Unveiling the Formation Mechanism of Pseudo-Single-Crystal Aragonite Platelets in Nacre

Order-Disorder Transition of Aragonite Nanoparticles in Nacre

“…Third, we suggest that it is quite difficult to discriminate aragonite nanoparticles in pristine nacre under TEM, because the crystallographic orientation is highly aligned. TEM results with singlecrystal appearance have independently been reported by several different methods, i.e., focused-ion-beam fabrication [10], ion milling [11], and microtome sectioning [18]. All previous TEM observations showing singlecrystal character are not contradictive with our explanation, as proposed by the monocrystal-polycrystal duality of aragonite platelet.…”

“…Apparently, the spontaneous self-assembly process can lead to a decrease of Gibbs free energy (ÁG < 0) [18], accompanied with the high ordering of aragonite nanoparticles, as validated by TEM observation [18,25]. In this regard, it seems to be counterintuitive that spontaneous self-assembly reaction should be towards disordering (entropy increase based on the third law of thermodynamics).…”

“…These results, however, sharply conflict with the recent observation that millions of nanoparticles were detected inside one single aragonite platelet by atomic force microscopy [10,17]. Based on two seemingly contradictive observations, the formation mechanism for individual platelets can be ascribed to the screw dislocation-driven growth model [18]. However, how to discriminate the isolated aragonite nanoparticle within platelets under TEM still remains elusive.…”

Novel Basic Protein, PfN23, Functions as Key Macromolecule during Nacre Formation

“…Pearls share an identical structure with the nacre of oyster shell (1,2). Nacre (mother of pearl) is an organo-mineral assemblage that is dominated by calcium carbonate with a minor organic matrix complex, which produces exceptional hardness, strength, and osteoinductive activity compared with the pure mineral (3,4).…”

Anisotropic nanowire growth via a self-confined amorphous template process: A reconsideration on the role of amorphous calcium carbonate

“…Once a liquid-like nanodroplet coalesced with the tip, it would not solidify instantly but remain liquid-like (light green). Hence, the polycrystalline domains (blue), which were created by the partly crystallized nanodroplets, were still rotation-free and assimilated by the singlecrystalline interior (steel blue) via axis rotation and lattice match, or via Ostwald ripening [54,55], and then the amorphous domains in the tip were left outside to form the new shell. As this process continued, the nanowire kept growing.…”