Crystallization of micrometer-sized particles with molecular contours

Area of Science:

• Colloid science
• Crystallography
• Materials science

Background:

• Molecular crystals exhibit complex packing symmetries.
• Understanding colloidal assembly can provide insights into molecular crystallization.
• Polyacenes like TBH and DBT are flat molecules with specific crystal structures.

Purpose of the Study:

• To investigate the 2D self-assembly of anisotropic colloidal particles in an electric field.
• To determine if colloidal particle packing can mimic molecular crystal symmetries.
• To explore the stability and symmetry of ordered colloidal assemblies.

Main Methods:

• Utilized dielectrophoresis (AC electric field) to induce self-assembly of micrometer-sized TBH- and DBT-shaped particles.
• Analyzed the resulting 2D packings for symmetry and density.
• Compared colloidal crystal symmetries with known molecular crystal structures of TBH and DBT.

Main Results:

• Ordered, high-density 2D packings with identifiable plane group symmetries were formed under an electric field.
• TBH- and DBT-shaped particles assembled into the p2 plane group, mimicking molecular crystal symmetries.
• The colloidal assemblies exhibited unexpected stability, attributed to jamming of interlocking particle shapes.

Conclusions:

• Colloidal particle shape dictates 2D packing symmetry, mirroring molecular crystallization.
• Electric field-induced dielectrophoresis is effective for creating ordered colloidal crystals.
• This work demonstrates scale-transcending packing principles from molecular to colloidal systems.