Temperature-Triggered Chiral Self-Assembly of Achiral Molecules at the Liquid-Solid Interface

Area of Science:

• Surface Science
• Nanotechnology
• Physical Chemistry

Background:

• Achiral molecules can self-assemble into ordered structures on surfaces.
• Controlling chirality in molecular assemblies is crucial for advanced materials.
• Temperature and solvent interactions influence molecular self-assembly.

Purpose of the Study:

• To investigate temperature-induced chiral nanostructure formation on two-dimensional (2D) surfaces.
• To explore the role of chiral solvents in controlling the chirality of 2D molecular assemblies.
• To understand the thermodynamic stability of different molecular structures.

Main Methods:

• Scanning tunneling microscopy (STM) for observing nanostructures.
• Controlled heating experiments to induce structural transitions.
• Density functional theory (DFT) calculations for stability analysis.
• Chiral solvent addition to study enantioselective assembly.

Main Results:

• Achiral molecules self-assembled into strip structures on graphite at room temperature.
• Heating induced the formation of R and S flower-like chiral nanostructures at specific transition temperatures (55°C for molecule 1, 60°C for molecule 2).
• DFT calculations confirmed that flower-like structures are thermodynamically more stable than strip structures.
• Addition of chiral solvents eliminated racemic mixtures and induced homochirality in the molecular assemblies.

Conclusions:

• Temperature is an effective trigger for creating chiral nanostructures from achiral molecules on 2D surfaces.
• Chiral solvents provide an efficient route to control and achieve homochirality in 2D molecular assemblies.
• The findings offer a method for precise control over chirality in surface-based molecular systems.