Comparison of Photocatalytic Performance of Sonochemically Synthesized ZnO with Different Capping Agents

This study investigates the influence of various organic modifiers that serve as capping agents on the structure, morphology, electronic properties, colloidal stability, and photocatalytic behavior of ZnO nanoparticles synthesized using the sonochemical method. The capping agents used include citric acid (CA), ethylene glycol (ETG), oleic acid (OA), and poly-(vinylpyrrolidone) (PVP). The synthesized ZnO nanoparticles were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray Spectroscopy (EDS), diffuse reflectance ultraviolet-visible spectroscopy (DRUV-vis), dynamic light scattering (DLS), and electrophoresis (EP). XRD analysis confirmed that all samples exhibited a Wurtzite-type hexagonal structure, with crystal sizes ranging from 17 to 22 nm and band gap energies (E _g) between 3.16 and 3.25 eV. Notably, samples synthesized with ETG and OA showed additional absorbance in the visible region. Among the samples, ZnO-ETG demonstrated the highest photodegradation efficiency for reactive black-5 azo-dye (RB5), serving as a model reaction. This work highlights the ability to modulate the properties of ZnO nanoparticles, such as crystal size, morphology, hydrodynamic size, surface charge and Urbach energy, through the choice of organic modifiers that serves as stabilizers, impacting their potential applications in photocatalysis.