Why does the addition of ethyl acetate cause the precipitation of ZnO nanoparticles and why does the addition of ethyl acetate cause the formation of larger nanoparticles?
Robert Blanchard
In the sol-gel process, first by the action of alkali on the zinc salt, a sol (zinc hydroxide) is obtained. Zinc hydroxide is amphoteric and can disappear (dissolve) in excess alkali. Ethyl acetate is added to bind the excess alkali. It is hydrolyzed to sodium acetate and ethyl alcohol. This promotes gel formation. The appearance of new hydroxyl groups is enhanced by H-bonds. Further heating leads to the formation of zinc oxide. It all depends on the temperature and amount of sodium acetate and ethyl alcohol. The size of the nanoparticles can increase and decrease.
Ethyl acetate is an excellent solvent for many sol-gel precursors such as metal acetylacetonates. It also has an excellent viscosity and boiling point for spin and dip coating. Controlling the concentration allows the size of the nanoparticles to be controlled (the more dilute, the smaller the resulting particles in general).
See this review paper:
Article An Overview of Metal Acetylacetonates: Developing Areas/Rout...
Robert Blanchard
One important thing I should have mentioned is that pregnant women (is there such a thing as pregnant men?!) should not be using this solvent. Some linkage or anecdotal evidence associated with birth deformities.
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