CO₂‐Assisted Fabrication of 2D Amorphous CeO₂ and Its Application in Photoluminescence Enhancement

Abstract 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 CeO_2−x with controllable defects from bulk CeO₂ by utilizing supercritical CO₂. The unique CeO_2−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 CeO_2−x nanosheets has been proposed.