Multivalent binding motifs for the noncovalent functionalization of graphene

Area of Science:

• Materials Science
• Electrochemistry
• Surface Chemistry

Background:

• Graphene is a conductive material ideal for interfaces with electroactive compounds.
• Aromatic groups typically interact with graphene via van der Waals forces, causing molecules to lie flat.
• Existing methods lack control over the orientation and projection of functional groups from the graphene surface.

Purpose of the Study:

• To design and characterize a tripodal molecule for robust and oriented binding to graphene.
• To investigate the binding thermodynamics and kinetics of this molecule using electrochemical methods.
• To assess the stability and electron transfer properties of graphene-modified surfaces.

Main Methods:

• Synthesis of a tripodal molecule with pyrene moieties and a redox-active cobalt complex.
• Electrochemical investigation of binding parameters (thermodynamics and kinetics) to single-layer graphene.
• Surface characterization to determine molecular footprint and monolayer stability.
• Comparison with model compounds having single aromatic binding groups.

Main Results:

• The tripodal molecule exhibits strong binding to graphene (ΔGads = -38.8 ± 0.2 kJ mol⁻¹).
• Stable monolayers with a molecular footprint of 2.3 nm² were formed.
• Monolayers demonstrated high stability (>12 h) and significantly slower desorption rates compared to model compounds.
• Electron transfer rates suggest the redox-active moiety is projected away from the graphene surface.

Conclusions:

• The tripodal motif enables strong, oriented adsorption of functional molecules onto graphene.
• This approach offers enhanced stability and controlled surface functionality for electrochemical applications.
• The designed molecule provides a versatile platform for developing advanced graphene-based interfaces.