Mixing Time between Organometallic Precursor and Ligand: A Key Parameter Controlling ZnO Nanoparticle Size and Shape and Processable Hybrid Materials

Since the advent of nanoscience, the grail of chemists is to perfectly and reproducibly elaborate nanoparticles (NPs) of fully defined size, shape, polydispersity, and surface state. It implies a total control of the experimental parameters affecting the synthesis. In the preparation of metal oxide nanoparticles using an organometallic approach, we evidenced that the mixing time between the precursor and the ligand is surprisingly a parameter of tremendous importance. Using NMR spectroscopy, wide angle X-ray scattering, and computational DFT studies, the formation of Zn-amido oligomers through an acid–base reaction between the organometallic zinc precursor and the amine ligand is demonstrated. Over time, this polymerization process plays a major role on the control of the size and shape of the ZnO nanoparticles formed through the hydrolysis reaction. Hence, nanorods are obtained for short mixing times before hydrolysis while isotropic NPs are obtained for longer times. Furthermore, mixing induces the formation of a gel with adjustable rheological properties, thus opening new opportunities for the design of processable hybrid materials.