Biomimetic synthesis of coexistence of vaterite-calcite phases controlled by histidine-grafted-chitosan

Biomimetic synthesis vaterite is promising in improving the application of calcium carbonate and providing a novel method for controlling synthesis other biomaterials. For the first time, the histidine-grafted-chitosan (NHCS) is used as an organic matrix to biomimetic synthesis of calcium carbonate. Effect of the pH value on the morphology and polymorph is investigated. The products are characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and field-emission scanning electron microscope (FESEM). The results show that the sole rhombohedral calcite phase can form in absence of NHCS, whereas the coexistence of vaterite-calcite phases is gained in the presence of NHCS. At pH=8.0, the content of vaterite reaches 93.7 wt%, but it drops to 62.2 wt% at pH 6.5. In addition, a possible mechanism is proposed to explain the formation of coexistence of vaterite-calcite phases in the study. The result indicates that NHCS is an effective template and pH responsive for biomimetic synthesis of vaterite, and offers a novel method for controlling synthesis of other biomaterials.