Preparation and photics properties of water-soluble Au monolayer protected clusters

The synthesis and characterization of mercaptosuccinic acid monolayer protected water-soluble gold clusters (Au MPC) are described. TEM photograph displays that when Au/S mole ratio is 1∶3, size of Au core of MPC is about 2 nm. Results of the FTIR spectra indicate that the mercaptosuccinic acid chains are assembled on the gold cores via the Au-S bond. UV-vis absorbance and luminescence of Au MPC in aqueous media were studied. There is no UV-vis absorbance around 520 nm but visible luminescence around 796 nm at the 451 nm and 480 nm excitation. Absorption band in the visible region around 520 nm reflects the surface plasmon band(SPB) that is due to the collective oscillations of the electron gas at the surface of nanoparticles (6 s electrons of the conduction band for Au MPC). The SPB is a