Surfactant-Induced Postsynthetic Modulation of Pd Nanoparticle Crystallinity

Modulation of Pd nanoparticle (NP) crystallinity is achieved by switching the surfactants of different binding strengths. Pd NPs synthesized in the presence of weak binding surfactants. such as oleylamine possess polyhedral shapes and a polycrystalline nature. When oleylamine is substituted by trioctylphosphine, a much stronger binding surfactant, the particles become spherical and their crystallinity cleciease significantly. Moreover, the Pd NPs reconvert their polycrystalline structure when the surfactant is switched back to oleylarnine. Through control experiments and molecular dynamics simulation, we propose that this unusual nanocrystallinity transition induced, by surfactant exchange was resulted from a counterbalance between the surfactant binding energy and the nanncrystal adhesive energy. The findings represent a novel postsynthetic approach to tailoring the structure and corresponding functional performance of nanomaterials.