A large quantity of ZnO nanorods grown at room temperature

High-quality ZnO nanorods were synthesized on stainless-steel substrates at room temperature in NaCl solutions with NaCl concentrations of 3.5 - 5.0 wt%. The ZnO nanorods were grown from a Zn film on a stainless-steel substrate in a NaCl solution without any extra process. Field-emission scanning electron microscopy images showed that the ZnO formed into rods with a uniform size at a NaCl concentration of 3.5 - 5.0 wt% while the ZnO became plates for NaCl concentration above 9 wt%. The mean sizes of the nanorods grown at 30 and 40 °C were about 100 and 70 nm, respectively. High-resolution transmission electron microscopy and selected area electron diffraction measurements demonstrated that the nanorods had a well-ordered wurtzite structure without any extra phase. Extended X-ray absorption fine structure measurements revealed that the initial Zn film on the stainless-steel substrate had a hexagonal close-packed structure and finally became nanorods with a wurtzite structure in a sea water environment. The zinc likely obtained oxygen from the solution, and Na ⁺ and Cl ^- ions acted as catalysts for the ZnO crystallization.