The Smallest, Atomically-Precise and Custom-Design Graphene Origami
The discovery of fullerenes (Nobel Prize in Chemistry 1996), carbon nanotubes (CNT), and, more recently, the isolation of monolayer graphene (Nobel Prize in Physics, 2010) sparked a revolution in the fabrication of a variety of carbon allotropes. Graphene can be viewed as the building block of several allotropes, e.g., carbon nanotubes, three-dimensional (3D) graphene-based nanostructures (GNSs) and devices that have been either fabricated or predicted theoretically for potential applications, even machines.
Origami, the ancient art of paper folding, has been widely used in diverse areas, from architecture to battery design and DNA nanofabrication. It has also inspired the fabrication or simulation of macroscale origami graphene structures and devices, even machines. However, due to technical difficulties, atomically precise and controllable graphene origami for the creation of custom-design GNSs with quantum features has remained an open challenge.
Recently, Professor Hong-Jun Gao's group from the Institute of Physics, Chinese Academy of Science, demonstrated that origami is an efficient way to convert graphene nano-fragments into complex nanostructures with atomic-scale precision. By scanning-tunneling-microscope manipulation at low temperatures, they repeatedly fold and unfold graphene nanoislands (GNIs) along an arbitrarily chosen direction. A bilayer graphene stack featuring a tunable twist angle and a tubular edge connection between the layers is formed. Folding single-crystal GNIs creates tubular edges with specified chirality, while folding bicrystal GNIs creates well-defined intramolecular junctions (IMJs). These tubular edges are structurally similar to carbon nanotubes (CNTs) and corresponding IMJs. Measurements of electronic properties combined with quantum calculations, based on atomic models of the structures, determine and explain these properties.
The present paper reports the first experimental construction of the smallest-ever, atomically-precise origami graphene nanostructures together with property measurements and corresponding quantum calculations, establishing a platform for the construction of custom carbon nanostructures with engineered quantum properties and, ultimately, quantum machines. Furthermore, the results reported in this paper set the stage for the discovery of new and unusual phenomena, as the folded GNIs are composite structures comprising a CNT-like fold and a twisted bilayer graphene. For example, it may be worth exploring the superconductivity of the twisted bilayer graphene part with a magic twist angle attached to either a semiconducting or metallic tube or an IMJ. This work has been published in Science on September 6 as a report entitled “Atomically precise, custom-design origami graphene Nanostructures” (Science 365, 1036(2019)).
This work was performed in collaboration with Professor Sokrates T. Pantelides from Vanderbilt University and Professor Min Ouyang from the University of Maryland in the U.S.A. This work was financially supported by the National Natural Science Foundation of China, National Key Research and Development Projects of China, and Chinese Academy of Sciences.
Fig. 1. Construction of atomically well-defined folded GNSs by STM origami.
Fig. 2. Precisely controlled folding of a GNI along preselected directions.
Fig. 3. Tunable 1D tubular carbon structures with different chirality and electronic properties.
Fig. 4. Creation of 1D carbon intramolecular junctions.