Aqueous graphene dispersions-optical properties and stimuli-responsive phase transfer

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Graphene's unique properties are hindered by challenges in achieving stable, high-concentration aqueous dispersions.
• Previous methods for graphene exfoliation in water yielded low concentrations and uncertain optical properties.

Purpose of the Study:

• To develop a method for high-concentration graphene exfoliation in water.
• To accurately characterize the optical properties of exfoliated graphene.
• To investigate the rheo-optical behavior and phase transfer capabilities of concentrated graphene dispersions.

Main Methods:

• Utilized novel triblock copolymers and copolymeric nanolatexes with a reactive ionic liquid acrylate surfactant for graphene exfoliation.
• Employed UV-Vis spectroscopy to determine the visible absorption coefficient of graphene dispersions.
• Analyzed rheo-optical properties under shear fields and demonstrated stimuli-responsive phase transfer.

Main Results:

• Achieved essentially complete exfoliation of graphene aggregates in water at concentrations up to 5% by weight, a 166-fold increase over previous reports.
• Determined a visible absorption coefficient of 48.9 ± 1.3 cm²/mg at 500 nm, approximately double the accepted value.
• Observed that graphene dispersions behave as rheo-optical fluids, exhibiting an isotropic to nematic transition under shear, and demonstrated stimuli-responsive phase transfer.

Conclusions:

• The developed triblock copolymers and nanolatexes enable unprecedented high-concentration graphene exfoliation in water.
• The revised optical absorption coefficient provides a more accurate understanding of graphene's interaction with light.
• Graphene dispersions exhibit complex fluid dynamics and phase transfer properties, opening avenues for advanced material applications.