Sustainable green synthesis of CeO2-ZnO nanocomposites using Rhazya stricta: enhanced synergistic solutions for biomedical challenges and environmental remediation.

Addressing the global demand for eco-friendly technologies, this study reports a sustainable 'green' route for the synthesis of cerium oxide (CeNPs), zinc oxide (ZnNPs), and their synergistic Ce-Zn nanocomposite (Ce-Zn Nc) using Rhazya stricta leaf extract. By replacing hazardous chemical reductants with renewable phytochemicals, this approach directly aligns with UN Sustainable Development Goal (SDG) 12 (Responsible Consumption and Production). GC-MS profiling identified 24 bioactive stabilizers, including Palmitic acid and Quebrachamine, which eliminate the need for toxic synthetic capping agents. Structural characterization (UV-Vis, XRD, FTIR, Raman, SEM/TEM) confirmed the successful synthesis of highly stable, crystalline particles, with the Ce-Zn Nc exhibiting a superior reduced average size of 10.7 nm and enhanced thermal stability compared to individual nanoparticles. Critically, the nanocomposite demonstrated enhanced synergistic efficiency in addressing challenges related to SDG 3 (Good Health) and SDG 6 (Clean Water). The Ce-Zn Nc showed superior antioxidant potential (Total Flavonoid Content: 342 ± 2.4 µg QE per mg) and robust antibacterial activity (26.7 ± 1.5 mm against E. coli). Furthermore, the composite provided an effective solution for environmental remediation, achieving 67.3 ± 4% catalytic degradation of methylene blue dye under solar irradiation. Hemolytic assays revealed a dose-dependent activity peaking at 59.1 ± 1.3%, indicating that while these materials possess significant membrane-disrupting potential, they offer a specialized bio-active alternative to traditional industrial catalysts. This research provides an evidence-based framework for scaling up multifunctional, bio-inspired nanomaterials to solve pressing sustainability challenges. Future research should focus on the multi-cycle stability and pilot-scale optimization of these green-synthesized nanocomposites to facilitate their practical implementation in industrial environmental remediation and clinical diagnostics.