Mesoscale Self-Assembly of Highly Luminescent Zinc Tellurite Nanoclusters

Zinc tellurite (ZnTeO3 or ZTO) nanoclusters synthesized in aqueous medium from zinc acetate and sodium tellurite are amorphous in nature and exhibit intense photoluminescence when excited at the UV region. These nanoclusters assembled in two different compositions with different morphologies by refluxing in water, depending on the pH of the refluxing medium. At pH 5.5, the ZTO transformed to a crystalline phase with rod-like morphology. At pH 4.5, crystalline Zn2Te3O8 resulted and the as-obtained nanoplates of this compound self-assembled in oval-shaped microstructures. On further decreasing the pH to 3.5, the nanoplates self-assembled to rose-like patterns (nanorose). Very big microspheres and a mixture of microcrystals were formed on further reduction of pH to 3. Interestingly, all the crystalline products with different morphologies display luminescence properties. Further, these new materials exhibit three-photon absorption with positive third-order and negative fifth-order nonlinear refraction.