Morphology‐Controlled Synthesis of Hierarchical Copper Hydroxyphosphate Microcrystals in Alkaline Buffer Solution and their Optical Properties

A series of copper hydroxyphosphate (Cu 2 (OH)PO 4 ) microcrystals with different shapes, including straw sheaf‐like microcrystals, microrods‐assembled microflowers, four‐edged arrow‐like microcrystals, and four‐pointed star‐like dendrites, are prepared by a hydrothermal method in Na 2 HPO 4 ‐NaOH buffer solutions. The buffer solutions serve as both reactant and solvent. More importantly, the pH values of the alkaline buffer solutions significantly affect the morphologies of Cu 2 (OH)PO 4 microcrystals. Four samples have absorption bands in the near‐ultraviolet, visible, and near‐infrared regions; furthermore, four Cu 2 (OH)PO 4 microcrystals exhibit different band gap energies (3.06, 2.78, 2.68, and 2.39 eV) owing to their different structures. This strategy can be scaled up for the simple, green, and low‐cost production of Cu 2 (OH)PO 4 microcrystals.