Probing the hierarchy of thymine-thymine interactions in self-assembled structures by manipulation with scanning tunneling microscopy

A study was conducted, using high-resolution scanning tunneling microscopy (STM) imaging and manipulation, to investigate the spontaneous assembly and STM-induced disassembly of one of the DNA base molecules, thymine (T), deposited on the gold (Au) surface under ultrahigh vacuum (UHV) conditions. The Au (111) substrate was chosen as a noble inert substrate, to minimize molecule-substrate interactions, allowing the self-assembly process to be dominated by intermolecular interactions. The STM images revealed a two-step self-assembly process, in which hydrogen bonds influenced the growth of one dimensional (ID) filaments of T molecules that reassemble into 2D T islands the weaker van der Waals (vdW) interactions. It was also demonstrated that the hierarchy bond strengths involved in the surface self-assembly of T molecules, with highly anisotropic interactions, can be directly probed using STM.