Stepwise Growth of CuO via Transformation of Cu₂(OH)₃Br Intermediate in Aqueous Solution of Long-Alkyl-Chain Copper Salt

Uniform CuO microspheres were successfully synthesized through a simply surfactant-free hydrothermal synthesis assisted by a soluble long-alkyl-chain tetraalkylammonium carboxylic copper salt. During the synthetic procedure, a botallackite-type Cu2(OH)3Br intermediate with 3D bamboo-leaf-like structure was obtained by careful time-controlled experiments. Subsequently, the intermediate was converted into CuO spheres via a solid-phase transformation competed with a dissolution–renucleation process. Additionally, ion-adjusted experiments were manipulated to analyze the effects on CuO morphologies of the various of ionic groups involved in the long-alkyl-chain tetraalkylammonium carboxylate. It confirms that the organic copper salt precursor used in this work not only supplies a constant copper source for crystal growth of CuO but also plays an important role in the spherical architecture building as a self-surfactant agent.