Direct synthesis of hollow vaterite nanospheres from amorphous calcium carbonate nanoparticles via phase transformation

Abstract

A new and simple method for preparation of hollow calcium carbonate nanospheres under mild conditions is developed. Hollow vaterite nanospheres are achieved by water-induced phase transformation of poly(4-sodium styrene sulfonate)-stabilized amorphous calcium carbonate (PSS-ACC) in water-ethanol solution at room temperature. It is found that the sizes of the resulting hollow-structured nanospheres can be easily regulated by the content of PSS and the phase transformation can be greatly affected by the ratio of water to ethanol in the mixed solvent. A combination effect of PSS and water is emphasized in this formation process. It is important to control the amounts of PSS and water in the experiments so that a large scale of hollow vaterite nanospheres with different sizes can be achieved. We suggest that the PSS-ACC particles use themselves as the templates to form the new crystallized shells, and its mechanism is also discussed.