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 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.

Supercritical CO2‐Induced Amorphization in 2D Materials: Mechanism and Applications

“…For example, the exfoliation of non-vdW VO 2 and CeO 2 has been achieved with the assistance of SC CO 2 , which is much difficult than the case in vdW materials. [23,30] The strong breaking effect of SC CO 2 on interlayer chemical bonds reveals the different underlying mechanism in comparison with the other exfoliation methods. Furthermore, the amorphization of nonlayered PdCu alloy shows that SC CO 2 could lead to amorphization without exfoliation or vacancies, which provides new understanding of the SC CO 2 assisted process.…”

“…Guo et al, for instance, fabricates the 2D amorphous CeO 2 with enhanced Photoluminescence. [23] Yan et al found the amorphization of non-vdW VO 2 (B) and TiO 2 in SC CO 2 . [24] What's more, they revealed that the amorphization in VO 2 originates from shear stress led by entropy deletion.…”

“…In contrast, the exfoliation and amorphization of non‐vdW materials or nonlayered materials are still challenging owing to the much stronger bonds. For example, the exfoliation of non‐vdW VO 2 and CeO 2 has been achieved with the assistance of SC CO 2 , which is much difficult than the case in vdW materials [23, 30] . The strong breaking effect of SC CO 2 on interlayer chemical bonds reveals the different underlying mechanism in comparison with the other exfoliation methods.…”

“…Despite the easy exfoliation of van der Waals (vdW) materials, amorphous non‐vdW nanomaterials with stronger interlayer bonds could also be fabricated with SC CO 2 . Guo et al., for instance, fabricates the 2D amorphous CeO 2 with enhanced Photoluminescence [23] . Yan et al.…”