Synthesis and Mechanism of 1D ZnO Based on Alkaline Dissolution-Conversion Strategy of High Stable and Soluble...

A high soluble and stable ɛ-Zn(OH)₂ precursor is synthesized at below room temperature to efficiently prepare ZnO whiskers. The experimental results indicate that the formation of ZnO whiskers is carried out mainly via two steps: the formation of ZnO seeds from ɛ-Zn(OH)₂ via the in situ solid conversion, and the following growth of whiskers via dissolution-precipitation route. The decrease of temperature from 25 to 5 °C promotes the formation of ɛ-Zn(OH)₂ with higher solubility and stability, which balances the conversion and dissolution rates of precursor. The Rietveld refinement, DFT calculations and MD simulations reveal that the primary reason for these characteristics is the expansion of ɛ-Zn(OH)₂ lattice due to temperature, causing difficulties in the dehydration of adjacent ─OH. Simultaneously, the larger specific surface area favors the dissolution of ɛ-Zn(OH)₂. Based on this precursor, well-dispersed ZnO whiskers with 9.82 µm in length, 242.38 nm in diameter, and an average aspect ratio of 41 are successfully synthesized through a SDSN-assisted hydrothermal process at 80 °C. The process has an extremely high solid content of 2.5% (mass ratio of ZnO to solution) and an overall yield of 92%, which offers a new approach for the scaled synthesis of high aspect ratio ZnO whiskers by liquid-phase method.