Green Synthesis of Cobalt Oxide/Gold (Coo/Au) Bimetallic Nanoparticles Using Sinapinic Acid: A Comprehensive Study

This study reports the successful green synthesis of cobalt oxide/gold (CoO/Au) bimetallic nanoparticles using sinapinic acid as both a reducing and stabilizing agent. The eco-friendly synthesis approach eliminates the need for hazardous chemicals while producing nanoparticles with superior properties. The formation of CoO/Au bimetallic nanoparticles was confirmed through visual observation of color changes from brown to greyish-black upon addition of HAuCl₄ to the CoO nanoparticle solution. Comprehensive characterization using UV-Visible spectroscopy revealed distinct surface plasmon resonance peaks at 350 nm and 650 nm corresponding to CoO and Au components, respectively. FTIR analysis confirmed the role of sinapinic acid functional groups in nanoparticle reduction and stabilization, with a characteristic Co-O-Au stretching band at 575 cm⁻¹. X-ray diffraction patterns demonstrated the face-centered cubic (FCC) crystalline structure of the bimetallic system, while transmission electron microscopy revealed discrete, spherical nanoparticles with an average diameter of 24.4 nm and single crystalline nature. The synthesized CoO/Au bimetallic nanoparticles exhibit enhanced structural stability and demonstrate significant potential for applications in catalysis, biosensing, and biomedical fields.