Thiol-yne adsorbates for stable, low-density, self-assembled monolayers on gold.

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Developing stable and functional monolayers on gold is crucial for various applications.
• Existing self-assembled monolayers (SAMs) often have limitations in stability and conformational freedom.
• Novel synthetic strategies are needed to overcome these challenges.

Purpose of the Study:

• To present a novel thiol-yne addition approach for creating carboxylate-terminated, low-density monolayers on gold.
• To investigate the structural, chemical, and electrochemical properties of these novel monolayers.
• To demonstrate the tunable conformational freedom and stability of the resulting interfacial functional groups.

Main Methods:

• Synthesis of adsorbates via thiol-yne addition of thiol-containing head groups to an alkyne-containing tail group.
• Characterization using ellipsometry, Fourier transform infrared (FTIR) spectroscopy, and contact angle measurements.
• Electrochemical stability testing and evaluation of water and ion transport resistance.

Main Results:

• The thiol-yne monolayers exhibit a unique two-phase structure with a crystalline head and low-density tail.
• Ellipsometric thickness and FTIR data confirm the proposed structure and presence of carbonyl groups.
• Contact angle measurements indicate intermediate surface energy due to exposed methylene and carbonyl groups.
• The monolayers demonstrate exceptional adsorbate stability, resistance to water/ion transport, and electrochemical stability exceeding that of typical SAMs.
• Conformational freedom was confirmed through potential-induced surface remodeling.

Conclusions:

• The thiol-yne monolayer approach provides exceptional adsorbate stability and conformational freedom.
• This method offers a versatile platform for creating low-density monolayers with varied functionalities beyond carboxylates.
• The enhanced electrochemical stability and transport resistance make these monolayers promising for advanced surface engineering applications.