Hydroxyl ions: flexible tailoring of CuO crystal morphology.

The precise control architectures of CuO crystals are very crucial, which have a significant influence on their various performances. Herein, CuO crystals with diverse architectures were achieved finely adjusting the concentration of NaOH. The intriguing results showed that the addition of specific amounts of OH to the solution was crucial to tailor the morphology and size of the resulting microcrystals. We observed the evolution of the shapes of the CuO microcrystals, which change from a rhombic dodecahedron to spherical, octahedral-like and then to hexapod upon the increase in the NaOH concentration. Adjusting the volume of NaOH added provides a means to vary the particle size. Furthermore, density functional theory (DFT) may reveal that OH ions serve as an efficient coordination agent selectively adsorbing onto different crystal faces of CuO crystals modifying the crystal energies, inducing the structure anisotropy on crystal growth. This work reveals that an effective and facile strategy has been developed for morphology-control of CuO crystals.