Chemical synthesis of large metal clusters and their properties

Abstract

The synthesis of ligand stabilized metal colloids and clusters in the size range of 1–30 nm succeeds by reduction of corresponding metal salts in the presence of appropriate ligand molecules. Due to the protection of the surface atoms by the chemically bonded ligands these materials can be isolated and handled as solid materials. The nano-sized particles so become available for various chemical and physical investigations. The main interest concerned with these materials is demonstrated in the question for the boundary of the metallic state. Susceptibility measurements indicate that 15 nm Pd colloids already show significant deviations from the bulk behavior. On the other hand, Mössbauer and NMR spectroscopic investigations as well as conductivity measurements prove that even 1–3 nm clusters still possess freely mobile electrons. Impedance and scanning tunneling spectroscopy identify 1.4 nm two-shell clusters as species with beginning semiconducting properties. Consequently, such clusters can act as individually working quantum dots and so may play a decisive role in future nanoelectronics.