Chiral Mesostructured Yb³⁺, Er³⁺ Codoped CeO₂ with Upconverted Circularly Polarized Luminescence

Upconverted circularly polarized luminescence (UC-CPL) active organic and organic-inorganic composite materials have garnered increasing attention due to their vast potential applications in areas such as 3D displays, encryptions, spintronics and optoelectronic devices. However, effective methods for fabricating chiral inorganic materials exhibiting UC-CPL remain a challenge. Herein, we propose an approach for the synthesis of UC-CPL active chiral mesostructured CeO₂ powders (CMCs) via a hydrothermal growth method, using L/D-aspartic acid as symmetry-breaking and structure-directing agents. Two levels of chirality exist in CMCs: primary nanoplates constructed from nanoparticles and the helical stacking of these nanoplates to form a twisting nanofusiform. Yb³⁺ and Er³⁺ ions can be codoped into the CMCs through a one-step synthesis to achieve UC-CPL. The 1 % Yb³⁺, 1 % Er³⁺ codoped CMCs exhibited absorption-based optical activities in the range of 350-500 nm, similar to undoped CMCs, and displayed circularly polarized luminescence in the range of 520-610 nm under the excitation by a 980 nm laser. This luminescence is attributable to the energy transfer process between Yb³⁺ and Er³⁺. This work may provide new insights into designing chiral photon upconversion inorganic materials.