Synthesis of template-free hollow vaterite CaCO3 microspheres in the H2O/EG system

We describe a simple and green method for synthesizing hollow calcium carbonate (CaCO3) microspheres composed of vaterite via the reaction of Ca(CH3COO)(2) with NaHCO3 in the solvent mixture of ethylene glycol (EG) and H2O, without any templates. We show that the reaction rapidly conducts to the formation of microspheres with an average diameter of 800 nm. XRD and FTIR analyses confirm that the hollow CaCO3 microspheres are the characteristic of the vaterite polymorph. SEM and TEM observations reveal that the microspheres have a hollow core of around 500 nm width and are composed of vaterite with an average diameter of 80 nm. A possible growth mechanism for the hollow structure has been proposed, which exhibits that the hollow CaCO3 microspheres are formed by an aggregation mechanism. This work may pave the way for the elaboration of a biomaterial with potential applications in therapy as well as drug delivery. (c) 2013 Elsevier B.V. All rights reserved.