Adsorption of Tryptophane on Graphite Investigated by Scanning Tunneling Microscopy

The adsorption behaviours of tryptophane on graphite (HOPG) have been investigated under low vacuum conditions at room temperature using scanning tunneling microscopy(STM). The acquired STM images exhibit that tryptophane can form a uniform adsorption layer at room temperature. Two kinds of structures were observed:two-dimensional stripe structure and two-dimensional monoclinic lattice.Possible models have been proposed for these two kinds of structures. The π stacking interactions between near tryptophane molecule's side chains are responsible for the formation of these two kinds of structures.