Surface Activity and Aggregation Behavior of Polyhydroxylated Fullerenes in Aqueous Solutions

Area of Science:

• Physical Chemistry
• Materials Science
• Nanotechnology

Background:

• Polyhydroxylated fullerenes (PHFs) exhibit unique surface activity.
• Understanding PHF behavior at interfaces is crucial for their applications.
• The air-water interface is a key area for studying molecular interactions.

Purpose of the Study:

• To investigate the surface activity and aggregation behavior of PHFs at the air-water interface.
• To determine the influence of ionic strength on PHF surface excess.
• To elucidate the role of PHF monomers and aggregates in surface nonlinear optical responses.

Main Methods:

• Surface tension measurements to quantify surface activity and excess.
• Conductivity measurements to determine PHF charge.
• Resonance-enhanced second harmonic generation (SHG) to probe nonlinear optical properties at the interface.

Main Results:

• PHFs are surface-active, with a limiting surface excess of 130 Ų/molecule in water.
• Increased ionic strength (NaCl) reduces PHF surface excess.
• PHF monomers cause a destructive interference, reducing SHG signals, while aggregates enhance the nonlinear optical response.

Conclusions:

• PHF adsorption at the air-water interface is concentration and ionic strength dependent.
• Surface-specific SHG reveals distinct contributions of PHF monomers and aggregates to interfacial nonlinear properties.
• The study provides insights into the interfacial behavior of PHFs, relevant for nanomaterial applications.