Two-dimensional arrangements of gold clusters and gold colloids on various surfaces

Unstabilized and P(C6H4SO3H)(3)-stabilized gold colloids, respectively, having diameters of 13 +/- 1 nm, as well as Au-55 clusters, were chemically fixed on various surfaces. Oxidized silicon and quartz glass surfaces were treated by (MeO)(3)Si(CH2)(3)SH to generate monolayers of the SH-functionalized silanes with elimination of MeOH. Contact with aqueous solutions of unstabilized 13 nm gold colloids formed stable S-Au-bonds and resulted in a partial or complete coating of the surface by gold colloids, depending on the reaction time. Atomic force microscopic (AFM) investigations made the fixed gold particles visible. Another kind of fixation of gold colloids was reached on poly(ethyleneimine) (PEI)-coated mica surfaces. For that, P(C6H4SO3H)(3) stabilized gold colloids were used. Simple acid-base interactions between the SO3H groups of the colloids and the NH functions of the imine led to the desired coverage by the colloids. AFM investigations again were used for characterization. Au-55 clusters were arranged on gold(111) faces which have been produced by a heating 200 nm thick gold layer on chrome-plated quartz glass (tempax glass) to red heat, followed by spontaneous cooling. The Au(111) faces were then coated by 2-mercapthoethylamine. The interactions of the free NH2 groups with the SO3H functions of the cluster molecules Au-55(Ph2PC6H4SO3H)(12)Cl-6 led to their chemisorption from the aqueous solution. In this case, the conducting gold substrate enabled the characterization of the cluster-monolayer by scanning tunneling microscopy (STM).