4.6 Article

Spontaneous surface adsorption of aqueous graphene oxide by synergy with surfactants

Journal

PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Volume 24, Issue 2, Pages 797-806

Publisher

ROYAL SOC CHEMISTRY
DOI: 10.1039/d1cp04317j

Keywords

-

Funding

  1. Australian Institute of Nuclear Science and Engineering
  2. Monash Centre for Atomically Thin Materials
  3. ARC Future Fellowship [FT160100191]
  4. Ernest Oppenheimer Fund through provision of an Oppenheimer Research Fellowship

Ask authors/readers for more resources

This study investigates the spontaneous adsorption of graphene oxide (GO) sheets at the air-water interface using X-ray reflectivity (XRR) measurements. It is found that GO sheets do not spontaneously adsorb at the air-water interface, but can be driven to the surface when incorporated with surfactant molecules at optimal ratios. However, excessive surfactant can inhibit GO surface adsorption.
The spontaneous adsorption of graphene oxide (GO) sheets at the air-water interface is explored using X-ray reflectivity (XRR) measurements. As a pure aqueous dispersion, GO sheets do not spontaneously adsorb at the air-water interface due to their high negative surface potential (-60 mV) and hydrophilic functionality. However, when incorporated with surfactant molecules at optimal ratios and loadings, GO sheets can spontaneously be driven to the surface. It is hypothesised that surfactant molecules experience favourable attractive interactions with the surfaces of GO sheets, resulting in co-assembly that serves to render the sheets surface active. The GO/surfactant composites then collectively adsorb at the air-water interface, with XRR analysis suggesting an interfacial structure comprising surfactant tailgroups in air and GO/surfactant headgroups in water for a combined thickness of 30-40 angstrom, depending on the surfactant used. Addition of too much surfactant appears to inhibit GO surface adsorption by saturating the interface, and low loadings of GO/surfactant composites (even at optimal ratios) do not show significant adsorption indicating a partitioning effect. Lastly, surfactant chemistry is also a key factor dictating adsorption capacity of GO. The zwitterionic surfactant oleyl amidopropyl betaine causes marked increases in GO surface activity even at very low concentrations (<= 0.2 mM), whereas non-ionic surfactants such as Triton X-100 and hexaethyleneglycol monododecyl ether require higher concentrations (ca. 1 mM) in order to impart spontaneous adsorption of the sheets. Anionic surfactants do not enhance GO surface activity presumably due to like-charge repulsions that prevent co-assembly. This work provides useful insight into the synergy between GO sheets and molecular amphiphiles in aqueous systems for enhancing the surface activity of GO, and can be used to inform system formulation for developing water-friendly, surface active composites based around atomically thin materials.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.6
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available