Abstract
<title>Abstract</title> <p>Engineering the electronic structure of MXenes through rare-earth intercalation offers a promising route to regulate their redox activity and multifunctional performance. Herein, we report the synthesis of erbium-intercalated V₂C MXene (Er@V₂C) as a sunlight-responsive nanoplatform for environmental remediation and biomedical applications. Structural analysis confirmed successful Al removal from the V₂AlC MAX phase and subsequent interlayer expansion upon Er³⁺ intercalation, with the (002) diffraction peak shifting from 13.4° to 9.1° and further to 8.9°, corresponding to an increased c-lattice parameter of 19.86 Å. Optical studies revealed band-gap narrowing from 2.21 to 1.98 eV which indicated the enhanced visible-light absorption. Raman and FTIR analyses demonstrated lattice distortion and modified surface terminations while BET measurements showed mesoporous architecture with a surface area of 90 m²g⁻¹ that reflecting suppressed nanosheet restacking. Under natural sunlight irradiation, Er@V₂C exhibited efficient photocatalytic degradation of Rhodamine B (82.6%) and sulfamethoxazole (90.2%) within 120 min, following pseudo-first-order kinetics. The catalyst also showed excellent stability over repeated cycles. Beyond environmental remediation, Er@V₂C demonstrated concentration-dependent antioxidant activity and selective cytotoxicity toward HeLa cancer cells while maintaining comparatively higher viability in normal HUVEC cells. These findings reveal that erbium intercalation effectively modulates charge separation, defect density, and redox behavior in V₂C MXene, enabling the integration of solar-driven photocatalysis and selective biological activity within a single multifunctional nanomaterial system. This study highlights rare-earth intercalation as a versatile strategy for designing redox-engineered MXenes for sustainable environmental and biomedical technologies.</p>