Ultrasonic mediated synthesis of zinc oxide nanoparticles: An insight into operative conditions to control key properties

Abstract

The advance of nanotechnology in last decades demands more efficient, improved and eco-friendly synthetic pathways. In this regard nanomaterial’s synthesis mediated by ultrasound appears as a very attractive option. Between the nanomaterials finding more diverse and wide application nowadays, the zinc oxide nanoparticles (ZnO NPs) are undoubtedly one of the most demanded due to its insertion in the market. This contribution deals with the study of the role of different experimental variables associated with US synthesis in the properties of interest of ZnO NPs. Factors such as US power density, time, temperature, reaction volume, tip diameter and the presence of surfactants have been rigorously evaluated and some of them optimized using a Design of Experiments (DOE) basis. The study primarily focused on crucial characteristics such as crystallite size, energy band gap and connection of the overall morphology pattern. The achieved data suggested that power density and tip diameter were the critical factors affecting ZnO NPs as band gap which ranged between 2.30 and 3.25 eV; and crystallite size between 34.6 and 63.3 nm, showing the adaptability of this methodology by changing these input factors. Diverse morphologies, from spherical to laminar ones, where reached by changing US conditions. The presence of surfactants, polyethylene glycol (PEG) and polyethyleneimine (PEI), as functionalizing agents may result in alternatives to modifying US experimental conditions due to similar effects on morphology, band gap and crystallite size may be reached. The findings from this work will be instrumental in selecting the conditions ensuring suitable properties of ZnO NPs.