Fabrication of Calcite Aggregates and Aragonite Rods in a Water/Pyridine Solution

Polymorphs of calcium carbonate (CaCO3) have been easily synthesized in a water/pyridine mixed solvent system under mild conditions without using any other organic additives. The phase transition from pure aragonite to almost pure vaterite, and then to pure calcite, can be nicely captured by the choice of a suitable water to pyridine ratio. The formation mechanisms of calcium carbonate crystals have been proposed. A novel morphology of calcite, wire-like shaped, was found in pure pyridine solvent. A self-assembly process for the formation of wire-like calcite in pure pyridine solution has been proposed. The effect of experimental time on morphology of calcite is investigated in pure pyridine solvent. The results obtained proved that such reaction media could give an alternative and versatile tool for controlling both the structure and the polymorphism of inorganic materials.