Many authors report when elaborated CuO and ZnO thin films by sol-gel spin coating method, they add Acetic acid to their precursor solution, to achieve a homogeneous solution. Which quantity of Acetic acid should be used? How acetic acid allows obtaining a homogeneous solution?
Thank in advance.
That depends on the precursor used. Acetic acid is a good acid for thin films production by sol-gel (using alcoxides as precursor) because gelification is slower using this acid when compared for example with nitric or chloridric acids. The quantity is not that easy for me to tell, as I don't know which is your precursor, my advise to you is: go for articles or go to Brinker's book: sol-gel science and technology (1990).
In these methods, the precursor used is usually metal acetate such as zinc acetate or copper acetate. These acetates belong to the Louis acids family, which are weak acids and therefore lead to the partial formation of metal ions. In aqueous solution the H+ / OH- acid-base couple leads to the formation of the metal hydroxide entities such us Zn(OH)2 .
The role of the acetic acid is to ensure the dissociation of this hydroxide to give the metal ion and consequently ensure both solubility and homogeneity of the solution.
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