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The work presented here investigates the nucleation sites and corresponding controlling mechanisms of biogenic aragonite crystals from bivalve nacre. We find that they always nucleate on the margin of the underlying tablets, which are spatially confined. To explain the reason, we proposed several new possible factors leading to nucleation on the margin of the underlying tablets: the strain, crystallinity, hydrophobicity of the ILM substrate and the Ehrlich–Schwoebel (ES) barrier. These findings advance our current knowledge of nacre biomineralization and may help to design novel biogenic composite materials. [ABSTRACT FROM AUTHOR]

To the best of our knowledge, there has been no investigation of non-classical crystallization on hydrophobic substrates occurring in natural systems. The work presented here investigates the early growth process of nacreous aragonite crystals. We found that, (1) the contact angle of organic membranes >90°, proving that the aragonite crystals grow on the hydrophobic substrate. (2) The periphery of the aragonite crystals is decorated with nanoparticles, which grow epitaxially on the earlier aragonite crystals. (3) Some nanoparticles exhibit a surprising overhanging attachment pattern, that is, a particle sticks at a position higher than the height of the substrate surface at that point, such that the space below the particle is not filled. The hydrophobic substrate has an effect on the non-classical crystallization of nacreous aragonite crystals. [ABSTRACT FROM AUTHOR]

In the field of shell biomineralization, one of the major challenges is to understand the interplay between the biopolymer framework and crystal growth. The widely accepted model proposes that the framework is pre-formed and stable, which directs the subsequent crystal growth. However, it remains unanswered whether the crystal growth can inversely influence the framework's configuration. Here, we find that, in the silver-colored spherulitic layer of a bivalve shell, the framework is reconfigured during mineralization. This result may provide a new direction in the study of shell biomineralization. [ABSTRACT FROM AUTHOR]