Zinc oxide (ZnO) has received much attention in recent years. It has attractive electronic properties, is relatively inexpensive, is easy to prepare, and is an environmentally friendly alternative to other semiconductors. This work explores how size, shape, and method of preparation and capping ligands influences zinc oxides photocatalytic activity. Zinc oxide was synthesized by alkali precipitation using water/methanol mixed solutions of zinc acetate and various amines and precipitated with the addition of NaOH. Both the rate of NaOH addition and the amine present were found to influence the size and shape of the ZnO nanoparticles. The materials were annealed under nitrogen at 200<sup>o</sup>C for two hours. The optical band gap of the materials was determined by diffuse reflectance. The materials were also characterized by powder X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and BET surface area. The photochemical reactivity of the different materials was evaluated by using them to degrade the organic dye malachite green in aqueous solutions under UVA irradiation. The observed first-order rate constants for the degradation of the dye were determined for each ZnO, assuming a first-order kinetics model. For particles ranging in size from 300nm to several microns, smaller particles yielded faster decomposition rates than larger particles. Additionally, morphologies with a high surface area-to-volume ratio, such as rod or needle-shaped particles, appear to increase the photocatalytic effectiveness. For 20-60nm particles, materials with fewer capping ligands yielded higher photocatalytic activity.

Synthesis and characterization of ZnO nanoparticles and their use to photocatalyze the degradation of malachite green

256th National Meeting (2018)

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