With the aforementioned aim, pure ACC and ACC doped with aspartic acid, polyaspartic acid (pAsp) and polystyrene sulfonate (PSS) crystallization experiments were performed under conditions of controlled humidity. These conditions mimic the low water activities present during crystallization in biomineralization systems, where the amorphous phase is enclosed in a membrane or compartment with a limited amount of water. The microscopic dynamics of ACC with and without the presence of different organic molecules such as those present in biogenic carbonates, and at different hydration states were studied. Through the research, we have confirmed that large changes in the dynamics can be caused by very small structural changes. In addition, the study carried out shed light into the dynamic behavior of ACC and the influence of different additives (e.g. proteins, as pAsp) and water (ACC with different hydration levels) on the crystallization kinetics. The X-ray photon correlation spectroscopy (XPCS) experiments revealed that the amount of adsorbed water has a strong control on its diffusive dynamics and they showed an unexpected reversible behavior of the dynamics upon dehydration and rehydration cycles (in pure ACC and ACC doped with pAsp) that has not been reported previously. Results of crystallization experiments under conditions of controlled humidity indicated that the adsorbed water is enough to spark crystallization of calcite and a direct proportionality was found between the relative humidity of the environment and the final calcite crystal size (Fig. 2). Control of the water activity and water content is, therefore, a possible way to regulate biomineral crystallinity both in nature and for the design of functional biomimetic materials.
During the development of the project, several dissemination activities were carried out to contribute to making science more accessible and interesting to students, teachers and the general public. Among the activities, the results were presented in several seminars for academic staff, undergraduates, postgraduates and postdoctoral researchers. Public dissemination was carried out by the website of the project, which explains the importance, main aims of the project, and its innovative aspects as well as the research team involved. The dissemination to the scientific community has been performed through the publication of the results in scientific articles (1 published, 2 under review, and 1 in preparation) and through the participation in the Goldschmidt conferences hold in Barcelona in 2019.
