A CLAY SELF-ASSEMBLED ON A GOLD SURFACE AS STUDIED BY ATOMIC-FORCE MICROSCOPY

A 2:1 smectite-type clay containing thiol groups on a basal plane was synthesized by reacting magnesium chloride with mercaptopropyltrimetho xysilane in an alkaline methanol/water mixture. The material (denoted as an HS-Mg layer) was identified by elemental analyses and X-ray diff raction measurements. The HS-Mg layer was revealed to be self-assemble d on a gold surface. The process was confirmed by monitoring the incre ase in mass of a gold electrode with a quartz crystal microbalance whe n the electrode was immersed in a chloroform dispersion of the HS-Mg l ayer. Nanoscale images of a gold surface treated with the HS-Mg layer were obtained by atomic force microscopy. The 400 x 400-nm image of th e sample showed that the surface was covered with platelets of about 3 0 mm in diameter and 1.9 nm in thickness. The 3.00 x 3.00-nm image sho wed that the bright spots on the surface of the particle displayed per iodicity. The spots were ascribed to the alkanethiol groups on the sil icate sheet of the HS-Mg layer, The observed periodicity coincided wit h the tetrahedral sheet of a model smectite clay. (C) 1997 Academic Pr ess.