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.