Nanojunction between Fullerene and One-Dimensional Conductive Polymer on Solid Surfaces

Bottom-up creation of huge molecular complexes by covalently interconnecting functional molecules and conductive polymers is a key technology for constructing nanoscale electronic circuits. In this study, we have created an array of molecule-polymer nanojunctions from C-60 molecules and polydiacetylene (PDA) nanowires at designated positions on solid surfaces by controlling self-assemblies and intermolecular chemical reactions of molecular ingredients predeposited onto the surfaces. In the proposed method, the construction of each nanojunction spontaneously proceeds via two types of chemical reactions: a chain polymerization among self-assembled diacetylene compound molecules for creating a single PDA nanowire and a subsequent cycloaddition reaction between the propagating forefront part of the PDA backbone and a single C-60 molecule adsorbed on the surface. Scanning tunneling microscopy has proved that the C-60 molecule is covalently connected to each end of the pi-conjugated PDA backbone. Furthermore, the decrease in the energy gap of the C-60 molecule in nanojunctions is observed as compared with that of pristine C-60 molecules, which is considered to be due to the covalent interaction between the PDA edge and the C-60 molecule.