CO 2 ‐Assisted Fabrication of 2D Amorphous CeO 2 and Its Application in Photoluminescence Enhancement

Two-dimensional (2D) non-van der Waals (non-vdW) amorphous nanomaterials have attracted much attention for optical, catalytic and biomedical applications owing to their rich dangling bonds and unsaturated coordination. CeO2, a typical non-vdW material, with amorphous 2D structure and intrinsic optical properties have rarely been prepared via a top-down method due to the lack of anisotropy in its 3D bonding network. Herein, we develop an environmentally-friendly top-down method to achieve ultrathin 2D amorphous CeO2−x with controllable defects from bulk CeO2 by utilizing supercritical CO2. The unique CeO2−x nanosheets exhibit outstanding ultraviolet-visible adsorption and photoluminescence (PL) properties due to the disordered atomic structure and increased vacancy defects resulting from the cleavage of Ce−O covalent bonds and amorphization of CeO2. In addition, the defect-related emission mechanism of the visible PL for the as-prepared 2D CeO2−x nanosheets has been proposed.