Hydroxyl ions: flexible tailoring of Cu₂O crystal morphology

The precise control architectures of Cu₂O crystals are very crucial, which have a significant influence on their various performances. Herein, Cu₂O crystals with diverse architectures were achieved via 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 Cu₂O 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 Cu₂O 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 Cu₂O crystals.