Nacre crystal growth as a paradigm of island growth mode: Hydrophobic substrate is one of the keys to the biomineralization

Abstract

Nacre is a multilayered film material consisting of alternating layers of aragonitic tablets and organic membranes (OMs). However, at this time, no authors have discussed the growth mode of nacre from the perspective of the science of typical film materials. Here, for the first time, we focus on measuring the contact angles of the nacre growth surface (GS) using the contact angle meter. Additionally, we also investigate the GS's structure and phases using field emission scanning electron microscopy and X-ray diffractometer, respectively. We firstly found that: (1) The contact angles of the GS are always greater than 90°, with a maximum value of 113° and minimum value of 91°, indicating that the GS is hydrophobic. (2) The growth mode of GS is similar to the island growth mode (V-W) of the typical films. (3) The hydrophobicity of OMs plays an important role in the nucleation and growth of nacre. This research may provide new insights into the mechanism underlying nacre formation. In the field of thin-film, this conclusion will provide a new direction for the preparation and research of hydrophobic substrates, and a new idea for the development of thin-film technology.

Phase-Field Modeling of Biomineralization in Mollusks and Corals: Microstructure vs Formation Mechanism

“…Under the conditions used in our simulation the organic component remains in an amorphous or nanocrystalline state. Remarkably, the predicted “nacre” structure recovers such details of the experimentally observed microstructure as the “mineral bridges” and the line defects across the organic layers termed “aligned holes”. ,,, We will show, however, in the next section that despite this close similarity, the formation mechanism of the nacre can be considerably more complex than predicted here.…”

“…Finally, we note that the thickness of the organic and mineral layers in the nacre are typically 10–40 nm and 300–600 nm, 136 − 140 respectively. Our qualitative simulations give a considerably larger relative thickness for the organic layer.…”

“…This is especially true for columnar nacre : experiments indicate that the formation of a quasi-periodic network of organic membranes precedes the formation of the CCC layers, which fill the space between the organic membranes later, as illustrated in Figure . − Although one could imagine that the organic membranes form periodically in space via an oscillating chemical reaction of the diffusion-reaction type, while the extrapallial fluid fills the space between the membranes, apparently, the real mechanism is more complex: first a multilayer outer membrane forms, of which the individual layers are exfoliated by nucleating CC crystals. , Furthermore, recent experimental works show a thin ACC layer on the surface of the CCC tablets of the nacre, , implying that (h)­ACC particles may play an essential role in the formation of nacre. This, in turn, indicates that a particle-by-particle addition is more appropriate for solidification, as in the case of coral skeletons (see discussion in section ).…”

“…Finally, to address the evolution of columnar nacre within the phase-field theory, one can incorporate preexisting organic membranes into the simulations “by hand”, including the mineral bridges/aligned holes seen in the experiments. ,,, We used PF1 to model the formation of CCC stacks shown in Figure . The thin organic walls were assumed to have amorphous structure (local orientation varied randomly pixelwise) and we applied a boundary condition that ensured a contact angle of 100° with the solid–liquid interface.…”

Effect of Substrate Surfaces for Crystal Growth of a Photochromic Diarylethene by Sublimation

“…Ikeda et al reported the difference in the in-plane crystal orientation on the glass substrate with different wettabilities in the graphoepitaxy of α-sexithiophene . Wang et al showed that hydrophobic substrate is one of the key factors to affect the Nacre crystal growth system. , As mentioned above, it is likely that the surface wettability has some influence on the produced crystal morphology. Thus, it is required to figure out the crystal growth mechanism for each substrate surface with different wettabilities through an investigation of the process where the crystal morphologies are formed.…”