Photocatalytic and Cytotoxic Behavior of Ce‐Modified ZnO/CuO Nanocomposite Anchored on Biochar

ABSTRACT

Biochar‐supported cerium‐doped metal‐oxide nanocomposites, namely BC–Ce/CuO (NC1), BC–Ce/ZnO (NC2), and a ternary BC–Ce/ZnO/CuO (NC3), were synthesized by a co‐precipitation‐assisted hydrothermal route using pine‐needle derived biochar as a porous support matrix that may facilitate adsorption and interfacial charge transfer. Comprehensive characterization (XRD, UV–vis DRS, XPS, FE‐SEM, HR‐TEM) suggested the coexistence of ZnO and CuO phases, nanoscale crystallite dimensions, mixed Ce ³⁺ /Ce ⁴⁺ oxidation states, and modified optical absorption behavior that may be associated with defect‐related electronic interactions. Among the synthesized nanocomposites, NC3 exhibited superior photocatalytic performance toward ciprofloxacin (CIP) removal under UV–visible light illumination, achieving 92.23% removal at a catalyst dosage of 45 mg with an apparent pseudo‐first order velocity constant of 0.02787 min ⁻¹ . Quenching experiments suggested that superoxide radicals (•O ₂ ⁻ ) were the dominant reactive species, with additional contributions from •OH radicals and photogenerated holes. In vitro cytotoxicity assessment using the MTT assay revealed promising in vitro antiproliferative activity of NC3 against HeLa cells (GI ₅₀ = 21.48 µg mL ⁻¹ ), while maintaining low toxicity levels against L‐929 fibroblast cells (GI ₅₀ ≈ 295.80 µg mL ⁻¹ ; selectivity index ≈ 13.77), with DAPI/Rhodamine‐123 staining suggesting apoptosis‐associated mitochondrial dysfunction. NC3 retained ∼85.7% activity after five cycles, demonstrating reasonable reusability.