Chemical and Structural Insights of the Nano Organo-Mineral Interfaces in Growing Abalone Nacre

Characterizingthe nano organo-mineral interfaces in nacreis of primary importance to understand the processes of nucleation,growth, orientation, and organization of the aragonite tablets. Here,we investigated these different interfaces in growing nacre of abalone Haliotis tuberculata shell using a combination ofadvanced techniques, i.e., focused ion beam milling coupled with fieldemission gun scanning electron microscopy, high-resolution transmissionelectron microscopy, scanning transmission X-ray microscopy, and electronenergy loss spectroscopy. We show the presence of "globules"-likeorganic-rich inclusions within the center of each tablet that extendfrom one tablet to another through mineral bridges surrounded by organics.These structures may control the growth of the columnar stacking oftablets supporting different findings from the literature. In thelateral growing surface of the tablets, we reveal the presence ofa thick organic domain rich in calcium but deficient in carbonateions strengthening the idea that calcium-binding acidic proteins areinvolved in tablet's lateral growth. Overall, this work emphasizesthe importance of nanoscale chemical and structural analysis of theorgano-mineral interfaces in growing nacre, allowing in particularfor the discrimination between organic and inorganic carbons.