Chemical Control of Crystal Growth with Multidentate Carboxylate Ligands: Effect of Ligand Denticity on Zinc Oxide Crystal Shape
Ligand denticity profoundly affects the ability of organic ligands to control crystal shape during aqueous crystallization of zinc oxide. A method is presented for rapidly screening the shape-control activity of organic molecules during zinc oxide crystallization. This method involves the solution-phase growth and isolation of zinc oxide crystals large enough to be quantified by optical microscopy. Crystals grown by this method were hexagonally prismatic with a rod-like morphology, but in the presence of multidentate carboxylate ligands, a platy morphology developed. By quantifying the aspect ratio of crystals as a function of ligand concentration, the shape-control activities of three carboxylate ligands were compared systematically. Shape control was strongest in a tridentate ligand (citrate), weaker in a bidentate ligand (malate), and absent in a monodentate ligand (glycolate). The effect of denticity, coupled with trends in crystal length and width, suggests that ligands alter the deposition rate on specific surfaces, possibly by binding to surface sites.
Crystal Growth & Design