Highly Efficient and Reproducible Sonochemical Synthesis of ZnO Nanocrystals

Sonochemical synthesis can be a facile, fast, efficient, versatile and economical way to prepare a large variety of conventional or novel nanostructured materials (metallic, magnetic, semiconducting, polymeric, etc.). In this work, zinc oxide nanocrystals were synthesized by irradiating and heating at 90 °C in a commercial ultrasonic bath a water solution of zinc nitrate hexahydrate and ammonia solution or hexamethylenetetramine as base catalysts. The evolution of the powder morphology and its crystalline structure were investigated at different times of ultrasonic irradiation (0–9 hours) and compared with those of samples obtained by only heating the solutions in a muffle furnace in order to enlighten the growth mechanism. It resulted that: i) the crystal morphology depends on the selected base, ii) for samples obtained by using ultrasounds, the homogeneity of the powders depends on the irradiation time, iii) by comparing all samples obtained at 7 hours of heating, the aspect ratio of the crystals is higher for those that also underwent to ultrasounds. The facile and low cost sonochemical synthesis in aqueous solution of ZnO hexagonal needles and prisms is performed by using a commercial ultrasonic bath reaching high efficiency, high reproducibility and crystals with high aspect ratio.