Bioinspired Synthesis of Quasi-Two-Dimensional Monocrystalline Oxides

Controllable synthesis of two-dimensional (2D) monocrystalline oxide nanomaterials beyond van der Waals solids is intriguing but very challenging. Inspired by the biomineralization processes that commonly implement organic templates with both positive and negative charges for regulating the crystal nucleation and growth, we adapted mix-charges amphiphilic monolayer to the ionic layer epitaxy and enabled the growth of monocrystalline 2D nanosheets. In situ grazing incidence X-ray diffraction and ex situ crystal and elemental analyses revealed that mixing charge in the template is able to tune the 2D crystal nucleation rate and promote the growth of monocrystalline domains. Molecular dynamics simulations suggested that mixing charges could yield a stable, flatter, and more ordered monolayer template with a nonuniform distribution of charges, which are favorable for the growth of monocrystalline nanosheets. Designing the mixed amphiphilic monolayers resulted in the creation of ultrathin nanosheets from various oxides including CoO, Bi₂O₃, MnO₂, and Fe₃O₄ as well as doped ones, opening up an opportunity to broaden the 2D nanomaterial family to functional oxides.