Solid-State Phase Transformation and Self-Assembly of Amorphous Nanoparticles into Higher-Order Mineral Structures

Area of Science:

• Materials Science
• Crystallization Studies
• Biomineralization Mimicry

Background:

• Nonclassical crystallization pathways, inspired by biomineralization, are crucial for fabricating advanced composite materials.
• Biomineralizing organisms like corals utilize metastable, amorphous calcium carbonate nanoparticles for hierarchical mineral structure formation.

Purpose of the Study:

• To investigate the abiogenic solid-state phase transformation of synthetic amorphous calcium magnesium carbonate nanoparticles.
• To elucidate the mechanism underlying nanoparticle transformation into crystalline structures in aqueous conditions.

Main Methods:

• Utilized high-resolution imaging techniques.
• Employed in situ solid-state nuclear magnetic resonance spectroscopy.
• Analyzed nanoparticle behavior and transformation under aqueous conditions.

Main Results:

• Identified a hydration shell facilitating fast chemical exchange between nanoparticle components and surrounding water molecules.
• Demonstrated that ion/molecule mobility enhancement drives solid-state transformation into crystalline domains.
• Observed nanoparticle aggregation and ordered structure formation via crystal growth by particle attachment, yielding distinct morphologies (sphere-like, spindle-shaped).

Conclusions:

• The study reveals a water-mediated solid-state transformation mechanism for amorphous calcium magnesium carbonate nanoparticles.
• This nonclassical crystallization pathway offers control over mineral structure design, surpassing limitations of traditional ion-by-ion growth.
• Findings provide a foundation for designing novel materials with tailored properties through controlled crystallization.