Synthesis and growth features of copper hydroxide iodide nanoneedles

Single-crystalline Cu2(OH)3I nanoneedles were synthesized by the reaction between Cu(CH3COO)2 and KI in aqueous solutions with or without poly(ethylene glycol) (PEG) in situ, and techniques of XRD, EDX, SEM and TEM were used to characterize their crystal structure, chemical composition and growth feature. The as-prepared nanoneedles had a high purity in composition and belonged to the botallackite-type Cu2(OH)3I. Nanoneedles, together with botallackite-type Cu2(OH)3I flakes, were produced in the absence of PEG, and their growth features were consistent with the theoretical predictions; however, the addition of PEG to the solution led to the exclusive formation of nanoneedles, in which the adsorption of PEG on the related crystal surfaces controlled a crystal growth different from theoretical expectations.