Synthesis and evolution of rod-like nano-scaled ZnC₂O₄·2H₂O whiskers to ZnO nanoparticles

A new route has been developed to prepare rod-like nano-scaled ZnC₂O₄·2H₂O whiskers using dodecylbenzenesulfonic acid sodium salt (DBS) as a template. Rod-like nano-scaled ZnC₂O₄·2H₂O whiskers with diameters of 200-300 nm and lengths in the range of 5-20 μm were prepared successfully. The structure and morphology changes on heat treatment of the as-prepared product were investigated by means of scanning electron microscopy (SEM), X-ray powder diffractometry (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). By heating the rod-like nano-scaled ZnC₂O₄·2H₂O whiskers below 280 °C, rod-like anhydrous nano-scaled β-ZnC₂O₄ whiskers with several small holes were obtained. On increasing the temperature to 500 °C, the rod-like nano-scaled whiskers broke into ZnO nanoparticles with diameters of 50-60 nm and display wurtzite crystal structure. On heating the products to 1280 °C, the particles gradually melted into each other to form blocks with smooth surfaces which keep the same phase structure. When we compare the products of this method with the crystalline octahedron ZnC₂O₄·2H₂O prepared in aqueous solution, we can conclude that the surfactant DBS plays a pivotal role in the shape and structure formation. ZnC₂O₄·2H₂O whiskers were formed in a microreactor formed by DBS, thus the size and shape of the microreactor determines and limits the product's shape and diameter as well as the temperature.