From superhydrophilic to superhydrophobic: controlling wettability of hydroxide zinc carbonate film on zinc plates.

Hydroxide zinc carbonate (HZC) films with different morphologies were deposited on zinc plates through a convenient chemical-bath deposition (CBD) process using urea solution. By altering deposition conditions, the structure of HZC crystals could be tuned from vertically aligned nanosheets to flowerlike microstructures. The upright-standing HZC nanosheets were developed from interconnected nanorods growing up on the zinc plates in aqueous urea solution and led to superhydrophilic properties because of the hydrophilic upside edges consisting of hydroxyl groups and large distance. In contrast, flowerlike microstructures formed in N,N-dimethylformamide-water solution and the exposed hydrophobic crystal planes resulted in superhydrophobic properties with a water contact angle as high as 155.2 degrees. The final surface wettabilities could be ascribed to both the atomic composition and hydrophilicity of HZC crystal planes exposed to the water-solid interface. All the surfaces with specific wettabilities can be one-step fabricated without subsequent modification, and tunable wetting properties can provide zinc substrates extending applications.