Liquid droplets encapsulated by two graphene sheets can abilities high stress (as much as 1 GPa) and can act as vessels for crystallization of two-dimensional materials. Wang et al. studied the crystallization of beryllium oxide (BeO) in such a cell with high-resolution transmission electron microscopy and electron energy loss spectroscopy. As an various of forming the bulk wurtzite structure, it crystallized into an sp2-coordinated hexagonal structure that used to be customarily 20 to 30 layers thick. This thickness makes the fabric metastable relative to wurtzite, and the authors argue that the noninteracting graphene surface kinetically templates the hexagonal segment.
Angew. Chem. Int. Ed. 10.1002/anie.202007244 (2020).
