Triptycene-terminated thiolate and selenolate monolayers on Au(111)

Area of Science:

• Surface Science
• Materials Chemistry
• Nanotechnology

Background:

• Self-assembled monolayers (SAMs) are crucial for surface functionalization.
• Understanding the impact of bulky organic groups on SAM properties is essential for designing advanced materials.

Purpose of the Study:

• To investigate how bulky triptycyl moieties influence the structure and properties of SAMs.
• To compare the performance of thiolate and selenolate SAMs with and without methylene spacers on Au(111).

Main Methods:

• Ultra-high vacuum infrared reflection absorption spectroscopy (UHV-IRAS)
• X-ray photoelectron spectroscopy (XPS)
• Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy
• Thermal desorption spectroscopy (TDS)

Main Results:

• Molecules in all SAMs are tilted due to packing effects, with less pronounced tilt when a methylene spacer is present.
• Selenolate SAMs exhibit lower defect densities and denser packing compared to thiolate SAMs.
• The selenium-gold (Se-Au) binding energy is higher than the sulfur-gold (S-Au) binding energy.

Conclusions:

• Bulky organic groups significantly affect SAM packing and molecular orientation.
• Selenolates form more robust and ordered SAMs than thiolates on Au(111).
• The findings provide insights into designing functional surfaces with tailored properties.