Green Synthesis and Characterization of TiO₂, ZnO and TiO₂/ZnO-Activated Maize Cob Composite Using Tithonia Diversifolia Leaf Extract as Capping Agent

Abstract

Green synthesis has emerged as an environmentally friendly and sustainable approach for producing metal oxide nanoparticles by eliminating the use of hazardous reducing agents and minimizing environmental pollution. This study focused on the green synthesis and characterization of titanium dioxide (TiO₂) and zinc oxide (ZnO) nanoparticles using Tithonia diversifolia leaf extract as a natural reducing, capping, and stabilizing agent, followed by the preparation and characterization of a TiO₂/ZnO-activated maize cob composite. The study aimed to develop an eco-friendly nanocomposite by integrating green nanotechnology with agricultural residuevalorization. TiO₂ and ZnO nanoparticles were synthesized through a plant-mediated green synthesis route and subsequently immobilized onto chemically activated maize cob using the impregnation method to enhance structural stability and surface functionality. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) were employed to characterize the synthesized nanoparticles and the resulting composite. Visual observation confirmed successful nanoparticle formation through the appearance of white precipitates during synthesis. FTIR analysis identified characteristic O-H stretching bands at approximately 3750 cm⁻¹ for TiO₂ and 3800 cm⁻¹ for ZnO, together with C=O, C-O, Ti-O, and Zn-O functional groups, confirming phytochemical-mediated stabilization and successful nanoparticle incorporation into the activated maize cob matrix. XRD analysis confirmed the formation of highly crystalline phase-pure rutile TiO₂ and hexagonal wurtzite ZnO nanoparticles with average crystallite sizes of 1.89 nm and 15.33 nm, respectively. The TiO₂/ZnO-activated maize cob composite retained the characteristic crystalline phases of both metal oxides while exhibiting enhanced surface functionality and structural stability. The findings demonstrate that Tithonia diversifolia is an effective biological resource for the green synthesis of stable TiO₂ and ZnO nanoparticles and that activated maize cob provides an efficient, sustainable support matrix for developing environmentally friendly bio-nanocomposites