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Emergence of Chirality in an Optically Active Two-Dimensional Crystal with a Spiral Surface Pattern
Hubiao Huang1,2, Gangfeng Chen1,2, Manabu Hoshino3
1RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Journal of the American Chemical Society
|January 17, 2025
Summary
Two-dimensional (2D) crystals with spiral surfaces can exhibit chirality and emit circularly polarized light, even when made of achiral building blocks. This arises from a unique helical structure formed by twinning.
Area of Science:
- Materials Science
- Crystallography
- Chirality Studies
Background:
- One-dimensional (1D) crystals with screw dislocations show helical twists and chirality.
- The structural chirality of two-dimensional (2D) crystals with spiral surfaces is not well understood due to internal structure inaccessibility.
Purpose of the Study:
- To investigate the structural chirality of 2D crystals with spiral surface patterns.
- To understand the origin of chirality in 2D crystals composed of achiral building blocks.
Main Methods:
- Transmission electron microscopy (TEM) for 1D crystal analysis.
- X-ray structural analysis for 2D crystal structure determination.
- Circularly polarized luminescence (CPL) measurements.
Main Results:
- A specific 2D crystal with a spiral surface pattern was found to emit circularly polarized luminescence.
- X-ray analysis revealed a helical structure with an achiral space group and distinctive twinning.
- The crystal comprises four centrosymmetric, achiral components that form a spirally arranged topology through twinning.
Conclusions:
- The observed chirality in the 2D crystal emerges from the specific arrangement of achiral components due to twinning.
- This study demonstrates how achiral building blocks can form chiral supramolecular structures in 2D crystals.
- The findings open new avenues for designing chiral nanomaterials with unique optical properties.
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