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

Abstract

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.