Functionalization of Inorganic Nanoclusters based on the Molecular Recognition Events at the Heterogeneous Interface

Semiconductor nanoclusters and nanoparticles of cadmium chalcogenides have attracted special attention due to their unique optical properties. We particularly take notice of the host-guest chemistry and molecular events at the surface of small clusters and have been exploring unique functions by designing the organic environment around the cluster. In this article we review our recent approaches utilizing molecular clusters with a general formula Cd10S16R12 having twelve surface organic groups. Aryl-substituted clusters trapped ammonium cations among the surface aromatics through cation-π interaction, and such an intercalative cation binding caused a notable enhancement of the cluster photoluminescence at -600 nm. A systematic study using a series of substituted-phenyl-capped clusters revealed that the electronic properties of the substituents on the phenyl rings notably affect the cation binding capability as well as the photoluminescence emission energy. It was also found that the cation intercalation promotes the formation ofπ-stacked dimer of the aromatic moiety on the cluster surface. Highly sensitive and selective turn-on photoluminescence response to Cu (I) and Ag(I) in neutral buffer was also achieved by using an oligo(ethyleneglycol)-modified aryl-substituted cluster.