Entropic colloidal crystallization pathways via fluid-fluid transitions and multidimensional prenucleation motifs

Area of Science:

• Materials Science
• Physical Chemistry
• Crystallography

Background:

• Complex crystallization pathways involving temporary precursor phases are observed in various systems like protein crystallization and biomineralization.
• Understanding the structural characteristics of these prenucleation phases is crucial for fluid-to-solid ordering models.
• Current models often attribute precursor emergence to specific system properties, but prenucleation phase structures remain unclear.

Purpose of the Study:

• To investigate complex crystallization pathways in hard-particle fluids.
• To identify and characterize prenucleation motifs within precursor fluid phases.
• To explore the role of fluid-fluid interfaces in crystal nucleation.

Main Methods:

• Studied three instances of two-step crystallization in hard-particle fluids.
• Analyzed the structural characteristics of precursor fluid phases, including clusters, fibers, layers, and networks.
• Measured changes in density and diffusivity across the fluid-fluid phase transition.
• Observed crystal nucleation at the interface between the two fluid phases.

Main Results:

• Identified two-step crystallization pathways in hard-particle systems.
• Observed distinct prenucleation motifs (clusters, fibers, layers, networks) in high-density precursor fluid phases.
• Demonstrated that density and diffusivity changes correlate with prenucleation motif dimensionality.
• Found that crystal nucleation is catalyzed by the interface between the precursor fluid phases.
• Synthesized complex crystals, including one with a large cubic unit cell.

Conclusions:

• Established the existence of complex crystallization pathways in entropic systems.
• Revealed diverse prenucleation motifs with varying dimensions in fluid-fluid phase transitions.
• Highlighted the catalytic role of fluid interfaces in crystal nucleation.
• Provided insights into the structural ordering during fluid-to-solid transitions.