Model Liposomes Seed the Concentrated Nucleation and Anisotropic Coalescence of CaCO3 Droplets

Heterogeneous mineral nucleation is a key step in many geological, biological, and industrial processes, where the roles of recently proposed precursors including prenucleation clusters and dense liquid phases remain a matter of debate. Taking inspiration from cloud droplet condensation around aerosol particles, we constructed carboxyl-/phosphate-rich biomimetic liposomes to induce CaCO3 formation. We observed nanometer-sized CaCO3 clusters at the onset, which are concentrated around liposomes by preformed electrical double layers. They nucleate and grow into liposome-embedded CaCO3 droplets through cluster aggregation with significant participation of curved lipid membranes. It is further seen that the coalescence of CaCO3 droplets with liposomal nuclei is kinetically arrested, which later solidify into nanosphere aggregates or anisotropic nanorods. In combination, our results show a liposome-mediated transition of CaCO3 from a cluster to a liquid and then to supracolloidal assemblies. A similar heterogeneous process may also be active in natural mineralization.

Automated summary

By constructing carboxyl-/phosphate-rich biomimetic liposomes, researchers induced the formation of nanometer-sized CaCO3 clusters, which then grew into CaCO3 droplets embedded in liposomes. This study demonstrates a liposome-mediated transition of CaCO3 from clusters to liquid and further to supracolloidal assemblies, suggesting similar heterogeneous processes may occur in natural mineralization.