Polyethylenimine-assisted synthesis of transparent ZnO nanowhiskers at ambient temperatures

Transparent ZnO nanowhiskers were synthesized at ambient temperature (5-30°C) assisted with pH buffer of polyethylenimine from an aqueous solution of sodium hydroxide and zinc acetate. X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy revealed their crystalline phase, morphology and formation mechanism. The ZnO nuclei were formed at the initial stage in a wide low temperature range by in-situ forced hydrolysis of anhydrous zinc acetate template layer. Subsequently ZnO nanowhiskers were formed on the F-doped SnO₂-coated glass substrate by heterogeneous nucleation and growth. Lower temperature was found to favor the hydrolysis, whereas higher temperature was found to promote the growth of ZnO. Such synthesized ZnO possessed good crystalline structure. The length, diameter, and density (number of whiskers per unit area) of ZnO nanowhiskers are controllable by simply varying the deposition time and/or solution temperature.