Mineralization and morphology control of CaCO3 induced by glutamic acid derivatized carbon dots

Calcium carbonate (CaCO3) exhibits multiple morphologies and properties to meet different requirements through biomineralization in nature. In this study, carbon dots (CDs) were prepared by a microwave method using glutamic acid and ethylenediamine as raw materials. The mineralization of CaCO3 was subsequently proceeded in the presence of CDs by means of gas diffusion. The effects of the ratio of glutamic acid to ethylenediamine, the concentrations of CDs and Ca2+ on the mineralization process were studied. Fourier transform infrared (FTIR) spectrometer, X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) were employed for characterizations of CDs and CaCO3. The results indicated that the CDs had a uniform size of 4–6 nm and good dispersion in the aqueous phase due to the numerous –COOH groups on the surface. The crystallization of CaCO3 was strongly affected by CDs, presenting various morphologies of rhombic, spherical, hexagonal, hydrangea-shaped, and cobblestone-shaped. The presence of CDs was conducive to the formation and stable existence of vaterite and the content of vaterite was up to 97.61%. The possible mechanism proposed was related to the –COOH groups on CDs. The multiple controllable forms of CaCO3 may provide various applications such as drug sustained release and so on.