The synthesis and electrical transport of ligand-protected Au13 clusters

The ligand-protected Au-13 clusters have been synthesized by using meso-2,3-dimercaptosuccinic acid as the reducing and stabilizing agent. Transmission electron microscopic analysis shows a size distribution of 1.4 +/- 0.6 nm. Optical spectrum shows an absorbance peak at 390 nm. The electrical transport measurement devices are fabricated using the electro-migration method. Coulomb blockade is observed at the temperature of 1.6 K, revealing the formation of the tunneling junction. The Coulomb oscillation's on/off ratio is nearly 5. Three peaks are extracted in the dI/dV data and attributed to the energy levels of Au13 clusters, gapped by about 60 meV. First principle calculations are carried out to interpret the energy diagram.