Quasi-two-dimensional or hcp palladium nanoparticles with host-guest interaction prepared at room temperature

Quasi-two-dimensional palladium nanoparticles with an average lateral dimension of 7 nm have been prepared by reduction of a PdCl2 graphite intercalation compound precursor by lithium-diphenylide in tetrahydrofuran at room temperature. Selected-area electron diffraction patterns provide evidence that the palladium nanoparticles are hcp single-crystal particles. Owing to the template effect of the graphite lattice, the lattice parameter of palladium was found to have a strong relation with the graphite, and a 3a graphite superstructure was inferred. The palladium structure is rotated by 30o with regard to the carbon host lattice. Raman spectroscopy on this sample showed that a charge transfer between carbon and palladium occurs. The sample can be considered as a common Pd-graphite intercalation compound with palladium nanoparticles as guest. This behaviour is different from palladium nanoparticles prepared by hydrogen reduction at higher temperatures from the same precursor material. These particles may represent an early stage of nanoparticle formation.