Effect of Cu(2+) on the nucleation kinetics and crystallization of rod-shaped CaSO(4)·2H(2)O in aqueous solution

In this study, a simple and efficient strategy is developed to synthesize rod-like CaSO(4)·2H(2)O (DH) crystals with tunable aspect ratio in aqueous solution using Cu(2+) as modifier. The aspect ratio and length of the DH crystals are effectively reduced to 5.7 : 1 and about 35 μm in the presence of Cu(2+), respectively. The interfacial tension value (γ) in the aqueous solution is improved significantly with the assistance of Cu(2+), yet the nucleation rate (J) of the DH crystal is decreased sharply. The interfacial tension value (γ) in the aqueous solution is improved and the nucleation rate (J) of the DH crystal is drastically decreased due to the introduction of Cu(2+), leading to the induction time of the DH crystallization being extended from 4 min to 25 min. The diversification of morphology for the DH crystals is incited by the changes of nucleation kinetics and Cu(2+) incorporated into the crystal lattice, affecting the crystal growth habit, and finally controlling the growth of DH crystals in aqueous solution.