Molecular Self-Assembly and Crystallization Induced by Nanoparticle Seeds

Molecular self-assembly and crystallization is an important bottom-up approach in nanotechnology. Incorporating both organic and inorganic components can combine and sometimes enhance the functions belonging to different material groups. This paper describes the crystallization of long-chain carboxylic acids induced by the surface of nanoparticles at the graphite/solution interface. Carboxylic acids adsorb epitaxially on graphite basal plane to form self-assembled nano-stripe patterns. We found that this persistent nano-stripe pattern is perturbed by the presence of thiol-protected cadmium selenide nanoparticles. Instead, the nanoparticles act as nucleation seeds to induce crystallization of carboxylic acid nanorods. Atomic force microscopy is used to characterize the nanoparticle/nanorod hybrid architecture and to understand the nanoconfinement effect imposed by the nanoparticle seed. The effect of nanoparticle and thiol capping layer chemical composition is studied. In addition, we identify a range of nucleating compound to nanoparticle size ratio that favors the seed-medicated nanorod formation by varying either carboxylic acid chain length or nanoparticle size. The study contributes a novel method for creating crystalline linkers among nanoparticles as well as fundamental understanding of seed-mediated crystallization under nanoconfinement.