Enhanced vaterite and aragonite crystallization at controlled ethylene glycol concentrations

Calcium carbonate (CaCO 3 ) has three distinct anhydrous polymorphs, namely vaterite, aragonite and calcite. Although there is a high demand for aragonite and vaterite polymorphs for biomedical use, their unstable nature makes it challenging to synthesize them compared to calcite, which is the most stable form of CaCO 3 . Despite the remarkable effort on stabilizing vaterite and aragonite polymorphs in aqueous solutions, phase-pure vaterite and aragonite polymorphs have not been synthesized yet, without referring to the use of additives, surfactants or elevated temperatures. Herein, the effect of ethylene glycol (EG) concentration and temperature on the formation of vaterite and aragonite particles were investigated at 25 °C and 70 °C. Results showed that 60% EG containing precursor solution -without any other additive- can prevent vaterite/aragonite-to-calcite transformation regardless of the synthesis temperature. Furthermore, the size of CaCO 3 particles decreased as EG concentration increased and it reached its minimum average values at 80% EG. The results of this study revealed the potential use of the proposed synthesis route to stabilize vaterite and aragonite polymorphs, tailor their content, morphology and size without using any additives, surfactants and elevated temperatures.