2D Crystal Engineering of Nanosheets Assembled from Helical Peptide Building Blocks.

The successful integration of 2D nanomaterials into functional devices hinges on developing fabrication methods that afford hierarchical control across length scales of the entire assembly. We demonstrate structural control over a class of crystalline 2D nanosheets assembled from collagen triple helices. By lengthening the triple helix unit through sequential additions of Pro-Hyp-Gly triads, we achieved sub-angstrom tuning over the 2D lattice. These subtle changes influence the overall nanosheet size, which can be adjusted across the mesoscale size regime. The internal structure was observed by cryo-TEM with direct electron detection, which provides real-space high-resolution images, in which individual triple helices comprising the lattice can be clearly discerned. These results establish a general strategy for tuning the structural hierarchy of 2D nanomaterials that employ rigid, cylindrical structural units.