Two-Step On-Surface Synthesis of One-Dimensional Nanographene Chains

Abstract

Controllable fabrication of low-dimensional graphene structures is a matter of scientific and technological interest. To date, significant efforts have been devoted to the fabrication of nanographene chains as well as nanographenes and graphene nanoribbons. Here, we present the on-surface synthesis of one-dimensional (1D) nanographene chains composed of hexa-peri-hexabenzocoronene (HBC) which is a common type of nanographene. Using dibromo-substituted hexaphenylbenzene (Br2-HPB) as a precursor, the 1D HBC nanographene chains are achieved through two reaction steps, namely polymerization and cyclodehydrogenation, on a Au(111) surface, which have been investigated by low-temperature scanning tunneling microscopy. The Br2-HPB molecules deposited on Au(111) are formed into a chiral selective self-assembled layer, and the following thermal annealing at 200–300 °C induces debromination and sequential polymerization of Br2-HPB, leading to the formation of long 1D HPB chains. In particular, we find that the same length 1D HPB chains are selectively ordered in a side-by-side arrangement. Finally, by annealing at 400 °C, HBC planar nanographenes are achieved through the cyclodehydrogenation process of HPB within the long 1D chains. The maximum length of the obtained 1D HBC nanographene chains reached is about 30 nm.