6533b837fe1ef96bd12a1eaa

RESEARCH PRODUCT

Monolayers of asymmetrical diethylalkanoat disulfides on gold(111):.the influence of chain length difference on atomic force microscope images

subject

description

Several symmetrical and asymmetrical long-chain diethylalkanoat disulfides were synthesized and character- ized. The differences in the chain lengths of the disul- fides ranged between zero and five methylene units. Self- assembled monolayers of these disulfides formed on Au(111) surfaces were studied by atomic force microscopy (AFM) in order to obtain information about the origin of the image contrast. Domains with hexagonal lattices (lattice constants 5:2- 5:3 A) were detected for all derivatives, independent of the chain length differences. This indicates that the contrast arises roughly at a depth of 4- 8 A in the monolayers at imag- ing forces between 0: 2a nd 3n N. For SAMs of diethylalkan- oat disulfides, the image contrast is therefore not entirely due to the terminal functional groups of the molecules, but is due to the lattice formed by the closely packed alkane chains in the bulk part of the monolayer. These results are of general importance with respect to the interpretation of AFM images of organic monolayers.