Encapsulation and Covalent Assembly of Nanoparticles

Metal nanoparticles (NPs) are three-dimensional structurally well-defined nanoclusters of around 10-100 atoms, which are best known for their unique size-dependent properties. It has been shown that the properties of a covalent ensemble of a number of NPs are greatly enhanced compared to those of the same number of single components. This, so-called collective, behavior can be useful, once controlled, for constructing NP nanocircuits of electronic devices. To build and study long chains of covalently linked NPs, their encapsulation by two shape- and size-complementary ligands is proposed. A series of bowl-shaped ligands, capable of (1) recognition and (2) covalent encapsulation of spherical NPs, is designed and the synthesis of these ligands is outlined. The ultimate goal is to connect the NP(ligand) 2 building blocks to generate long linear [(ligand)NP(ligand)] n chains and investigate their collective-behavior effect. In addition to standard analytical methods to characterize NPs, high-resolution transmission electron microscopy will be used to provide insight into this unusual phenomenon displayed by covalent NP ensembles. This project is geared towards (1) control over the organization of NPs through their covalent interconnection by chemical means to (2) enhance their electronic properties. The knowledge gained through this investigation can lead to a set of design principles, which can be used in future for making NP-based functional materials. This work can also result in an unprecedented methodology to separate NPs into fractions of extremely low size-distribution.