Graphene oxide (GO) sheets has been known to disperse well in water since its first discovery, and thus has been routinely described as hydrophilic. GO's water dispersity and hydrophilicity has been mainly attributed to the ionizable edge -COOH groups. However, its basal plane is essentially a network of hydrophobic polyaromatic islands of unoxidized benzene rings. Therefore, GO should be viewed as an amphiphile with a largely hydrophobic basal plane and hydrophilic edges. Meanwhile, GO is characterized by two abruptly different length scales. While its thickness is determined by a single atomic layer, the lateral dimension extends up to tens of micrometers. Since GO has both the characters of a molecule and a colloidal particle, would it behave like molecular amphiphiles or colloidal surfactants? To test the hypothesis, we studied the activity of GO at air-water, liquid-liquid, and liquid-solid interfaces.
展开▼
