hydrothermally grown ZnO nanostructures using Zinc nitrate and HMTA usually tend to take the 1-D wire structure. I am trying to understand the effect of the nitrate ions in the solution.
Nitrate ions dont 'bind' to zinc ions in solution. The ions bind (bond) in a solid (undissolved state) due to electrostatic forces. In solution, the polar water molecules pull them apart and they are drifting around in brownian motion. For hydrothermal growth of ZnO, the pH of the solution increases (slowly) due to decomposition of HMTA at elevated temperatures. This causes the Zn ions to precipitate as zinc hydroxide or zinc oxide depending on the conditions. Due to the crystal growth habit of wurtzite structure the shape of the ZnO crystals are rod-like. Some anions are known to bind to the Zn in the polar planes to form exotic structures (for e.g. citrate ions to form sheets, or step-pyramids). Generally ions or functional groups with lone pair electrons (COOH, NH2, SH) are the usual suspects (nucleophiles). My guess is that, zinc nitrate is commonly used because nitrate ions dont show much affinity to Zn site, so it does not interfere with the crystallization of nanorods.
is there a way to prove or show why nitrate ions show low affinity to Zn site
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