Hexagons to Ribbons: Flipping Cyanide on Au{111}

Area of Science:

• Surface Science
• Materials Chemistry
• Nanotechnology

Background:

• Cyanide monolayers on Au(111) exhibit a hexagonal close-packed lattice in their as-adsorbed state.
• Understanding surface restructuring is crucial for designing novel materials and catalysts.

Purpose of the Study:

• To investigate the structural and chemical changes of cyanide monolayers on Au(111) upon thermal annealing.
• To elucidate the bonding configurations in the restructured monolayer.

Main Methods:

• Surface characterization using techniques sensitive to surface structure and vibrational modes.
• Thermal annealing to induce structural transformations.
• Analysis of vibrational spectroscopy data (e.g., Infrared Spectroscopy).

Main Results:

• A transition from a hexagonal lattice to a mixed-orientation "ribbon" structure was observed after annealing.
• Significant changes in vibrational frequencies, including a blue shift of the CN stretch to 2235 cm⁻¹ and a new low-frequency mode at 145 cm⁻¹.
• The new structure features domain boundaries and orientationally offset regions influenced by the gold substrate.

Conclusions:

• The annealed cyanide monolayer adopts a novel ribbon structure with mixed cyanide/isocyanide bonding.
• The bonding scheme involves both Au-CN and Au-NC configurations oriented perpendicular to the Au(111) surface.
• The observed spectral changes indicate a significant alteration of the chemical environment, akin to gold-cyanide crystallization.