Resolving the structure of organic nano strands self-assembled at a graphite-liquid interface using STM

Abstract

Scanning tunneling microscopy (STM) at solution-graphite(0001) interface is used to identify nanometer-wide elementary strands of custom-designed ampiphilic benzamides and elucidate their internal structure with submolecular resolution. Evidences against graphitic artifacts that often mimic organic strands are provided, thereby unambiguously establishing the molecular origin of these strands. The aliphatic chain lengths are chosen based on bulk studies so as to promote strand architectures and avoid monolayer structures. Two different chain lengths are used to decipher the structural parameters and the results suggest hitherto unknown precursor routes to strand formation on a surface that is different from columnar mesophases in bulk. An on-surface self-assembly into hydrogen-bonded tetramer precursors and their subsequent interaction with other units via van der Waals forces between the dangling alkyl chains is proposed for strand formation on the surface.