Formation mechanism of bead-chain-like ZnO nanostructures from oriented attachment of Zn/ZnO nanocomposites prepared via DC arc discharge in liquid

Bead-chain-like ZnO nanoparticles (NPs) formed in colloidal solution from oriented attachment (OA) of spherical nanoparticles. Arc discharge in liquid is a cost-effective method for quick mass production of nanostructured materials without considerable environmental footprints. Applying voltage across two zinc rods as electrodes, which were immersed in water cause explosion of electrodes and plasma generation. Zn/ZnO nanocomposites produced by interaction of different active species in high-pressure and high-temperature plasma at the solid-liquid interface. Different sized nanoparticles with diameters of 26, 35, 40 and 60 nm at applied discharge currents of 150, 100, 50 and 20 A respectively, were fabricated in water without any chemical additives. The results showed bead-like oriented attachments appeared with increasing the applied current during synthesis. Length of aggregates increases from 114 nm to 120 nm with the applied current of the arc discharge. The mechanism of OA of ZnO NPs was investigated by calculating the attractive and repulsive forces based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed for characterization of particle size, shape, and investigation of bead-like aggregates. X-ray diffraction (XRD) analysis was used to study the crystal structure and phase composition of the bead-chain like nanostructures. Finally, zeta potential analysis was used to measure surface charges and study the mechanism of oriented attachment. The results provide a simple and flexible method for synthesis of Zn/ZnO bead-chain like nanostructures.