Competing thermodynamic and dynamic factors select molecular assemblies on a gold surface

Area of Science:

• Surface science
• Nanotechnology
• Computational chemistry

Background:

• Controlling molecular self-assembly into nanostructures is crucial for nanotechnology.
• Understanding multi-scale physical mechanisms governing assembly is essential.

Purpose of the Study:

• To investigate the self-assembly of 1,4-substituted benzenediamine (BDA) molecules on a gold (111) surface.
• To elucidate the interplay of thermodynamics and dynamics in nanostructure selection.

Main Methods:

• Combining scanning tunneling microscopy (STM) with hierarchical ab initio and statistical mechanical modeling.
• Analyzing intermolecular forces, surface modulation, and assembly dynamics.

Main Results:

• Identified mechanically stabilized nanostructures by hydrogen bonding.
• Demonstrated that thermodynamics and dynamics competition selects specific BDA nanostructures.
• Observed selection of low free energy oriented linear chains and high free energy branched chains at low temperatures.

Conclusions:

• Nanostructure selection is governed by a complex interplay of forces and kinetics.
• Thermodynamic and dynamic factors dictate the final arrangement of adsorbed molecules.
• Specific nanostructures, like linear chains, are favored under certain conditions.