Cyclic growth and tillering of layered polycrystalline zinc hydroxide sulfate and the resulting dendritic fractals

• Published in: Thin solid films 2023-03, Vol.768, p.139689, Article 139689
• Main Authors: Dong, Rulin, Yin, Ziran, Qi, Zhixin, Chen, Zhidong, Chen, Yukai
• Format: Article
• Language: English
• Subjects: Dendritic fractal; Layered polycrystalline structure; Wetting behavior; Zinc hydroxide sulfate; Zinc oxide
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2023.139689

•Two-dimensional dendritic fractals of LZHS crystals.•Plant-like growing mode of layered LZHS polycrystalline structure.•Tiller mechanism of LZHS polycrystalline structure.•Hydrophobicity enhanced by dendritic fractal structure. Two-dimensional dendritic fractals of layered zinc hydroxide sulfate (LZHS) were allowed to grow on a porous ZnO substrate-coated glass slide in an aqueous ZnSO4 solution through the dissolution-redeposition process. The generated LZHS seeds with polycrystalline structure gradually evolved into two-dimensional dendritic fractals with a diameter of 50∼100 μm through a plant-like growth mode involving tillering and the formation of layered tiller buds at branch ends. Such tiller mechanism is proposed to explain the evolution of LZHS fractals based on results obtained by the scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, and energy dispersive X-ray detection. The synthesized polycrystalline LZHS fractals can be topologically converted into hierarchical nanostructured zinc oxide by thermal pyrolysis combined with an alkaline wash process. After the modification by octyltrimethoxysilane, the topological zinc oxide surfaces, corresponding to the immersion time of 2, 4 and 6 h, showed superhydrophobic property with a water contact angle of 153.4°, 157.6°, and 164.7°, respectively. The enhanced hydrophobicity of zinc oxide films compared with the porous ZnO substrate surface is mainly attributed to the topological fractal morphologies and hierarchical nanostructures.