Reversible Switching Of Magnetism In Thioiate-protected Au_(25) Superatoms

摘要

Single gold atoms (e.g., in gas beams or adsorbed on a support) are paramagnetic because of the unpaired 6s electron, while bulk gold is diamagnetic because the paramagnetism of the conduction electrons is counteracted by the orbital and ionic core diamagne-tism. The evolution of magnetism in going from gold atoms to nanoparticles to the bulk is of fundamental interest and importance. Previous work has observed magnetism in small Au nanoparticles, and a size-dependent magnetization was found for ～1- 5 nm Au nanoparticles. However, contradictory results exist in the literature, as the nanoparticle size distribution and ill-defined surface properties complicate the interpretation. Therefore, it is of critical importance to create a well-defined nanoparticle system and to achieve crystal-structure-property correlations in order to study the fundamentals of magnetism in gold nanoparticles.