Effects of NaOH on formation of ZnO nanorods from ε-Zn(OH)2

• ZnO nanorods were synthesized from ε-Zn(OH)2 in 0–2.0 mol L−1 NaOH solutions.
• The aspect ratios of the ZnO nanorods could be tuned from 5 to 40.
• The in-situ crystallization and the dissolution–precipitation mechanisms coexisted.
• The effects of NaOH on the two competitive mechanisms were demonstrated.

ZnO nanorods with varying aspect ratios were synthesized by aging ε-Zn(OH)2 precursors in 0–2.0 mol L−1 NaOH solutions at 80 °C, via competing in-situ crystallization and dissolution–precipitation routes. The effects of NaOH on the growth process and morphological evolution of ZnO nanorods were investigated. An increase of NaOH concentration from 0 to 2 mol L−1 led to increased average aspect ratio of the ZnO nanorods from 5 to 40, and decrease of conversion time from 420 min to 40 min. ε-Zn(OH)2 was converted to ZnO nanorods primarily by in-situ crystallization in water, while for NaOH solutions they were converted mainly by dissolution–precipitation.

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