How to make 'stable' ACC: protocol and preliminary structural characterization

A reproducible and simple protocol to synthesize and stabilize the metastable CaCO3 center dot nH(2)O phase termed amorphous calcium carbonate (ACC) was developed in order to allow the characterization of its structure at the nanoscale using high-resolution microscopy combined with Raman spectroscopy and X-ray diffraction. 'Stable' ACC consists of relatively smooth spherical particles, 50-200 nm in size, that have XRD and Raman patterns with no intense peaks or sharp bands, as expected from amorphous material. Furthermore, high-resolution imaging also supports this finding but in addition, beam-damage induced crystallization and the concomitant formation of locally ordered domains in the ACC spheres are discussed.