Nanoscale assembly processes revealed in the nacroprismatic transition zone of Pinna nobilis mollusc shells

Abstract

Intricate biomineralization processes in molluscs engineer hierarchical structures with meso-, nano- and atomic architectures that give the final composite material exceptional mechanical strength and optical iridescence on the macroscale. This multiscale biological assembly inspires new synthetic routes to complex materials. Our investigation of the prism–nacre interface reveals nanoscale details governing the onset of nacre formation using high-resolution scanning transmission electron microscopy. A wedge-polishing technique provides unprecedented, large-area specimens required to span the entire interface. Within this region, we find a transition from nanofibrillar aggregation to irregular early-nacre layers, to well-ordered mature nacre suggesting the assembly process is driven by aggregation of nanoparticles (∼50–80 nm) within an organic matrix that arrange in fibre-like polycrystalline configurations. The particle number increases successively and, when critical packing is reached, they merge into early-nacre platelets. These results give new insights into nacre formation and particle-accretion mechanisms that may be common to many calcareous biominerals.

Molecular Modeling and Mechanics of Acrylic Adhesives on a Graphene Substrate with Roughness

“…The mechanics of amorphous polymeric adhesives on a solid substrate is critical for interfacial interaction for both natural and synthetic composite materials [1][2][3][4][5][6][7][8]. In nature, they are often found in the forms of biological polymers, such as protein, chitin, and glucose, and they play an important role to integrate different materials of contrasting mechanical or chemical properties, allowing these material building blocks to synergistically assemble and form new composite materials with mechanical functions superior to each of their building blocks [3,[6][7][8].…”

“…In nature, they are often found in the forms of biological polymers, such as protein, chitin, and glucose, and they play an important role to integrate different materials of contrasting mechanical or chemical properties, allowing these material building blocks to synergistically assemble and form new composite materials with mechanical functions superior to each of their building blocks [3,[6][7][8]. For example, the shell of nacre is mainly composed of the assembly of polygonal mineral tablets with hundreds of nanometers in thickness that are made of calcium carbonate, and they bind with each other on the contact surface by organic polymeric materials [1]. Molecular nonbonded interactions including van der Walls forces, hydrogen bonding, and electrostatic interactions play the dominating role for adhesion, and it is fascinating that these relatively weak interactions can integrate the mineral tablets to achieve both outstanding stiffness and toughness at the same time, which is usually a drawback for many engineering materials [9].…”

“…Referring to natural systems such as nacre interface and suture of the bone as shown in Fig. 1a, b, respectively, covalent bonds are rarely used but the structure of the interface plays an important role in governing the interfacial mechanics [1,7,14]. Graphene is known to be extremely flexible, and a small mechanical fluctuation can lead to non-zero roughness because of its out-of-plane deformation such as wrinkle and crumple.…”

On Mineral Retrosynthesis of a Complex Biogenic Scaffold

“…Several complex biominerals present an organic scaffold (or matrix), which plays a crucial role in regulating mineral growth by incorporating inorganic precursors, such as ions, ion-clusters and amorphous phases. For instance, in nacre and bone material, the physicochemical properties of the scaffold tune interactions with mineral precursors and subsequently lead to hierarchically-organized composite biominerals [3,7,8]. Thus, the niche conditions of crowding and confinement presented by the scaffold offer a defined physicochemical environment towards mineralization reactions [9,10].…”

Desiccator Volume: A Vital Yet Ignored Parameter in CaCO3 Crystallization by the Ammonium Carbonate Diffusion Method

“…Nature precisely controls crystallization pathways to form functional crystalline materials with non-equilibrium morphologies that feature properties which often exceed those of their artificial counterparts [1][2][3]. As a consequence, significant research efforts have focused upon the synthesis and characterization of ordered structures of assembled crystallites which mimic the architectures found in nature [4,5].…”