Organic nanoparticles composed of Fréchet-type dendrons: synthesis, characterization, self-assembly and reversible guest encapsulation.

Novel organic nanoparticles composed of Fréchet-type dendrons have been synthesized by a simple one-pot reaction, which involved etching off the gold core in a first generation gold nanoparticle-cored dendrimer (AuG). Dissolution of the Au core leads to the generation of numerous dendron radicals in a small volume, which underwent very fast coupling and addition reactions to form the Fréchet-type dendron nanoparticles (FDNs). The FDNs were found to be nearly monodispersed with an average size of 3 nm. NMR, TEM and MALDI-TOF analysis suggested that the FDNs are extremely dense organic structures made up of Fréchet-type dendrons. Although the FDNs do not contain any self-assembling motifs, such as hydrogen bonding moieties, they exhibited time and concentration dependent morphological transformations, leading to the formation of larger spherical aggregates and fibrous networks. Morphological transformations were probed using TEM, AFM and DLS studies. The self-assembly was found to be reversible. The morphological transformation of FDNs was exploited for the encapsulation and on-demand release of guest molecules.