Researchers from the University of Amsterdam, New York University and Spain's CSIC have developed a way to build micrometer-size models of atomic graphene using 'patchy particles’ - particles which are large enough to be easily visible in a microscope but small enough to reproduce many of the properties of actual atoms, can interact with the same coordination as the atoms in graphene, and form the same structures.
Using these patchy particles, the team built a model system and used it to obtain insight into the defects in 2D materials, including their formation and evolution over time.
To achieve the same structure as graphene with their model, the researchers used tiny particles of polystyrene, decorated with three even tinier patches of a material known as 3-(trimethoxysilyl)propyl (TPM). The configuration of the TPM patches mimicked the coordination of carbon atoms in the graphene lattice. The researchers then made these patches attractive so that the particles could form bonds with each other, again in analogy with the carbon atoms in graphene.
After a few hours, microscope observations revealed that the ‘mock carbon’ particles did in fact arrange themselves into a honeycomb lattice. The researchers then looked in more detail at defects in this model graphene lattice, finding that they showed characteristic defect motifs known from atomic graphene. Unlike with real graphene, however, the researchers were able to follow these defects from the very start of their formation, up to their integration into the lattice.
This novel approach reportedly led to new knowledge about these 2D structures. Unexpectedly, the researchers found that the most common type of defect forms in the very initial stages of growth, before the lattice is properly established. They also observed how the lattice mismatch is then ‘repaired’ by another defect, leading to a stable defect configuration, which either remains or only very slowly heals to form a more perfect lattice.
The model system thus not only offers the ability to replicate the graphene lattice on a larger scale for all sorts of applications, but also allows direct observations that provide insights into atomic dynamics in this class of materials. As defects are central to the properties of all atomically thin materials, these direct observations could prove useful for engineering their atomic counterparts, such as for applications in ultra-lightweight materials and optical and electronic devices.
The team's results could open the door to the assembly of complex 2D colloidal materials and investigation of their dynamical, mechanical and optical properties.