Four self-assembled monolayer surfaces terminated with–COOH,–OH,–NH_(2)and–CH_(3)functional groups are used to direct the biomineralization processes of calcium carbonate(CaCO_(3))in low Ca^(2+)concentration,and the mechanism of nucleation and initial crystallization within 12 h was further explored.On-COOH surface,nucleation occurs mainly via ion aggregation mechanism while prenucleation ions clusters may be also involved.On-OH and-NH_(2)surfaces,however,nucleation forms via calcium carbonate clusters,which aggregate in solution and then are adsorbed onto surfaces following with nucleation of amorphous calcium carbonate(ACC).Furthermore,strongly negative-charged-COOH surface facilitates the direct formation of calcites,and the-OH and-NH_(2)surfaces determine the formation of vaterites with preferred crystalline orientations.Neither ACC nor crystalline CaCO_(3)is observed on-CH_(3)surface.Our findings present a valuable model to understand the CaCO_(3)biomineralization pathway in natural system where functional groups composition plays a determining role during calcium carbonate crystallization.
Hua DengShuo WangXiumei WangChang DuXingcan ShenYingjun WangFuzhai Cui
