Free-standing crystalline CaCO3 films composed of three-dimensional microstructures with different morphologies

Crystalline vaterite CaCO3 self-standing films composed of three-dimensional microstructures were synthesized by a simple gas diffuse method with the assistance of poly(vinyl alcohol) (PVA). The microstructures with different morphology (sphere-like, rose-like, and pumpkin-like) were self-assembled by three-dimensional oriented attachment of faceted micro-platelets, and the films were all stable in air for more than one year. The concentrations of Ca2+ ions and PVA all played important roles in the formation of vaterite crystal phase. In addition, the introduction of salt (NaCl, NaNO3) would reduce the size of the micro-platelets significantly. A possible mechanism for the formation of the self-standing films is put forward.

► Self-standing CaCO3 vaterite crystalline films were synthesized.
► The films were composed of three-dimensional microstructures.
► The microstructures were of different morphology and self-assembled by faceted micro-platelets.
► Salt (NaCl, NaNO3) effect would reduce the size of the micro-platelets significantly.