FRET) from the QD to H2P and can be explained according to the Forster model. The quantitative interpretation of PL quenching due to complexation reveals that (i) on average only about 1/5 of the H2P molecules at a given H2P/QD molar ratio are assembled on the QD and (ii) only a limited number of vacancies accessible for H2P attachment exist on the QD surface.