Via on-surface synthesis organic nanostructures can be created, which are not accessible via solution based synthetic approaches. The two-dimensional confinement of the molecular educts on a flat surface facilitates certain reaction pathways that would not show up in solution where more degrees of freedom are present. This enables the synthesis of low dimensional molecular structures, such as nanographenes, graphene nanoribbons or quantum rings, whose unique (opto-)electronic properties depend strongly on their dimensions and precise atomic structure. These new types of functional materials are particularly interesting for applications in electronics devices such as organic field effect transistors (OFETs), organic light-emitting diodes (OLEDs, e.g. for smartphone displays), or organic solar cells.
However, the on-surface reaction processes are so far not well understood, often difficult to control and sometimes not precise enough to build custom structures. Therefore, we recently developed an approach for constructing organic nanoarchitectures molecule by molecule on a salt surface using scanning probe manipulation. The relatively inert salt surface ensures the precise alignment of the molecular building blocks in the plane but keeps them movable. The sharp tip of an atomic force microscope, which has only a single atom or molecule at its apex, serves as our second tool. With this “finger” three successive reaction steps are performed: 1) Activation of the molecular precursors to enable a subsequent intermolecular coupling reaction. 2) Bringing the activated building blocks on the surface into close proximity. 3) Inducing the chemical reaction between the two molecular educts, which leads to the formation of a covalent bond. These reaction steps are induced by short voltage pulses that are applied between the surface and the AFM tip.
This opens ways for creating functional organic nanomaterials from their building blocks and for studying not yet well-known systems such as carbon allotropes or heterojunctions. The ability to follow the reaction processes step by step will help us to elucidate the mechanisms behind these unexplored bond-formation pathways, which is important for the emerging field of on-surface synthesis.
- Scientific exchange and discussion
- Initiating research cooperations in the field of SPM-Based On-Surface Synthesis