Significance of the amide functionality on DOPA-based monolayers on gold

Area of Science:

• Materials Science
• Biomaterials Science
• Surface Chemistry

Background:

• Marine mussels utilize 3,4-dihydroxyphenylalanine (DOPA) for powerful adhesion.
• DOPA's unique structure provides cohesive and adhesive properties to mussel glue.
• Understanding these adhesive mechanisms can inspire synthetic biomaterials.

Purpose of the Study:

• Investigate the role of amide functionality in N-stearoyldopamine monolayers on gold.
• Determine the packing, orientation, and substrate interactions of self-assembled monolayers.
• Compare amide-containing and amide-absent molecules for monolayer formation.

Main Methods:

• Langmuir-Blodgett technique for aqueous monolayer formation.
• X-ray photoelectron spectroscopy (XPS) for surface composition.
• Contact angle measurements (CA) for surface wettability.
• Surface-enhanced Raman spectroscopy (SERS) for molecular structure.
• Infrared reflection-absorption spectroscopy (IRRAS) for bonding.
• Atomic force microscopy (AFM) for surface morphology.

Main Results:

• Catecholic oxygen atoms coordinate to the gold surface.
• Molecules exhibit a perpendicular orientation relative to the aromatic ring.
• Alkyl chains are tilted, and amide groups stabilize the monolayer.
• Amide-absent molecules show different packing and interaction.

Conclusions:

• Amide functionality is crucial for stabilizing adhesive monolayers on gold.
• The orientation and coordination of DOPA derivatives influence interfacial properties.
• This research provides insights into designing bio-inspired adhesives.