Redispersible Reduced Graphene Oxide Prepared in a Gradient Solvent System

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Graphene oxide (GO) reduction often leads to aggregation and instability.
• Controlling the hydrophilic properties during reduction is crucial for stable dispersions.
• Achieving high carbon-to-oxygen (C/O) ratios in reduced graphene oxide (RGO) is desirable for advanced applications.

Purpose of the Study:

• To develop a gradient solvent strategy for stable GO reduction.
• To optimize RGO properties, including particle size, C/O ratio, and conductivity.
• To investigate the effectiveness of different post-reduction treatments for adsorbate removal.

Main Methods:

• Designed a continuous gradient solvent system to match GO and RGO hydrophilicity.
• Utilized dropwise addition of a third solvent to control hydrophilic variation.
• Employed ultrasonic redispersion in N-methyl-pyrrolidone (NMP) for solid RGO powder.
• Investigated successive solvent rinsing, thermal solvent extraction, and thermal treatment for surface modification.

Main Results:

• Achieved stable RGO dispersions without aggregation during reduction.
• Obtained RGO with an average particle size as low as 200 nm after redispersion.
• Prepared RGO with a high C/O ratio of 13.75.
• Demonstrated varying efficiencies of different treatments for surface adsorbate removal, with fatty alcohol polyoxyethylene ether (AEO) showing a good balance.
• Significantly enhanced electrical conductivity from an initial 5236 S m⁻¹ to 18,000 S m⁻¹ after 500 °C thermal treatment.

Conclusions:

• The gradient solvent strategy provides a robust method for producing stable RGO dispersions.
• Post-reduction thermal treatment is effective in further enhancing RGO conductivity.
• The choice of dispersant and post-treatment method impacts surface properties and adsorbate removal.