Fig. 6 | Nature Communications

Fig. 6

From: Microscopic structure of the polymer-induced liquid precursor for calcium carbonate

Fig. 6

Scheme of the CaCO3 thin film or nanorod formation processes induced by negatively charged polymer. a CaCO3 thin film formation process starts with the formation of a Ca2+/polymer complex (stage 1). Upon binding of CO32−, ~2 nm-sized ACC clusters develop from the polymer-bound Ca2+, which are further cross-linked and stabilized by polymer molecules, forming 30–50 nm-sized polymer-ACC NPs (stage 2). The NPs aggregate into μm-sized structures in bulk solution (stage 3). In the presence of a flat substrate, the NPs deposit to form thin films (stage 4). Subsequently nucleation of CaCO3 crystals (stage 5) generates platelets within the thin film. The majority of polymer molecules is excluded after crystallization (stage 6), while some of them become occluded inside the crystal. b CaCO3 nanorods are formed when a track etch membrane is exposed to the reaction solution. Short calcite nanorods with crystal facets on their tips are formed without the presence of polymers. In the presence of negatively charged polymers, the ~2 nm-sized ACC clusters covered by polymers deposit to the walls of the nanopores and form nanorods with concave tips

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