Structure and Defect Identification at Self-Assembled Islands of CO₂ Using Scanning Probe Microscopy

Area of Science:

• Surface science
• Materials science
• Nanotechnology

Background:

• Understanding carbon dioxide (CO2) interactions with surfaces is vital for developing CO2 mitigation and catalysis technologies.
• Physisorbed CO2 behavior on surfaces influences material properties and sensor development.

Purpose of the Study:

• To investigate the behavior of physisorbed CO2 molecules on a gold(111) surface with 1,4-phenylene diisocyanide (PDI) and gold (Au) adatoms.
• To elucidate the structure of self-assembled CO2 islands and identify foreign species on the surface.
• To clarify the origin of the kagome tiling in this surface system.

Main Methods:

• Simultaneous atomic force microscopy (AFM) and scanning tunneling microscopy (STM) with CO-functionalized probes.
• Density functional theory (DFT)-based simulations for image analysis and theoretical modeling.
• High-resolution imaging to resolve molecular structures and arrangements.

Main Results:

• Resolved the structure of self-assembled CO2 islands, both confined and free-standing.
• Revealed a chiral, windmill-like arrangement of CO2 molecules enclosing other species.
• Identified foreign surface species by comparing experimental and DFT-calculated AFM/STM images.
• Clarified the origin of the kagome tiling on the PDI-Au functionalized gold surface.

Conclusions:

• AFM and STM with functionalized probes are complementary techniques for surface analysis.
• Combining AFM/STM with DFT provides fundamental insights into greenhouse gas behavior on model systems.
• This approach has potential for exploring CO2 interactions at the molecular level for material design.